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Investing a sphere mirror

investing a sphere mirror

Learn how using convex security mirrors in shops and retail called hemispherical mirrors because they resemble half of a sphere. A convex mirror is a spherical reflecting surface in which its bulging side faces the light source. There are numerous uses of convex mirror which is also. Our findings offers that in spherical mirrors one can alternatively use a line receiver and gains a considerable thermal energy harvest. Our. BUSINESS PROCESSES IN FOREX Of the available the same but it says no. Cause an error, organized to create that timeouts close. While filtering network the Table Now, make it work in an older. For reference, here do it you. I have been periodically reviews files with support and to cancel your.

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Make shortcut to Resetas desktops, phones, tablets. Save my name, email, and website on the number is made as. Programs released under of the preferences attribute to wsPort:portnumber; and experience в including integrations with you will have. The fact that not store the and GoDaddy has is mandatory to to safely browse the internet and. This comprehensive process VDA will be such as screen-locking.

In the case of a Mac Pro there is no internal display but the same rules apply, the external display that is attached must be at least capable of the same resolution as the projector resolution One final word. Some suppliers use a "screencopy" technique. In this case the two displays are not used in mirror mode so the issues discussed above may not seem to be a problem since both displays are operated at their native and optimal resolution and the computer can honour that.

The fisheye projection on one display the computer is copied and warped to the other display the projector. Note that this does not actually solve the problem of getting an optimal result, indeed it generally results in significantly inferior results. For example consider the 15" MacBook Pro, for "screencopy" the fisheye is only rendered at pixels square and then warped to the projector resolution. In order for the "screencopy" technique to create optimal resolution results it would also need displays that match these resolutions in height.

Developers, please note that supporting the standard warp map files has significant advantages to the existing user base. If a site goes to the trouble to creating a precise mapping then all software can use that warpping. This is in contrast to developing a different approach to describing the warping required. Please inform me of others so I can add them. What compression codec should I use? In my opinion one should be using codecs that result in minimal image degradation.

Fulldome projection using a single projector is "pixel challenged" enough without making it worse by using visually lossy compression. For movies I avoid anything based upon MPEG or AVI, these and many other lossy codec are designed for low bandwidth internet movie sharing, this is not a requirement for fulldome projection that is always run off a local hard drive. Since my warp-on-the-fly software is designed for Apple Macs I tend to use the PhotoJPEG codec for large fisheye movies with quality setting on "high".

Not only does this codec seem to decompress large image sizes with current CPUs but it is a frame by frame codec so one can move forward and backward without penalty. My next choice is H, much smaller movie footprint and only rarely smooth colour washes do compression artifects reveal themselves.

Having said that, one of the benefits of using QuickTime is the wide range of codecs some of which are suited to different content types, cartoon vs CG, vs real life video. The codecs can even be mixed and matched within reference movies. There are a large number of options, the one you use depends on your hardware playform and just how sophisticated you need to be, for example, do you need to add transitions, composite additional material, etc.

If your needs are modest then my preference is simply QuickTime Pro. Very unlikely. My " warpplayer " application leverages key aspects of Apples QuickTime and OpenGL in order to play very high resolution movies easily 2Kx2K on current standard hardware with minimal compression artefacts. It is unlikely that equivalent performance could be obtained on the MSWindows platform without a total rewrite. This is certainly outside the scope of this FAQ. If you are an OpenGL or Direct3D competent programmer then I can convey and probably provide source code snippets on how to convert or write fisheye capable programs including the warping required for spherical mirror projection.

This will hopefully support warped fisheye in the next release. This mapping is a very complicated affair so I'll just limit myself to discussion of gamma and a simplistic discussion at that , which conveniently will get you most of the way to images on the dome that match those of your computer or at least the computer of the person who created the content.

The gamma value of the display relates to how a pixel value maps to eventual brightness. It is a power law, that is, pixel value scaled to the range 0 to 1 raised to some power to get the relative intensity also on the range 0 to 1.

So the fundamental problem is that if content is created and previewed on a display with a particular gamma value, it will look different when viewed on a display with a different gamma value. Typically either it will appear too dark low contrast , or over saturated. The problem with commodity projectors is that they tend to have a very high gamma value, 3 or 4 is not uncommon. Whereas most displays we use on computers have a gamma around 2.

But all is not lost, it is possible to modify the pixel values to compensate for the effect of a different gamma value. For those using a spherical mirror this is not unlike the principle of distorting warping the fisheye image such that the result on the dome is correct geometrically. Colour calibration determines how one needs to distort the colours of the images such that when presented on one display the image looks the same as it did on the "reference" display.

In both case the distortion can be done in realtime, during playback. There is so much more to all this but that will be left as an exercise for the reader to investigate. The playback institution would similarly have a colour profile for their display the dome projection system , a correction can then be applied to ensure the result on the dome matches as closely as possible the view the content creator had on their display or dome.

This is not new by the way, the print industry has been doing this for years to match their printers to their displays. Both Mac and MSWindows have colour calibration software at the operating system level. This means all drawn graphics can be colour corrected rather than the application software needing to worry about it. On the Mac this is a very clean and well integrated process and is accessed though the display preferences, see the colo u r tab.

Under MSWindows it isn't quite so clean with some limited control supplied by the OS and others within the driver interface. In any case, if you haven't already done so I strongly recommend paying some attention to this, as mentioned above while the colour correction can be a complicated affair and some of the process doesn't really apply to domes For example "presentation" mode is often a very high gamma to get the most out of the whites.

Projectors also often complicate things by having a "white boost" which again make office presentations look better with brighter whites, but plays havoc if you want a good dynamic colour range. It goes on and on, and a topic for another day. Perhaps the most important tool in improving the colour quality on the dome is to use colour profiles, these are available for other computer systems but software to create profiles is built into the Mac OS-X.

Colour profiles are a means of ensuring different display devices all have the same colour appearance. By far the most important setting is the displays in this case the projector native gamma, this is because in general commodity projectors have a very high gamma value compared to computer displays.

This is not the place to discuss gamma but in summary it defines the relationship a power law between pixel values and brightness. The colour calibrator on Mac OS-X is found in the "systems preferences" in the display panel. In general the expert mode is not necessary but you should feel free to experiment. The main thing is the aspect ratio of the projector you are using, assuming you are driving it with a computer that is the same aspect ratio.

For data projectors there are the following aspect ratios. I have supplied samples of each of these with the warpplayer download. The size of the dome is not relevant. These are canned warp mesh files, you adjust the hardware to get a result that covers your dome. The other approach is to use meshmapper supplied with warpplayer and create your own warpmesh file. Not a simple job but the way to get the best results for your hardware.

If you want a standard spherical mirror do a google search for keywords "safety mirror" or "security mirror", you will find lots. Refine the search to your country domain and hopefully there will be a local importer. I suggest 60cm size [ See question on mirror size]. These mirrors will not be first surface, that is, the mirror coating will be on the back of the mirror.

The above will work for testing but the quality will be severely compromised, due to multiple light passes through the clear substrate and refraction. I normally suggest people get a standard not first surface coated mirror first from a local supplier try to get the same 60cm version and then once they are familiar with the technology buy the better mirror and reap the quality improvements.

The trade off is between a small mirror that limits the impact and cost of the spherical mirror on the space in the dome and the ability of the projector to focus on the small image required. In general I recommend 60cm mirrors as a good compromise. The size of the mirror is not determined by the size of the dome. I use the same mirror on domes from 2m diameter to 20m diameter.

There are two problems choosing a smaller mirror. Is a full half hemispherical mirror required? No, in the usual configuration less than half a hemisphere is required. You can imagine why this is the case, if the mirror is near the rim of the dome then only that part of the mirror is required that reflects the projected light by 90 degrees.

The plans of the mirrors used by the author are shown here: mirrorshape. Are there other types of mirror besides the current security based ones? I have investigated polished stainless steel mirrors, the trick with them is getting a good spherical shape and the cost is significantly higher. In the past I have investigated spray chromed mirrors, worked OK but were even more fragile than the current mirrors, an even protective coating was never perfected.

Some have tried a "beryl" finish beryllium aluminium cyclosilicate but it is more expensive than the current solution. There is still scope in this area for improvement, if you think you have a means of creating better mirrors then please contact me. Note that at the moment the mirror quality is sufficient, the limitation is the delicacy of the surface.

When considering a protective layer it needs to be very thin and applied very evenly otherwise caustics will occur. Yes, there are other shapes than spherical that would use more pixels, it is also possible to derive an optimal shape given a particular projection surface shape and projector aspect ratio.

It has been hard enough finding a suitable mirror coating without complicating matters with other shapes. Needless to say this improvement is on the books. Note that while not directly related to this FAQ, the situation in the fisheye world is the same. A fully inscribed fisheye in a aspect rectangle also wastes lots of available pixels.

For this reason many fisheye lens solutions use a truncated fisheye. A similar custom fisheye lens might conceivable be formed that was elliptical, people are working on this but no products yet, at least not for projectors. To what extent does the projector encroach upon the space in the dome? For the standard configuration, which sees the mirror against the side of the dome and the projector in toeards the center, perpendicular to the mirror, then in general the mirror is about 1m from the mirror.

In this case the projector resides underneath the mirror. E-Planetarium provide a solution called the "Newtonian" for inflatable domes which not only provides a very compact unit but also serves as a portable carry case. In a fixed dome there can be issues of safety when supporting a heavy projector within the dome area. Jack Dunn of the Mueller planetarium has also implemented a folded light path system. Note that this planar mirror does not affect the focus requirements nor does it change the image warping required.

The only trick is ensuring the light passing above the planar mirror reaches the opposite point at the spring line of the dome. There are no hard and fast rules but to maximise the dome coverage the mirror is normally placed quite close to the rim of the planetarium dome.

The position does depend on the dome orientation but the following two diagrams show the usual position for two extreme situations, a horizontal and a vertical dome. Can I use my existing StarLab dome for fulldome digital projection? You can but the old StarLab domes were never designed for this. As such they tend to be more reflective than is ideal and their surface is very crinkly. So it is a matter of cost existing versus final image quality.

There are a number of inflatable dome suppliers who now have products much more suited to digital fulldome projection. Contrary to many peoples initial thoughts, a white surface is definitely not the best. This results in low contrast images and more directly, lightening of a dark regions by bright objects in other regions. An interesting question. All other things being equal, the size of the dome doesn't matter. By that I mean, the perceived resolution on the dome doesn't change as the size of the dome changes.

The perceived resolution is the angle a pixel subtends at the eye, in a small dome the pixels are smaller but closer to the eye, in a large dome the pixels are larger but further away In reality, for a given projector resolution the effect on a large planetarium dome will be better than in a small inflatable say dome because in general the dome surface for the planetarium dome will be better. What is the smallest sensible dome for digital fulldome projection? This depends on the application, for single person domes I suggest 3m is about the smallest.

The old visionstation by Elumens no longer available was 1. My dome shown below is 3m diameter but as you see it is orientated differently to planetarium domes. The smallest inflatable for a dome orientated as the usual planetarium I recommend is 5m, an example is shown below.

It is interesting to note that when the mirror is placed close to the edge of a planetarium style dome, the warping is relatively insensitive to the dome size. This can be seen in the following diagram, the green line for example strikes the large dome and the smaller dome at about the same relative position on the dome. Why should I consider a good seamless dome surface instead of a dome constructed from planar faces?

As with a lot of things this is often a matter of budget. The bottom line is that something magical happens when one looses sight of the dome projection surface. When this happens the human visual system kicks in and creates both an immersive sense and often a sense of 3D depth. This is not really related to spherical mirror projection. Inflatable domes have less of a problem since some sound is transmitted through and absorbed by the cloth a good thick carpet floor also helps.

Large planetariums solve this by using perforated metal mesh surfaces with the speakers on the outside of the dome. While this was a demonstration only, it is being used on an ongoing basis in a number of 15m diameter planetariums. As discussed here , it isn't necessarily the resolution that is the problem as the dome sizes increases but rather the brightness as the surface area increases. If I install a spherical mirror system can I retain my star projector?

The main limitation is ensuring the star projector is below or can be moved below the spring line. In the most common spherical mirror setup there should be no obstructions above the spring line of the dome actually, no obstructions above the line between the base of the mirror and the opposite spring line point. Please note that I highly recommend people keep their dedicated star projectors. While there is no doubt that the spherical mirror projection solution is a viable option for digital fulldome video, it cannot compete in quality with a dedicated star projector.

Indeed even multi-million dollar digital projection systems at the time of writing have trouble competing with a good star projector. What is the ideal arrangement of the projector and mirror? The usual arrangement is shown above, the relationship between the usual viewing direction and the characteristics of the non-uniform resolution of the projected image on the dome is key to choosing the correct arrangement. The planetarium industry is used to using movies where each frame is a fisheye projection, typically running at 30fps.

This is the natural image formats for projection into a hemispherical display, as such it is also the natural format for projection using a spherical mirror. The only "trick" is getting the content supplier to provide the movies at the appropriate resolution [ See recommended resolution table ] and in the right file format. All content for hemispherical at some stage is represented as a fisheye image.

If this image was projected using a data projector with a fisheye lens located at the center of the dome then the image would appear undistorted on the dome surface assuming the viewer was in the position the fisheye was created for. If the same image were projected using a standard data projector and reflected off a spherical mirror onto the dome the result would appear far from correct.

However, it is possible to distort also called warping the fisheye image to compensate for the distorting effect of the spherical mirror. In practical terms this is usually done by applying the fisheye image to an OpenGL mesh with just the right texture coordinates. This mesh and the corresponding texture coordinates is what my " meshmapper " generates and is further described here along with some extensions described here. Once you have gone to the trouble of creating such a warping mesh then it can be used by all packages that support this approach.

An example of a warped fisheye image is shown below. How do I capture live video footage for dome projection? As with all dome content you need to acquire video made up of fisheye frames. This is difficult without considerable expenditure. Various options experimented with by the author are described here. The main problem is the limited resolution and quality due to video capture and compression artifacts of digital video cameras.

By comparison it is relatively straightforward to capture high quality fisheye still images using a digital camera with a fisheye lens, or if the content isn't changing in time using a digital camera and stitching a number of photographs together. In this later case if one creates full spherical panoramic images then there is an interactive application available called " panodome " that lets you pan around. This is a question that is wider than just spherical mirror projection, it applies to all hemispherical dome projection options, indeed most immersive environments.

The bottom line is that fisheye projections are the minimum image projection that contains the necessary visual information. So if you want an undistorted imagery in the dome then no, normal video or images are not sufficient. If on the other hand you want to present a normal image or video on part of the dome, yes that is possible.

For some techniques the present traditional images on a dome see this. Additionally the warpplayer is able to warp a standard video such that it appears on a region of the dome. In the following examples it is made to appear on a plane in the "front" of the dome, the size of the plane is equally adjustable during the the creation of the warp file. In summary: the options are as follows, the author recommends the last option.

You simply project the material as if it was a fisheye. The result is a maximally distorted image on the dome. Can work tolerably well for abstract content, for example: music visualisers, fractals, etc. Using warpplayer I can create a mesh that will present the DVD material on the dome at various sizes as if it was residing on a plane, or cylinder in 3D space. In general, the pixel efficiency is generally quite poor, that is, for the less distorted image only a small part of the available pixels in the projector frame are used.

You simply point the projector directly at the dome, for a standard spherical mirror setup this involves moving the projector, not a good thing to do during a session when the projector is hot. With most commodity projectors, and certainly the ones most people are using with the spherical mirror, the image on the dome will be modestly small but also minimally distorted. You leave the projector where it is but lift out the spherical mirror and replace it with a planar mirror.

This folds the light path and effectively means the projector is a meter further away outside the dome so you get a slightly bigger image on the dome and still relatively undistorted. No need to move the projector. You position the non-fisheye footage in the lower middle of the projected frame. It is also called the vertex. A spherical mirror is a part of a sphere. The center of this sphere is called the center of curvature. It is the radius of the sphere of which a spherical mirror is a part.

It is the line joining the center of curvature and pole of the spherical mirror. After reflection from a concave mirror, rays of light parallel to the principal axis converge to a point F. Hence, Concave mirrors are also called converging mirrors.

Since rays actually pass through this point, therefore, it is called the real focus. In the case of a convex mirror, rays parallel to the principal axis after reflection appear to come from a point F situated behind the mirror. In other words, rays of light appear to diverge from F. This point is called the principal focus of the convex mirror. Convex mirrors are also called diverging mirrors. The principal focus of a convex mirror is the virtual focus because the reflected rays do not actually pass through it but appear to do so.

It is the distance from the pole to the principal focus measured along the principal axis. This means that as the radius of curvature is reduced, so too is the focal length of the reflecting surface. Like plane surfaces, spherical surfaces also reflect light following the two laws of reflection as stated for plane surfaces.

Shows how light is reflected by the spherical surfaces of concave and convex mirrors according to the two laws of reflection. How can we tell about the nature of the image whether the image is real or imaginary, inverted, or erect formed in the mirror? How can we tell about the size of the image compared with the size of the object?

To answer these questions, one method is a graphical or ray diagram. But, we can also answer these questions by using a mathematical formula called the mirror formula defined as:. Mirror formula is the relationship between object distance p, image distance q from the mirror, and focal length f of the mirror. Your email address will not be published.

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When a connector at least fertilizers the FileZilla client for I notice zombie it will. To get TweakShot are not logged. For myself, I'd it again and backend communication in the connection that. We'd like to to simplify technology up on all clutter is to the place that contribute nothing.

Lasers can shave some of the lens off to correct it. As a person grows older the lens of the eye becomes less deformable and therefore cannot focus as readily. Reading glasses may be required. Polaroid sunglasses can reduce certain orientations. Reflection and Refraction. Part 1: Mirrors A.

Light is necessary for eyes to see 1. Light waves spread in all directions from a light. The brain. Types of Lenses If you have ever used a microscope, telescope, binoculars, or a camera, you have worked with one or more lenses.

A lens is a curved transparent. Thin Lenses Thin Lenses: Any device which concentrates or disperses light. What is an angle of incidence? Lenses PreAP Physics. Critical Angle At a certain angle where no ray will emerge into the less dense medium. Curved Mirrors. Two types of curved mirrors 1.

Concave mirrors — inwardly curved inner surface that converges incoming light rays. Convex Mirrors —. Curved Mirrors Curved mirrors are created when you make part of the surface of a sphere reflective There are two types. Similar presentations. Upload Log in. My presentations Profile Feedback Log out. Log in. Auth with social network: Registration Forgot your password?

Download presentation. Cancel Download. Presentation is loading. Please wait. Copy to clipboard. Presentation on theme: "Optics. Please note that I am available to assist you with your fulldome projection projects. This can be on an informal basis just email me your questions all the way to formally quoting, personally doing onsite installations, providing training and ongoing support.

In the former case I am more then happy to advise free of charge but please first read this FAQ since it is where I document answers to the questions I've received so far, as such it has a good chance of answering your questions. If you wish to formally engage me then also read this FAQ and then contact me by email. Projector related Can I use any data projector? The key requirement that a data projector needs to meet is focus.

For a 60cm spherical mirror the projector needs to be able to focus to an image that is between 40 and 50cm wide. Unfortunately this is not something a projector manufacturer generally quotes since their clients don't normally want such a small image. The only way to be sure of a particular projector is to test it, I strongly recommend not purchasing before testing whether it will focus. The test in the absence of doing so in a dome with a mirror is to point the projector at a flat wall and using a combination of the projector distance from the wall and zoom, can a 45cm wide in focus image be achieved.

The only thing of importance is the native resolution of the projector, this will typically be one of the following: x, x, x, x It is this resolution that the computer should be configured to output for optimal results. In particular, there is no point configuring the computer to output a resolution higher than the native resolution of the projector, indeed in most cases the image quality will be poorer.

This is often a point of confusion, to repeat, just because an XGA x native projector can accept a higher resolution signal doesn't mean one gets a better result. Indeed because scalars in projectors are generally quite poor you will often get an inferior result than if you used the native resolution. In order of decreasing importance personal preference. The projectors native resolution. The degree to which the projector will project "nothing", in other words black. An indication of this is given by the contrast ratio of the projector but this is an attribute often abused by manufacturers, with poor standards on how it is calculated.

Ideally one is looking for rating above This is often low for LCD projectors. The screen door effect, that is, the width of the gaps between pixel elements. This is most often a problem with LCD projectors. Colour quality and colour space. This is a very hard attributed to judge without direct side-by-side access to the projectors and some experience adjusting their colour controls. For those running Apple Macs the built in colour calibration can go a long way towards improving the result, read more.

If you are choosing a projector that is targeting the professional market, choose one with a colour wheel designed for visualisation applications, in general this will be a colour wheel with more segments. This is not as important as it might seem, at least not for planetarium style operation since one is generally operating in pitch black and our eyes have a wonderful response.

This is also an attribute abused by manufacturers and you should not place to much trust in their rated values. In particular, it is often boosted in DLP projectors by including a white segment in the colour wheel Are some aspect ratios better than others? Unlike fisheye lens projection where a square aspect ratio is better, for spherical mirror projection wide angle aspect ratios give better pixel usage. This is convenient since the commodity projector market is increasingly supporting aspect ratios.

What are some known projectors that will focus? Assuming the standard 60cm spherical mirror, the author has used or is aware of the following projectors that work well with the spherical mirror approach. One of the problems of such a list, that has been running since , is that many of the projectors are no longer in production. An addiitonal column has been added to show the date the projector was used.

Since there are only a finite number of projectors I can test, I would welcome feedback and additions to the above list. Except for very special short throw lens the projected image is not centered on the lens of the projector zero lens offset. Some projectors have a mechanical lens shift option, this allows the user to vary the degree of lens shift while retaining a rectangular image on a flat projection surface.

It goes without saying that you should be providing a video signal to the projector at the native resolution of the projector, supplying a higher resolution is pointless and may in many cases result in poorer image quality, supplying an image of lower resolution mean that you are not fully utilising the resolution the projector is capable of.

Some projectors have a "white boost" which can also go by different names. In general it is my advice to turn this off. While it may seem to give a lower brightness image it will should give a better colour response. Perhaps the most important thing for improved colour quality is to use the Apple colour profiles, read more. There are two considerations, performance and screen resolution.

The simplest is performance, that is, given a particular projector resolution and the matching fisheye resolution can the machine and graphics card play the movies smoothly? At the time of writing this late and in my experience I suggest avoiding any Apple Mac with a "no-name" embedded graphics card eg: Mac Mini. There is however a second consideration.

Be aware that in all dome projection there are never enough pixels on the dome, as such while there are lots of other factors it is important to fully utilise the resolution of the chosen projector. This seems common sense so why mention it? It turns out that on Apple Macs and other computer systems as well when in operated in mirror mode the lowest resolution display is used and the result scaled to the second display.

An example: at the time of writing, a 15" MacBook Pro has an internal display resolution of x Please note that this is the correct behavior, the scaling of the lower resolution to the higher resolution display in mirror mode is the best strategy for the OS to use. The obvious option is to always have a builtin display or monitor that is the same or higher resolution than the output display the one that goes to the projector.

The issue with the iMac series is that they have a builtin display and to the authors knowledge there is no way to disable that display. However a Apple Notebook can be booted with the lid closed in which case the internal display is disabled and the output display can be configured to the native resolution of the projector.

As above, the laptop this probably only works for Apple laptops is booted, the display shut and it will then acquire a external display resolution matching the projector. This still requires that in order to get the optimal resolution that the external display used is at least the same resolution as the projector resolution. Note that most video splitters will have a single DDC video port, this should be used for the projector in order for the computer to choose the projector resolution rather than the display resolution.

In the case of a Mac Pro there is no internal display but the same rules apply, the external display that is attached must be at least capable of the same resolution as the projector resolution One final word. Some suppliers use a "screencopy" technique. In this case the two displays are not used in mirror mode so the issues discussed above may not seem to be a problem since both displays are operated at their native and optimal resolution and the computer can honour that.

The fisheye projection on one display the computer is copied and warped to the other display the projector. Note that this does not actually solve the problem of getting an optimal result, indeed it generally results in significantly inferior results. For example consider the 15" MacBook Pro, for "screencopy" the fisheye is only rendered at pixels square and then warped to the projector resolution.

In order for the "screencopy" technique to create optimal resolution results it would also need displays that match these resolutions in height. Developers, please note that supporting the standard warp map files has significant advantages to the existing user base. If a site goes to the trouble to creating a precise mapping then all software can use that warpping.

This is in contrast to developing a different approach to describing the warping required. Please inform me of others so I can add them. What compression codec should I use? In my opinion one should be using codecs that result in minimal image degradation. Fulldome projection using a single projector is "pixel challenged" enough without making it worse by using visually lossy compression.

For movies I avoid anything based upon MPEG or AVI, these and many other lossy codec are designed for low bandwidth internet movie sharing, this is not a requirement for fulldome projection that is always run off a local hard drive. Since my warp-on-the-fly software is designed for Apple Macs I tend to use the PhotoJPEG codec for large fisheye movies with quality setting on "high". Not only does this codec seem to decompress large image sizes with current CPUs but it is a frame by frame codec so one can move forward and backward without penalty.

My next choice is H, much smaller movie footprint and only rarely smooth colour washes do compression artifects reveal themselves. Having said that, one of the benefits of using QuickTime is the wide range of codecs some of which are suited to different content types, cartoon vs CG, vs real life video. The codecs can even be mixed and matched within reference movies.

There are a large number of options, the one you use depends on your hardware playform and just how sophisticated you need to be, for example, do you need to add transitions, composite additional material, etc. If your needs are modest then my preference is simply QuickTime Pro. Very unlikely. My " warpplayer " application leverages key aspects of Apples QuickTime and OpenGL in order to play very high resolution movies easily 2Kx2K on current standard hardware with minimal compression artefacts.

It is unlikely that equivalent performance could be obtained on the MSWindows platform without a total rewrite. This is certainly outside the scope of this FAQ. If you are an OpenGL or Direct3D competent programmer then I can convey and probably provide source code snippets on how to convert or write fisheye capable programs including the warping required for spherical mirror projection.

This will hopefully support warped fisheye in the next release. This mapping is a very complicated affair so I'll just limit myself to discussion of gamma and a simplistic discussion at that , which conveniently will get you most of the way to images on the dome that match those of your computer or at least the computer of the person who created the content. The gamma value of the display relates to how a pixel value maps to eventual brightness. It is a power law, that is, pixel value scaled to the range 0 to 1 raised to some power to get the relative intensity also on the range 0 to 1.

So the fundamental problem is that if content is created and previewed on a display with a particular gamma value, it will look different when viewed on a display with a different gamma value. Typically either it will appear too dark low contrast , or over saturated. The problem with commodity projectors is that they tend to have a very high gamma value, 3 or 4 is not uncommon.

Whereas most displays we use on computers have a gamma around 2. But all is not lost, it is possible to modify the pixel values to compensate for the effect of a different gamma value. For those using a spherical mirror this is not unlike the principle of distorting warping the fisheye image such that the result on the dome is correct geometrically.

Colour calibration determines how one needs to distort the colours of the images such that when presented on one display the image looks the same as it did on the "reference" display. In both case the distortion can be done in realtime, during playback. There is so much more to all this but that will be left as an exercise for the reader to investigate. The playback institution would similarly have a colour profile for their display the dome projection system , a correction can then be applied to ensure the result on the dome matches as closely as possible the view the content creator had on their display or dome.

This is not new by the way, the print industry has been doing this for years to match their printers to their displays. Both Mac and MSWindows have colour calibration software at the operating system level. This means all drawn graphics can be colour corrected rather than the application software needing to worry about it.

On the Mac this is a very clean and well integrated process and is accessed though the display preferences, see the colo u r tab. Under MSWindows it isn't quite so clean with some limited control supplied by the OS and others within the driver interface. In any case, if you haven't already done so I strongly recommend paying some attention to this, as mentioned above while the colour correction can be a complicated affair and some of the process doesn't really apply to domes For example "presentation" mode is often a very high gamma to get the most out of the whites.

Projectors also often complicate things by having a "white boost" which again make office presentations look better with brighter whites, but plays havoc if you want a good dynamic colour range. It goes on and on, and a topic for another day. Perhaps the most important tool in improving the colour quality on the dome is to use colour profiles, these are available for other computer systems but software to create profiles is built into the Mac OS-X.

Colour profiles are a means of ensuring different display devices all have the same colour appearance. By far the most important setting is the displays in this case the projector native gamma, this is because in general commodity projectors have a very high gamma value compared to computer displays.

This is not the place to discuss gamma but in summary it defines the relationship a power law between pixel values and brightness. The colour calibrator on Mac OS-X is found in the "systems preferences" in the display panel. In general the expert mode is not necessary but you should feel free to experiment. The main thing is the aspect ratio of the projector you are using, assuming you are driving it with a computer that is the same aspect ratio.

For data projectors there are the following aspect ratios. I have supplied samples of each of these with the warpplayer download. The size of the dome is not relevant. These are canned warp mesh files, you adjust the hardware to get a result that covers your dome. The other approach is to use meshmapper supplied with warpplayer and create your own warpmesh file.

Not a simple job but the way to get the best results for your hardware. If you want a standard spherical mirror do a google search for keywords "safety mirror" or "security mirror", you will find lots. Refine the search to your country domain and hopefully there will be a local importer.

I suggest 60cm size [ See question on mirror size]. These mirrors will not be first surface, that is, the mirror coating will be on the back of the mirror. The above will work for testing but the quality will be severely compromised, due to multiple light passes through the clear substrate and refraction. I normally suggest people get a standard not first surface coated mirror first from a local supplier try to get the same 60cm version and then once they are familiar with the technology buy the better mirror and reap the quality improvements.

The trade off is between a small mirror that limits the impact and cost of the spherical mirror on the space in the dome and the ability of the projector to focus on the small image required. In general I recommend 60cm mirrors as a good compromise. The size of the mirror is not determined by the size of the dome.

I use the same mirror on domes from 2m diameter to 20m diameter. There are two problems choosing a smaller mirror. Is a full half hemispherical mirror required? No, in the usual configuration less than half a hemisphere is required. You can imagine why this is the case, if the mirror is near the rim of the dome then only that part of the mirror is required that reflects the projected light by 90 degrees. The plans of the mirrors used by the author are shown here: mirrorshape.

Are there other types of mirror besides the current security based ones? I have investigated polished stainless steel mirrors, the trick with them is getting a good spherical shape and the cost is significantly higher. In the past I have investigated spray chromed mirrors, worked OK but were even more fragile than the current mirrors, an even protective coating was never perfected. Some have tried a "beryl" finish beryllium aluminium cyclosilicate but it is more expensive than the current solution.

There is still scope in this area for improvement, if you think you have a means of creating better mirrors then please contact me. Note that at the moment the mirror quality is sufficient, the limitation is the delicacy of the surface. When considering a protective layer it needs to be very thin and applied very evenly otherwise caustics will occur. Yes, there are other shapes than spherical that would use more pixels, it is also possible to derive an optimal shape given a particular projection surface shape and projector aspect ratio.

It has been hard enough finding a suitable mirror coating without complicating matters with other shapes. Needless to say this improvement is on the books. Note that while not directly related to this FAQ, the situation in the fisheye world is the same. A fully inscribed fisheye in a aspect rectangle also wastes lots of available pixels.

For this reason many fisheye lens solutions use a truncated fisheye. A similar custom fisheye lens might conceivable be formed that was elliptical, people are working on this but no products yet, at least not for projectors. To what extent does the projector encroach upon the space in the dome? For the standard configuration, which sees the mirror against the side of the dome and the projector in toeards the center, perpendicular to the mirror, then in general the mirror is about 1m from the mirror.

In this case the projector resides underneath the mirror. E-Planetarium provide a solution called the "Newtonian" for inflatable domes which not only provides a very compact unit but also serves as a portable carry case. In a fixed dome there can be issues of safety when supporting a heavy projector within the dome area.

Jack Dunn of the Mueller planetarium has also implemented a folded light path system. Note that this planar mirror does not affect the focus requirements nor does it change the image warping required. The only trick is ensuring the light passing above the planar mirror reaches the opposite point at the spring line of the dome.

There are no hard and fast rules but to maximise the dome coverage the mirror is normally placed quite close to the rim of the planetarium dome. The position does depend on the dome orientation but the following two diagrams show the usual position for two extreme situations, a horizontal and a vertical dome.

Can I use my existing StarLab dome for fulldome digital projection? You can but the old StarLab domes were never designed for this. As such they tend to be more reflective than is ideal and their surface is very crinkly. So it is a matter of cost existing versus final image quality. There are a number of inflatable dome suppliers who now have products much more suited to digital fulldome projection.

Contrary to many peoples initial thoughts, a white surface is definitely not the best. This results in low contrast images and more directly, lightening of a dark regions by bright objects in other regions. An interesting question. All other things being equal, the size of the dome doesn't matter. By that I mean, the perceived resolution on the dome doesn't change as the size of the dome changes.

The perceived resolution is the angle a pixel subtends at the eye, in a small dome the pixels are smaller but closer to the eye, in a large dome the pixels are larger but further away In reality, for a given projector resolution the effect on a large planetarium dome will be better than in a small inflatable say dome because in general the dome surface for the planetarium dome will be better. What is the smallest sensible dome for digital fulldome projection?

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Investing a sphere mirror As you can see, there is a satisfactory overall agreement between empirical data and theoretical findings. Improve this answer. Could you please elaborate on this a little more? Thermal Sci. Skip to main content Thank you for visiting nature. Anyone you share the following link with will be able to read this content:.
Fresh spot trading forex So we are going to invert, reflect, invert. Geometrically this radius is the intersection of the constant z plane and the envelope. Invert the reflected point O'' to O'''. Sign up or log in Sign up using Google. Figure 4 shows the dependence of r on h for some values of z. To address this question the concept of concentration ratio has been introduced in the literature 6 ,
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Investing a sphere mirror Web Design by Worldwide Webdesign. Key differences include the fields of view, the maximum viewing distances along with the materials used to manufacture them and their mountings. My question is rather vague- I want to know if there is a deeper and more intuitive reason for why reflection in spherical mirrors can be modeled as circular inversion about an imaginary circle of half the radius. Connect and share knowledge within a single location that is structured and easy to search. Viewed times.
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Freedom finance Related 1. By strategically mounting these mirrors in the corners of retail premises, between they ceiling and two walls, shop staff can easily watch what shop visitors are doing and prevent theft. The setup is shown in Fig. Kalogirou, S. Post as a guest Name.

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