This is my first post on instructables and I'm excited to share with you, my adventures in building a pretty good quality stereoscopic projection system.
It all really started when I saw James Cameron's Avatar in 3D at the theater, but I originally had my first encounter with 3D when seeing an IMAX 3D film, "Space Station 3D" at a science center, I was amazed by the feeling of immersion and feeling almost as if I was actually there. Avatar was another one of those amazing immersive experiences, I made the mistake of seeing it at night and then going straight to bed after I got home from the theater. When I woke up the next day I felt like I had this crazy dream, while my mind was still fogged as it always is for about the first 10 minutes after I wake up, I thought it was a lucid dream, but then I remembered that it was a movie.
I couldn't stop thinking about this movie at least once a day for the next month, I even heard stories of some people having depression called "the avatar blues" because this movie tricked their subconscious into believing this was a fully real-life place, but they realized that it was not real and they could never go to Pandora. Luckily I didn't feel depression, but I really wanted to be able to have something like this at home, mainly because it's just so frickin' awesome!
So the google searches began and I settled on using 2 DLP projectors with circular polarization filters, I wanted to be able to use the industry standard realD glasses because the theaters let you keep them. A more broad term for my setup is passive-polarized stereoscopic projection. One of the biggest problems with this setup was to keep it cheap because I'm a nearly broke college student. Many people have been led to believe that 3D is "new-fangled" or "very expensive", it's not new, there are stereoscopic photos from the civil war! And we have had movies projected to large audiences using polarized systems since the 1950's! Finally I'm going to prove that it doesn't have to be expensive and the quality of the overall experience rivals that of any super-duper fancy 3D TV at best buy or the home theater store. or any single projector active glasses solution for that matter.
Here is the big reason that pretty much all current 3D TV totally suck: They run a frame rate that does not match the source content in most cases, movies run at 23.976 fps (James Cameron and a few others are pushing for 48 fps and I love them for it, Avatar 2&3 should be 48fps per eye) and your 3D tv runs at 120 hz, so what does this mean? What it means is that the TV really wants 30fps or 60fps content so it can alternate the left and right images sequentially, "LRLRLRLR....." and this gives you 60 fps PER EYE. Now, if you can see a CRT monitor flicker when set at 60HZ (I can) you know that it is awful! Your LCD runs at 60 HZ, so why no flicker you ask? Because it UPDATES the image every 1/60th of a second WITHOUT going dark in between frames. With an active 3D system each eye sees black half the time, what a rip-off! You pay thousands for a 3D tv and it will be black for half of the movie (I must acknowledge that film based projection in the theater has flicker and 1/3rd of your movie is just black, this flicker also bugs me and is why I'm not really into going to a non-digital theater). Alright, back to how we get 23.976hz converted to 60hz and for all intents and purposes lets call it 24hz, we use a dirty secret called 2:3 pullup and this essentially shows some frames for 2 of the 60 frames and for 3 of the 60 frames, 3D display is all about good timing and alignment, 2:3 pull up introduces a lot of judder in the motion and the problem is compounded in 3D different TVs handle it slightly different, but they all share a common problem: the timing of frames is mis-matched between your left and right eyes.
Now before you yell at me saying that most theaters use 1 projector and have alternating frames, listen here. Theaters with alternating systems such as RealD, RealD-XL, Masterimage3D or Dolby 3D don't have these issues because they run at 144Hz which is exactly 6 times 24. They use a triple flash system and what this means is that for one stereo pair (1 frame of left and 1 frame of right) it alternates the left and right eyes 3 times each (6 flashes total) and then moves the next frame, etc... Using this technique, perfectly equal timing is maintained for both eyes and for every frame. TV manufacturers need to figure this out and they are idiots for not implementing the ability to do 144 HZ or better! The least they could do is to kill 2:3 pullup, there are many artifacts of the analog TV and film days and this is one of those and I HATE IT! I will never buy a 3D TV until they figure this crap out.
IMAX uses dual projectors for their systems and I love them for it! A newer system is RealD XLS which takes advantage of the new 4k digital cinema projectors and uses a special over-under lens to essentially "emulate" dual projectors, just think about it, 4k imaging device and dual 2k pictures, lets do over-under! I can tell you that both of these systems rock!
Alright on to the project!
Step 1: 3D Home Theater for Under a Grand - Getting Started
To start off, here are the main things I had to buy:
-3 infocus LP-650 projectors DLP 1024x768, one was used for parts, you need 2 working projectors (must be DLP or other non-polarized projector) ebay.com about $500 total after getting el-cheapo chinese replacement lamps. brightness is key and matching the color and brightness between projectors is key, the polarizers will cut about half of your light, these projectors are rated at 2500 lumens and ended up being perfect for my 85" screen I bet I could go up to 120", but really need more resolution for that. If you don't count the fact that these are 4:3 and treat them like 16:9 projectors you are looking at a native resolution around 576p, it's not terrible and for the most part is the only weak link in the system. If you can, get a projector with LENS SHIFT, I cannot stress this enough, this will save you hours of headache in aligning your images, the LP-650 does not have this feature and it makes hours of extra work to align the images perfectly.
-set of circular polarization filters (NOT AVAILABLE ANY MORE) polarization.com $25
I suggest contacting this company, I have not used them, but their filters would work: http://www.apioptics.com/3d-projection-filters.html
-something to build a mounting rig or chassis out of, in my case, steel. also, materials for a screen (4 2x4's, sheet of masonite and paint). Lowes about $100
-stereoscopic player, free demo limited to 5 minutes of playback at a time 3dtv.at 39 EURO around $60 (I bought it, this is the bet program and when paired with AnyDVD HD it will play 3D blu-rays without having to rip or convert it first) this program plays everything I throw at it and can use directshow codecs to play virtually ANY format.
-FINALLY a computer with a mid to high power quad core CPU or the fastest dual core and 2 matching video outputs on the same graphics card, in my case 2 DVI ports, but VGA will work pretty good as well. My CPU is an AMD phenom II x4 3GHz and GPU is an nVidia 7950 GT. If you have to buy a computer you are going to have to pay over a grand for the project overall, but most of us already have decent computers, I hope.
First, you need a way to mount your projectors and it must be VERY SOLID, any misalignment and I mean ANY, like more than a half an inch at the screen will cause headaches after a very short amount of use.
I'm building my mount out of steel as I have access to a welder and other metal working tools. See photos.
Take into consideration that you need to be able to move at least one projector in any axis and that you need to hold a polarizer filter out in front of the lens. A word of caution, keep your polarizer as far in front of the lens as possible to maximize the surface area that is used, it WILL heat up and melt if you put it too close, trust me.
I cannot stress this enough, that you must maintain perfect image alignment, so take your time in building a good mount that you can easily adjust.
A note on projectors: There are many types of projectors out there, DLP, 3 chip DLP, LCD, 3LCD, SXRD, D-ILA, LCOS, CRT and what ever type you choose, make sure the light output is not polarized (DLP) or you will regret it. You may be able to fashion a depolarizer out of at least 3 layers of quarter-wave retarder film, also from polarization.com, but you many get some slight color shift.
A note on polarization: In my setup I initially used circular polarization like RealD, but switched to linear like IMAX (more on this later). The benefit of circular polarizers is that they are essentialy a linear filter and a quarter-wave retarder laminated together, which means you have a 2 in 1 filter. So you are ready for IMAX or RealD in the same system, all you need to do is flip the filters.
Next, construct your screen, you could also paint directly on a wall if this is going to be more permanent installation. I will detail painting in the next step. You can also buy a silver screen, but a good one is going to cost at least $500!
Step 2: 3D Home Theater for Under a Grand - the Screen
Basically you need a smooth surface to start with.
You need to paint it flat black and all painting must be sprayed on or you will get lines and odd textures, I have not experimented with white, but I may some day or maybe try different mixes of white and black or white and silver.
After the black is dry you need to paint it silver, it is very hard to get a good texture without drips or blotches, you cannot rush this! You will need to do many thin coats to get it to look right. I had to do around 7 coats to get my screen done and it turned out as good as any commercial screen.
To make this paint sprayable I needed to mix it with about 1/3 mineral spirits, I wouldn't want to try "rattle can" variety spray paint, the spray pattern is just not consistent enough, I bought a pneumatic sprayer just for this project.
It is important to have a clean air source, a clean sprayer, clean paint (filter into the sprayer to get rid of any chunks) and no wind.
One thing I would like to try is a curved or parabolic screen design to help widen the optimal viewing angles, silver screens by their very nature have a narrow viewing angle before you start to loose a lot of light.
While I was waiting for the paint to dry I went ahead and started throwing some 2d movies on it out in the shop just for fun.
Step 3: 3D Home Theater for Under a Grand - the Final Setup
You need to connect your projectors to your computer and set them up as side-by-side multi monitors once you are getting an image on both projectors you need to align them, to do this use stereoplayer and an alignment pattern.
Install stereoscopic player and run it. To set it for dual-output, navigate to View>viewing method>Dual Screen Output.
Then select your displays in View>Full Screen Monitor (left view) and View>Full Screen Monitor (right view) for now it doesn't matter if your left and right is mixed up.
Now load up your left and right test patterns. FIle>Open Left and Right FIle... You can open still images in stereoplayer.
Go into full screen. press alt+enter on your keyboard, get your glasses and see if the left and right images are separated from each other and going to the appropriate eyes. If the views are swapped go out of full screen mode and change the setting View>Full Screen Monitor and then try again.
Next, without the glasses you need to make the alignment pattern match up on both projectors as close as possible, now if for some reason you cannot get the images to line up and you must make a sacrifice, do it on horizontal alignment, as some horizontal misalignment will not cause headaches, it will slightly mess up the depth of the image.
Alright once you have the hardware up and running try opening a good 3D still image one can be found here: http://mtbs3d.com/gallery/albums/userpics/10002/Crysis_%230083.jpg this image is reversed for cross-eyed viewing so the left is on the right and vice verse.
If you have a 3D blu-ray disc laying around you can watch it too. you need AnyDVD HD it is a driver that decrypts blu-rays on the fly and is pretty awesome. you will navigate to your BD drive letter and <drive>:\BDMV\STREAM\SSIF\<probably the largest xxxxx.ssif file>
sometimes the ssif files will be split up. You can open these with stereoplayer.