Stereoscopic rendering + camera position + believable extension of the real world?

# 1 12-07-2011 , 03:08 AM

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Stereoscopic rendering + camera position + believable extension of the real world?

Hey gang - I spent 4 hours tonight on the following problem with no luck - hopefully someone out there has figured this out and can shed some light on a solution...

I'm working on a stereoscopic 3d scene of a room that will be projected on a floor-to-ceiling screen. The goal is to make the projected 3d room appear as an extension of the room you're standing in.

The problem is that I can't figure out the right combination of camera position, rotation, etc. The objects in the room have to appear as they would if they were real, which requires the correct camera angle, etc. I don't think this is as hard as trying to match the floor, ceiling, and walls in the real world to the ones in the projected image - I found that nearly impossible tonight - the angles are just never right.

I created a grid on the floor of the real-world room and attempted to match the grid lines to those in Maya but was never able to. The grid lines in Maya diverge too sharply as they extend away from the camera (I used the center cam for this test instead of 3d).

I got to believe this is possible but I just can't find the right combination. Has anyone attempted this before and had luck? Maybe you have an example scene already that you should share? Many thanks in advance!

-Zach

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# 2 12-07-2011 , 07:21 AM

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did you ever change the camera focal length? do you know the focal length?

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# 3 12-07-2011 , 11:38 AM

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Yeah, I adjusted the focal length a bit but kept it locked at 35mm for the most part. From what I understand, a focal length of ~55mm should approximate the human eye - correct?

More tests tonight...

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# 4 12-07-2011 , 12:02 PM

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ehh, but you are matching a photo taken with a camera with a lens. right?

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# 5 12-07-2011 , 12:57 PM

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No, actually I'm creating a scene that will be projected on a floor-to-ceiling screen in stereoscopic 3d with the idea that when you look at it, the projected image is an extension of the room you're standing in. So the camera position, angle, lens characteristics have to match the human eye, correct?

I really thought this would be somewhat easy - just slap a camera in the scene and place it roughly 6' off the ground and viola - but in reality it's not working out. When I use the grid lines as a guide, it looks like they diverge too sharply compared with the grid lines I painted on my floor.

I attached a sketch to illustrate the issue. Thanks for your time!

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# 6 12-07-2011 , 01:57 PM

The Nurb Herd
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you need to match the position and lens of the projector.

is it something like this you want to achieve?
YouTube - ‪The Official Ralph Lauren 4D Experience - London‬&rlm;

this is a 3d projection i worked on. not stereo tho.

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# 7 12-07-2011 , 02:01 PM

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also what kind of stereo projector are you using?

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# 8 12-07-2011 , 02:14 PM

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That's a great video - amazing effect!

I'm not projecting on a building per se, I'm just projecting onto a wall (screen). People will stand roughly 8' away from the wall and it should look like the room on the screen is an extension of the room they're standing in. So if they're in a 12'x12 room, and the imagery is of a 12'x12' room, then the end effect should be as if the people are standing in a 12'x24' with the additional 12' depth coming from the stereoscopic projection.

So in order to pull that off, the lines of the real room have to match the perspective of the projected image. For ex. the line between the walls and the floor have to appear to extend into the projected image at the same rate of perspective - if that's the correct term. Right now the projected lines (grid lines) bend too acutely.

I'm using a short-throw HD projector (Optoma GT720) mounted 9' off the ground at a screen (wall) that's about 12' away. It gives me a nice 9'x16' image. I'm afraid matching the Maya camera to the projector lens is going to be trial and error since this is a short-throw lens with special distortion attributes.

Other than the focal length, what other Maya camera attributes should I adjust in order to control the perspective angle? Sorry if that's not an accurate term - not sure what to call it user added image

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# 9 19-11-2011 , 06:19 PM

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i am not here with the solution. but with a simple question. i don't know anything about 3d projection on wall. Hows it possible? please tell me. and what all one need to achieve this 3d projection effect on wall or building.

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Stereoscopic rendering + camera position + believable extension of the real world?

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