PDA

View Full Version : Stereoscopic

Skinner3D
02-27-2006, 12:07 PM
I need to create a 3D heart for my biology teacher. The sticky part is that it needs to work with the IMAX type theater here at school. Can this be done?

ehallein
02-27-2006, 08:47 PM
Hi,

We use Lightwave to create feature movies in Stereo, and have been doing so for over 5 years. It is easy to setup, you will need two cameras, a left and right eye.

Next you will have to pick an eye separation, this is normally based on your focal distance (the distance at which objects appear on the screen, not in-front or behind).

eg if the distance to the screen in your scene is 20 meters than your separation is 20/30 = 0.667m

so offset the x axis of the cameras by this amount.

In order to render correct stereo you also need to produce a non symmetric camera frustum. To do this you need to over render your image, and then crop one side. There is some math involved to work this over render part out.

this function:

c = ew/2ftan(a/2)

where:
e = eye separation in your units
w = desired render size in pixels
f = focal distance to screen in scene in your units
a = horizontal aperture of your camera in degrees
c = amount to over render and crop in pixels

eg:

e = 0.667 m
w = 1024 px
f = 20 m
a = 45 degrees

c = (0.667 x 1024) / 2 x 20 x tan(45/2)

c = 41 pixels.

add this to you render size

ie 1024 + 41 = 1065

render your left and right images

crop 41 pixels off the left side of the left image, and 41 pixels off the right side of the right image.

http://astronomy.swin.edu.au/~pbourke/raytracing/raystereo/

hope this helps

Evan

Skinner3D
02-28-2006, 08:31 AM
:thumbsup: I think this will help a lot, though at the moment I am only using the demo version. Does this also work with polarized screen stereoscopy?
I plan to buy the full version within the week. Should I get Vue 5 or not?

ehallein
03-02-2006, 11:35 PM
this will work for both passive (polarized) and active stereo as it is your playback system that determines how the two images are displayed.

I have not used vue in stereo, so can not say if it is good or not.

regards
Evan
http://astronomy.swin.edu.au/~ehallein/

LMUSIC
03-05-2006, 08:52 PM
Thanks for the info and link. I always just figured it out by doing a test render and aligning the 'target' spot to the screen. This is much better and quicker.

Skinner3D
03-22-2006, 08:56 AM
:bangwall: :stumped: :confused: etc.
I search the forum for stereoscopic and found the post that mentioned anaglyph rendering setup. I tried it today, but it didn't work. The render didn't look any different than normal. I have to do a full fledged animation, all in stereoscopic, and at the moment the person I am doing this for is frusterated and not sure that Lightwave it what they want me to use. Please help

kruemel_1
03-22-2006, 12:13 PM
http://www.newtek.com/forums/attachment.php?attachmentid=29386&stc=1&d=1143050993
Hm, i tried the eye separation in the camerasettings until the images had about the distance i expected them. Then in the image filter anaglyph stereo:compose.
The first image is one side, the second is the red-cyan image.

LMUSIC
03-22-2006, 02:37 PM
Skinner3D - it sure can be frustrating to get the first good results! I have been playing with the stereo stuff for a while now and I can assure you LW does a great job of creating stereo material.

Everybody's workflow is a little different. Mine (in brief) is:

Build the content
1. Model to scale. Set the eye separation at 60mm (the default). If not modeling to scale set the eye separation so it is equivalent to 60mm in scene units. Example, if the scene is composed where a '1 meter' object is actually scaled to 2 meters in the scene, set the eye separation to 120mm.

2. ALWAYS render the scene to individual full color frames and compose the stereo after rendering. There are many modes of presenting the final work and individual frames give the most flexibility without re-rendering (not to mention it is good for other reasons). Antialiasing and Motion Blur really help the final results.

Package the stereo
3. Build separate full color video files for the left and right eye streams. I use Premiere and the free CamStudio lossless compression for these 'master' streams, but any lossless compression or uncompressed stream will do.

4. Use the fantastic (and free) StereoMovie Maker program http://stereo.jpn.org/eng/ to compose the stereo output. This program supports all the different stereo output modes and has good tools for adjusting the alignment of the stereo depth.

Beyond these "mechanical" aspects, there are a lot of things that affect the believability of the 3D illusion for stereo presentation.

The most significant one is to adjust the stereo alignment so that the closest stereo depth is behind the screen or right at the screen depth. This is particularly important for the edge of the image. The stereo can extend in front of the screen more successfully when it is not at the screen edge since the human eye does not have a real world depth to compare the image against.

The screen depth corresponds to where the red and blue images directly overlap.

[edit: grammar]

LMUSIC
03-22-2006, 02:43 PM
Another important technique to get good stereo imagery is to NOT target the camera to 'Look at' any object in the scene. This will cause significant distortion in the stereo effect. Particularly when the target object is close to the camera.

To have the camera 'look at' an object, create a null object, parent the camera to the null, then set the null to look at the desired object.

LMUSIC
03-22-2006, 04:11 PM
Here are two stills of the same shot. One b&w and one color anaglyph.

I can't seem to upload the animation (avi or zipped).