Forum Discussion
360x180 CG Renders
I'm facing a problem when rendering any pair of equirectangular images from inside a 3D modelling package (Maya in my case, but no doubt the same issues apply to many different packages). The attached (side-by-side format) image is an example. I'm hoping the good folk on this forum can help.
I render out my panorama (I use the Lat-Lon Mental Ray lens plug-in) and it looks as you'd expect. Looking at it through the excellent VRPlayer, it works well. I then shift my camera to another position approx 6.5 'virtual' cm to the side of the first position and re-render. Again this panorama works fine on its own.
I was hoping that I could just place these x2 renders side-by-side (as they are in the attached example) to make a 3D version of the scene. Not so. What's happening is that the 'forward' view works fine but the depth gets reversed towards the peripheries of the image (which just looks bad) until the 'back' view is completely inverse (and so look pretty much OK again).
Logically I can see that the reason is that the 'Right camera' becomes the 'Left camera' as it renders the part of the view directly behind itself. However, I haven't got a clue how to fix it and output an equirectangular panorama that works in 3D. Help!
I render out my panorama (I use the Lat-Lon Mental Ray lens plug-in) and it looks as you'd expect. Looking at it through the excellent VRPlayer, it works well. I then shift my camera to another position approx 6.5 'virtual' cm to the side of the first position and re-render. Again this panorama works fine on its own.
I was hoping that I could just place these x2 renders side-by-side (as they are in the attached example) to make a 3D version of the scene. Not so. What's happening is that the 'forward' view works fine but the depth gets reversed towards the peripheries of the image (which just looks bad) until the 'back' view is completely inverse (and so look pretty much OK again).
Logically I can see that the reason is that the 'Right camera' becomes the 'Left camera' as it renders the part of the view directly behind itself. However, I haven't got a clue how to fix it and output an equirectangular panorama that works in 3D. Help!
165 Replies
- There are a couple of ways of rendering spherical 3d panoramas ..
see here for example
http://paulbourke.net/papers/vsmm2006/vsmm2006.pdf - Many thanks mediavr - I'll chew through this with interest, I couldn't find anything which discussed CG render + 360 panoramas + stereoscopy. Any other info much appreciated
- When he talks about synthetic stereoscopic panoramas he is talking about CG renders. A recipe to do what you want is this - the article he describes this - with variants
1. Set up a virtual camera rig with two parallel cameras say 3" apart.
2. Configure each camera to render in equirectangular (spherical) mode -- except that you want each camera to render say 1 degree wide, 180 degree high strips -- your renderer will have to support partial equirectangular renders.
3. Have the dual camera setup rotate 360 degrees on a point half way between each camera, rendering from each camera the 1 degree wide strips at each successive 1 degree increment.
4. Now you have 360 L and R 1 degree wide, 180 degree high strips. They make very skinny pairs of stereo images.
5. Join (concatenate) the L strips by assembling them side by side (you can use the Mosaic tool in Stereophoto Maker to do this). ditto the R strips. - Thanks again mediavr. I was on the wrong track initially because I was using the Metal Ray lens shader to give instant (and very nice) *monoscopic* 360 renders. But as the virtual camera doesn't move for this, the same technique couldn't be used for stereoscopic views.
For anyone wishing to do the same, I'm starting to have better luck moving both virtual cameras (in tandem) around a common point, as suggested by mediavr. This is very similar to assembling 'real world' (photographic) equirectangular pans. So far I haven't needed to render the views in really thin strips (which I don't know how to do anyway).
So rendering, say 90 degree views with overlaps and assembling these in PTGui seems to work. My next problem is that I can't get PTGui to any stitch two (L &R) pans in identical ways (even using batch mode - and yes I've been through the online tutorials!) so the 3D illusion doesn't work yet.
Ah well, another day another technical Eiger for me to climb... - You are doing things the hard way. Here is a more detailed recipe.
1. Find a renderer for 3ds Max that will let you render partial equirectangular images. VRay I think can do it.
http://www.pixelsonic.com/2011/04/360%C2%B0-in-3ds-max-with-vray-2/
See where in the settings where it says "Camera type" and it is set to "spherical".
See where it says "Override FOV". Set it to 1 degree here.
Then you can render equirectangular (aka spherical) images from each camera of your rotating pair that are 1 degree wide and 180 degree high.
2. Now you have 360 images from the Left camera say. Then open Stereophoto Maker.
http://stereo.jpn.org/eng/stphmkr/
Go File/Mosaic images
Choose "Connect all files"
3. Do the same thing with the images from the Right camera. - Thanks again - don't suppose you know of any partial equirectangular render plug-in for Maya? I can only find full panorama renderers. I did get stereophotomaker and it looks very promising.
- I installed the demo of Vray for Maya but the (Spherical camera type/1 degree FOV) override doesn't seem to work as you describe. I end up with a very narrow horizontal strip when I connect the renders so perhaps Vray can't unhook the vertical and horizontal proportions to generate the required 'long strip' render sections?
- Well you might have to go back to rectilinear renders -- render each view 1 degree wide, 140 degree high
Load them into PTGui (you might have to use PTGui Pro)
Set the Panorama output to Equirectangular 1 degree by 180 degree.
In the Render section set the output to "Individual layers"
Join them with Stereophoto Maker
Then you will have black nadirs and zeniths but the central zone should be ok
Maybe some of the dome renderers here might be usable somehow
http://thefulldomeblog.com/2013/06/28/fisheye-lens-shader-options/ - Well you might have to go back to rectilinear renders -- render each view 1 degree wide, 140 degree high
Load them into PTGui (you might have to use PTGui Pro)
Set the Lens information to FOV 1 degree, type Rectilinear
Set the Panorama output to Equirectangular 1 degree by 180 degree.
In the Render section set the output to "Individual layers"
Join them with Stereophoto Maker
Then you will have black nadirs and zeniths but the central zone should be ok
Maybe some of the dome renderers here might be usable somehow
http://thefulldomeblog.com/2013/06/28/fisheye-lens-shader-options/ - mediavr! you're full of useful info! It just clicked to me, reading how you setup vray with a spherical camera but keep the fov at 1. This whole time I've been setting my camera to spherical with 360 fov, and then cropped on a strip of the view to render. This always caused me having to figure out the pixel overlap when using that stereo maker.
can't wait to try this method out :lol:
although this is still a very cumbersome approach.. I have renewed interest in using since nothing else is out there. I have been using single spherical renderings along with a depth map in vr player. Which gives you a quasi-acceptable view - but it's still not ideal - and even more difficult when working with GI. If not using a brute force approach you'd need to pre-calc the movement of the cameras to avoid any issues. Although I haven't extensively tested this. And it makes rendering 3d animation almost impossible... although now with your 1 fov trick I might be able to find another way to stitch the batch of slices.
I'll keep prodding vray to update their stereo helper to work with spherical cameras :)
cheers
