Hi all, I just found that vwright, which looked like the perfect tool to support stereoscopic image pair generation, generates a new view by simply moving the view-point -vp. This does not consider the fact that our eyes (hopefully) are able to focus on an object, not looking parallel into infinity. So my resulting frames do not really match (I tried it and it looked ugly...). Paul Bourke provides a great page explaining the background of such stereo pairs on his website:
http://paulbourke.net/miscellaneous/stereographics/stereorender/ To correct this, I would propose to manipulate the -vs and -vh parameters in the view file generated by vwright. I am not that great in doing reprojections, but from what I understand, this should work. I have made a simple sketch to visually explain what I attempted to do (and probably what I did wrong): web-browsers with svg-support http://static.larsgrobe.de/stereoscopic_vwright.svg pdf of the same sketch http://static.larsgrobe.de/stereoscopic_vwright.pdf Here is my approach: e [scene units]: eye seperation is given as input to vwright, known f [scene units]: distance from either eye point to the image plane can simply be calculated from view direction vector vd_x, vd_y, vd_z: f = sqrt(vd_x^2+vd_y^2+vd_z^2) alpha [degrees]: half horizontal view angle can simply be calculated from view's vh: alpha = vh/2 a [scene units]: alpha projected on the image plane a = f * tan(alpha) 1) Calculate horizontal shift value vs for views: vs [] : shift fraction (eye separation e / projected image width 2*a) can be calculated from above as vs = e / 2*a For the left view, I modify vs as above, for the right view I use its negative value. 2) Correct the horizontal field of view vh for views: The stereoscopic image can be displayed only the overlapping image area for both views. Thus we need to cut the left border from the left and the right border from the right view. beta [degrees]: the angle corresponding to this border (having the same width as the eye separation, but being located in the image plane) calculated as beta = alpha - atan ( (a-e)/f ) This allows calculating the corrected horizontal view angle vh_corr, which will replace the vh in my view files: vh_corr [degrees]: corrected horizontal field of view as vh_corr = vh - beta 3) The full procedure: - take a view, derive left and right views from it by running vwright (+/-) e/2 - calculate vs and vh_corr and replace the corresponding values in both views - render, take on your glasses, and enjoy stereoscopic 3d images.... I hope this is correct, for me it gave results looking much better then those by simply using vwright's view parameters. I think that having this in vwright as an option (either active by default, or, to preserve backwards compatibility, switched by e.g. -s as stereographic) would make rendering of stereo pairs with Radiance much more fun. Any comments? Cheers, Lars. _______________________________________________ Radiance-dev mailing list Radiance-dev@radiance-online.org http://www.radiance-online.org/mailman/listinfo/radiance-dev
