10-09-2020, 07:13 AM
(This post was last modified: 10-10-2020, 09:51 AM by sciroccorics.)
To understand the visible artefact generated by PovRay on the bottom corner of the horizontal box, I've made a couple of images where the camera is zooming on the corresponding area. I've put the resulting images on the same Google drive folder (link in the OP above).
The results are pretty interesting : PovRay seems to have a heavy heavy bug on the normal interpolation when using quadrangular faces ! Look at the reflected image on the mirror sphere provided by PovRay (left hand side of the picture) and compare it with the same part on the YafaRay image. The reflected box visible on the sphere is totally deformed on the PovRay's sphere, while it is almost straight on the YafaRay's one. To prove that the problem comes from the interpolation on quadrangles, I've applied the "triangulate" operator on the spheres and the boxes. As a result, the reflected box is straightened and even the odd-looking triangular shadow on the box becomes much more natural (see "Cornell_POV+GI+Zoom+Tri.png" in the folder). Strange to find that a software as mature as PovRay contains such a strong bug that has never been discovered...
Even without that bug, I would still find the results obtained by Yafaray much more convincing. For instance, on the zoom image, the green color bleeding that appears on the front face of the vertical box is quite awesome as it corresponds to a double diffuse interreflection : the green wall illuminates the back face of the horizontal box, which in turn illuminates the front face of the vertical box. Very nice ! This complex phenomenon is not visible in the PovRay image...
The results are pretty interesting : PovRay seems to have a heavy heavy bug on the normal interpolation when using quadrangular faces ! Look at the reflected image on the mirror sphere provided by PovRay (left hand side of the picture) and compare it with the same part on the YafaRay image. The reflected box visible on the sphere is totally deformed on the PovRay's sphere, while it is almost straight on the YafaRay's one. To prove that the problem comes from the interpolation on quadrangles, I've applied the "triangulate" operator on the spheres and the boxes. As a result, the reflected box is straightened and even the odd-looking triangular shadow on the box becomes much more natural (see "Cornell_POV+GI+Zoom+Tri.png" in the folder). Strange to find that a software as mature as PovRay contains such a strong bug that has never been discovered...
Even without that bug, I would still find the results obtained by Yafaray much more convincing. For instance, on the zoom image, the green color bleeding that appears on the front face of the vertical box is quite awesome as it corresponds to a double diffuse interreflection : the green wall illuminates the back face of the horizontal box, which in turn illuminates the front face of the vertical box. Very nice ! This complex phenomenon is not visible in the PovRay image...
>>> sciroccorics <<<