IR map doesn't seem to follow camera

[phildlight]

Vray 2.20.03, Max 2012 x64. I'm rendering an animation with moving objects and camera. I'm doing an IR prepass with "use camera path" checked. When I render the animation render using the precalced IR, the resulting frames on one side of the camera path aren't right. Some objects are rendering black as if the shadows weren't calculated for that area. The camera path is a slight arc from one side of the object to the other. On the left side of the object where the camera starts, I get the black objects and a poor shadow solution for the rest of the object. Then as the camera gets to the right side of the object the solution seems good. It's as if the prepass is ignoring the camera path on the left side. Any help?

[phildlight]

here's 2 shots to show the issue.



The first shows the major problem of blotchy spots across the panel. The second shows how this issue goes away as the camera moves to the opposite end of the panel. The second image shows too that there are some objects (screws in this case) that are rendering black.

When I render still frames across the entire length of the panel, I don't get any of these issues. I assume that it has to do with the IR prepass settings. I'm at a loss.

[phildlight]

One thing I forgot to mention: The section I'm rendering is only a small piece of the camera's path. The sequence is around 4000 frames but I'm only rendering a small 350 frame chunk in the middle. Does the IR calc only look at the range in render settings or the entire path? When I render the prepass, I notice that the previews only show the ending angle. I know that preview isn't an accurate view, but it's odd that the part showing in the preview is the somewhat acceptable range of the animation.

[phildlight]

Ok, apparently, the camera path length/sequence length relative to the render length DOES matter. I saved a copy of the file and deleted the camera path and all animation except for the section I'm working on. Then re-rendered the prepass and frames and it fixed the issue. So the IR calc ignores the animation range in the render settings and uses the entire camera path? Is that right?

[phildlight]

Which brings up the question of what is the proper way to setup the IR prepass on large moving object/camera animations. This explains some artifacts I encountered while rendering other large sequences. What is the proper way to handle such a large sequence with a lot of camera path animation and moving objects? Obviously, this solution: http://www.chaosgroup.com/forums/vbu...380#post391380 isn't applicable in long sequences? Also, what is the proper way to handle rendering small sections of a larger animation?

[svetlozar.draganov]

Use camera path option is not recommended for a large animations. Large animation are considered to be animations with a thousand frames and with a very long camera path - where you want to view every part of your project with a single camera. Using camera path is optimized to work well with small camera paths, for long animations (paths) you have to switch it off.
Camera path option always shoot samples from the entire camera path regardless whether you render a part of animation or the entire animation - so if you want to create a additional samples where you have a blotchy render - you have to turn this off and to calculate additional IM samples in these areas.

Having a blotchy result might be caused by poor IM quality - is it possible to send us your scene and a couple of rendered frames - we would like to see your settings.

[phildlight]

Thanks Svetlozar, I discovered what you say above and was able to get good results without using "use camera path".

Phil