BiDir Advanced Settings

[forgeflow]

I'm trying to do a test render where there is a light source inside of a glass container. If I render the scene with Pathtracing mode, or MLT, I can get the glass to clear, eventually. MLT clears better than Pathtracing. Shadowed areas of the scene, however, remain somewhat grainy, even after rendering to 10,000 samples per pixel.

If I use BiDir with either rendering method, the glass container the light is in ends up with a number of ugly spotty artifacts that never clear, no matter how long I leave the rendering to cook. Almost like the glass has a number of tiny imperfections or bubbles in it, distorting what can be seen through it.

My question is, are there some "better" settings to use than the defaults in the "Advanced Settings"? I tried smaller (0.001) and larger (0.1) settings for Max Change, each of which had a dramatic effect on the quality of the render but really didn't solve the problem. (The smaller value made the render look like a kind of sketchy Van Gogh, the higher value make the glass look like a Serrault - all dots.) I'm doing a test right now with the Max Num. Consecutive Rejections set to 500 (from the default of 1000). But basically I'm muddling around in the dark. The MLT render without BiDir produced the cleanest results (aside from the shadows) but took a fairly long time.

Is this a limitation of BiDir, or a flaw in the algorithm?

I'll post some demonstration renders once this latest test finishes rendering some time tomorrow. But I thought maybe someone would have some advice on other setting adjustments to try. The scale of the test scene is small - the objects are in the 10cm to 15cm range in size (a drinking glass, a glass container with a cylindrical light, and a solid sphere).

[Zom-B]

Maybe this quite old thread can help explaining some of the advanced settings: http://www.indigorenderer.com/forum/vie ... 4803#34803

Anyway.... some images could help us to see your problem better, also providing a example scene could be a good starting point for other users to play around and find a solution

[forgeflow]

Here are some images to illustrate what I'm talking about. All of these images were rendered for roughly 18 hours or so each:

result with pathtracing

illumination_pathtracing.jpg (98.95 KiB) Viewed 3432 times

In this one, the glass looks clear, but overall the image is grainy. I put this result down to the limitations of pathtracing alone. The light object in this image looks white because I was playing with the options in the tonemapping section.

result with mlt

illumination_mlt.jpg (75.46 KiB) Viewed 3434 times

In this one, the glass is very clear, but the shadows are grainy. Might improve with much longer rendering time allowed.

result with mlt / bidir

illumination_mlt_bdir.jpg (75.99 KiB) Viewed 3435 times

Here, I activated the BiDir option. The overall image is clear (enough, probably could use more rendering time). But the glass is quite noisy and distorted looking, and never clears no matter how long I leave the render. The only difference in setup between this one and MLT alone is the addition of the BiDir option.

[forgeflow]

Maybe third try is the charm? This post keeps going missing in the forums here...

Here is the C4D file (Its in 11.5 format).

[Zom-B]

Maybe third try is the charm? This post keeps going missing in the forums here...

New server.... backup missed all new posts from yesterday -.-