Messages

1

[Max] I need help! / Corona VDB Artifacting

« on: 2021-11-06, 15:29:29 »

No matter how hard I try, I can't get Corona to render a VDB of any substantial "thickness" (increasing the scale, for example) without it visibly rendering the voxels. I've tried modifying the step size, the scale, the interpolation type, adjusting the channel mapping...everything I can think of.  Ordinarily I'd chock this up to the limitations of grid-simulations, but the attached image shows V-Ray handling the cloud much better. I'm not sure what manner of witchcraft they're doing but the difference is staggering. Is this just a current VDB implementation limit, or am I doing something wrong? Is there a setting someplace I can tweak in the engine itself?

I would attach the scene but this is a dense VDB (nearly 75 million cells). A single simulation frame can be over 500mb, with the last in the sequence nearly a gigabyte in size. It should be noted that the cloud was simulated with Phoenix FD. Could the simulation engine make a difference? Any help would be appreciated!

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[Max] I need help! / Re: Anemone Material

« on: 2021-10-20, 03:05:36 »

Thank you so much for responding! It means a great deal to me that the Corona team takes the time to interface with its community.

I continued to experiment for many hours after posting. One thing I found in my research is that anemones actually have transparency in addition to subsurface scattering and the only way I found to achieve that was to treat the material like a glass and dial up its refractivity. This greatly increases the rendering time but provided some really gorgeous and accurate effects.

The second thing I had to recognize is that a lot of images of corals and anemones we see are from fish tanks under really bright lights. Trying to mimic these materials without consideration for the lighting was a poor decision on my part and stands in defiance of PBR principles. To remedy this, I found that a 14000 kelvin Corona Sun at 3x intensity does the trick to mimic the lighting conditions of most aquariums.

The material ended up being relatively simple. Gradient map controlling the coloring along the stalk and also piped into the Volume Absorption and Scattering slots. Refractivity at .5 and volumetric scattering distance variable depending on the translucency of the anemone in question. Subsurface scattering at 1, with a variable radius depending on the model's scale. Sheen Layer amount 1, roughness about .5, with a nice powder-blue color.

A lot of these could be tweaked to one's tastes. I hope this helps others looking to create a similar effect.

I've attached some images of my results. There's some noise because I don't have the patience for such long rendering times, but I'm satisfied with the results. :)

3

[Max] I need help! / Re: Render Effects

« on: 2021-10-12, 03:45:34 »

Good ideas! Points me in the right direction. Thank you!

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[Max] I need help! / Anemone Material

« on: 2021-10-12, 03:44:47 »

Anyone have any idea how to create an anemone material with the PBR workflow? What IOR values, sheen, refraction, subsurface scattering, etc? I've been experimenting for hours and I'm running around in circles.

5

[Max] I need help! / Render Effects

« on: 2021-10-11, 04:14:00 »

Ages ago I wrote a Render Effect with MaxScript that replaced any pixel's alpha channel to 0 if it's beneath a certain threshold. To do this, it would go through and analyze the pixels in the frame buffer. Very simple and saved me a ton of post-processing time for some old-school sprite work.

It still works, but Corona uses it's own VFB. How can I get my maxscript to affect the Corona VFB? Is it even possible?