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Sunny Suppy avatar image
Sunny Suppy asked

For better Arnold - Chapter 2/50: Deep volume scatter

The more thick cloud is, the more different they are. This is the results rendered by Arnold ( with 100 volume bounce ) vs 3Delight. The rendertime of 3Delight is 6 times faster, and it's more realistic, too. I think we both know which image is by which renderer :

c4dtoa-test-1-raydepth-100-for-comparing0048.jpg


3delight-test-1-for-comparing-2.jpg


I try to do some trick ( change color shadow to make it brighter inside ) but the result is still not like 3DL

tfd-fast-cloud-1-arnold-33m.jpg

tfd-fast-cloud-1-3deligkt.jpg


Thank you!

arnoldc4dtoa
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Ciro Cardoso avatar image
Ciro Cardoso answered

Is this the vdb Disney Cloud?

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No, this is cloud I create inside Cinema 4D. I can send you if you want but it's quite heavy, it's about 3GB. But anyway I'm focusing to deep scatter. Arnold step bounce is limitted so in the big / thick cloud, they are still very dark . Otherwise 3Delight can shine the light through all of volume no matte how it's thick. That's cool. And Hyperion do it with AI.

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Sunny Suppy avatar image
Sunny Suppy answered

No, this is cloud I create inside Cinema 4D. I can send you if you want but it's quite heavy, it's about 3GB. But anyway I'm focusing to deep scatter. Arnold step bounce is limitted so in the big / thick cloud, they are still very dark . Otherwise 3Delight can shine the light through all of volume no matte how it's thick. That's cool. And Hyperion do it with AI.

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Thiago Ize avatar image
Thiago Ize answered

Assuming you also increased the total depth to 100 in addition to the volume depth, then another suggestion would be to try reducing the volume's step_size, though it will make the render slower. It's also possible that adjusting your shader settings in other ways could produce more of the look you want (hard to say without knowing what you used). Take a look at https://docs.arnoldrenderer.com/display/A5ARNTUT/Rendering+a+Cloud where several things are mentioned for ways to brighten up the cloud. https://docs.arnoldrenderer.com/display/A5AFCUG/Standard+Volume will explain in more detail all the parameters you can use.

But I'm guessing this could simply be due to Arnold's volume phase function not approximating Mie scattering well enough (Mie scattering has a big forward scattering lobe and a smaller backward lobe). This is something we are aware of and do want to improve so that clouds can look better with minimal impact on render time. While I haven't tried this, in the meantime, what you might be able to do is use a mix_shader on two volumes to do the forward scattering and backward scattering of the clouds. It will double the render time, but if it allows for you to then lower volume depth and/or use larger step sizes maybe in the end you'll have better looking clouds without that much of a speed hit?

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Heribert Raab avatar image
Heribert Raab answered

3dLight change setpscale automatically which the renders faster, in Arnold you do manually. you can similar speed. you can have almost the some look you tweak in the shader correct. 3dlight make hit-run solution for volume rendering they break into houdini market. still 3dlight volume render is strong !

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