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Volumetric Clouds Shading/Lighting

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Phunt
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Hello fellow HouHous.

I've started playing around with volumetric clouds in Houdini so I can finally realize my dream of flying like a bird. Yes, I know this is pretty exciting. The problem I'm having is getting controllable definition on the dark side of the clouds. I've tried adding more lights, tweaking shaders (density) to fill in the dark side with some detail but had little success.

I'm using the isooffset and volumeramp nodes with the v_volumecloud shader. Being lit with a spot light using depth map shadows.

What am I missing here? Thanks,

Phunt

Attachments:
cloud.jpg (23.0 KB)
publish.mov (4.3 MB)

Peter “Phunt” Hunt
bumbling Houdini newbie
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jason_iversen
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You're missing the “multiple scattering” component of cloud lighting - which is the sunlight being diffused throughout the volume. This can be pretty hard to achieve “the right way”, but you can try take a look at the Bake Volume SOP for a way to get this multiple scattering effect create you a “light-field” for adding into your render – but this that's pretty tricky SOP to handle sometimes.

You can try embed (non-shadowing) lights inside your cloud too, and you can get very good mileage from this approach.

Good luck,
Jason

Attachments:
bakevolume_example.hip.gz (42.5 KB)

Jason Iversen, Technology Supervisor & FX Pipeline/R+D Lead @ Weta FX
also, http://www.odforce.net [www.odforce.net]
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mrbag
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Have you considered an env light with a HDRI containing a bright sun and nice sky. I have had some success lighting volumes with that?

You can control the direction of the sun by rotating the world via the env light. And the extra fill lighting can be somewhat controlled by manipulating the HDRI sky color.
Nathan Ortiz
CG Supervisor, Framestore Melbourne
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Phunt
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mrbag
Have you considered an env light with a HDRI containing a bright sun and nice sky. I have had some success lighting volumes with that?

I thought about at env light, but assumed that would be render suicide! However, render suicide can lead to interesting results so I'll give 'er a whirl!

Thanks for the suggestion.

Phunt
Peter “Phunt” Hunt
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Phunt
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jason_iversen
You're missing the “multiple scattering” component of cloud lighting - which is the sunlight being diffused throughout the volume. This can be pretty hard to achieve “the right way”, but you can try take a look at the Bake Volume SOP for a way to get this multiple scattering effect create you a “light-field” for adding into your render – but this that's pretty tricky SOP to handle sometimes.

Hi Jason,

Yes, right you are! Left the question vague to see what people would say, but there's no “SSS” like effect going through the clouds and it needs it. Thanks for the hip file, very helpful… And tricky as you said. Going to play with it more today as I was not able to get a look anywhere near what I liked.

In other cloud news, I was able to get a better render with my existing set up. As per my sig, I made a newbie mistake. I had a fill light casting shadows, but those shadows were being blocked by the sphere of blue sky. I had excluded all lights from my sky sphere, but forgot about the other end excluding the sky sphere from the light Shadow Mask. Anyway, attached a better, but not good enough render.

Cheers,

Phunt

Attachments:
publish.mov (4.3 MB)
cloud_f0085.jpg (23.0 KB)

Peter “Phunt” Hunt
bumbling Houdini newbie
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