Caustics with HDRI!?

[ThirdEye]

Add a light source casting caustics.

[Brent Turbo]

Cinema's renderer treats 'proper' lights and light generated by GI as two totally different things. GI light can't affect things like caustics and plugin shaders (like chanlum and translucent), because to those shaders, it's not technically light.

Don't quote me on this, but I think the only two renderers out there that'll bust out some caustics from an HDRI map are lightwave and Brazil.

[ZeBoxx]

I'll testify that Brazil r/s will do this...

...and so will any other renderer that has a half-decent QMC implementation.

Caustics, in QMC, are just a direct result of the method used.

If Cinema4D doesn't do QMC, or equivalent engine, then it would most likely need special directives to handle it, yes.

Best regards,
Richard Annema

[Per-Anders]

on the other hand, get yourself a copy of ditools from remotion.de.vu, and just use dicloner to clone clights that only emit caustics accross a sphere with your hdrimap on it...(i.e. switch off diffuse and specular),

this should work a treat, will try it tou later, but right now i've got some other work to be getting on with.

[AdamT]

Or use the Lightgen plugin which was written exactly for this purpose (generating Cinema lights from HDRI). *But*, can you imagine the render times with that many caustic-generating lights?! Even if Cinema did see the HDRI as "real" light, you'd need a frightening number of samples to get caustics out of it. Better just to use a caustic-only spot or two.

[MJV]

If you study nature, you will observe that any caustics coming from any light source that is less than about 20% of the strength of the primary (strongest) light source is virtually undetectable by the human eye. So the solution is simple: Place a caustic only emitting light (as described by mdme sadie) at the vector matching the brightest point of the image.

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