Nicolas Heluani

Nicolas Heluani

About Me

Expertise
Not Specified
Location
Not Specified
Website

Connect

Recent Forum Posts

A request for a Masterclass on Mantra Rendering...with focus on refractions. March 30, 2017, 11:52 a.m.

jsmack
There's a trick to reducing refraction noise, but it's super annoying to implement. If you disable refract on all your lights, then the refractive object will no longer directly refract them, and will not split rays sampling lights. However refractions of your environment will no longer appear. To make up for it, you can make emissive objects that are visible to refract only. This is incredibly annoying with cube map textures, but not so bad with a typical lat-long image. Most other renderers I have experimented with won't even allow direct refractions, and require setting up emissive surrogates in this way, notably arnold and redshift are both this way.

Another setting that contributes to the noise greatly is dispersion. I know it's pretty, but it very expensive in terms of sampling requirements for low noise. In your test scene, the values you are using were also extremely high, physically plausible values are between 0.001 and 0.05 depending on the IOR. If you simply like the look, then by all means, go nuts.

Wow! that does sound complex I will give it a try. I am really focusing a lot on refractions because I is the only area in Mantra I have problems, and I am a bit of a hardheaded type that will not give up .
And thanks for the tips on dispersion aswell….

Glass in Houdini v16 March 29, 2017, 4:51 a.m.

tamte
I think you are referring to the blackness behind the glass
the easiest way to solve that is to exclude your glass from shadow casting
or you can play with faux caustics parameters to get some varying amount of shadowing based on light angle
or directly modify shader to alter opacity for shadow rays any way you want
or more expensive way is to actually render with caustics through caustic light
the most expensive would be turning on All Paths on mantra and making sure the diffuse limit is at least 1, but that would be probably too noisy as mantra doesn't do VCM yet

Hahaha, yes. I didn´t realize what the original post was really asking. Definitely Faux Caustic is your friend…is fast and quite good.

My first robo March 29, 2017, 3:51 a.m.

Looks amazing….like a puppy robot.