Slow translucency

[medzo]

Hi

I am trying to make a plastic translucent material.

I am following the formula:
Color*Diffuse+Reflection+Translucency<100%

i am satisfied with result but the rendering is just too slow.

Any good ideas how to render material with translucency faster?

[jure]

This renders fine here. Are you sure this is slowing down your render?

Your node setup is not completely correct though because diffuse component could actually become negative with some values.

[medzo]

How would you set up the surface?

I am attaching the scene. It is (wants to be) hi quality ... anyway i render a closeup for like 30 min...

[jure]

Are you trying to make this lamp?

[medzo]

Well a model is just a model... i am trying to make a material...what did you mean that node setup isnt correct, whre did i go wrong?

[Skonk]

I think it's because you are subtracting numbers like 1.0, from numbers like 0.5 which means you are passing negative numbers to some of the material channels.

[medzo]

huh....how to setup a node like that?... wouldn't it be nice if we had a kray sufrace shader where you would just put in textures, set up some values of textures and the shader would calculate what needs to be calculated for a realistic result....

[jure]

I think it's because you are subtracting numbers like 1.0, from numbers like 0.5 which means you are passing negative numbers to some of the material channels.

Yes this is correct. Although in your example it does seem that translucency is taking a long time to render. Maybe it's due to several lights in the scene having effect on translucency.

[jure]

huh....how to setup a node like that?... wouldn't it be nice if we had a kray sufrace shader where you would just put in textures, set up some values of textures and the shader would calculate what needs to be calculated for a realistic result....

Here's a basic node setup that should properly adjust reflection/translucency/diffuse strenght. I've added texture nodes in the mix in case you want to drive your values with textures.

[medzo]

Tnx Jure! I see the difference, but isnt translucency also affected by fresnel like reflection? Acctualy I have nothing to back this up... is there any paper that would explain how shaders work?

[jure]

Tnx Jure! I see the difference, but isnt translucency also affected by fresnel like reflection? Acctualy I have nothing to back this up... is there any paper that would explain how shaders work?

Sure, you could throw fresnel in the mix if u wanted. Translucancy is not "physicaly accurate" shading model though, it's just an approximation of the SSS on thin materials.

[medzo]

Thanks!