I am a student currently learning houdini by myself.
Is there anyway that I can smooth the value of “fresnel 's reflected Light” in the vex builder? (like smoothstep) I tried to plug the “smooth” vop in to it but I did not quite get it working. Should I try to use a “ramp” to control it?

Also, Does mantra support raytraced shadow?

thank you for your attention!

Hi Bruce, not sure exactly what you need the falloff for but you could try the Edge Falloff VOP.



And the regular shadows in Houdini are raytraced (for example when you pick fastShadow in your light). You'll notice if you disable raytracing in mantra, they will no longer work. Small tip, if you increase the Shading Quality on the surface that you're casting shadows on, they will appear sharper and not so ragged.

DaJuice
thank you for your reply! This is exactly what I want but the Edge Falloff VOP only work for Vex Surface shaders. I am also interested to know how I can achieve this in Rman surface shader. Because edge fall off is not available in RSLsurface shader.

How would you do it in RSL surface shader with Vex Builder?

brucelay
How would you do it in RSL surface shader with Vex Builder?

The EdgeFalloff VOP is a subnet – if you go inside it (select and press Enter), you'll see it's really just a network of VOPs, all of which are available in the RMan context. So you can either copy/paste the VOPs over to your RMan shader, or open up its “Operator Type Properties” dialog, select the “Basic” tab, change the “Save To Library” field to something local, append the string “rsl_*” (without quotes) to the end of the “VopNet Mask” field, and hit “Accept”. Now this VOP should be available in the RMan context.

Last but not least, EdgeFalloff is similar but *not* the same as Fresnel, and Fresnel *is* available in the RMan context.

P.S: Since you seem to want to learn PRMan, I thought you might be interested in seeing what the EdgeFalloff VOP *really* looks like in Renderman Shading Language (RSL):

color Cfall = basecolor * pow ( abs ( normalize(N).normalize(I) ), falloff );

If we ignore RIB for a moment, then we could safely say that RSL *is* Renderman. Worth learning even if you choose to use VOPs.

thank you!
I successfully made the “facing Ratio” node in the Vex builder for Rman!
Thank you for giving me the equation!