G'morning,

encountered these render artifacts while using dent_fractal. At first i thought the problem lies in my rock geo, not until i unplugged the displacement shader and all of them were gone. Low or high values for the displacement didn't make them go away.

I turned to Micropoly instead of PBR which miraculously gave me a much better result with tiny black spots still haunting me. Really puzzled what's happening here, somebody please. =_=

eitht.

I guess you should increase your shading quality in your object under render/dicing

you need to add Displacement Bound property to your shader or object and tweak it a little

roughsporty - Tried increasing my rock's Shading Quality, the artifacts shuffled around the rock, no signs of decrease. But i came across this Ray Predicing > set it to Full Predicing, and that fixed everything. Didn't understand what exactly that did after reading the help docs. Render time remained almost the same, 1:03 (Full Predicing) & 1:00 (Disable Predicing).
If anybody is willing to explain it in a simpler manner, big thanks in advance!

tamte - I see what you've done, is there a difference installing parameters in shader or object or is it just where i prefer to see it? Is there a reason for having Bound's value relative to Amplitude? Love to take up more of your time to answer these if it's not too inconvenient.

Cheers roughsporty & tamte. :wink:

everything is in docs:
here http://www.sidefx.com/docs/houdini11.0/props/mantra [sidefx.com]
look for
vm_displacebound
vm_raypredice
and others are around

then here http://www.sidefx.com/docs/houdini11.0/rendering/rendermanypolys [sidefx.com]

so you can see that ray_predicing may not in/decrease your rendertime but it will ensure displacements are rendered correctly at the expense of using more memory (it may increase you rendertime with raytracing)

setting bounds value relative to amplitude just assures that it will be set more or less correctly when you change amplitude if your amplitude is the only multiplier to the displacement and if it scales displacement linearly
however, it may not be equal relationship you may need to find a ratio between them and then it should work
depends on how is your displacement build, and in which space you specify bounds (vm_displacespace)

setting property at material vs object level is purely your decision, just keep in mind that if it's set on both levels, lower level is used in this case material

Got that, will try to grind through as much as the docs (No pictures!) as i can and thanks for the heads-up on shader level > object level.

eitht.