Houdini Octane

Octane

Shading Guide

For C4D, still good: https://www.behance.net/gallery/102948251/Octane-Universal-Material-Guide-Starter-File

Shading instances with custom colors

Is a little more hands on than getting custom attributes

If you have a single object that you want to instance but have it have a random shader (in my example, using color), you can use a trick/weird workaround.

To make it work:

• in your scattered points (the ones that hold @instance, @orient, @pscale, @Cd) /obj/ level geo, make sure you choose 'Packed RGBA Values from 'Cd' Point Attribute'.
• in your instance shader, you need to grab 'Texture Instance Color' and go pick a .ppm texture that sits in the install directory of octane under the /tex folder called rgb4k_map.ppm
• plug it in directly your diffuse or use it to drive other textures like a ramp in my example

Shadow catcher with diffuse bounce

I think default shadow catching doesn't get the bounce so you can whip it up with a rayswitch. I sort of plugged stuff into stuff for it to work (topright pigheads -- bottom left is normal shadowcatcher,plane grid is a green material):

(also i cropped the rayswitch like an idiot but camera ray is at 0 the rest at 1

Double sided material in Octane

You can use tool_polygon_side to drive a material mixer:

Arnold

Weird render procedural stuff: https://arnoldsupport.com/2018/11/21/backdoor-setting-visibility/