TIL: Instancing and Houdini 11 and Volume SOPs

I’ve been working on updating and expanding on the asset I created a while back for making an led / pin board effect. Thus far I’ve added exciting things like camera based culling to speed up viewport and render times and various controls for attribute mapping and so far so good. But I shall elaborate on that in another post. Below are some things that I learned on setting up a test scene with the asset:

Instancing and the Mantra Surface Material

The new (for Houdini 11) Mantra Surface Material is generally awesome. However it can cause quite a severe performance hit when instancing. This is largely due to the fact that it defines a displacement shader even when there is no displacement on the object.

See this link on sidefx for details. As detailed by Jason Iversen the fix is simply to ad a property to the material. Or, as I did, simply use the surface model node to create your own (since I didn’t need most of the parameters).

Today I Learned

In putting together the asset I came across a few nodes that I hadn’t used before (usually by mistyping in the tab menu :–) ).

The match size nodes matches the size of one object to the bounding box of another. Not very glamorous but really rather useful.
The main discovery was the new volume nodes. The volume from attribute creates a volume based on a point attribute, is awesome. Using this I created the coloured fog you see in the render by:
1. Transferring the colour from points to a volume field via volume from attribute .
2. Merging that with an existing density field to create fog.
3. After which noise was added using a volume vop.
Bundles are very hand in organising a scene and including/excluding groups of objects from render or being matte or phantom objects.

Animated Pixels