Don’t download Arnold from your Autodesk Account.
That’s not what you need.
It’s the Arnold SDK.
You don’t need that.
Get it here: https://www.solidangle.com/arnold/download/
There’s an Arnold error that recommends setting the load_at_init parameter, but people don’t always know where to find that in their favorite Arnold plugin.
ERROR| [proc] c4d|Arnold_Procedural: bounds supplied to procedural node are not large enough to contain the actual underlying geometry. Replace given bounds: (-1, -1, -1) X (1, 1, 1), with: (-9.4028616, -9.43616867, -9.21633244) X (9.3304739, 9.43616867, 9.21633244). Setting the procedural's load_at_init parameter to true would also fix this.
The load_at_init parameter controls whether the procedural (standin) is loaded during scene intialization (before rendering starts), or during rendering (when a ray hits the procedural bounding box).
By default, load_at_init is false, which means that procedural loading is deferred until render time.
And so, in MtoA, C4DtoA, and SItoA, the load_at_init parameter is exposed as Defer Standin Load, which is enabled by default. In HtoA, you have a Load At Init parameter on for the Arnold Procedural node.
Merging your velocity vel.x, vel.y, and vel.z grids into a single vector grid using a Vdb Vector Merge node can speed up your renders.
You can safely ignore the “component grids have different transforms” warning on the VDB Vector Merge. The x, y, and z components of the velocity have slightly different transforms because they located on the center of the cell faces in each direction; that’s coming from the marker-and-cell (MAC) grid used in the simulation.
A few quick notes about instancing support in HtoA:
Here’s how to set up your custom camera in Houdini. I’ll use the Oculus camera as an example.