[HtoA] [Tip] Speeding up motion blur on VDB volumes


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.

vdb_vector_merge

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.

If you really want to be precise with the velocities, you need to resample them on the same grid, say the density grid:
unnamed
Hat tips to Saber, Fred

[HtoA] Using custom Arnold cameras in Houdini


Here’s how to set up your custom camera in Houdini. I’ll use the Oculus camera as an example.

  1. Copy OculusCamera.dll and OculusCamera.mtd to your HtoA arnold\plugins folder. For example, on my machine, that’s here:
    C:\Users\StephenBlair\htoa\htoa-1.5.0_r1338_houdini-14.0.258\htoa-1.5.0_r1338_houdini-14.0.258\arnold\plugins
  2. In the Shop network, create an Arnold Shader Network.
    shop_ArnoldShaderNetwork
  3. In the Arnold Shader Network (arnold_vopnet), create an Camera > Oculus Camera and an Output > Camera Output. Connect the Oculus Camera to the OUT_Camera.
    shop_arnold_vopnet
  4. In the Obj network, select your camera, and in the Camera properties, set the Camera Shader to point to your arnold_vopnet.
    camera_shader

[Houdini] License Error: Unable to connect to hserver for license acquisition


houdini_license_error
Yeah, this isn’t about a Solid Angle product, but about one of the DCCs that host our plugins (HtoA in this case).

So, I installed Houdini 13.0.476 the other day, and I got this “License Error: Unable to connect to hserver for license acquisition” when I tried to start HoudiniFX. I thought that was strange, because I had been running 13.0.401 moments before.

According to the licensing FAQ, that error means that the hserver service isn’t running. And, in fact, neither hserver nor sesinetd were running: they were both Disabled and marked for deletion, so I couldn’t start them from the Services console. After closing down Process Explorer, Task Manager, and the Services console, I was able to delete the services from the command line with sc delete.

At this point, I could have tried creating the services with sc create, but I was curious to see if the Houdini installer would do it for me. So I uninstalled and reinstalled. The installer asked me if I wanted to replace the newer version of sesinetd that was already on my system (huh???), and I clicked Yes. After the install finished, I had a running sesinetd service but no hserver, so I had to create it myself:

sc create HoudiniServer binPath= C:\windows\system32\hserver.exe

After that, I was able to start HoudiniFX and acquire a license.