Operating system: Windows-10-10.0.18362 64 Bits
Graphics card: Quadro P6000/PCIe/SSE2 NVIDIA Corporation 4.5.0 NVIDIA 436.02
Broken: version: 2.80 (sub 75), branch: master, commit date: 2019-07-29 14:47, hash: rBf6cb5f54494e
Short description of error
The Title says it all. If an object has a Particle Instance Modifier on it, it does not generate a Vector Map nor does it Motion Blur.
Exact steps for others to reproduce the error
- Create a Particle System on the default cube (I used a plane for clarity in my demo scene).
- Create a new object (I used a cone)
- Bake the the Particle System to a cache (for ease of scrubbing the timeline)
- On the new object, cone, add a Particle Instance Modifier
- Select the emitting object (cube) and choose the particle system (default is ParticleSettings for me)
- Any combination of modifier settings is fine; for clarity I checked on Regular and Size and then adjusted the size to be smaller in the Render > Scale section of the ParticleSettings system.
- Switch to Cycles in Render Settings
- Turn on Motion Blur in Render Settings
- Turn on Vector in Layer passes
- Scrub to a point where you see particles in your timeline moving
- Turn on Use Nodes in Compositor
- Render image
- In Compositor you can drag Vector to your Composite Image input. You'll note no image appears, nor does any Motion Blur appear.
Attached is a demo scene, with a few Forces to move the system around for clarity's sake.