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Maniphest T97908

No motion blur with rendering pointcloud
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Description

System Information
Operating system: Windows-10-10.0.22000-SP0 64 Bits
Graphics card: NVIDIA GeForce RTX 3070/PCIe/SSE2 NVIDIA Corporation 4.5.0 NVIDIA 511.65

Blender Version
Broken: version: 3.3.0 Alpha, branch: master, commit date: 2022-05-05 19:01, hash: rB108963d508d4
Worked: none

Short description of error
There's no motion blur for pointclouds generated and transformed inside of geonodes and rendered directly as pointcloud.
There *is* motion blur if you
1: Transform the container object of the geonode tree
2: Instance a mesh, which is significantly slower though.

Exact steps for others to reproduce the error

  • In geometry nodes, add a distribute points on faces node
  • add a transform node and set the z rotation (for example) to #frame
  • go to cycles and enable motion blur. Render the frame. No motion blur appears
  • you can try instancing any mesh to these points, which will produce motion blur

Point cloud motionblur bug.blend866 KBDownload

Revisions and Commits

rB Blender
rB81b797af669d Fix T97908: Cycles missing motion from on pointcloud generated by geometry nodes

Event Timeline

Tamino Fischer (Oristur) created this task.May 6 2022, 3:43 PM
Tamino Fischer (Oristur) added projects: Geometry Nodes, Render & Cycles.
James Redmond (redjam9) added a subscriber: James Redmond (redjam9).May 8 2022, 4:17 AM
Giff (GifCo) added a subscriber: Giff (GifCo).May 9 2022, 4:34 AM

I can confirm the same issue on todays build: blender-3.3.0-alpha+ master_2a2261d7e193

RTX 3080Ti - Driver 512.59

James Redmond (redjam9) added a comment.EditedMay 9 2022, 4:49 AM

It is a hack, but you can add motion blur to geonodes point clouds if you add an attribute called "velocity" to the group output node. This is seen by Cycles for motion blur.

If you can work out the vector between the previous frame and current frame of each point and feed it into the velocity attribute, it does work. This is far from ideal, but can be a temporary workaround. Of course, I would much prefer to have this happen automatically!

Brecht Van Lommel (brecht) closed this task as Resolved by committing rB81b797af669d: Fix T97908: Cycles missing motion from on pointcloud generated by geometry nodes.May 10 2022, 8:56 PM
Brecht Van Lommel (brecht) claimed this task.
Brecht Van Lommel (brecht) added a commit: rB81b797af669d: Fix T97908: Cycles missing motion from on pointcloud generated by geometry nodes.