I am not sure what is happening.

I have an animating point cloud, its mb is set to Deformation Blur. Its rendering attributes are set to Render Points Only.
Deform BLur is set for Camera and in MantraROP.
The scene renderes, but there is no apparent motion blur visible in either C or A channels, and the weirdest thing is that the colors are inveresed in both C and A channels. In A, where the point appears, there is a black dot, where there is empty, its white. Inveresed. Not a world ending trategy, as image can be inversed back, but is this a bug, or what is going on?
The particle cloud has VEX SuperMaterial (100% luminant), and there is one light in scene.
V 6.286 distribution Apprentice.

Dave

Have you ensured that your point count doesn't change frame by frame? Number 1 with a bullet reason for mblur failing is a changing point count(the renderer can't keep track of each point's previous/current/future position if points keep getting created/destroyed). Have you tried velocity blur instead?

Cheers,

J.C.

Actually the point cloud is changing counts. BUT. I can't have Velocity Attribute enabled. As Render As Points option only renders points when MB is set to Deformation Blur.
Still, a good tip. I did not know that. Does this explain why a BGEO sequence of a particles (baked motion), does not render as points (even with Deformation BLur), but the popnet that created it does when read in using POP SOP?

Dave

I'm not sure that's a symptom of this problem - hard to say. However - one of the symptoms of this thing is that you'll be doing an interactive render test in Houdini and it's fine, it's fine, it's…*broken*, it's fine, it's fine…
If you've never encountered it before it's frustrating and it seems like a bug, but in fact it's a universal issue with any package. Velocity blur is the way to get around it - I understand why you can't use it in your case, however I believe you'll need to rethink your pipeline - as you say Render As Points can't do Velocity because it has no-where to “get” the Velocity attribute from. I would do this as a straight POP, or if your geo is simply too big perhaps baked out points with velocity attributes…
Of course, I don't know all the variables of your job…

Cheers,

J.C.