Does anyone have an existing workflow for post blur in Fusion (ideally with RSMB)?
The motion vectors are 3d space and need to be converted to screen space. Can this be done with magma? I would think it could?
Thanks.
Yes, you can use a Custom Render Element (which is Magma-based) to produce whatever velocity space you want.
All channels in the Render Element are already in World Space. While you can export nagative and positive values to OpenEXR, you might want to normalize the R anf G values in the 0.0 to 1.0 range where 0.5 represent 0.0…
The vectors in the render element are XYZ, no? I am looking for X and Y in screen space for Real Smart Motion Blur.
Also, does additive mode support motion vectors? I am using Force Additive for this project.
Thanks, Bobo.
Looks like I need absorption turned on and force additive off to get the motion. Actually, not sure I am getting any real motion.
Does the motion vector element work with PRTVolumes and PRTSurfaces? I am animating the camera. I guess a moving PRTVolume object (where you animate the source object in world space) would not have any motion vectors of its own?
I am also rendering in voxel mode. Will try points (not that point mode would work for my project).
PRT Volume now supports velocities/motion blur from deforming geometry in Krakatoa v2.3.
If you switch PRT Volume to “In World Space” mode, then the Velocities will include the transformation animation AND deformations on the stack.
PRT Surface does not create Velocity yet.
Animated Camera only produces motion blur in the renderer because its transforms are sampled once per particle segment, but its motion is of course not included in the Velocity channel of moving particles (for obvious reasons). It might be possible to read the motion of the camera using InputScript operators, but using that to actually produce velocity data in the Render Element might be tricky, so you better get your camera exported to your compositing application.
If you would take the time to read the text in the Parameters rollout of the Krakatoa Velocity render element, you will discover that the values are in CAMERA space, so R and G are parallel to the camera plane, and B is motion along the camera’s -Z axis. Normally, the values are encoded between -Infinity and Infinity as Reals, useful when stored in an EXR file to be loaded in Nuke, Fusion etc. If you need to normalize the values in the 0 to 1 range, you check the “Use Max Velocity” checkbox and define what the fastest velocity per frame is. Default is 100.0, so a particle moving along the +X axis at speed of 100.0 units will produce a value of 1.0. A Particle not moving at all along the X will have a Red value of 0.5. A particle moving at 50 units/frame along the -X axis will have a value of 0.25 and so on…
If you need anything fancier than this, you can write a Custom Render Element.
Voxel mode seems to work for me. Additive mode does not work because it produces no Alpha, so no values are written to the Render Element. You might have to render in separate passes - once in Additive mode for the Beauty, once with Additive mode off for the Render Elements (you could check “Ignore Scene Lights” to speed up things a bit)
I logged in the Wish List “Support Camera Animation in Krakatoa Velocity Render Element”.
Sounds like it would be an useful option.
LOL. Here I was searching all over the website for documentation on the velocity channel, and it is right there staring me in the face!
Thanks. And thanks for adding that to the wishlist.
Don’t worry, I had the same problem! Until I opened Max and looked at it, I did not remember what space it was working in and how… 
Might be nice to put that info, with a more verbose description, in the section of the Krakatoa online docs that covers the render elements. You guys have just about everything so nicely layed out and clearly explained on the website. I was trying to figure out when there was no clear explanation of the details in that section.
Thanks again for all your help.
I think the problem was that originally there was no Velocity Render Element, and we rewrote the Render Elements a few times. And then we had two versions of the page in two places. So somehow me managed to totally miss to document the Velocity render element on one of the two pages. And when I say “we” I mean “I”.
Will fix ASAP.
Edit: Fixed here: thinkboxsoftware.com/krak-render-elements
The other page under User Reference which is sort of a duplicate but contains some of the v2.x info still needs an update with more facts: thinkboxsoftware.com/krakato … -elements/
Excellent. Thanks. The Krakatoa docs are one of its strongest features.