Ive got to achieve a particular effect (a set of objects with a nice raytraced “blur” training off them, which remains fixed in 3d space as i rotate a cam around them). im hoping there is some neat trick to use the velocity channel vray uses to blur fluid meshes etc.. anyone care to suggest a method i might use? maybe something with data channel modifier? at its most basic id be happy with applying a blur along a single vector/axis.. stretch goal would be controlling it with an animated map.
You can get some interesting effects with the Camera motion blur alone if you set the Shutter speed really low. The axis will be the path of the camera’s movement.
I found a way that’s probably exactly what you wanted, but you need tyFlow, because it uses the tyVertexVelocity modifier. The setup is the following: Add a VertexPaint modifier to the object, paint the whole object (r,g,b refer to x,y,z), and select a channel. Afterwards, use the tyVertexVelocity with “Velocity from UVWs” mode and select the same channel. This way, you can control the axis as you’d like. Video.
thats exactly the method i worked out after posting. quite a cool effect but on further investigation motion blur doesnt give me quite the effect im after. even with the moblur controls (bias and interval center) it does not seem really possible to have a trail just “behind” an object with this method. i guess if i can change the vertex colour from black to say, blue from one frame to the next (is it animateable? never really used vertex colours much) then id get closer to what i want. as it is, the blur rate is constant every frame so the blur is inevitably both before and after the object.
on a related note, literally every time i want to do something wierd, tyflow can do it.. amazing.
Maybe some parts of this might help Robin Long shutter motionblur, only trail behind, not infront? - V-Ray for Maya :: General - Chaos Forum
I think it should work with the motion blur Interval Center / Bias overrides. Tried it with Interval center = 0.5 and Bias = 5, and the trail is behind/infront the object. Attaching a sample scene where the result seems good (at least to me).
vertexvelocity_sample.7z (36.2 KB)
That’s a cool technique, although it does crash Max for me after a few moments rendering for some reason. Maybe the Maya ocio error warning I get, dunno.
you can do some interesting things with a velocity pass in nuke
Or get actual long motion blur trails using the still camera with a long shutter.
Of course all of this would be much easier if VRay just let you set the shutter angle greater than 360 in the movie camera. This is a silly limitation.