This is an example that shows how to support rendering motion vectors within the standard particle system of Unity.
Particles/Standard Opaque with Motion Vectors
This shader only supports rendering mesh particles without transparency. It may not sound very useful for particle effects in a general sense, but actually useful in some specific cases, like when rendering many small moving objects (asteroids, confetti, etc.) by using a particle system.
When using this shader, "Simulation Space" in the main module and "Render Alignment" in the renderer module have to be set to "World". This is needed to calculate rotations correctly in the motion vector writer.
Also the custom vertex streams have to be set up in the following order:
- UV (TEXCOORD0.xy)
- Center (TEXCOORD0.zw|x)
- Velocity (TEXCOORD1.yzw)
- Rotation3D (TEXCOORD2.xyz)
- RotationSpeed3D (TEXCOORD2.w|xy)
- Unity 2017.1 or later
In the current implementation, change of the particle size is ignored in the calculation of motion vectors. This may introduce artifacts when animating the particle size with using the "Size over Lifetime" module or the "Size by Speed" module.
How about transparency?
I haven't tried transparency with motion vectors because I think it works only if someone tweaks it very carefully (and I have no time to invest in it). I won't recommend it, but you can try it anyway.
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