I have a scene withan animated character with tufts of hair on, and some grass (which isalso hair) sprouting from a mesh that never deforms.
Fairly soon intorendering it, I noticed that motion blur made the fur on thecharacter (which is mesh deformed via armature) would disappear or bevery faint. The grass would flicker but only very slightly; it wouldnot disappear like the fur on the character.
I disabled thegrass’ motion blur at deformation level and removed the character furcompletely. From that point onward, the scene rendered perfectly andthe grass was fine.
However, suddenlyjust the other day, the grass started completely disappearing. If Irender it again with global level motion blur disabled, the grass ispresent. Nothing much has changed apart from I have added otherparticles such as boids flying around in the air to look like flies,and some volumetric mist, and in general the file has got a bitbigger. I have tried gradually removing things to eliminate theproblem whilst still rendering with global motion blur. My process ofelimination has been:
Remove all other particles (such asboids) apart from grass – grass still disappears.
Remove transparentshader node from grass material – grass still disappears.
Reduce cameraclipping distance – grass still disappears.
Remove volumetricmaterials – grass still disappears.
Exclude ALL layers(and therefore all objects) that apart from the layer which only hasthe grass on it – grass still disappears.
In short, I havestripped back the file to what I think it was before the grassstarted disappearing, but nothing works!
As soon as I disable motion blur, the grass appears again.