Prevent Unity from reordering DrawMeshNow calls

Question

I was under the impression that using DrawMeshNow gives me complete control over the order of draw call submissions in Unity. After a gazillion hours of debug, I've realized that isn't the case.

I call DrawMeshNow from OnPostRender (and not OnRenderObject because Blit doesn't work right with the latter).

My shader originally had Tag = "Transparent", and I thought that was the problem. Didn't fix it. Removed the blend state in my shader. Didn't fix it. Recreated the material (to avoid stale stuff from the previous one) -- no luck.

Unity doesn't just reverse the order. That'd be easy to work around. I've seen (using Intel GPA) my submitted order of 1,2,3 being rendered as 3,1,2.

I'm clueless on how to go about fixing it. Someone, anyone.. please help me!

Answer 1

Best Answer

Answer by raja-bala · Jan 14, 2015 at 08:01 PM

Figured it out. It was a single line of misplaced code that created the havoc.

myMat.SetPass(0); needs to be called AFTER all the material properties are set, just prior to DrawMeshNow.

i.e,

 for(int ii = 0; ii < 5; ii++) {
    myMat.SetInt("_OrderIndex", ii);
    myMat.SetPass(0); // this has to be AFTER all properties are set
    Graphics.DrawMeshNow(myMesh, meshPos[ii], meshRot[ii]);
 }

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Prevent Unity from reordering DrawMeshNow calls

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