Wireframe/mesh instancing oddity

Tags: #<Tag:0x00007f70365af750>

I’m not entirely sure how much of this is bug/feature, but while messing around with some mesh instancing stuff, I might have found some weird interactions between the wireframeMaterial shader and the mesh instancer.

Link to a patch reproducing the issue: https://cables.gl/p/60a1902f183621548182bf5f?s=6kJ128PeHtK3F2PL

errorlog tl;dr:

ERROR: 0:62: ‘mMatrix’ : undeclared identifier
ERROR: 0:62: ‘assign’ : l-value required (can’t modify a const)
ERROR: 0:62: ‘assign’ : cannot convert from ‘in highp 4X4 matrix of float’ to ‘const highp float’

and something to do with this line in the shader error logs:

62: mMatrix*=instMat;

Not that I’m anywhere near a graphics dev/well-versed in cables/js programming in general (or even entirely what this means), but just on-the-nose it seems like something is being set incorrectly, or not at all in the wireframe shader, and that ends up propagating down to the mesh instancer op somehow, because the instancer seems to work just fine with other materials.