Fix webgl_gpgpu_birds references error

[gonnavis]

references should be computed from birdIndex not triangleIndex.

The most obvious problem of current version is the diferent colors of one bird.
Second is that WIDTH and trianglesPerBird must be one odd and one even, can't both even or both odd, otherwise will produce very messy result.

By the way, also changed the left right of the wings' names by bird's self view, not camera view.

[mrdoob]

By the way, also changed the left right of the wings' names by bird's self view, not camera view.

I find this change confusing. These names are in "world space". If you look at the bird top-view. The left wing has negative values on the x, and the right wing has positive values on the x.

[gonnavis]

Okay, I just personally use to judge the left and right from the perspective of the creature itself.
Shall I roll back the change of LEFT RIGHT to let this pr purely target the modification of references？
May change the geometry to sync self space and world space later.

[mrdoob]

Shall I roll back the change of LEFT RIGHT to let this pr purely target the modification of references？

Yes please.

[gonnavis]

@mrdoob Restored.

[WestLangley]

If the bird is facing the positive-z axis, then the "right wing" points in the negative-x direction in our coordinate system.

@gonnavis is correct.

[Mugen87]

Merging. The left/right issue can be changed with another PR if necessary.

[mrdoob]

Thanks!

[mrdoob]

1912046 😇