The matrices were converting the wrong values with non-diagonal-only matrices.
e.g. a typical yflip matrix in [-1,1]^3 such as
1 0 0 0
0 -1 0 0
0 0 1 0
0 0 0 1
Would have actually required a matrix like this in [0,1]^3
1 0 0 0
0 -1 0 0
0 0 1 0
0 -2 0 1
Which is
1. not consistent with our multiplication convention and would require
transposing matrices or changing our multiplication order (from what is
generally used on opengl matrix guides/tutorials).
2. Produces incorrect values when input with actual vertices accounting for
the difference in multiplication order. e.g. some vertices multiplied by
the yflip matrix using vertex * yflip(== transpose(yflip) * vertex):
vertex: -> result: expected:
vec4(1,0,1,1) -> vec4(1,-2,1,1) vec4(1,1,1,1)
vec4(1,1,1,1) -> vec4(1,-3,1,1) vec4(1,0,1,1)
With the updated values, we now get the expected values.
Includes a test for this behaviour and the example above
