matrix4 method
Writes a 4×4 matrix (column-major, as both the engine and GLSL store
it) at offset.
Implementation
void matrix4(int offset, Matrix4 m) {
final s = m.storage;
for (var i = 0; i < 16; i++) {
bytes.setFloat32(offset + i * 4, s[i], Endian.host);
}
}