The page at https://webglfundamentals.org/webgl/lessons/webgl-2d-matrices.html provides an example for rotating around the center of the image:
// make a matrix that will move the origin of the 'F' to its center.
var moveOriginMatrix = m3.translation(-50, -75);
Similarly, the library I'm using (gl-matrix), provides an ability to rotate around an
fromRotationTranslationScaleOrigin [...] Creates a matrix from a quaternion rotation, vector translation and vector scale, rotating and scaling around the given origin
However, I'd like to generically set a rotation vector based on the relative local transform - e.g. something like giving [0.5,0.5, 0] as the
origin parameter to
fromRotationTranslationScaleOrigin() and have it always rotate around the center.
Would this require handling it somewhere else in the pipeline? (e.g. after composing with the perspective matrix) - or are there some best-practices ways of handling this?
I'd also like a matrix to allow centering within another's
world matrix but that's a different question I guess :)