This is what my IBakedModel::handlePerspective() method looks like:

 

    @Override
    public Pair<? extends IBakedModel, Matrix4f> handlePerspective(ItemCameraTransforms.TransformType cameraTransformType) {
        switch (cameraTransformType) {
            case THIRD_PERSON_RIGHT_HAND:
                Matrix4f transform = new Matrix4f();
                transform.setIdentity();
                float degree90 = (float)(Math.PI/2);
                transform.mul(0.1F);
                transform.rotX(degree90);
                transform.rotZ(degree90);
                transform.rotY(degree90);
                return Pair.of(this, transform);
        }

        return Pair.of(this, null);
    }

 

The model rotates correctly but its size doesn't change. What am I doing wrong?

That's what I was thinking aswell, but it doesn't seem to make a difference:

 

      Matrix4f scale = new Matrix4f(
          0.1F,   0,      0,      0,
          0,      0.1F,   0,      0,
          0,      0,      0.1F,   0,
          0,      0,      0,      1
      );
      transform.mul(scale);

 

Still the same size

Ok. I found the problem.

The rot methods in Matrix4f set m00 and m33 (first element in first row, last element in last row) to 1. I had to first rotate it and then multiply it by 0.1 and finally set m33 back to 1.