public PoseStack getModelViewMatrixStack() {
        PoseStack stack = new PoseStack();
        stack.setIdentity();
        stack.mulPoseMatrix(viewMatrix.toMatrix4f());
        return stack;
    }
Calculates a view matrix based on camera position, x rotation, and y rotation.
core/src/main/java/mrtjp/projectred/redui/PVMMatrix.java