Thanks for this. I've managed to change the alpha of the layers depending on the day light. It works perfectly!
I have another question. Suppose I have lots of frames for character animations. I've been using both material maps and normal maps in addition to the original sprites. I haven't really needed to develop material maps for some sprites (say if there isn't a difference in metal/roughness across the entire sprite). I've also noticed that you can manually change the roughness/metalic of an object. Is there a way to simply redraw the original sprite according to these object values, instead of having to use material maps? In the draw material event, could I clear the pixels in the sprite_index (of the original sprite) to a specific material map color instead of using all these extra sprites?