Unreal 4.27, newbie and experimenting, will switch to 5 if supporting features are not available in 4.
I have a light on the left side of the room pointed toward the right side. In the middle of the room is a complex shape: a humanoid doing a yoga pose. There is a single color shape of the correct yoga pose in a fixed position on the right wall (like a poster).
How do I determine if the shadow the yoga mesh casts on the wall matches the 2D target shape perfectly? Even better would be some way to access the per-pixel data to calculate a percentage: how much of the 2D target was successfully hidden in shadow, vs failures (shadows falling outside the target on the wall, or target areas not covered in shadow).
I feel like some rendering pass should let me access a 2D representation of the shadowed material on the wall, but maybe I'm overthinking it. If there's no straightforward way to compare the pixels shaded versus not, maybe I could project N rays in a grid from the source of the light to the wall (or vice versa) to build a low resolution 2D representation of the shadow map. Ideally I wouldn't do that route, because the detail (down to the finger position) of the pose is very important to this experiment.