Shadows are cast from entities without ShadowCaster2D with the ray_marching feature

[jgayfer]

Summary

When using the ray_marching feature, shadows are still cast from entities that do not have the ShadowCaster2D component.

When using catalinzz, shadows are not cast.

Steps to reproduce

1. Comment out / remove the ShadowCaster2D components from the basic example
2. Run the basic example with the ray_marching flag

Expected behaviour

Shadows are not cast

Actual behaviour

Shadows are cast

[jgayfer]

I might poke this myself, but putting up an issue for posterity.

[jgayfer]

Dug in a bit deeper.

It looks like on our JFA pre-pass we consider any texture with an alpha greater than our threshold to be an occluder; we make no distinction if that texture comes from something with the ShadowCaster2d component on it.

In practice, this means that lighting and shadows both will only work in a world where we have a (mostly) transparent background.

In this example, I added a large "background" sprite with a gray color, and it occludes all light (whether or not it has the ShadowCaster2d component).

My hunch is that in our JFA pre-pass, we need to have some information about whether or not a given position is within a light occluder or not, instead of only relying on the alpha value (as this won't work if we have a background in play).

Alternatively, if we could create a texture that only contains entities with a ShadowCaster2d component, we could carry on using the alpha value, but I'm not 100% sure if that's possible.