AmbientLight2D Node, Separating Sprite Tint and Ambient Light.

[ditiem-games]

The CanvasModulate node changes the tint of sprites, and as the documentation states (thanks @huwpascoe):

CanvasModulate is used to darken the scene by specifying a color that will act as the base "ambient" color.

You can see this "issue" here: GitHub Issue #94383

What I think is happening is that the normal (0, 0, 1) is used for light illumination in the absence of a normal map. So, subtracting just negates the normal (0, 0, 1). This means white for add, and black for subtract. When the normal map is present, that normal map is used instead of the default one, which results in what we see. But now CanvasModulate introduces the ambient light.

These are different features: one is the sprite tint, and the other is the ambient color of a light. In other words, a tint is not the ambient color, but the opposite is correct: an ambient color produces a tint in the sprite.

My proposal is to separate these two features by creating a new node, AmbientLight2D. You can have several AmbientLight2D nodes (only one CanvasModulate per scene is allowed). Here is how some effects could be applied:

1. 2D top-view: Like in GitHub Issue #64939. A white color AmbientLight2D on a light layer used in the tilemap cell will remove the shadow cast by the LightOccluder2D.
2. Eyes glow in darkness: The eyes can be on light layer 2, and a dark AmbientLight2D only affects sprites on light layer 1. Another AmbientLight2D on light layer 2 could define the color in RAW and be used to produce a glow with WorldEnvironment node.