changed toon shader to step the accumulated light instead of each light separately

[QbieShay]

In this proposal the issue is highlighted. This is a different solution than the one proposed, but breaks compatibility with existing toon shaded games.

Here you can see on the left current Godot's toon shader, and on the right the look with this implementation

[realkotob]

Great fix! If this also applies to GLES2 then it would be nice to merge to master as well.

[QbieShay]

@asheraryam unfortunately it's not possible to implement this fix for GLES2, which is why it won't be merged. There is an open source toon shader linked in the issue, I recommend to use that one, which looks really pretty even with the banding issue.

[akien-mga]

Style issues (indentation should be tabs, and two empty lines of separation is too much):

Suggested change

	#ifdef DIFFUSE_TOON
	diffuse_light *= step(0.1, max(diffuse_light.r, max(diffuse_light.g, diffuse_light.b)));
	# endif // DIFFUSE_TOON
	#ifdef DIFFUSE_TOON
	diffuse_light *= step(0.1, max(diffuse_light.r, max(diffuse_light.g, diffuse_light.b)));
	# endif // DIFFUSE_TOON

[lyuma]

The godot-vrm project contains a shader which illustrates some techniques that can be used to recreate toon shaded output using existing Godot functionality.

https://github.com/V-Sekai/godot-vrm/blob/godot3/addons/Godot-MToon-Shader/mtoon.shader

Though the above shader simply adds each light and does not need post-light, one technique that can be used to emulate this proposal would be to accumulate the lighting into a "fragment-to-light varying" variable, and assign the post-lighting function directly to DIFFUSE_LIGHT each time light is called.

See here for an example of a "post_light" type function implemented using current 3.4 branch: https://gist.github.com/lyuma/a1a2093637f8216e5c53ec9e4081cd31

but nothing fundamentally changes the fact that this technique requires doing all lights in one render pass.

[Note that the shader I linked above depends on overriding NORMAL to get a single irradiance sample, but this disrupts metallic / PBR type materials (SPECULAR_LIGHT != 0) if they are to be mixed with toon shading, such as the MiHoYo style. These PBR toon shaders with specular light would require GLSL or engine modificaitons]

[QbieShay]

There are some toon shaders here: https://godotshaders.com/?s=toon

Someone smarter than me figured out how to do it :D

For the time being, I'm closing this issue.
@lyuma I'll leave toon shading in your hands for 4.0, super hyped to see all your work 🎉