Godot version

v4.0.beta2.official [f8745f2]

System information

Windows 10, default, GTX 970

Issue description

blend_mul can no longer make an image brighter, and negative alpha values no longer work (I think it functioned like blend_mul).

Steps to reproduce

shader_type canvas_item;
render_mode blend_mul;

void fragment() {
	vec4 baseCol = texture(TEXTURE, UV);
	baseCol.r *= 5.0;
	baseCol.g *= 5.0;
	baseCol.b *= 5.0;
	baseCol.a *= 1.0;
	COLOR = baseCol;
}

Minimal reproduction project

blend_mul 3.5.zip
blend_mul 4.0.zip