How do I recreate the blend_mul render mode?

Help Shaders
1

Godot Version

4.3

Question

I’m trying to write a shader that blends a texture with everything in the background using the multiply blending technique.

I know I can use render_mode blend_mul for this, and although that works, I want to be able to turn the effect on and off with a bool later.

I came up with this shader code, simplified to show my problem:

shader_type spatial;
render_mode unshaded;

uniform sampler2D _texture: source_color;
uniform sampler2D _screenTexture : hint_screen_texture;

void fragment()
 {
	vec4 textureColor = texture(_texture, UV);
	vec4 backgroundColor = texture(_screenTexture, SCREEN_UV);
	
	vec4 blend = backgroundColor * textureColor;
	
	ALBEDO = blend.rgb;	
}

The problem is that it doesn’t seem to blend with the other mesh textured with the same shader underneath.

My shader code that doesn’t blend well with its background:

My shader code that doesn't blend well with its background.
My shader code that doesn't blend well with its background.1131×991 155 KB

The way it should look:
The way it should look.
The way it should look.1157×995 151 KB