2D Fragment shaders not working when 2 instances are on screen

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:bust_in_silhouette: Asked By quijipixel

I’m new to shaders and can’t make them work properly in Godot 3.0. I have an Area2D scene that has a Node2D with a fragment shader. The shader works fine, but if I use another instance of the same scene and both are on screen, the shader only works for the closest scene to the player.

This is the shader’s code:

shader_type canvas_item;

uniform float frequency=30;
uniform float depth = 0.005;

void fragment() {
	vec2 uv = UV;
	uv.x = clamp(uv.x+sin(uv.y*frequency+TIME)*depth,0,1);
	vec3 c = textureLod(TEXTURE,uv,0.0).rgb;

How does this shader thing works? It seems that the shader is somehow shared between instances instead of each having its own. The scene is to be a platform, so being able to have several instances on screen is important.

:bust_in_silhouette: Reply From: jarlowrey

You need a back buffer copy