initial setup

shaders/dissolve.gdshader

@@ -0,0 +1,11 @@
+shader_type canvas_item;
+
+uniform sampler2D sim_texture;
+
+uniform float decay_factor;
+
+void fragment() {
+	float c = texture(sim_texture, UV).r;
+	c = c * decay_factor;
+	COLOR = vec4(c, c, c, 1.0);
+}