Why doesn't my custom 2D shader react to PointLight2D?

Default canvas shader's fragment doesn't apply lights. Implement a light() function in the shader; engine calls it per-light pass and adds the contribution.

What's light_only render mode?

light_only restricts visibility to lit areas. Useful for fog-of-war effects or light-revealed sprites.

How do I sample LIGHT_COLOR?

Inside light(), use LIGHT_COLOR for the incoming light, LIGHT_VEC for direction. Multiply with COLOR and add to LIGHT output.

Fix: Godot 2D Shader Doesn't React To Lights

Quick answer: Implement void light() in the canvas shader. Multiply COLOR with LIGHT_COLOR and add to LIGHT output.

Custom canvas shader for water. Place a PointLight2D nearby. No effect. Default fragment doesn’t loop through lights.

The Fix

shader_type canvas_item;

void fragment() {
    COLOR = texture(TEXTURE, UV);
}

void light() {
    LIGHT = COLOR.rgb * LIGHT_COLOR.rgb * LIGHT_COLOR.a * LIGHT_ENERGY;
}

The light() function runs per-light. LIGHT_COLOR includes light's energy and color; LIGHT_ENERGY broadcasts the source's intensity.

Verifying

Add PointLight2D in scene. Sprite brightens within radius. Without light(): unaffected.

“Implement light(). Lights affect.”

Related Issues

For shader UV flip, see UV flip. For SCREEN_TEXTURE, see SCREEN_TEXTURE.

light() function. Lights apply.