Basic Fog of War Shader

This shader implements a fog of war, as long as it is passed a series of points and the proper camera variables it will accurately judge whether or not something should be occluded.

Shader code

shader_type canvas_item;

uniform sampler2D SCREEN_TEXTURE:hint_screen_texture,filter_linear_mipmap;

// --- UNIFORMS PASSED FROM GDSCRIPT ---
// The array of points where circles will be drawn.
uniform vec2 points[500];//this unfortunately has to be a constant size
// The actual number of points currently in the array.
uniform int points_count = 0;
// Camera/Viewport info for coordinate conversion.
uniform vec2 camera_global_position;
uniform vec2 camera_zoom;
uniform vec2 viewport_size;

// --- SHADER PARAMETERS (Editable in Inspector) ---
// The radius of the circles in pixels.
uniform float distance_threshold : hint_range(1.0, 400.0) = 50.0;
// The color to draw.
uniform vec4 hidden_color : source_color = vec4(0.0, 0.0, 0.0, 1.0);


void fragment() {
	// 1. Calculate the world coordinate of the current pixel.
	// SCREEN_UV is the pixel's position on the screen (from 0.0 to 1.0).
	// We use the camera and viewport info to convert this to a global coordinate.
	vec2 world_pos = (SCREEN_UV - vec2(0.5)) * viewport_size / camera_zoom + camera_global_position;

	// 2. Assume the pixel is not within the threshold distance of any point.
	bool is_near_point = false;

	// 3. Loop through the provided points and check the distance.
	for (int i = 0; i < points_count; i++) {
		if (distance(world_pos, points[i]) < distance_threshold) {
			is_near_point = true;
			break; // Optimization: A point was found, so no need to check others.
		}
	}

	// 4. Get the original color of the pixel from the screen texture.
	vec4 original_color = texture(SCREEN_TEXTURE, SCREEN_UV);

	// 5. Set the final color for the pixel.
	if (is_near_point) {
		// If near a point, show point
		COLOR = original_color;
	} else {
		// Otherwise, hide point.
		COLOR = hidden_color;
	}
}

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