Blur with Clearing Over a Node

This shader is designed for a scenario like a tutorial or intro where you want to highlight a particular thing on the screen but blur everything else.  It should be used in concert with gdscript where you tell it what node you want to highlight (ie keep clear).  For the calculations to be right, this shader should be applied to a TextureRect that is the full size of your application dimensions.  The node you want to highlight must be something that has “rect_size”.  If you are using a sprite, put it inside a node type that has rect_size.

Note: If you just have the need to do this one time for something static, is it much easier to just put the highlighted object above the overlay.

Im this example, my textureRect is called ScreenOverlay and I want to highlight a node called Bomb, and used this gdscript:

extends Node

onready var bomb = $Bomb
onready var screen_overlay = $ScreenOverlay

func _ready():
	pass

func _process(delta):
	update_shader_exclude_area()

func update_shader_exclude_area():
	var bomb_global_rect = bomb.rect_size
	var bomb_center = bomb.rect_position + bomb.rect_size * 0.5
	var bomb_size =bomb.rect_size

	var screen_size = screen_overlay.rect_size
	var normalized_center = bomb_center / screen_size
	var normalized_size = bomb_size / screen_size

	screen_overlay.material.set_shader_param("exclude_center", normalized_center)
	screen_overlay.material.set_shader_param("exclude_size", normalized_size)

 

Shader code
shader_type canvas_item;

uniform vec2 exclude_center; // Center of the area to exclude from blur
uniform vec2 exclude_size;   // Size of the area to exclude from blur
uniform float lod: hint_range(0.0, 5) = 0.0;

void fragment() {
    vec2 uv = UV;

    // Check if the current pixel is inside the excluded area
    bool is_inside_exclude_area = 
        uv.x > exclude_center.x - exclude_size.x / 2.0 &&
        uv.x  exclude_center.y - exclude_size.y / 2.0 &&
        uv.y < exclude_center.y + exclude_size.y / 2.0;

    if (is_inside_exclude_area) {
        // If inside the excluded area, just output the original texture
		COLOR = vec4(0.0, 0.0, 0.0, 0.0);
    } else 
{
	vec4 color = texture(SCREEN_TEXTURE, SCREEN_UV, lod);
	COLOR = color;
}
}
Tags
blur, clear, highlight, Tutorial
The shader code and all code snippets in this post are under CC0 license and can be used freely without the author's permission. Images and videos, and assets depicted in those, do not fall under this license. For more info, see our License terms.

Related shaders

Loading effect (color over grayscale)

Vignette with changeable blur size

Tilemap Blur

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