Edge Detection (Sobel Filter and Gaussian Blur)

A shader that can be used for interesting post-processing effects and uses the Sobel operator along with other algorithms, such as Gaussian blur.

Please find the tutorial here: https://www.youtube.com/watch?v=bCGq1_gnnIk

Shader code
shader_type canvas_item;
render_mode unshaded;

uniform sampler2D SCREEN_TEXTURE: hint_screen_texture, repeat_disable, filter_nearest;

vec3 convolution(sampler2D tex, vec2 uv, vec2 pixel_size) {
	vec3 conv = vec3(0.0);
	// Gaussian blur kernel
	float gauss[25] = {
		0.00390625, 0.015625, 0.0234375, 0.015625, 0.00390625,
		0.015625, 0.0625, 0.09375, 0.0625, 0.015625, 0.0234375,
		0.09375, 0.140625, 0.09375, 0.0234375, 0.015625,
		0.0625, 0.09375, 0.0625, 0.015625, 0.00390625,
		0.015625, 0.0234375, 0.015625, 0.00390625
	};
	for (int row = 0; row < 5; row++) {
		for (int col = 0; col < 5; col++) {
			conv += texture(tex, uv + vec2(float(col - 2), float(row - 2)) * pixel_size).rgb * gauss[row * 5 + col];
		}
	}
	return conv;
}

void fragment() {
	vec3 pixels[9];  // Sobel kernel
	// [0, 1, 2]
	// [3, 4, 5]
	// [6, 7, 8]
	for (int row = 0; row < 3; row++) {
		for (int col = 0; col < 3; col++) {
			vec2 uv = SCREEN_UV + vec2(float(col - 1), float(row - 1)) * SCREEN_PIXEL_SIZE;
			pixels[row * 3 + col] = convolution(SCREEN_TEXTURE, uv, SCREEN_PIXEL_SIZE);
		}
	}

	// Sobel operator
	vec3 gx = (
		pixels[0] * -1.0 + pixels[3] * -2.0 + pixels[6] * -1.0
		+ pixels[2] * 1.0 + pixels[5] * 2.0 + pixels[8] * 1.0
	);
	vec3 gy = (
		pixels[0] * -1.0 + pixels[1] * -2.0 + pixels[2] * -1.0
		+ pixels[6] * 1.0 + pixels[7] * 2.0 + pixels[8] * 1.0
	);
	vec3 sobel = sqrt(gx * gx + gy * gy);
	COLOR = vec4(sobel, 1.0);
}
Tags
blur, edge, Gaussian, Post processing, Sobel
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.

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