simple trail effect

This shader is inspired by celestialmaze’s https://twitter.com/cmzw_/status/1636729471486279680

I took it as a challenge to write it from scratch as spatial gdshader but it should also work in 2D / canvas with some minor tweaks. 

Shader code
shader_type spatial;

uniform sampler2D noise:source_color,repeat_enable;
uniform vec4 gradientRemap = vec4(0.708, -2.683, 0, 0.264);
uniform vec4 beamRemap = vec4(0.404, 1.12, 1, 200.0);
uniform vec4 color1:source_color;
uniform vec4 color2:source_color;
uniform vec3 scale = vec3(1.0, 50.0, 0);
uniform float threshold = 0.993;
uniform float offset = 1.5;


vec3 blend_linear_light(vec3 base, vec3 blend, float opacity) {
	blend.r = base.r > 0.5 ? blend.r + opacity * ((2.0 * base.r) - 0.5) : blend.r + opacity * ((2.0 * base.r) - 1.0);
	blend.g = base.g > 0.5 ? blend.g + opacity * ((2.0 * base.g) - 0.5) : blend.g + opacity * ((2.0 * base.g) - 1.0);
	blend.b = base.b > 0.5 ? blend.b + opacity * ((2.0 * base.b) - 0.5) : blend.b + opacity * ((2.0 * base.b) - 1.0);
	return blend;
}
float map(float value, float from_min, float from_max, float to_min, float to_max) {
	return abs(from_max - from_min) > 0.0001 ? 
		to_min + (from_min > from_max ? 1.0 - smoothstep(from_max, from_min, value) : smoothstep(from_min, from_max, value)) * (to_max - to_min) : 
		0.0;
}

void fragment() {
	vec2 uv = vec2((UV.x*2.0)-1.0, (UV.y*2.0)-1.0);
	vec3 n = texture(noise, uv+vec2(TIME*offset, 0)).rgb;
	float remap = map(uv.x, gradientRemap.x, gradientRemap.y, gradientRemap.z, gradientRemap.w);
	vec3 col = (blend_linear_light(n, vec3(uv.xy, 1), remap));
	vec3 scaled_col = col * scale;
	float len = length(scaled_col);
	float clamped = len < threshold ? 1.0 : 0.0;
	vec3 color = mix(color1, color2, clamped).rgb;
	float scale_factor = map(uv.x, beamRemap.x, beamRemap.y, beamRemap.z, beamRemap.w);
	EMISSION = color * scale_factor;
	ALBEDO = color;
}
The shader code and all code snippets in this post are under MIT license and can be used freely. 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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Godotter
Godotter
1 year ago

Hi! Could you please convert this to Godot 3, supporting GLES2 as well? The effect is so nice that other users could definitely benefit out of it!

nd123
nd123
29 days ago

interesting, but this doesn’t seem to be applied on a 2D line…