Waving Particles

Waving particle effect suitable for falling snow, leaves, confetti and dust, or rising bubbles, etc.

By default the shader is set-up to be applied to a ColorRect in Godot 4 but there are comments explaining how to use it with a TextureRect and in earlier versions of Godot.

There are sections of code for rendering the particles as hard and soft edged circles or crosses, or as squares or diamonds or using a texture.

Shader code

// Waving Particles shader by Brian Smith (steampunkdemon.itch.io)
// MIT licence

shader_type canvas_item;

// Uncomment the following line if you are using a version of Godot before 4:
//	const float PI = 3.14159;

// Comment out the following line if you are not applying the shader to a ColorRect:
uniform vec2 dimensions = vec2(1152.0, 648.0); // Resolution of ColorRect in pixels

uniform float rows = 20.0;
uniform float columns = 5.0;
uniform float vertical_scroll : hint_range(-1.0, 1.0, 0.01) = 0.5;
uniform float horizontal_scroll : hint_range(-1.0, 1.0, 0.01) = 0.1;
uniform float size_min : hint_range(0.1, 1.0, 0.1) = 0.3;
uniform float size_max : hint_range(0.1, 1.0, 0.1) = 0.7; // If 'size_max' is larger than 0.7 the corners of the particles will be clipped if they are rotating.
uniform float wave_min : hint_range(0.0, 1.0, 0.1) = 0.1;
uniform float wave_max : hint_range(0.0, 1.0, 0.1) = 1.0; // If the particles are waving into the neighbouring columns reduce 'wave_max'.
uniform float wave_speed : hint_range(0.0, 2.0, 0.1) = 0.5;
uniform float wave_rotation : hint_range(-1.0, 1.0, 0.1) = 1.0;

// Replace the below references to 'source_color' with 'hint_color' if you are using a version of Godot before 4:
uniform vec4 far_color : source_color = vec4(0.5, 0.5, 0.5, 1.0);
uniform vec4 near_color : source_color = vec4(1.0, 1.0, 1.0, 1.0);

// Remove the below reference to ': source_color, filter_nearest_mipmap' if you are using a version of Godot before 4.0:
uniform sampler2D particle_texture : source_color, filter_nearest_mipmap;

float greater_than(float x, float y) {
	return max(sign(x - y), 0.0);
}

void fragment() {
// You can comment out the below line and add a new uniform above as:
// uniform float time = 10000.0;
// You can then update the time uniform from your _physics_process function by adding or subtracting delta. You can also pause the particles' motion by not changing the time uniform.
	float time = 10000.0 + TIME;

// Comment out the following two lines if you are not applying the shader to a TextureRect:
//	COLOR = texture(TEXTURE,UV); // This line is only required if you are using a version of Godot before 4.
//	vec2 dimensions = 1.0 / TEXTURE_PIXEL_SIZE;

	float row_rn = fract(sin(floor((UV.y - vertical_scroll * time) * rows)));
	float column_rn = fract(sin(floor((UV.x + row_rn - horizontal_scroll * time) * columns)));
	float wave = sin(wave_speed * time + column_rn * 90.0);
	vec2 uv = (vec2(fract((UV.x + row_rn - horizontal_scroll * time + (wave * (wave_min + (wave_max - wave_min) * column_rn) / columns / 2.0)) * columns), fract((UV.y - vertical_scroll * time) * rows)) * 2.0 - 1.0) * vec2(dimensions.x / dimensions.y * rows / columns, 1.0);
	float size = size_min + (size_max - size_min) * column_rn;
	vec4 color = mix(far_color, near_color, column_rn);
	
// Comment out the below two lines if you do not need or want the particles to rotate:
	float a = ((column_rn + wave) * wave_rotation) * PI;
	uv *= mat2(vec2(sin(a), -cos(a)), vec2(cos(a), sin(a)));

// Render particles as circles with soft edges:
//	COLOR.rgb = mix(COLOR.rgb, color.rgb, max((size - length(uv)) / size, 0.0) * color.a);

// Render particles as circles with hard edges:
//	COLOR.rgb = mix(COLOR.rgb, color.rgb, greater_than(size, length(uv)) * color.a);

// Render particles as crosses with soft edges:
//	COLOR.rgb = mix(COLOR.rgb, color.rgb, max((size - length(uv)) / size, 0.0) * (max(greater_than(size / 10.0, abs(uv.x)), greater_than(size / 10.0, abs(uv.y)))) * color.a);

// Render particles as crosses with hard edges:
//	COLOR.rgb = mix(COLOR.rgb, color.rgb, max(greater_than(size / 5.0, abs(uv.x)) * greater_than(size, abs(uv.y)), greater_than(size / 5.0, abs(uv.y)) * greater_than(size, abs(uv.x))) * color.a);

// Render particles as squares:
//	COLOR.rgb = mix(COLOR.rgb, color.rgb, greater_than(size, abs(uv.x)) * greater_than(size, abs(uv.y)) * color.a);

// Render particles as diamonds:
//	COLOR.rgb = mix(COLOR.rgb, color.rgb, greater_than(size, abs(uv.y) + abs(uv.x)) * color.a);

// Render particles using the 'particle_texture':
// The texture should have a border of blank transparent pixels.
	vec4 particle_texture_pixel = texture(particle_texture, (uv / size + 1.0) / 2.0) * color;
	COLOR.rgb = mix(COLOR.rgb, particle_texture_pixel.rgb, particle_texture_pixel.a);
}

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