【Godot】ディゾルブエフェクトの作り方

shader_type canvas_item;

// ノイズテクスチャ
uniform sampler2D noise_img : hint_albedo;

// ディゾルブのかかり具合
uniform float dissolve_value : hint_range(0, 1);

void fragment() {
    // 現在のテクスチャの色を取得
    vec4 main_texture = texture(TEXTURE, UV);

    // ノイズテクスチャを取得
    vec4 noise_texture = texture(noise_img, UV);

    // ノイズテクスチャの色でアルファ値を決定
    // 0.0〜1.99の範囲におさめて floor() で 0.0〜1.0にする
    main_texture.a *= floor(dissolve_value + min(0.99, noise_texture.r));

    // 色を反映
    COLOR = main_texture;
}

tool
extends Sprite

# ノイズテクスチャ
export(Texture) var noise_img;
# ディゾルブの値
export(float, 0, 1) var dissolve; 

func _process(delta):
    # シェーダーパラメータに反映
    material.set_shader_param("noise_img", noise_img)
    material.set_shader_param("dissolve_value", dissolve)

/*
Shader from Godot Shaders - the free shader library.
godotshaders.com/shader/teleport-effect

This shader is under CC0 lincense. Feel free to use, improve and 
change this shader according to your needs and consider sharing 
the modified result on godotshaders.com.
*/

shader_type canvas_item;

// ディゾルブのかかり具合
uniform float progress : hint_range(0.0, 1.0);

// ノイズの抽出範囲
uniform float noise_desnity : hint_range(0.0, 60.0);

// 色の残るサイズ
uniform float beam_size : hint_range(0.01, 0.15);
// 残る色
uniform vec4 color : hint_color = vec4(0.0, 1.02, 1.2, 1.0);

// We are generating our own noise here. You could experiment with the 
// built in SimplexNoise or your own noise texture for other effects.
vec2 random(vec2 uv){
    uv = vec2( dot(uv, vec2(127.1,311.7) ),
               dot(uv, vec2(269.5,183.3) ) );
    return -1.0 + 2.0 * fract(sin(uv) * 43758.5453123);
}

float noise(vec2 uv) {
    vec2 uv_index = floor(uv);
    vec2 uv_fract = fract(uv);

    vec2 blur = smoothstep(0.0, 1.0, uv_fract);

    return mix( mix( dot( random(uv_index + vec2(0.0,0.0) ), uv_fract - vec2(0.0,0.0) ),
                     dot( random(uv_index + vec2(1.0,0.0) ), uv_fract - vec2(1.0,0.0) ), blur.x),
                mix( dot( random(uv_index + vec2(0.0,1.0) ), uv_fract - vec2(0.0,1.0) ),
                     dot( random(uv_index + vec2(1.0,1.0) ), uv_fract - vec2(1.0,1.0) ), blur.x), blur.y) * 0.5 + 0.5;
}

void fragment()
{
    vec4 tex = texture(TEXTURE, UV);

    float noise = noise(UV * noise_desnity) * UV.y;

    float d1 = step(progress, noise);
    float d2 = step(progress - beam_size, noise);

    vec3 beam = vec3(d2 - d1) * color.rgb;

    tex.rgb += beam;
    tex.a *= d2;

    COLOR = tex;
}