Pixei Transition Shader

Pixelation Transition Shader
This shader creates a pixelated tile–based transition between two textures.
It gradually reveals the new texture over the old one by adjusting the size of the pixel blocks, producing a smooth and visually appealing scene swap.

Usage Notes:

Scene transitions: provide snapshots of the current scene and the target scene as from_tex and to_tex.
The shader animates the pixelation effect to reveal the new scene. The transition goes from clear → highly pixelated → clear.

Transition Behavior:

At progress = 0 → fully shows from_tex (clear).
At progress = 0.5 → shows the most pixelated version of the image.
At progress = 1 → fully shows to_tex (clear).
The pixelation dynamically adjusts based on progress to create a smooth animation.

Shader code

shader_type canvas_item;

// ========================
// 输入纹理
// ========================
uniform sampler2D from_tex;
uniform sampler2D to_tex;

// ========================
// 过渡控制
// ========================
uniform float progress : hint_range(0.0, 1.0) = 0.0;

// ========================
// 像素分辨率控制
// ========================
uniform float min_tiles = 1.0;    // 最低分辨率（最像素化）
uniform float max_tiles = 200.0;  // 最高分辨率（过渡中接近原图）

void fragment() {
    vec2 screen_size = vec2(1.0) / SCREEN_PIXEL_SIZE;
    vec2 fragCoord = UV * screen_size;

    // 定义最终采样的UV坐标
    vec2 sample_uv = UV;

    // 仅在 0 < progress < 1 时启用像素化采样
    if (progress > 0.0 && progress < 1.0) {
        // 过渡曲线：0→0.5→1 对应 清晰→最像素→清晰
        float transition_curve = abs(progress - 0.5) * 2.0;
        float count = mix(min_tiles, max_tiles, transition_curve);
        count = floor(count);

        // 计算瓦片尺寸并做中心采样
        vec2 tileSize = screen_size / count;
        vec2 sample_pos = floor(fragCoord / tileSize) * tileSize + tileSize * 0.5;
        sample_uv = sample_pos / screen_size;
    }

    // 过渡混合纹理
    vec4 from_col = texture(from_tex, sample_uv);
    vec4 to_col   = texture(to_tex, sample_uv);
    COLOR = mix(from_col, to_col, progress);
}