metal13.metal

metal13.metal

#include <metal_stdlib>
using namespace metal;

struct VertexOut {
    float4 position [[position]];
    float2 texCoord;
};

vertex VertexOut multi_vertex(uint vertexID [[vertex_id]]) {
    float2 positions[4] = {
        {-1, -1},  // Bottom-left
        { 1, -1},  // Bottom-right
        {-1,  1},  // Top-left
        { 1,  1}   // Top-right
    };
    
    float2 texCoords[4] = {
        {0, 0},  // Bottom-left
        {1, 0},  // Bottom-right
        {0, 1},  // Top-left
        {1, 1}   // Top-right
    };
    
    VertexOut out;
    out.position = float4(positions[vertexID], 0, 1);
    out.texCoord = texCoords[vertexID];
    return out;
}

fragment half4 multi_fragment(VertexOut in [[stage_in]], constant float &time [[buffer(0)]]) {
    // Three animated control points with different movement patterns
    float2 p1 = float2(
        0.3 + 0.25 * sin(time * 0.8),
        0.3 + 0.25 * cos(time * 0.8)
    );
    
    float2 p2 = float2(
        0.7 + 0.25 * cos(time * 0.7),
        0.7 + 0.25 * sin(time * 0.7) 
    );
    
    float2 p3 = float2(
        0.5 + 0.25 * sin(time * 0.6 + 2.0),
        0.5 + 0.25 * cos(time * 0.9 + 1.0)
    );
    
    // Calculate distance to each point
    float d1 = distance(in.texCoord, p1);
    float d2 = distance(in.texCoord, p2);
    float d3 = distance(in.texCoord, p3);
    
    // Maximum influence distance
    float maxDist = 0.3;
    
    // Calculate influence for each circle (0 to 1)
    float i1 = 1.0 - min(d1 / maxDist, 1.0);
    float i2 = 1.0 - min(d2 / maxDist, 1.0);
    float i3 = 1.0 - min(d3 / maxDist, 1.0);
    
    // Apply smooth falloff
    i1 = pow(max(i1, 0.0), 2.0);
    i2 = pow(max(i2, 0.0), 2.0);
    i3 = pow(max(i3, 0.0), 2.0);
    
    // Define colors for each circle
    half3 color1 = half3(1.0, 0.3, 0.1);  // Orange-red
    half3 color2 = half3(0.1, 0.6, 1.0);  // Blue
    half3 color3 = half3(0.1, 0.9, 0.3);  // Green
    
    half3 backgroundColor = half3(0.1, 0.1, 0.1);  // Dark gray
    
    // Blend all colors based on their influence
    half3 finalColor = backgroundColor;
    
    if (i1 > 0.0) finalColor = mix(finalColor, color1, i1);
    if (i2 > 0.0) finalColor = mix(finalColor, color2, i2);
    if (i3 > 0.0) finalColor = mix(finalColor, color3, i3);
    
    return half4(finalColor, 1.0);
}