Shaders_Step5.metal

Shaders_Step5.metal

// Shaders.metal
#include <metal_stdlib>
using namespace metal;

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

vertex VertexOut circle_vertex(uint vertexID [[vertex_id]]) {
    float2 positions[4] = {
        float2(-1.0, -1.0), float2(1.0, -1.0),
        float2(-1.0,  1.0), float2(1.0,  1.0)
    };

    VertexOut out;
    out.position = float4(positions[vertexID], 0.0, 1.0);
    out.texCoords = float2((positions[vertexID].x + 1.0) / 2.0, (1.0 - positions[vertexID].y) / 2.0);
    return out;
}

fragment half4 circle_fragment(VertexOut in [[stage_in]], constant float &time [[buffer(0)]]) {
    float2 p1 = float2(0.3 + 0.2 * sin(time * 0.8), 0.3 + 0.2 * cos(time * 0.8));
    float2 p2 = float2(0.7 + 0.2 * cos(time * 0.6), 0.7 + 0.2 * sin(time * 0.6));
    float2 p3 = float2(0.5 + 0.2 * sin(time * 1.5), 0.5 + 0.2 * cos(time * 1.5));

    half3 color1 = half3(1.0, 0.47, 0.2);
    half3 color2 = half3(0.2, 0.55, 1.0);
    half3 color3 = half3(1.0, 0.31, 0.12);

    float maxDist = 0.3;

    float influence1 = 1.0 - min(distance(in.texCoords, p1) / maxDist, 1.0);
    float influence2 = 1.0 - min(distance(in.texCoords, p2) / maxDist, 1.0);
    float influence3 = 1.0 - min(distance(in.texCoords, p3) / maxDist, 1.0);

    influence1 = pow(max(influence1, 0.0), 2.0);
    influence2 = pow(max(influence2, 0.0), 2.0);
    influence3 = pow(max(influence3, 0.0), 2.0);

    float maxInfluence = max(max(influence1, influence2), influence3);
    half3 finalColor;

    if (maxInfluence <= 0.001) {
        finalColor = half3(0.1, 0.1, 0.1);
    } else if (influence1 >= influence2 && influence1 >= influence3) {
        finalColor = color1;
    } else if (influence2 >= influence1 && influence2 >= influence3) {
        finalColor = color2;
    } else {
        finalColor = color3;
    }

    return half4(finalColor, 1.0);
}