WobblingPlane.metal

struct SceneConstants {
    simd_float4x4 viewMatrix;
    simd_float4x4 projection;
    float noiseDencity;
    float noiseStrength;
};

vertex VertexOut vertex_main(uint vertexID [[vertex_id]],
     constant VertexIn *vertices [[buffer(0)]],
     constant ModelConstants &modelConstants [[buffer(1)]],
     constant SceneConstants &sceneConstants [[buffer(2)]]) {
    VertexIn in = vertices[vertexID];
    VertexOut out;
    float noiseDencity = sceneConstants.planeModifiers.noiseDencity;
    float noiseStrength = sceneConstants.planeModifiers.noiseStrength;
    
    float3 normal = float3(0.1, 0.5, 0.1);
    float4 position = in.position;
    
    float distortion = 0.75 * cnoise(0.43 * position * noiseDencity);
    
    float3 distorted_pos = position.xyz + normal * distortion * noiseStrength;
    
    out.position = sceneConstants.projection * sceneConstants.viewMatrix * modelConstants.modelMatrix * float4(distorted_pos, 1);
    out.color = in.color;
    
    return out;
}

float3 mod289(float3 x) {
    return x - floor(x * (1.0 / 289.0)) * 289.0;
}

float4 mod289(float4 x) {
    return x - floor(x * (1.0 / 289.0)) * 289.0;
}

float4 permute(float4 x) {
    return mod289(((x*34.0)+1.0)*x);
}

float4 taylorInvSqrt(float4 r) {
    return 1.79284291400159 - 0.85373472095314 * r;
}

float3 fade(float3 t) {
    return t*t*t*(t*(t*6.0-15.0)+10.0);
}

float cnoise(float3 P) {
    float3 Pi0 = floor(P); // Integer part for indexing
    float3 Pi1 = Pi0 + float3(1.0); // Integer part + 1
    Pi0 = mod289(Pi0);
    Pi1 = mod289(Pi1);
    float3 Pf0 = fract(P); // Fractional part for interpolation
    float3 Pf1 = Pf0 - float3(1.0); // Fractional part - 1.0
    float4 ix = float4(Pi0.x, Pi1.x, Pi0.x, Pi1.x);
    float4 iy = float4(Pi0.yy, Pi1.yy);
    float4 iz0 = Pi0.zzzz;
    float4 iz1 = Pi1.zzzz;
    
    float4 ixy = permute(permute(ix) + iy);
    float4 ixy0 = permute(ixy + iz0);
    float4 ixy1 = permute(ixy + iz1);
    
    float4 gx0 = ixy0 * (1.0 / 7.0);
    float4 gy0 = fract(floor(gx0) * (1.0 / 7.0)) - 0.5;
    gx0 = fract(gx0);
    float4 gz0 = float4(0.5) - abs(gx0) - abs(gy0);
    float4 sz0 = step(gz0, float4(0.0));
    gx0 -= sz0 * (step(0.0, gx0) - 0.5);
    gy0 -= sz0 * (step(0.0, gy0) - 0.5);
    
    float4 gx1 = ixy1 * (1.0 / 7.0);
    float4 gy1 = fract(floor(gx1) * (1.0 / 7.0)) - 0.5;
    gx1 = fract(gx1);
    float4 gz1 = float4(0.5) - abs(gx1) - abs(gy1);
    float4 sz1 = step(gz1, float4(0.0));
    gx1 -= sz1 * (step(0.0, gx1) - 0.5);
    gy1 -= sz1 * (step(0.0, gy1) - 0.5);
    
    float3 g000 = float3(gx0.x,gy0.x,gz0.x);
    float3 g100 = float3(gx0.y,gy0.y,gz0.y);
    float3 g010 = float3(gx0.z,gy0.z,gz0.z);
    float3 g110 = float3(gx0.w,gy0.w,gz0.w);
    float3 g001 = float3(gx1.x,gy1.x,gz1.x);
    float3 g101 = float3(gx1.y,gy1.y,gz1.y);
    float3 g011 = float3(gx1.z,gy1.z,gz1.z);
    float3 g111 = float3(gx1.w,gy1.w,gz1.w);
    
    float4 norm0 = taylorInvSqrt(float4(dot(g000, g000), dot(g010, g010), dot(g100, g100), dot(g110, g110)));
    g000 *= norm0.x;
    g010 *= norm0.y;
    g100 *= norm0.z;
    g110 *= norm0.w;
    float4 norm1 = taylorInvSqrt(float4(dot(g001, g001), dot(g011, g011), dot(g101, g101), dot(g111, g111)));
    g001 *= norm1.x;
    g011 *= norm1.y;
    g101 *= norm1.z;
    g111 *= norm1.w;
    
    float n000 = dot(g000, Pf0);
    float n100 = dot(g100, float3(Pf1.x, Pf0.yz));
    float n010 = dot(g010, float3(Pf0.x, Pf1.y, Pf0.z));
    float n110 = dot(g110, float3(Pf1.xy, Pf0.z));
    float n001 = dot(g001, float3(Pf0.xy, Pf1.z));
    float n101 = dot(g101, float3(Pf1.x, Pf0.y, Pf1.z));
    float n011 = dot(g011, float3(Pf0.x, Pf1.yz));
    float n111 = dot(g111, Pf1);
    
    float3 fade_xyz = fade(Pf0);
    float4 n_z = mix(float4(n000, n100, n010, n110), float4(n001, n101, n011, n111), fade_xyz.z);
    float2 n_yz = mix(n_z.xy, n_z.zw, fade_xyz.y);
    float n_xyz = mix(n_yz.x, n_yz.y, fade_xyz.x);
    return 2.2 * n_xyz;
}