Porta tots els shaders a Vulkan i Metal

shaders/just_another_cube/just_another_cube.frag.msl

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+#include <metal_stdlib>
+using namespace metal;
+
+// Just Another Cube — mrange
+// MSL port of just_another_cube.vk.glsl. The Shadertoy original uses
+// mutable file-scope globals; in MSL we pass them by reference.
+
+struct ShadertoyUBO {
+    float iTime;
+    float2 iResolution;
+};
+
+struct PassthroughVOut {
+    float4 pos [[position]];
+    float2 uv;
+};
+
+constant float M = 1e-3;
+
+static float D(float3 p,
+               thread float2x2& R,
+               thread float& d,
+               thread float& G) {
+    p.xy = p.xy * R;
+    p.xz = p.xz * R;
+
+    float3 S = sin(123.0 * p);
+
+    float shell = abs(length(p) - 0.6);
+    p *= p * p * p;
+    d = pow(dot(p, p), 0.125) - 0.5
+        - pow(1.0 + S.x * S.y * S.z, 8.0) / 1e5;
+
+    G = min(G, max(shell, d));
+
+    return d;
+}
+
+fragment float4 just_another_cube_fs(PassthroughVOut in [[stage_in]],
+                                      constant ShadertoyUBO& U [[buffer(0)]]) {
+    float2 C = in.uv * U.iResolution;
+
+    float2x2 R;
+    float d = 1.0, z = 0.0, G = 9.0;
+
+    float3 r = float3(U.iResolution, U.iResolution.y);
+    float3 I = normalize(float3(C - 0.5 * r.xy, r.y));
+    float3 B = float3(1, 2, 9) * M;
+    float3 p = float3(0.0);
+    float3 O = float3(0.0);
+
+    {
+        float4 cs = cos(0.3 * U.iTime + float4(0, 11, 33, 0));
+        R = float2x2(cs.x, cs.y, cs.z, cs.w);
+    }
+
+    for (; z < 9.0 && d > M; z += D(p, R, d, G)) {
+        p = z * I;
+        p.z -= 2.0;
+    }
+
+    if (z < 9.0) {
+        for (int i = 0; i < 3; ) {
+            r = float3(0.0);
+            r[i] = M;
+            O[i++] = D(p + r, R, d, G) - D(p - r, R, d, G);
+        }
+
+        O = normalize(O);
+        z = 1.0 + dot(O, I);
+
+        r = reflect(I, O);
+
+        C = (p + r * (5.0 - p.y) / abs(r.y)).xz;
+
+        float3 colorTerm;
+        if (r.y > 0.0) {
+            d = sqrt(length(C * C)) + 1.0;
+            colorTerm = 5e2 * smoothstep(5.0, 4.0, d) * d * B;
+        } else {
+            colorTerm = exp(-2.0 * length(C)) * (B / M - 1.0);
+        }
+
+        O = z * z * colorTerm + pow(1.0 + O.y, 5.0) * B;
+    }
+
+    float4 result = sqrt(float4(O + B / G, O.x + B.x / G));
+    return result;
+}