cleanup and refactoring

raytracer/nvpro_core/nvvkhl/shaders/random.glsl

@@ -0,0 +1,62 @@
+/*
+ * Copyright (c) 2022, NVIDIA CORPORATION.  All rights reserved.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ *
+ * SPDX-FileCopyrightText: Copyright (c) 2014-2022 NVIDIA CORPORATION
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+#ifndef RANDOM_GLSL
+#define RANDOM_GLSL 1
+
+precision highp float;
+
+// Generate a seed for the random generator.
+// Input - pixel.x, pixel.y, frame_nb
+// From https://github.com/Cyan4973/xxHash, https://www.shadertoy.com/view/XlGcRh
+uint xxhash32(uvec3 p)
+{
+  const uvec4 primes = uvec4(2246822519U, 3266489917U, 668265263U, 374761393U);
+  uint        h32;
+  h32 = p.z + primes.w + p.x * primes.y;
+  h32 = primes.z * ((h32 << 17) | (h32 >> (32 - 17)));
+  h32 += p.y * primes.y;
+  h32 = primes.z * ((h32 << 17) | (h32 >> (32 - 17)));
+  h32 = primes.x * (h32 ^ (h32 >> 15));
+  h32 = primes.y * (h32 ^ (h32 >> 13));
+  return h32 ^ (h32 >> 16);
+}
+
+//-----------------------------------------------------------------------
+// https://www.pcg-random.org/
+//-----------------------------------------------------------------------
+uint pcg(inout uint state)
+{
+  uint prev = state * 747796405u + 2891336453u;
+  uint word = ((prev >> ((prev >> 28u) + 4u)) ^ prev) * 277803737u;
+  state     = prev;
+  return (word >> 22u) ^ word;
+}
+
+//-----------------------------------------------------------------------
+// Generate a random float in [0, 1) given the previous RNG state
+//-----------------------------------------------------------------------
+float rand(inout uint seed)
+{
+  uint r = pcg(seed);
+  return float(r) * (1.F / float(0xffffffffu));
+}
+
+
+#endif  // RANDOM_GLSL