Fog uses interleaved gradient noise instead of white noise

This lets us use a much higher step size before noise becomes too gross
to look at.

1 files changed, 37 insertions, 0 deletions

diff --git a/atrix256.cginc b/atrix256.cginc
new file mode 100644
index 0000000..5236715
--- /dev/null
+++ b/atrix256.cginc
@@ -0,0 +1,37 @@
+#ifndef __ATRIX256_INC
+#define __ATRIX256_INC
+/*
+MIT License
+
+Copyright (c) 2021 Alan Wolfe
+
+Permission is hereby granted, free of charge, to any person obtaining a copy
+of this software and associated documentation files (the "Software"), to deal
+in the Software without restriction, including without limitation the rights
+to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+copies of the Software, and to permit persons to whom the Software is
+furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in all
+copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+SOFTWARE.
+*/
+
+// Interleaved gradient noise.
+// ported from this repo: https://github.com/Atrix256/IGNLDS
+// blog post: https://blog.demofox.org/2017/10/31/animating-noise-for-integration-over-time
+float ign(float2 screen_px) {
+  return fmod(52.9829189 *
+      fmod(0.06711056 * screen_px.x +
+        0.00583715 * screen_px.y, 1), 1);
+}
+
+#endif  // __ATRIX256_INC
+