From bd57f345ed9dbed1d81683e48199626de2ea9044 Mon Sep 17 00:00:00 2001
From: 3gg <3gg@shellblade.net>
Date: Fri, 27 Jun 2025 10:18:39 -0700
Subject: Restructure project

---
 shaders/cubemap_filtering.vert | 39 +++++++++++++++++++++++++++++++++++++++
 1 file changed, 39 insertions(+)
 create mode 100644 shaders/cubemap_filtering.vert

(limited to 'shaders/cubemap_filtering.vert')

diff --git a/shaders/cubemap_filtering.vert b/shaders/cubemap_filtering.vert
new file mode 100644
index 0000000..d0cf73f
--- /dev/null
+++ b/shaders/cubemap_filtering.vert
@@ -0,0 +1,39 @@
+precision highp float;
+
+#define PI 3.1415926535897932384626433832795
+#define FOVY (90.0 * PI / 180.0)
+
+uniform mat4 CameraRotation; // From camera space to world space.
+uniform float Flip;
+
+layout (location = 0) in vec2 vPosition;
+
+out vec3 Ray;
+
+// DEBUG
+// out vec2 Texcoord;
+
+// This is very similar to the skyquad vertex shader.
+//
+// The ray is not normalized because it isn't necessary for cubemap sampling.
+//
+// We also use a fixed fovy = 90 degrees because we want the frustum to pass
+// exactly through each face of the cube. The aspect ratio is also just 1.
+vec3 sky_ray(vec2 FilmPosition)
+{
+  float d = 0.5 / tan(FOVY/2.0);
+  return vec3(FilmPosition, -d);
+}
+
+void main()
+{
+  vec2 FilmPosition = vPosition * 0.5; // map [-1,1] -> [-1/2, +1/2]
+  FilmPosition *= Flip;
+  Ray = mat3(CameraRotation) * sky_ray(FilmPosition);
+  // TODO: Should disable depth test when rendering.
+  gl_Position = vec4(vPosition, 0.99999, 1.0); // z=1 -> send to background
+
+  // DEBUG
+  // Texcoord   = FilmPosition + 0.5;
+  // Texcoord.y = 1.0 - Texcoord.y;
+}
-- 
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