1 files changed, 27 insertions, 0 deletions

diff --git a/shaders/skyquad.vert b/shaders/skyquad.vert
new file mode 100644
index 0000000..c0c46e6
--- /dev/null
+++ b/shaders/skyquad.vert
@@ -0,0 +1,27 @@
+uniform mat4  CameraRotation; // From camera space to world space.
+uniform float Fovy;
+uniform float Aspect;
+
+layout (location = 0) in vec2 Position;
+
+out vec3 Ray;
+
+// We would typically normalize the vector, but there is no need to do so when
+// sampling a cube map.
+vec3 sky_ray(vec2 FilmPosition)
+{
+  //float d = 0.5 / tan(Fovy/2.0);
+  // return vec3((FilmPosition.x - 0.5) * Aspect,
+  //              FilmPosition.y - 0.5,
+  //              -d);
+  float d = 0.5 / tan(Fovy/2.0);
+  return vec3(FilmPosition, -d);
+}
+
+void main()
+{
+  vec2 FilmPosition = Position * 0.5; // map [-1,1] -> [-1/2, +1/2]
+  Ray = mat3(CameraRotation) * sky_ray(FilmPosition);
+  // Set z to the background.
+  gl_Position = vec4(Position, 0.99999, 1.0); // z=1 -> send to background
+}