Annotations

shaders/fisheye-reproject/shader.slang

@@ -43,6 +43,8 @@ float normalizedFisheyeRadius(float theta, float halfFov)
 {
 	float safeHalfFov = max(halfFov, 0.0001);
 
+	// Different fisheye lenses map angle to image radius differently. Normalize
+	// each model by the selected half-FOV so the outer lens edge stays at 1.0.
 	if (fisheyeModel == 1)
 	{
 		return sin(theta * 0.5) / max(sin(safeHalfFov * 0.5), 0.0001);
@@ -67,6 +69,8 @@ float4 shadeVideo(ShaderContext context)
 	float virtualFov = radiansFromDegrees(clamp(virtualFovDegrees, 1.0, 175.0));
 	float tanHalfFov = tan(virtualFov * 0.5);
 
+	// Build a virtual output-camera ray, then rotate it into the fisheye lens
+	// coordinate system before asking where that ray lands on the source image.
 	float3 ray = outputProjection == 1
 		? buildCylindricalRay(screen, outputAspect, tanHalfFov)
 		: buildRectilinearRay(screen, outputAspect, tanHalfFov);
@@ -86,6 +90,7 @@ float4 shadeVideo(ShaderContext context)
 	float phi = atan2(ray.y, ray.x);
 	float fisheyeRadius = normalizedFisheyeRadius(theta, halfFov);
 
+	// Polar lens coordinates become UVs inside the circular fisheye image.
 	float2 sourceUv = float2(
 		center.x + cos(phi) * fisheyeRadius * radius.x,
 		center.y - sin(phi) * fisheyeRadius * radius.y