diff --git a/shaders/lib/raymarching.glsl b/shaders/lib/raymarching.glsl
index 21a574d..ff61320 100644
--- a/shaders/lib/raymarching.glsl
+++ b/shaders/lib/raymarching.glsl
@@ -102,17 +102,17 @@ float RM_TanPhi(
 	// ...
 	// ...
 	// or we could just pass it as a fucking uniform
-	const float fov = PI * .5 - atan( u_NearPlane * .5 );
+	const float hfov = ( PI * .5 - atan( u_NearPlane * .5 ) ) * .5;
 
 	vec2 e = ( abs( uv.x ) > abs( uv.y ) )
 		? vec2( uv.x < 0 ? -1 : 1 , 0 )
 		: vec2( 0 , uv.y < 0 ? -1 : 1  );
 
-	vec3	d = normalize( vec3( uv , -1 / tan( fov ) ) ) ,
+	vec3	d = normalize( vec3( uv , -1 / tan( hfov ) ) ) ,
 		a = vec3( ( e + e.yx ) * pixelRadius + uv ,
-			-1 / tan( fov ) ) ,
+			-1 / tan( hfov ) ) ,
 		b = vec3( ( e - e.yx ) * pixelRadius + uv ,
-			-1 / tan( fov ) ) ,
+			-1 / tan( hfov ) ) ,
 		p2ca = a / dot( a , d ) ,
 		p2cb = a / dot( b , d ) ,
 		diff = p2cb - p2ca ,
@@ -123,13 +123,6 @@ float RM_TanPhi(
 	return sqrt( sinPhiSquared / ( 1 - sinPhiSquared ) );
 }
 
-float RM_ErrFunc(
-	in vec3 origin ,
-	in vec3 pos )
-{
-	return 0; // FIXME
-}
-
 vec3 RM_ReduceDiscontinuity(
 	in vec3 origin ,
 	in vec3 rayDir ,