More tweaking + UI for the correction stuff

shaders/chunks/raymarcher.glsl

@@ -8,6 +8,7 @@ layout( location = 4 ) uniform vec3 u_CamUp;
 layout( location = 5 ) uniform float u_NearPlane;
 layout( location = 6 ) uniform vec4 u_Render;
 layout( location = 7 ) uniform float u_FogAttenuation;
+layout( location = 8 ) uniform int u_Correction;
 
 layout( location = 0 ) out vec3 o_Color;
 layout( location = 1 ) out float o_Z;