Divide direction by w-component

Fixes #616

data/shaders/nv_ray_tracing_basic/raygen.rgen

@@ -19,7 +19,7 @@ void main()
 
 	vec4 origin = cam.viewInverse * vec4(0,0,0,1);
 	vec4 target = cam.projInverse * vec4(d.x, d.y, 1, 1) ;
-	vec4 direction = cam.viewInverse*vec4(normalize(target.xyz), 0) ;
+	vec4 direction = cam.viewInverse*vec4(normalize(target.xyz / target.w), 0) ;
 
 	uint rayFlags = gl_RayFlagsOpaqueNV;
 	uint cullMask = 0xff;