[core] optimize intersect-aabb-frustum?, add docs

geom-core/src/intersect.org

@@ -112,27 +112,32 @@ Also works for rect/circle...
 
 #+BEGIN_SRC clojure
   ;; usage
-  (isec/intersect-aabb-frustum? box-p box-size (vals (mat/frustum-planes view-mat proj-mat)))
+  (isec/intersect-aabb-frustum? box-p box-size (mat/frustum-planes view-mat proj-mat))
 #+END_SRC
 
-http://pastebin.com/PEeDKLET
+https://groups.google.com/forum/#!topic/comp.graphics.algorithms/M6lvyWC6PqU
 
 #+BEGIN_SRC clojure :noweb-ref isec
-  (defn aabb-vertex-for-normal
-    [[x1 y1 z1] [x2 y2 z2] [nx ny nz]]
-    (vec3 (if (>= nx 0.0) x2 x1) (if (>= ny 0.0) y2 y1) (if (>= nz 0.0) z2 z1)))
-
   (defn intersect-aabb-frustum?
-    [p size planes]
-    (let [q (g/+ p size)]
+    "Takes 2 vectors defining an AABB (min-p & size) and a seq of plane
+    parameters (each element [normal w]). The plane normals must be
+    pointing *inwards*. Returns :inside, :intersect or :outside"
+    [[px py pz :as p] size planes]
+    (let [[qx qy qz] (g/+ p size)]
       (reduce
-       (fn [res [n w]]
-         (if (neg? (+ (g/dot n (aabb-vertex-for-normal p q n)) w))
-           (reduced -1)
-           (if (neg? (+ (g/dot n (aabb-vertex-for-normal q p n)) w))
-             0
-             res)))
-       1 planes)))
+       (fn [res [[nx ny nz] w]]
+         (let [vx (if (pos? nx) px qx)
+               vy (if (pos? ny) py qy)
+               vz (if (pos? nz) pz qz)]
+           (if (pos? (mm/madd nx vx ny vy nz vz w))
+             (reduced :outside)
+             (let [vx (if (pos? nx) qx px)
+                   vy (if (pos? ny) qy py) 
+                   vz (if (pos? nz) qz pz)]
+               (if (pos? (mm/madd nx vx ny vy nz vz w))
+                 :intersect
+                 res)))))
+       :inside planes)))
 #+END_SRC
 
 ** Sphere

geom-core/src/matrix.org

@@ -852,6 +852,8 @@ ordering (row major).
 ** Matrix functions
 *** Frustum helpers
 
+https://github.com/stefanmirea/view-frustum-culling/blob/master/lab_camera.hpp#L163
+
 #+BEGIN_SRC clojure :noweb-ref helpers
   (defn frustum
     "Sets up a viewing frustum, shaped like a truncated pyramid with the