From 252bc3b3eee61ee52b099694234b1cae1b096b76 Mon Sep 17 00:00:00 2001
From: ZappoMan <bradh@konamoxt.com>
Date: Wed, 19 Mar 2014 11:51:47 -0700
Subject: [PATCH] optimized ViewFrustum::getFurthestPointFromCamera()

---
 libraries/octree/src/OctreeElement.cpp |  7 ++++---
 libraries/octree/src/ViewFrustum.cpp   | 25 +++++++++----------------
 libraries/octree/src/ViewFrustum.h     |  5 +++--
 3 files changed, 16 insertions(+), 21 deletions(-)

diff --git a/libraries/octree/src/OctreeElement.cpp b/libraries/octree/src/OctreeElement.cpp
index 72ac5b14d6..3f31ad928a 100644
--- a/libraries/octree/src/OctreeElement.cpp
+++ b/libraries/octree/src/OctreeElement.cpp
@@ -1222,10 +1222,11 @@ bool OctreeElement::calculateShouldRender(const ViewFrustum* viewFrustum, float
 float OctreeElement::furthestDistanceToCamera(const ViewFrustum& viewFrustum) const {
     AABox box = getAABox();
     box.scale(TREE_SCALE);
-    glm::vec3 furthestPoint = viewFrustum.getFurthestPointFromCamera(box);
+    glm::vec3 furthestPoint;
+    viewFrustum.getFurthestPointFromCamera(box, furthestPoint);
     glm::vec3 temp = viewFrustum.getPosition() - furthestPoint;
-    float distanceToVoxelCenter = sqrtf(glm::dot(temp, temp));
-    return distanceToVoxelCenter;
+    float distanceToFurthestPoint = sqrtf(glm::dot(temp, temp));
+    return distanceToFurthestPoint;
 }
 
 float OctreeElement::distanceToCamera(const ViewFrustum& viewFrustum) const {
diff --git a/libraries/octree/src/ViewFrustum.cpp b/libraries/octree/src/ViewFrustum.cpp
index 66f1445ddc..00caafa095 100644
--- a/libraries/octree/src/ViewFrustum.cpp
+++ b/libraries/octree/src/ViewFrustum.cpp
@@ -695,39 +695,32 @@ OctreeProjectedPolygon ViewFrustum::getProjectedPolygon(const AABox& box) const
     return projectedPolygon;
 }
 
-
 // Similar strategy to getProjectedPolygon() we use the knowledge of camera position relative to the
 // axis-aligned voxels to determine which of the voxels vertices must be the furthest. No need for
 // squares and square-roots. Just compares.
-glm::vec3 ViewFrustum::getFurthestPointFromCamera(const AABox& box) const {
+void ViewFrustum::getFurthestPointFromCamera(const AABox& box, glm::vec3& furthestPoint) const {
     const glm::vec3& bottomNearRight = box.getCorner();
-    glm::vec3 center = box.calcCenter();
-    glm::vec3 topFarLeft = box.calcTopFarLeft();
+    float scale = box.getScale();
+    float halfScale = scale * 0.5f;
 
-    glm::vec3 furthestPoint;
-    if (_position.x < center.x) {
+    if (_position.x < bottomNearRight.x + halfScale) {
         // we are to the right of the center, so the left edge is furthest
-        furthestPoint.x = topFarLeft.x;
+        furthestPoint.x = bottomNearRight.x + scale;
     } else {
-        // we are to the left of the center, so the right edge is furthest (at center ok too)
         furthestPoint.x = bottomNearRight.x;
     }
 
-    if (_position.y < center.y) {
+    if (_position.y < bottomNearRight.y + halfScale) {
         // we are below of the center, so the top edge is furthest
-        furthestPoint.y = topFarLeft.y;
+        furthestPoint.y = bottomNearRight.y + scale;
     } else {
-        // we are above the center, so the lower edge is furthest (at center ok too)
         furthestPoint.y = bottomNearRight.y;
     }
 
-    if (_position.z < center.z) {
+    if (_position.z < bottomNearRight.z + halfScale) {
         // we are to the near side of the center, so the far side edge is furthest
-        furthestPoint.z = topFarLeft.z;
+        furthestPoint.z = bottomNearRight.z + scale;
     } else {
-        // we are to the far side of the center, so the near side edge is furthest (at center ok too)
         furthestPoint.z = bottomNearRight.z;
     }
-
-    return furthestPoint;
 }
diff --git a/libraries/octree/src/ViewFrustum.h b/libraries/octree/src/ViewFrustum.h
index da4a6997f1..f841566652 100644
--- a/libraries/octree/src/ViewFrustum.h
+++ b/libraries/octree/src/ViewFrustum.h
@@ -102,8 +102,9 @@ public:
 
     glm::vec2 projectPoint(glm::vec3 point, bool& pointInView) const;
     OctreeProjectedPolygon getProjectedPolygon(const AABox& box) const;
-    glm::vec3 getFurthestPointFromCamera(const AABox& box) const;
-
+    //glm::vec3 getFurthestPointFromCamera(const AABox& box) const;
+    void getFurthestPointFromCamera(const AABox& box, glm::vec3& furthestPoint) const;
+    
 private:
     // Used for keyhole calculations
     ViewFrustum::location pointInKeyhole(const glm::vec3& point) const;