From 2c44bd12019eea0b22f2725a1e17e9ebae3b7c24 Mon Sep 17 00:00:00 2001
From: hiker <henrichsjoerg@gmail.com>
Date: Tue, 14 Apr 2015 16:21:43 +1000
Subject: [PATCH] Removed unnecessary copy, precompue area of triangle to
 reduce work when smoothing normals.

---
 src/physics/btKart.cpp        |  2 +-
 src/physics/triangle_mesh.cpp | 21 ++++++++++++---------
 src/physics/triangle_mesh.hpp | 30 ++++++++++++++++++++----------
 3 files changed, 33 insertions(+), 20 deletions(-)

diff --git a/src/physics/btKart.cpp b/src/physics/btKart.cpp
index dc1904740..c21737e0c 100644
--- a/src/physics/btKart.cpp
+++ b/src/physics/btKart.cpp
@@ -999,7 +999,7 @@ void btKart::debugDraw(btIDebugDraw* debugDrawer)
         // Draw the (interpolated) normal of the ground at the wheel position
         debugDrawer->drawLine(getWheelInfo(v).m_raycastInfo.m_contactPointWS,
                               getWheelInfo(v).m_raycastInfo.m_contactPointWS+getWheelInfo(v).m_raycastInfo.m_contactNormalWS,
-            btVector3(0, 0, 1));
+            btVector3(0.5f, 0.5f, 0.5f));
 
     }   // for i < getNumWheels
     btVector3 yellow(1.0f, 1.0f, 0.0f);
diff --git a/src/physics/triangle_mesh.cpp b/src/physics/triangle_mesh.cpp
index ca28aa623..d0d0f4617 100644
--- a/src/physics/triangle_mesh.cpp
+++ b/src/physics/triangle_mesh.cpp
@@ -77,6 +77,11 @@ void TriangleMesh::addTriangle(const btVector3 &t1, const btVector3 &t2,
     m_normals.push_back( normal.angle(n3)>stk_config->m_smooth_angle_limit
                          ? normal : n3                                     );
     m_mesh.addTriangle(t1, t2, t3);
+
+    // Area of triangle ABC
+    btVector3 edge1 = t2 - t1;
+    btVector3 edge2 = t3 - t1;
+    m_p1p2p3.push_back(edge1.cross(edge2).length2());
 }   // addTriangle
 
 // -----------------------------------------------------------------------------
@@ -228,24 +233,22 @@ void TriangleMesh::removeAll()
 btVector3 TriangleMesh::getInterpolatedNormal(unsigned int index,
                                               const btVector3 &position) const
 {
-    btVector3 p1, p2, p3;
+    btVector3 *p1, *p2, *p3;
     getTriangle(index, &p1, &p2, &p3);
-    btVector3 n1, n2, n3;
+    const btVector3 *n1, *n2, *n3;
     getNormals(index, &n1, &n2, &n3);
 
     // Compute the Barycentric coordinates of position inside  triangle
     // p1, p2, p3.
-    btVector3 edge1 = p2 - p1;
-    btVector3 edge2 = p3 - p1;
 
-    // Area of triangle ABC
-    btScalar p1p2p3 = edge1.cross(edge2).length2();
+    btScalar p1p2p3 = getP1P2P3(index);
 
     // Area of BCP
-    btScalar p2p3p = (p3 - p2).cross(position - p2).length2();
+    btScalar p2p3p = (*p3 - *p2).cross(position - *p2).length2();
 
     // Area of CAP
-    btScalar p3p1p = edge2.cross(position - p3).length2();
+    btVector3 edge2 = *p3 - *p1;
+    btScalar p3p1p = edge2.cross(position - *p3).length2();
     btScalar s = btSqrt(p2p3p / p1p2p3);
     btScalar t = btSqrt(p3p1p / p1p2p3);
     btScalar w = 1.0f - s - t;
@@ -266,7 +269,7 @@ btVector3 TriangleMesh::getInterpolatedNormal(unsigned int index,
     }
 #endif
 
-    return s*n1 + t*n2 + w*n3;
+    return s*(*n1) + t*(*n2) + w*(*n3);
 }   // getInterpolatedNormal
 
 // ----------------------------------------------------------------------------
diff --git a/src/physics/triangle_mesh.hpp b/src/physics/triangle_mesh.hpp
index 5557ed4a7..bd297755c 100644
--- a/src/physics/triangle_mesh.hpp
+++ b/src/physics/triangle_mesh.hpp
@@ -47,6 +47,8 @@ private:
     btCollisionShape            *m_collision_shape;
     /** The three normals for each triangle. */
     AlignedArray<btVector3>      m_normals;
+    /** Pre-compute value used in smoothing. */
+    AlignedArray<float>          m_p1p2p3;
 public:
          TriangleMesh();
         ~TriangleMesh();
@@ -92,28 +94,36 @@ public:
     /** Returns the points of the 'indx' triangle.
      *  \param indx Index of the triangle to get.
      *  \param p1,p2,p3 On return the three points of the triangle. */
-    void getTriangle(unsigned int indx, btVector3 *p1, btVector3 *p2,
-                     btVector3 *p3) const
+    void getTriangle(unsigned int indx, btVector3 **p1, btVector3 **p2,
+                     btVector3 **p3) const
     {
         const IndexedMeshArray &m = m_mesh.getIndexedMeshArray();
         btVector3 *p = &(((btVector3*)(m[0].m_vertexBase))[3*indx]);
-        *p1 = p[0];
-        *p2 = p[1];
-        *p3 = p[2];
+        *p1 = &(p[0]);
+        *p2 = &(p[1]);
+        *p3 = &(p[2]);
     }   // getTriangle
     // ------------------------------------------------------------------------
     /** Returns the normals of the triangle with the given index.
      *  \param indx Index of the triangle to get the three normals of.
      *  \result n1,n2,n3 The three normals. */
-    void getNormals(unsigned int indx, btVector3 *n1, btVector3 *n2,
-                    btVector3 *n3) const
+    void getNormals(unsigned int indx, const btVector3 **n1, 
+                    const btVector3 **n2, const btVector3 **n3) const
     {
         assert(indx < m_triangleIndex2Material.size());
         unsigned int n = indx*3;
-        *n1 = m_normals[n  ];
-        *n2 = m_normals[n+1];
-        *n3 = m_normals[n+2];
+        *n1 = &(m_normals[n  ]);
+        *n2 = &(m_normals[n+1]);
+        *n3 = &(m_normals[n+2]);
     }   // getNormals
+    // ------------------------------------------------------------------------
+    /** Returns basically the area of the triangle, which is needed when
+     *  smoothing the normals. */
+    float getP1P2P3(unsigned int indx) const
+    {
+        assert(indx < m_p1p2p3.size());
+        return m_p1p2p3[indx];
+    }
 };
 #endif
 /* EOF */