Ticket #2039: FasterNormalCalc.patch

source/graphics/Terrain.cpp

@@ -146 +146 @@
     CVector3D left, right, up, down;
 
     // Calculate normals of the four half-tile triangles surrounding this vertex:
-
+    
     // get position of vertex where normal is being evaluated
-    CVector3D basepos;
-    CalcPosition(i, j, basepos);
+    ssize_t hi = clamp(i, (ssize_t)0, m_MapSize-1);
+    ssize_t hj = clamp(j, (ssize_t)0, m_MapSize-1);
+    float baseHeight = float(m_Heightmap[hj*m_MapSize + hi]);
 
-    if (i > 0) {
-        CalcPosition(i-1, j, left);
-        left -= basepos;
+    // I have no idea if it's faster to check for != or >
+    if (i != 0) {
+        left.X = -4.0f;
+        left.Y = (float(m_Heightmap[hj*m_MapSize + (hi-1)])-baseHeight)*HEIGHT_SCALE;
+        left.Z = 0.0f;
         left.Normalize();
     }
 
-    if (i < m_MapSize-1) {
-        CalcPosition(i+1, j, right);
-        right -= basepos;
+    if (i != m_MapSize-1) {
+        right.X = 4.0f;
+        right.Y = (float(m_Heightmap[hj*m_MapSize + (hi+1)])-baseHeight)*HEIGHT_SCALE;
+        right.Z = 0.0f;
         right.Normalize();
     }
 
-    if (j > 0) {
-        CalcPosition(i, j-1, up);
-        up -= basepos;
+    if (j != 0) {
+        up.X = 0.0f;
+        up.Y = (float(m_Heightmap[(hj-1)*m_MapSize + hi])-baseHeight)*HEIGHT_SCALE;
+        up.Z = -4.0f;
         up.Normalize();
     }
 
-    if (j < m_MapSize-1) {
-        CalcPosition(i, j+1, down);
-        down -= basepos;
+    if (j != m_MapSize-1) {
+        down.X = 0.0f;
+        down.Y = (float(m_Heightmap[(hj+1)*m_MapSize + hi])-baseHeight)*HEIGHT_SCALE;
+        down.Z = 4.0f;
         down.Normalize();
     }
 
@@ -195 +201 @@
     // Calculate normals of the four half-tile triangles surrounding this vertex:
 
     // get position of vertex where normal is being evaluated
-    CFixedVector3D basepos;
-    CalcPositionFixed(i, j, basepos);
-
-    if (i > 0) {
-        CalcPositionFixed(i-1, j, left);
-        left -= basepos;
+    ssize_t hi = clamp(i, (ssize_t)0, m_MapSize-1);
+    ssize_t hj = clamp(j, (ssize_t)0, m_MapSize-1);
+    // fixed max value is 32767, but height is a u16, so divide by two to avoid overflow
+    int baseHeight = (m_Heightmap[hj*m_MapSize + hi]/ 2 );
+    
+    if (i != 0) {
+        left.X = fixed::FromInt(-4);
+        left.Y = fixed::FromInt((m_Heightmap[hj*m_MapSize + hi-1]/2 - baseHeight) / ((int)HEIGHT_UNITS_PER_METRE / 2));
+        left.Z = fixed::Zero();
         left.Normalize();
     }
 
-    if (i < m_MapSize-1) {
-        CalcPositionFixed(i+1, j, right);
-        right -= basepos;
+    if (i != m_MapSize-1) {
+        right.X = fixed::FromInt(4);
+        right.Y = fixed::FromInt((m_Heightmap[hj*m_MapSize + hi+1]/2 - baseHeight) / ((int)HEIGHT_UNITS_PER_METRE / 2));
+        right.Z = fixed::Zero();
         right.Normalize();
     }
 
-    if (j > 0) {
-        CalcPositionFixed(i, j-1, up);
-        up -= basepos;
+    if (j != 0) {
+        right.X = fixed::Zero();
+        right.Y = fixed::FromInt((m_Heightmap[(hj-1)*m_MapSize + hi]/2 - baseHeight) / ((int)HEIGHT_UNITS_PER_METRE / 2));
+        right.Z = fixed::FromInt(-4);
         up.Normalize();
     }
 
-    if (j < m_MapSize-1) {
-        CalcPositionFixed(i, j+1, down);
-        down -= basepos;
+    if (j != m_MapSize-1) {
+        right.X = fixed::Zero();
+        right.Y = fixed::FromInt((m_Heightmap[(hj+1)*m_MapSize + hi]/2 - baseHeight) / ((int)HEIGHT_UNITS_PER_METRE / 2));
+        right.Z = fixed::FromInt(4);
         down.Normalize();
     }