Ticket #3588: optimize-rasterize.patch

source/simulation2/helpers/Rasterize.cpp

@@ -65 +65 @@
         // Find the min/max range of cells that are strictly inside the square+rasterClearance.
         // (Since the square+rasterClearance is a convex shape, we can just test each
         // corner of each cell is inside the shape.)
-        // (TODO: This potentially does a lot of redundant work.)
+        // When looping on i, if the previous cell was inside, no need to check again the left corners.
+        // and we can stop the loop when exiting the shape.
+        // Futhermore if one of the right corners of a cell is outside, no need to check the following cell
         i16 spanI0 = std::numeric_limits<i16>::max();
         i16 spanI1 = std::numeric_limits<i16>::min();
+        bool previousInside = false;
+        bool skipNextCell = false;
         for (i16 i = i0; i < i1; ++i)
         {
-            if (Geometry::DistanceToSquareSquared(CFixedVector2D(cellSize*i-shape.x, cellSize*j-shape.z),
-                                                  shape.u, shape.v, shapeHalfSize, true) > rasterClearance)
+            if (skipNextCell)
+            {
+                skipNextCell = false;
                 continue;
+            }
 
             if (Geometry::DistanceToSquareSquared(CFixedVector2D(cellSize*(i+1)-shape.x, cellSize*j-shape.z),
-                                                  shape.u, shape.v, shapeHalfSize, true) > rasterClearance)
+                                    shape.u, shape.v, shapeHalfSize, true) > rasterClearance)
+            {
+                if (previousInside)
+                    break;
+                skipNextCell = true;
                 continue;
+            }
 
-            if (Geometry::DistanceToSquareSquared(CFixedVector2D(cellSize*i-shape.x, cellSize*(j+1)-shape.z),
-                                                  shape.u, shape.v, shapeHalfSize, true) > rasterClearance)
-                continue;
-
             if (Geometry::DistanceToSquareSquared(CFixedVector2D(cellSize*(i+1)-shape.x, cellSize*(j+1)-shape.z),
-                                                  shape.u, shape.v, shapeHalfSize, true) > rasterClearance)
+                                    shape.u, shape.v, shapeHalfSize, true) > rasterClearance)
+            {
+                if (previousInside)
+                    break;
+                skipNextCell = true;
                 continue;
+            }
 
-            spanI0 = std::min(spanI0, i);
-            spanI1 = std::max(spanI1, (i16)(i+1));
+            if (!previousInside)
+            {
+                if (Geometry::DistanceToSquareSquared(CFixedVector2D(cellSize*i-shape.x, cellSize*j-shape.z),
+                                    shape.u, shape.v, shapeHalfSize, true) > rasterClearance)
+                    continue;
+
+                if (Geometry::DistanceToSquareSquared(CFixedVector2D(cellSize*i-shape.x, cellSize*(j+1)-shape.z),
+                                    shape.u, shape.v, shapeHalfSize, true) > rasterClearance)
+                    continue;
+
+                previousInside = true;
+                spanI0 = i;
+            }
+
+            spanI1 = i+1;
         }
 
         // Add non-empty spans onto the list