Reversed Y-coordinate, to reflect usual orientation of images

panda/src/grutil/heightfieldTesselator.cxx

@@ -88,14 +88,14 @@ get_vertex(int x, int y) {
   if (px >= _heightfield.get_x_size()) px--;
   if (py >= _heightfield.get_y_size()) py--;
   double drx = _heightfield.get_gray(px,y) - _heightfield.get_gray(nx,y);
-  double dry = _heightfield.get_gray(x,py) - _heightfield.get_gray(x,ny);
+  double dry = _heightfield.get_gray(x,ny) - _heightfield.get_gray(x,py);
   LVector3f normal(drx * _vertical_scale * 0.5, dry * _vertical_scale * 0.5, _horizontal_scale);
   normal.normalize();
   double z = _heightfield.get_gray(x,y);
   if (z > 2.0) {
     cerr << "What the heck?";
   }
-  _vertex_writer->add_data3f(x*_horizontal_scale,y*_horizontal_scale,z*_vertical_scale);
+  _vertex_writer->add_data3f(x*_horizontal_scale,-y*_horizontal_scale,z*_vertical_scale);
   _normal_writer->add_data3f(normal);
   vtx = _next_index++;
   _dirty_vertices[vtx] = x+y*xsize;