[xmoto-dev] polygon gap pb fixed

[Nicolas Adenis-Lamarre <nadenislamarre@xxxxxxx>]

Hi,

i think i fixed the gap problem
(
* [14:04] <keesj> I think it is a well knwn problem that every developer 
gets when spliting area's in two
[14:05] <keesj> it's a pixel rounding problem
[14:07] <keesj> http://www.gameprogrammer.com/5-poly.html
[14:07] <keesj> If pixels that fall on an edge are counted as part of 
the polygon then pixels on an edge between two polygons will be filled 
in by both polygons. Filling the pixel twice is wasteful. And, in an 
animation it can cause a "twinkling" effect along the edge. If edge 
pixels are not part of the polygon then edges never get colored and you 
get gaps between polygons. Really ugly.
)

I applied an algo than rasmus sent me today (make polygon slighly larger 
on rendering)
0.003 seems to be a good value. To much will make pixels appear over the 
grass.

Nicolas

   /* fix the gap problem with polygons */
   float a = 0.003; /* seems to be a good value, put negativ value to 
make it worst */
   for(int k=0; k<pPoly->nNumVertices; k++) {
     Vector2f V = Vector2f(pPoly->pVertices[k].x - v_center.x,
               pPoly->pVertices[k].y - v_center.y);
     if(V.length() != 0.0) {
       V.normalize();
       V *= a;
       pPoly->pVertices[k].x += V.x;
       pPoly->pVertices[k].y += V.y;
     }
   }