rearranged the failure handling code

git-svn-id: svn://anubis/fart/trunk@241 7f9b0f55-74a9-4bce-be96-3c2cd072584d

main/fart.cc

@@ -195,13 +195,12 @@ int main(int argc, char * argv[])
     else
     {
         /* "sequential" version */
-        unsigned char * pixel = &data[0];
         for (int i = 0; i < height; i++)
         {
             for (int j = 0; j < width; j++)
             {
-                scene.renderPixel(j, i, pixel);
-                pixel += 3;
+                int pixel = i * width + j;
+                scene.renderPixel(j, i, &data[3 * pixel]);
             }
         }
     }