I am a little confused about costMap and globalPlanner

edit

Hi,

for (unsigned int i = 0; i < size_y; ++i)  
            {    
               for (unsigned int j = 0; j < size_x; ++j)

                {

                unsigned char value = new_map->data[index];
                costmap_[index] = interpretValue(value);
                  ++index;

                }
            }

the above is from ros navigation package , /navigation/costmap_2d/plugins/static_layer.cpp 198~206 it update the map according to laserScan.But I am confused why it update costmap from 0 to xy not from x to xy

costmap use the Index(x*nx+y) to represent the two dimensional coordinate,doesn't it?

I have this confusion becuase I see that in globalPlanner,the dijkstra.cpp use index() to getCost,and then it calculatePotentials

dijkstra.cpp 95~116

int k = toIndex(start_x, start_y);
if(precise_)
{
    double dx = start_x - (int)start_x, dy = start_y - (int)start_y;
    dx = floorf(dx * 100 + 0.5) / 100;
    dy = floorf(dy * 100 + 0.5) / 100;
    potential[k] = neutral_cost_ * 2 * dx * dy;
    potential[k+1] = neutral_cost_ * 2 * (1-dx)*dy;
    potential[k+nx_] = neutral_cost_*2*dx*(1-dy);
    potential[k+nx_+1] = neutral_cost_*2*(1-dx)*(1-dy);//*/

    push_cur(k+2);
    push_cur(k-1);
    push_cur(k+nx_-1);
    push_cur(k+nx_+2);

    push_cur(k-nx_);
    push_cur(k-nx_+1);
    push_cur(k+nx_*2);
    push_cur(k+nx_*2+1);
}

when it push_cur,it calls the function getCost() in dijkstra.h.But I find that float c = costs[n] in Function getCost() n represents index(x*nx+y)

So,why we use x and y when we put value into char* costmap,But we use index() get value from costmap. where is the value from costmap[0] to costmap [nx],nx means the x size of map.

help me , Did I make a mistake

I wanna know costmap use x and y or index to represent the values in map

thx~ PS:why MarkDown Grammar ``` can't be used in this