Okay, so I'm trying to draw a tilemap on the screen with SDL, and my fps is really bad cause of it. And I've tried doing it in SFML a different way, but that way makes my ram useage go way up.

the way I'm trying to draw it in SDL is having a SDL_Surface *tilemap; that I chop up, and render like this:


void apply_surface ( int sourceX, int sourceY, int sourceW, int sourceH, int x, int y, SDL_Surface* source, SDL_Surface* destination ){

// make a temporary rectangle to hold the offsets
SDL_Rect offset;
SDL_Rect sourceRect;

// give the offsets to the rectangle
offset.x = x;
offset.y = y;
sourceRect.x = sourceX;
sourceRect.y = sourceY;
sourceRect.h = sourceH;
sourceRect.w = sourceW;

// blit the surface
SDL_BlitSurface( source, &sourceRect, destination, &offset );
}


void render(){
for(int x = 0; x < lv.width; x++){
for(int y = 0; y < lv.height; y++){
if(x * lv.tileSize < 640 && y * lv.tileSize < 480){
int tileXCoord = 0;
int tileYCoord = 0;
int tileSheetWidth = tilemap->w / lv.tileSize;

if (lv.tile[x][y] != 0)
{
tileXCoord = lv.tile[x][y] % tileSheetWidth;
tileYCoord = lv.tile[x][y] / tileSheetWidth;
}

apply_surface(tileXCoord * lv.tileSize, tileYCoord * lv.tileSize, lv.tileSize, lv.tileSize, x * lv.tileSize, y * lv.tileSize, tilemap, screen);
}
}
}
}

This way brings my CPU way up, and drops my FPS.

I tried in SFML to draw the level to a Image, and than display that image (with cropping) but that made my ram go up to 50,000k.

so what I am asking is how can I draw a tilemap (in SDL) without making my cpu or ram go way up?

I don't see anything obviously wrong. The looping looks a little wasteful but unless lv.width and lv.height are hugh it should not make a big difference. An easy mistake to make in SDL is to not call SDL_DisplayFormat (or SDL_DisplayFormatAlpha) to convert the surface to the display format. If the surface is not in the display format it will have to make the conversion every time SDL_BlitSurface is called. When calling SetVideoMode with the bitsperpixel argument different from what the display can also cause big slowdown.

Adding hardware rendering and calling SDL_DisplayFormat(tilemap); made a huge difference! thank you