I'm using HGE to render a one-dimensional array of tiles. Each tile in this array stores vertex, color and texture information, which is pre-calculated (only once, before the first render cycle) and does NOT change. Instead, I have implemented a virtual camera system, storing an X/Y pixel offset + view width/height information, allowing a tilemap to be rendered at any given offset without actually changing the vertices of any tiles. This means that tilemaps are always located at 0,0 world-space coordinates, but the user is allowed to scroll through the map using the camera system.

I had this system working rather nicely for a while, until it was time to apply a few optimizations... One of which included calculating which tiles are within range of the camera view, and only rendering these tiles. This optimization nearly doubled my rendering speeds, but I realized the downfall is that I am still looping through each & every tile in the array. For smaler maps, this wasn't a big deal. But for larger maps, the performance hit is almost unbearable... And this is only for a single layer of tiles!

So, given the following variables:

• One-dimensional Tile Array (stores vertex info)
• Camera X Offset (pixel, world-space)
• Camera Y Offset (pixel, world-space)
• Camera View Width (pixel, screen-space)
• Camera View Height (pixel, screen-space)
• Tilemap Size (logical # of columns & rows)
• Tile Dimensions (logical width & height, in pixels)

How could I create a loop which ONLY iterates through tiles within range of the camera's current view?

Thanks! With a couple of minor tweaks, I was able to get this algorithm to work:

void Render(HGE* hge, float cameraX, float cameraY, float cameraWidth, float cameraHeight) {
	int firstcolumn = int( floor(cameraX / m_tileWidth) );
	int firstrow = int( floor(cameraY / m_tileHeight) );
	int lastcolumn = int( ceil((cameraX + cameraWidth) / m_tileWidth) );
	int lastrow = int( ceil((cameraY + cameraHeight) / m_tileHeight) );

	for(int r = firstrow; r < lastrow; r++)
	{
		for(int c = firstcolumn; c < lastcolumn; c++)
		{
			hge->Gfx_RenderQuad(&m_tiles[r * m_nColumns + c].quad);
		}
	}
}