rogue-like rendering

Newbie & Debugging Questions
#1

Hello,

I want to write a rogue-like game and decided not to use any of the curses libraries and use ogl instead. Right now I want to represent a standart sized console window with 80x25 characters. This is how I draw the tiles at the moment:

  1. I use vertex arrays with 2 triangles for every tile I want to draw as background.
  2. Then I draw the same geometry again with textures and alphablending on and other colors(foreground color)

With that I can draw every letter with any background/foreground color combination. The letters are stored in the texture. This method is not very fast so I wanted to ask you what kind of improvement you would suggest. Vertex sharing was my first idea, but that would mean that every vertex has only one colorattribute and therefore the colors would mix over tile boundaries, which is bad…

Thanks
thala

#2

That’s 4000 triangles and 12000 vertices. Should be fast enough. What’s your system’s spec? Have you profiled the bottleneck? Maybe it’s the way you are filling the vertex array.

#3

It’s 4000 triangles for the background and 4000 triangles for the foreground!

I tried the netbeans profiler and found out that I spent almost 40 % of the time in the rendering method in “self time”. I guessed that this high number reflects the large amount of array operations I did for filling up the vertex arrays. So I implemented a update method that only changes the parts of the vertex array that actually need an update. That doubled the framerate instantly, but at the moment there is only one tile that needs an update so the framerate will drop again the more tiles change on the map(for a visibility algorithm for example).

Thx cylab you were right!
Do you got more tips on performance?

#4

Don’t do infinite loops.

Anyway, you can see a major speedup when using interleaved vertex-arrays, with optimal type-ordering (VCT).
If there are large parts of the geometry static over time, switch to VBOs, for another incredible speedup.
If you change the whole VBO every frame, it will be exactly as fast as a VA. So switch to VBOs anyway.