OpenGL

I am attempting to integrate OpenGL into the code, so that the game uses hardware graphics acceleration. Hopefully, this will improve some of the framerate issues.

Below, I have documented the process I went through to enable OpenGL, including all of the issues I came across.

Get code to compile with a single line of OpenGL

I can compile a program using #include "SDL_opengl.h", but I am getting errors about missing functions when an OpenGL method is called.

I installed the OpenGL libraries in cygwin, so I'm not sure if those were necessary:

Installing these files may help

http://www.libsdl.org/extras/win32/cygwin/

Found out that I was using the wrong parameters to compile. I should have been using this:

gcc test.c `sdl-config --libs --cflags` -lglut32 -lglu32 -lopengl32

Display a bitmap to the screen

I got a simple square to display in OpenGL:

Added Tux:

Tux on an image background:

One of the vertices was off, which made the background skewed.

Moving Block

Next Step is to get the player block moving

Pseudo Code:

 INTEGER playerX
 INTEGER playerY
 INTEGER playerVelocityX
 INTEGER playerVelocityY
 
 Setup_SDL
 Setup_OpenGL
 Load_Bitmaps
 
 GameLoop {
 
   While (User hasn't Quit) {
     IF (User presses up) THEN
       playerVelocityY = - PLAYER_SPEED
 
     IF (User presses down) THEN
       playerVelocityY = PLAYER_SPEED
 
     IF (User presses left) THEN
       playerVelocityX = - PLAYER_SPEED
 
     IF (User presses right) THEN
       playerVelocityX =  PLAYER_SPEED
 
     playerX = playerX + playerVelocityX
     playerY = playerY + playerVelocityY
 
     Render_Screen
   }
 }

Change BMP to PNG

Next step is to replace the BMP with a PNG

Some "gotchas"

• Add "IMG_Init(IMG_INIT_PNG);" to the program's startup code
• Replace "SDL_LoadBMP" with "IMG_Load"
• Add -lSDL_image on the compile line (Makefile or go script)
• Add required DLLs to the working directory (libpng12-0.dll, zlib1.dll, SDL_image.dll, etc)
• If the PNG will not display, try passing a BMP to IMG_Load to see if it works

Got SDL and OpenGL to accept the PNG image with transparency, but there are display issues:

PNG with transparency disabled, and background color saved. Basic image is correct, but some discoloration.