Zanir

Why I started with DX

    OpenGL has ponderously using extensions. For example there are more extensions for pixel shader for ATI and NVidia which are not compatible. Another issue is that there are two API and I wanted to know both.

Why DX 8.1 and no DX 9?

I chosed DX8.1 for my programs due to I owned graphics card ATI Radeon 9100, which supported majority features which DX8.1 includes.

Bigger diferences between OpenGL and DX 8.1

• Coordinate system:
  OpenGL uses right-handed (z axis goes out of screen)
  DX uses left-handed (z axis goes into screen)

• texture coordinations:
  OpenGL: y goes upwards and left bottom texture point has coordination 0,0
  DX: y goes below and left bottom texture point has coordination 0,1

Necessary things for compiling DX program

The best is have DX81SDK_FULL.exe (165MB), but it is sufficed to download header files and libraries (2.8MB).
Documentations for DX8.1 is here (9.5MB).