Contents  Introduction  Basic Blending  Get it Working  Tried them all!  Who needs MMX?  Who needs  MMX? (cont)  MMX Version  Conclusion  Printable version

CONCLUSION:

The MMX version is more than 3 times as fast as the basic alpha blending routine and can alpha blend a 640x480 16bpp screen in about 16 milliseconds. I hope I was clear enough for you to be able to follow my theories. If you have questions about anything e-mail me and I will do my best to answer them. Also, if you see additional improvement please drop me a line, I am always interested in improving this code. Although I feel some of the ideas I have outlined here are original they would not have been possible without all the excellent information I mined from the web. Therefore, thy taketh from the web thy shall giveth back to the web. All that is contained in this document is public domain. All I ask is that the document be maintained as a whole.

SOURCE CODE:

A zip file named "ht_alpha.zip" contains all the source code and a sample application to demonstrate what I have talked about in this article. The zip file should contain a VC++ project and these main files:

Ht_alpha.doc	This article in Word '97 format.
Ht_ddutil.cpp	Modified ddutil.cpp from the DX SDK
Ht_Ddutil.h	Modified ddutil.h from the DX SDK
Ht_logo.bmp	HoundstootH logo bitmap
Ht_bkgrnd.bmp	Background bitmap
Ht_alpha.cpp	Contains all the alpha blending code

There are also debug and release versions of the executable. To run the app you need to move one of these exe's into the directory where the bmp files are located (or visa versa). The sample application uses the function keys 1-7 and the ESC key.

F1 - Use DX BltFast to render image (no alpha blending) F2 - Use the 50/50 function to alpha blend the image F3 - Use the basic alpha blending function to render image F4 - Use the improved alpha blending function to render the image F5 - Use the MMX alpha blending function to render the image F6 - Render in transparent mode F7 - Render in block mode (no transparency) ESC - Exit the application

By: John Hebert
Email: hebertjo@w-link.net


You can also contact me through the CDX mailing list. CDX is an open source DirectX wrapper that has many great features, one of which is alpha blending contributed by myself. CDX can be found at: http://www.cdx.sk/