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A question about DWORDs and WORDs...

Joel Bennett · 2001-08-23T01:35:28

I have a question to do with using DWORDs for color values in DirectX 8 (but its more of a general question, so thats why I''m posting it here). When DirectX uses a DWORD for a color value, its something like 0x00ffffff where the first 2 zeros are alpha values, the next 2 fs are the red color, the next 2 fs are the green color, and the last 2 are the blue color. Now lets say I want to do some blending by using the difuse color with alpha blending enabled. How would I specifically change just the alpha value by using something like an int? I don''t want to have to wrtie out 30 different alpha values and have a giant switch statement to sort it out. Could I specify and integer that would be below 225 and then bitshift it by 6, like so? int alphavalue = 50; DWORD color = 0x00ffffff; //turn on alpha blending and set the alphavalue to whatever it should be, as long //as its under 255 //now modify the color color += alphavalue<6; Would something like that work?

General and Gameplay Programming Programming

Started by Moe August 17, 2001 11:44 AM

10 comments, last by Moe 23 years, 6 months ago

jaxson

127

August 23, 2001 12:32 AM

You can even save yourself the trouble of figuring out the bitshifts on your own by using some handy macros that are supplied by DirectX 8.

D3DCOLOR_XRGB(r, g, b) will give you a DWORD with the correct red, green, and blue values and opaque alpha (0xff).

D3DCOLOR_ARGB(alpha, r, g, b) will do basically the same thing, but also set the alpha value that you specify. These macros can save you a lot of excess typing as well as compacting down all that color stuff to just one little line