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Textures and Transparencies

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Okay that would work. Actually I have done that before.

But my texture is applied to a primitive (cube) and I''m using DX8 for rendering. So locking the backbuffer and redering the cube myself would would take forever. So is there a way to get directX to do it for me. I''m assuming I''m going to have to trun alpha blending on and then set the source and dest blend states to something. I''m just no sure what. The SDK is really abstract when it expains what all the differint blend states do and how to use them. And I can''t find any tutorials that tell you how to do it without using an alpha channel. So is it even possible. I really don''t want to write my own software rasterizer just to have transparencies!


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Original post by Abstraction
If my video card doesn''t support textures with an alpha channel then how do I render textures where black is transparent.


Just out of curiosity, what video card are you using that doesn''t support textures with an alpha channel? I''m not aware of any 3D cards that don''t support at least a 1-bit alpha.

Stay Casual,

Drunken Hyena

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I too am surprised that someone is still using a card which doesn''t support alpha.

The Matrox Mystique was about the last card I can think of which didn''t support alpha. The Matrox Millenium didn''t, but then again that didn''t support texturing either!

If you''re using a card from that era (1996ish), then it won''t work with the newer DirectX interfaces. Using the old interfaces (<=DX7) there is a render state for "Stippled Alpha", this simulates alpha with a stipple pattern.

An alternative with the old interfaces is colour keying. You shouldn''t use it with newer cards, but with the older ones it may be worth it.

Just noticed that you mentioned you''re using DX8. *EVERY* graphics card I know of which works under DX8 supports alpha channels. In fact most older ones do too. (I''ve developed commercial 3D games which have been through extensive hardware compatibility testing and the above Matrox cards were the only ones where translucency setup failed).

Simon O''''Connor
Creative Asylum Ltd

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