How to make transparency in images

Graphics and GPU Programming Programming

Started by Sundarlsr January 23, 2009 05:00 AM

4 comments, last by riruilo 15 years, 2 months ago

122

Author

January 23, 2009 05:00 AM

hai friend, i have a doubt, to make transparency in images..please give me idea to make two images transparent with one another. sundar..

O-san

1,900

January 23, 2009 06:02 AM

Use blending, glEnable(GL_BLEND). If you want your image to have the same transparency all over you only need to draw the image with glColorf4(1,1,1,0.5). If you want varying transparency your image needs an alpha channel. PNG and TGA image formats supports alpha channel. You also need to set the blend function, glBlendFunc(GL_SRC_ALPHA,GL_ONE_MINUS_SRC_ALPHA) is a good blend mode to start with.

Reference:
glBlendFunc C Specification

[Edited by - O-san on January 23, 2009 6:02:22 AM]

riruilo

218

January 23, 2009 12:58 PM

Quote:Original post by O-san
Use blending, glEnable(GL_BLEND). If you want your image to have the same transparency all over you only need to draw the image with glColorf4(1,1,1,0.5). If you want varying transparency your image needs an alpha channel. PNG and TGA image formats supports alpha channel. You also need to set the blend function, glBlendFunc(GL_SRC_ALPHA,GL_ONE_MINUS_SRC_ALPHA) is a good blend mode to start with.

Reference:
glBlendFunc C Specification

@O-san: What about if I want these two different transparencies together? Using fixed pipeline.

Thanks.

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Cornstalks

7,033

January 23, 2009 01:03 PM

Have you tried this NeHe lesson? And if that doesn't answer your question, could you please explain your question in greater detail?

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riruilo

218

January 23, 2009 01:54 PM

Quote:Original post by MikeTacular
Have you tried this NeHe lesson? And if that doesn't answer your question, could you please explain your question in greater detail?

Of course, actually I ask something similar yesterday:

http://www.gamedev.net/community/forums/topic.asp?topic_id=521985

But I still don't know how to dot it.

Any suggestion?

Thanks a lot.

riruilo

218

January 23, 2009 02:44 PM

Quote:Original post by MikeTacular
Have you tried this NeHe lesson? And if that doesn't answer your question, could you please explain your question in greater detail?

Thanks, I got it reading NeHe. Thanks a lot.

How to make transparency in images

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