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Old 09-13-08, 06:59 PM   #1
EvilGuru
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Default glBlendColor Broken?

Hi,

I am running a GeForce 7950 GX2 (non-SLI) under X.org server 1.5 using the nvidia-drivers-173.14.12. However, I have also had it confirmed under Linux with an 8400GS (unknown driver version and X server).

The problem is that the following code does not function as expected:
Code:
float blendColour[4];

[...OpenGL init, GLUT or SDL]

glEnable(GL_BLEND);
glBlendFunc(GL_CONSTANT_ALPHA, GL_ONE_MINUS_SRC_ALPHA);
glBlendColor(1.0f, 1.0f, 1.0f, 1.0f);
glGetFloatv(GL_BLEND_COLOR, blendColour);
printf("Alpha is: %f\n", blendColour[3]);
The output is 0.0, as opposed to 1.0. It seems to be related to http://www.nvnews.net/vbulletin/showthread.php?t=80878 .

I will post the output from the bug-reporting utility in the morning.

Regards, Freddie.
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Old 09-14-08, 11:08 AM   #2
EvilGuru
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Default Re: glBlendColor Broken?

Bug report attached.
Attached Files
File Type: gz nvidia-bug-report.log.gz (29.0 KB, 104 views)
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Old 09-14-08, 01:28 PM   #3
Fackamato
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Default Re: glBlendColor Broken?

Any difference with 177.70?
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Old 09-14-08, 01:41 PM   #4
EvilGuru
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Default Re: glBlendColor Broken?

Quote:
Originally Posted by Fackamato View Post
Any difference with 177.70?
Exactly the same; the blend colour is not set.

Regards, Freddie.
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Old 09-17-08, 06:52 PM   #5
AaronP
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Default Re: glBlendColor Broken?

Please be sure to compile your test application with the -Wall compiler flag. You probably need to use something like glew or define GL_GLEXT_PROTOTYPES before including gl.h. Without that flag, you get the implicit declaration of glBlendColor with the wrong argument types.
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Old 09-18-08, 06:14 PM   #6
EvilGuru
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Default Re: glBlendColor Broken?

Quote:
Originally Posted by AaronP View Post
Please be sure to compile your test application with the -Wall compiler flag. You probably need to use something like glew or define GL_GLEXT_PROTOTYPES before including gl.h. Without that flag, you get the implicit declaration of glBlendColor with the wrong argument types.
I double checked my extension loading and found that I was loading GLEE after <gl.h>, hence glBlendColor wasn't getting defined.

Thanks, sorry to have wasted your time.

Regards, Freddie.
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