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glVertexPointer and glColor4fv


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#1 amtri   Members   -  Reputation: 175

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Posted 25 April 2012 - 11:36 AM

Hello,

I am using glVertexPointer to set my point coordinates. The only primitives I have are triangles. I could use glColorPointer, but all triangles - possibly millions - are the same color. So rather than using glColorPointer I would like to use glColor(3,4).

If I use glColor3f, this works just fine on my machine. However, if I use glColor4f and the transparency value is set, the resulting triangles are NOT transparent.

I'm wondering...:

1) Is it legal to enable VertexPointer but NOT ColorPointer? In other words, am I just lucky that the call to glColor3f on my machine worked when the true behavior when pointers are being used is undefined?

2) If this is legal - as I hope it is - is there anything special that needs to be done to make glColor4f work to get transparency? Or is this the result of a probable bug in my code?

The code is rather large and I cannot post it here. So I thought I'd just ask about the rules to make sure I'm using them correctly.

Thanks.

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#2 Brother Bob   Moderators   -  Reputation: 8429

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Posted 25 April 2012 - 11:56 AM

It is legal to do that. You probably haven't set up and enabled blending for transparency to work though.

#3 amtri   Members   -  Reputation: 175

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Posted 25 April 2012 - 12:32 PM

Brother Bob,

You are right. I have to glEnable(GL_BLEND).

Thanks!




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