Accessing Alpha of an RGB texture

OpenGL
1

Hi

What happens if i try to access the alpha-component of a texture, which contains only RGB values?

Do i get defined behaviour, like a 1 or a 0 ? That would be pretty cool.

Thanks,
Jan.

2

I am almost 100% sure you get 1.0 in the alpha if you do not supply it. (can’t find the spec page off hand) I’m sure other people will correct me if other parts of OpenGL behave differently. (I don’t think so)

3

Originally posted by sqrt[-1]:
I am almost 100% sure you get 1.0 in the alpha if you do not supply it. (can’t find the spec page off hand) I’m sure other people will correct me if other parts of OpenGL behave differently. (I don’t think so)
The OpenGL Graphics System: A Specification
(Version 2.0 - October 22, 2004)

Table 3.21 on p. 184 provides the mapping from Texture Base Internal Format to Texture Source Color.

RGB internal format maps to Rt, Gt, Bt, 1.0 .

-mr. bill

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