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Lowercase
08-03-2010, 03:00 PM
Another stupid question for you gurus :-[

using delphi, I use this instruction : gltexcoord2f(111/128, 21/128)

Despite to the fact values "111/128" and "21/128" are constants, are they evaluated every frame or only at build time ?

thanks

Brainer
08-03-2010, 05:05 PM
If they are constants, they are calculated only once. But if not, they are every frame.

Lowercase
08-03-2010, 06:10 PM
well that was my question.. I Wasn't so clear.

in my mind "111/128" is constant, since the value never change.

So, how does the compiler evaluate "111/128" ?

In other words, what is stored at compilation time, is it 111/128 or 0.8671875 ?

I use fractions to store texture coordinates, because it's more expressive to me (retrieve coordinate faster).
I feel my app is very slow, that let me think that for every value, there is a division slowing the rendering process.

VilleK
08-03-2010, 08:35 PM
At compile time the compiler calculates the constant expression. So typing "111/128" or "0.8671875" will generate identical code. In other words there are no run-time penalties for using a constant expression.