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View Full Version : Insane typo in the spec ???



zeckensack
05-31-2002, 08:21 AM
Somehow the texture function formula stuff is messed up and nobody noticed?

Regarding the currently downloadable 1.3 version GL spec, look at this, page 147:


Cf and Af 3 are the primary color components of the incoming fragment; Cs
and As are the components of the texture source color, derived from the filtered
texture values Rt , Gt , Bt , At , Lt , and It as shown in table 3.21; Cc and Ac are
the components of the texture environment color; Cp and Ap are the components
resulting from the previous texture environment (for texture environment 0, Cp and
Ap are identical to Cf and Af , respectively); and Cv and Av are the primary color
components computed by the texture function.
And then table 3.22 on page 148:



REPLACE MODULATE DECAL
RGB Cv = Cs Cv = Cf*Cs Cv = Cs
(or 3) Av = Af Av = Af Av = Af
RGBA Cv = Cs Cv = Cf*Cs Cv = Cf*(1 - As) + CsAs
(or 4) Av = As Av = Af*As Av = Af

That can't be true, can it? I was a little worried about the decal function (which I never used anyway ...), but the MODULATE thing just can't be what it was intended to be.

zeckensack
05-31-2002, 08:23 AM
Err, let me explain (somehow I can't seem to edit the above post without losing half of it...)

The functions all use Cf and Af which is primary fragment color (as explained in the snip from page 147) when they should be using Cp and Ap (the previous tex env result).

Old GLman
05-31-2002, 12:52 PM
Hi, to me it wouldnt make any sense to use the previous texture environment component because if they were used then the results would different from the specified texture environement ( hope this makes sense ). I could be wrong, hopefully someone more experienced than me will take a look. Im interested to know myself.

Old GLman

zeckensack
06-02-2002, 01:37 PM
So, nobody cares about the spec contradicting
a)common sense about texture application
b)shipping driver behaviour
???