3dLabs Siggraph presentations..

In rts_a.pdf, about the OpenGL shading language, there was one thing I found annoying…

Page 13, it says

Vector components
–Named (.rgba, .xywz, .stpq)

Where did this stpq come from all of a sudden? I thought OpenGL used strq notation for texture coordinates?

I know its a minor thing, but it really bugs me.

its in the notes…

since you can mask out only one component you must be able to know which one…

myvec.r = 1;

shoud this set the first component ( RGBA)
or the 3:rd ( STRQ ) ?

there was 2 solutions on the table, one was to rename the ‘r’ in strq to ‘p’, or to change the order of rgba to bgra. I think they made the right choice.


[This message has been edited by Mazy (edited 08-28-2003).]

GL_ARB_fragment_program spec:
b What characters should be used to identify individual components in swizzle selectors and write masks?

RESOLVED: ARB_vertex_program provides “xyzw”. This extension supports “xyzw” and also provides “rgba” for better readability when dealing with RGBA color values. Adding support for special identifiers for dealing with texture coordinates was considered and rejected. “strq” could be used to identify texture coordinate components, but the “r” would conflict with the “r” from “rgba”. “stpq” would be another possibility, but could be a source of confusion.[/b]


– Tom

ah well. STPQ it is then…

Originally posted by Nutty:
ah well. STPQ it is then…

Mind your p’s and q’s.

It’s “stpq” then.

(BTW, another alternative considered but quickly rejected was “rstq”. “s” and “t” are too well established for 2D texcoords. “STRQ” was also considered, but rejected, because of case confusion. “foo.r” would have selected the 1st component, “foo.R” would have selected the 3rd complenent.)

And it’s also “gl_EyePlaneR[0].p”.

-mr. bill

For Nutty

Nutty, you have 3DLabs card?

Could you test our demo on 3DLabs?

It Is Thanked beforehand.

[This message has been edited by bozland (edited 08-28-2003).]

I dont have a 3dlabs card sorry, well except for a VX1 Oxygen card, but that supports hardly any OpenGL extensions, so I doubt if anyones demo would run on it.

Only a GF4 in my pc at the moment.

Thank you for answer.