WHERE TO FIND OPENGL INFORMATION - (Bi-weekly posting)

WHERE TO FIND OPENGL INFORMATION - (Bi-weekly posting)

The Official OpenGL Site - News, downloads, tutorials, books & links:-
http://www.opengl.org/

The archive for this mailing list can be found at:-
http://www.egroups.com/list/opengl-gamedev-l/

The OpenGL Repository - Downloads for OpenGL implementations:-
http://www.fortunecity.com/skyscraper/nuclear/274/

The OpenGL GameDev FAQ:-
http://www.3dgamedev.com/resources/openglfaq.txt

The EFnet OpenGL FAQ:-
http://www.geocities.com/SiliconValley/Park/5625/opengl/

The Omniverous Biped's FAQ:-
http://www.sjbaker.org/steve/omniv

OpenGL 1.0 Reference
http://www.cevis.uni-bremen.de/~uwe/opengl/

OpenGL 1.1 Reference - This is pretty much the Blue book on-line:-
http://tc1.chemie.uni-bielefeld.de/doc/OpenGL/hp/Reference.html

Information on the GLUT API:-
http://www.opengl.org/developers/documentation/glut.html

Apples OpenGL web site is at:-

GlGetHistogram opengl 1.4

Hi all
This is my pb:
I want to calculate the DOT3_RGB between two "rendered" quad polygon in
which a mipmapped texture change over time.
Rendered because the model view matrix also changes.
I want to obtain the color histogram of the rendered
results with GlGetHistogram for each mipmap levels.
What is the best way to do that, all in hardware ?
Can i do all in Opengl 1.4 (latest nvidia driver) ?
Is GlGetHistogram accelerated in the latest nvidia driver ?

TIA
FED

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OpenGL 1.4 Spec and RGB_SCALE/ALPHA_SCALE

Hi,

how is RGB_SCALE set according to the OpenGL 1.4 spec? It was part of 
the texture_env_combine extension and was accessed as a TexEnv 
parameter there. However, nothing is said in the 1.4 spec to this 
extent:

"When target is TEXTURE_ENV, the possible environment parameters are 
TEXTURE_ENV_MODE, TEXTURE_ENV_COLOR, COMBINE_RGB, and COMBINE_ALPHA."

RGB_SCALE is only mentioned briefly on page 153:

"If the value of TEXTURE_ENV_MODE is COMBINE, the form of the texture 
function depends on the values of COMBINE_RGB and COMBINE_ALPHA, 
according to table 3.24. The RGB and ALPHA results of the texture 
function are then multiplied by the values of RGB_SCALE and 
ALPHA_SCALE, respectively."

Also it is listed as possible parameter for GetTexEnvfv() on page 232:

	"RGB_SCALE 2*x R3 GetTexEnvfv 1.0 RGB post-combiner scaling 3.8.12 
texture"

So one could infer that RGB_SCALE is indeed a TexEnv() parameter. Was 
this simply forgotten in the spec? Actually, the 1.3 spec has the same 
problem - did nobody notice until now?

-- Bert

----- 

Clamp between stages

Re: Clamp between stages

At 16:54 3/07/2003 -0800, you wrote:
>Hello all,
>
>does anyone know if color values are clamped to 0..1 when passed between 
>texture stages or is it just clamped when it is about to be written to the 
>color buffer?

Hm, 3.8.5 does say about the result of the
"texture function", R_v...A_v : "All of these
color values are in the range [0, 1]", and
appendix F in 1.2.1 doesn't override that
(at least not that part of it).

However it should be easy to find out :)

Bert

-=<Short Controlled Bursts>=-

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RE: OpenGL 1.4 Spec and RGB_SCALE/ALPHA_SCALE

Bert,

IIRC, RGB_SCALE in OpenGL 1.4 should be functionally equivalent to that
found in the EXT/ARB_texture_env_combine extensions.  

There should probably be language in the spec soon after TexEnv is
introduced that says "if <target> is RGB_SCALE or ALPHA_SCALE, the RGB or
alpha scale factors are set to...".  That would make it much more clear.

Pat

--
Pat Brown (pbrown <at> nvidia.com)
OpenGL Developer, NVIDIA Corporation

-----Original Message-----
Sent: Wednesday, July 02, 2003 3:16 PM
To: Multiple recipients of list OPENGL-GAMEDEV-L

Hi,

how is RGB_SCALE set according to the OpenGL 1.4 spec? It was part of 
the texture_env_combine extension and was accessed as a TexEnv 
parameter there. However, nothing is said in the 1.4 spec to this 
extent:

"When target is TEXTURE_ENV, the possible environment parameters are 
TEXTURE_ENV_MODE, TEXTURE_ENV_COLOR, COMBINE_RGB, and COMBINE_ALPHA."

RGB_SCALE is only mentioned briefly on page 153:

"If the value of TEXTURE_ENV_MODE is COMBINE, the form of the texture 
function depends on the values of COMBINE_RGB and COMBINE_ALPHA, 
according to table 3.24. The RGB and ALPHA results of the texture 
function are then multiplied by the values of RGB_SCALE and 
ALPHA_SCALE, respectively."

Also it is listed as possible parameter for GetTexEnvfv() on page 232:

	"RGB_SCALE 2*x R3 GetTexEnvfv 1.0 RGB post-combiner scaling 3.8.12 
texture"

So one could infer that RGB_SCALE is indeed a TexEnv() parameter. Was 
this simply forgotten in the spec? Actually, the 1.3 spec has the same 
problem - did nobody notice until now?

-- Bert

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Author: Bert Freudenberg
  INET: bert <at> isg.cs.uni-magdeburg.de

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? Good material on Collision

Does anyone know some good material to download about colliding contact and resting contact with or
without friction? I'm trying to implement a domino simulation.
 I already got Baraff's "Fast Contact Force Computation for Nonpenetrating Rigid Bodies" and Mirtich's
"Impulse-based Dynamic Simulation", but I'm still needing a 'light'.
 Thanks

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-- 
Author: Roberto Soares Caldas                                       
  INET: roberto.caldas <at> poli.usp.br

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GL_COLOR_ARRAY affecting color set by glColor*()?

Should the use of GL_COLOR_ARRAY affect the color stored using the
glColor*() functions?

This seems to be happening on the nVidia cards that I have (GeForce2 MX,
GeForce4 Ti), but not on the ATI card that I have (Radeon 9700).  (Note
- I installed the latest drivers for the GeForce4 Ti and I see the same
results).  Here's the scenario:

I'm rendering two triangle lists using vertex arrays.  Triangle list [C]
uses a color array.  Triangle list [N] does not use a color array.
Before rendering [C] I specifically enable GL_COLOR_ARRAY and set the
ColorPoitner.  Before rendering [N] I specifically disable
GL_COLOR_ARRAY.

NOTES:

  1- I also specifically enable / disable other arrays - but their
     inclusion/exclusion does not seem to make a difference.

  2- If I texture [N] then I use GL_MODULATE so the fragment color (set
     using glColor*() is apparent) - if not, then the fragment color is
     directly used (since [N] is not using a color array). 

If I render the frame in the following sequence:

  set arrays for / render [C]; 
  glColor*(); // This is the ONLY place glColor is called
  set arrays for / render [N];

On both the GeForce and Radeon cards the fragment color used when [N] is
rendered is as expected (i.e. comes from the glColor*() call).  No
surprises here.

However, if I render the frame in the following sequence:

  glColor*(); // This is the ONLY place glColor is called
  set arrays for / render [C]; 
  set arrays for / render [N];

On the GeForce cards the fragment color used when [N] is rendered seems
to have been affected by the color array used by [C].  On the Radeon
card, the fragment color used when [N] is rendered comes from the
glColor*() call.

What is the correct behavior (or is this unspecified)?

Thanks,
--Jaek
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Re: GL_COLOR_ARRAY affecting color set by glColor*()?

Jaek wrote:

> Should the use of GL_COLOR_ARRAY affect the color stored using the
> glColor*() functions?
> 

 From Red Book (2.ed page 73)

"After execution of glDrawElements(), current RGB color, color index,
normal coordinates, texture coordinates and edge flag are indeterminate
if the corresponding array has been enabled"

(the same is true for glDrawArrays (but not glArrayElement))

		Eero

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OFF-TOPIC (was Re: ? Good material on Collision)

Roberto,

This is off-topic. A better forum for this subject can be found in the
gd-algorithm mailing list. Make sure to read their FAQ and search their
archive before posting there:

GDAlgorithms-list mailing list Archives:
http://sourceforge.net/mailarchive/forum.php?forum_id=6188

(that link seems to be down, you can find older archives there too:
http://www.geocrawler.com/archives/3/4856)

Christian Laforte
Rendering&Vis Team, Alias | wavefront

----- Original Message ----- 
To: "Multiple recipients of list OPENGL-GAMEDEV-L"
<OPENGL-GAMEDEV-L <at> fatcity.com>
Sent: Monday, July 07, 2003 6:54 PM

> Does anyone know some good material to download about colliding contact
and resting contact with or without friction? I'm trying to implement a
domino simulation.
>  I already got Baraff's "Fast Contact Force Computation for Nonpenetrating
Rigid Bodies" and Mirtich's "Impulse-based Dynamic Simulation", but I'm
still needing a 'light'.
>  Thanks

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