Reg Combiners ... Clueless

[Shag]

OK - this is the first time I've used register combiners, and I'm stuck.

I want to take an RBG texture and occasionally convert it to gray scale. But I haven't got a clue how to do it quite frankly.

I know that I need to ...
input RGBA

and output
R = (R * 0.3) + (G * 0.59) + (B * 0.11)
G = (R * 0.3) + (G * 0.59) + (B * 0.11)
B = (R * 0.3) + (G * 0.59) + (B * 0.11)
A = A

But I'm looking at sample code which seems to bear no resmeblence to the spec. I think I've confused myself here. Or maybe getting up at 3am didn't help!!!

My code so far is ...

glEnable(GL_REGISTER_COMBINERS_NV);
glDisable(GL_REGISTER_COMBINERS_NV);


Impressive huh? All I need is the bits in the middle. Can anyone help? Please?

Regards

[NitroGL]

Originally posted by Shag:
OK - this is the first time I've used register combiners, and I'm stuck.

I want to take an RBG texture and occasionally convert it to gray scale. But I haven't got a clue how to do it quite frankly.

I know that I need to ...
input RGBA

and output
R = (R * 0.3) + (G * 0.59) + (B * 0.11)
G = (R * 0.3) + (G * 0.59) + (B * 0.11)
B = (R * 0.3) + (G * 0.59) + (B * 0.11)
A = A

But I'm looking at sample code which seems to bear no resmeblence to the spec. I think I've confused myself here. Or maybe getting up at 3am didn't help!!!

My code so far is ...

glEnable(GL_REGISTER_COMBINERS_NV);
glDisable(GL_REGISTER_COMBINERS_NV);


Impressive huh? All I need is the bits in the middle. Can anyone help? Please?

Regards

Ok, I've never used the registry combiners before, but what you want is (using NVParse):

const0 = (0.3, 0.59, 0.11, 1);
out.rgb = tex0.const0

I think that's right...

[NitroGL]

Nope, that's not right...

const0 = (0.3, 0.59, 0.11, 1);
{
    rgb
    {
        spare0 = tex0.const0
    }
}
out.rgb = spare0

That should work.


[This message has been edited by NitroGL (edited 03-07-2002).]

[Shag]

And in terms of

glCombinerInputNV()
glCombinerOutputNV()
etc

Regards

[PH]

Using the spec and sample code to understand RC's is probably not the easiest way. Have a look at the RC presentations on NVIDIA's site, these contain invaluable diagrams.

[Eric]

Funny, that was actually the purpose of an Effect I submitted to the nVIDIA contest that took place some time ago (no wonder why I didn't win a thing...).

Actually, I did two versions: one with texture shaders (which was the aim !) and then one with the register combiners (after I realised that it was the most obvious and simple solution...).

Anyway, here is the snippet that sets the RC up:

  // Texture 0 - Normal texture//
  glActiveTextureARB(GL_TEXTURE0_ARB);
  glBindTexture(GL_TEXTURE_2D,1);
  glEnable(GL_TEXTURE_2D);
  glEnable(GL_REGISTER_COMBINERS_NV);
  glCombinerParameteriNV(GL_NUM_GENERAL_COMBINERS_NV,2);
  float fGreyscale[4]={0.3,0.59,0.11,1};
  glCombinerParameterfvNV(GL_CONSTANT_COLOR0_NV,fGreyscale);
  float fAlpha[4]={0,0,0,fFade};
  glCombinerParameterfvNV(GL_CONSTANT_COLOR1_NV,fAlpha);
  // Combiner 0 calculates the grey texture //
  glCombinerInputNV(GL_COMBINER0_NV,GL_RGB,GL_VARIABLE_A_NV,GL_TEXTURE0_ARB,GL_UNSIGNED_IDENTITY_NV,GL_RGB);
  glCombinerInputNV(GL_COMBINER0_NV,GL_RGB,GL_VARIABLE_B_NV,GL_CONSTANT_COLOR0_NV,GL_UNSIGNED_IDENTITY_NV,GL_RGB);
  glCombinerOutputNV(GL_COMBINER0_NV,GL_RGB,GL_SPARE0_NV,GL_DISCARD_NV,GL_DISCARD_NV,GL_NONE,GL_NONE,GL_TRUE,GL_FALSE,GL_FALSE);
  // Combiner 1 interpolates between grey and color //
  glCombinerInputNV(GL_COMBINER1_NV,GL_RGB,GL_VARIABLE_A_NV,GL_TEXTURE0_ARB,GL_UNSIGNED_IDENTITY_NV,GL_RGB);
  glCombinerInputNV(GL_COMBINER1_NV,GL_RGB,GL_VARIABLE_B_NV,GL_CONSTANT_COLOR1_NV,GL_UNSIGNED_IDENTITY_NV,GL_ALPHA);
  glCombinerInputNV(GL_COMBINER1_NV,GL_RGB,GL_VARIABLE_C_NV,GL_SPARE0_NV,GL_UNSIGNED_IDENTITY_NV,GL_RGB);
  glCombinerInputNV(GL_COMBINER1_NV,GL_RGB,GL_VARIABLE_D_NV,GL_CONSTANT_COLOR1_NV,GL_UNSIGNED_INVERT_NV,GL_ALPHA);
  glCombinerOutputNV(GL_COMBINER1_NV,GL_RGB,GL_DISCARD_NV,GL_DISCARD_NV,GL_SPARE1_NV,GL_NONE,GL_NONE,GL_FALSE,GL_FALSE,GL_FALSE);
  glFinalCombinerInputNV(GL_VARIABLE_A_NV, GL_ZERO, GL_UNSIGNED_IDENTITY_NV, GL_RGB);
	glFinalCombinerInputNV(GL_VARIABLE_B_NV, GL_ZERO, GL_UNSIGNED_IDENTITY_NV, GL_RGB);
	glFinalCombinerInputNV(GL_VARIABLE_C_NV, GL_ZERO, GL_UNSIGNED_IDENTITY_NV, GL_RGB);
	glFinalCombinerInputNV(GL_VARIABLE_D_NV, GL_SPARE1_NV, GL_UNSIGNED_IDENTITY_NV, GL_RGB);

Hopefully this is enough for you to go on (I don't remember the effect itself very well but I can have a look if something is missing).

If you want the full source code, I can e-mail it to you.

Regards.

Eric

EDIT: Just remembered that this actually more than you need ! This piece of code also interpolates between the greyscale version and the colored one according to the alpha value of GL_CONSTANT_COLOR1_NV... Anyway, you should be able to remove the useless part !

[This message has been edited by Eric (edited 03-07-2002).]

[Shag]

Cheers Eric/Opla, much appreciated.

The spec implies

glCombinerInputNV(GL_COMBINER0_NV, GL_RGB
should be ...
glCombinerInputNV(GL_RGB, GL_COMBINER0_NV

or am I just reading this wrong?

*Head spinning* lol

Thanks again

[This message has been edited by Shag (edited 03-07-2002).]

[Eric]

The specs says:

GLvoid glCombinerInputNV(GLenum stage,GLenum portion,GLenum variable,GLenum input,GLenum mapping,GLenum componentUsage);

Stage is GL_COMBINERi_NV and portion is GL_RGB or GL_ALPHA.

Why do you say that the specs imply the opposite ?

Regards.

Eric

[opla]

it's glCombinerInputNV(GL_COMBINER0_NV, GL_RGB, ...

[opla]

Arghh, Eric was faster ...

Eric, je n'ai toujours pas reussi a t'envoyer d'email. a chaque fois j'ai un message d'erreur. peut-etre un filtre anti-spam ...