What is fog mode?

[ChupaReaper]

I use mode="2" for fog, what are the other modes?
Here's the wiki entry:

<fog enabled="true" mode="2" density="0.03" color-red="0.6" color-green="1" color-blue="0.4"/> Enable fog (as in main menu); fog density (more=harder to see through it); colours of fog (range 0-1); mode= (???)

[Omega]

... I don't know... This is the only mention of it in the source, other than to get it from the INI.

Code: [Select]

if(tileset->getFog()){
   glEnable(GL_FOG);
   if(tileset->getFogMode()==fmExp){
      glFogi(GL_FOG_MODE, GL_EXP);
   }
   else{
      glFogi(GL_FOG_MODE, GL_EXP2);
   }
}Unfortunately, I don't really understand it, but hopefully someone with more experience than me can...

[hailstone]

It seems like it's different ways to calculate the fog blending.

GL_FOG_MODE - This parameter can be GL_LINEAR, GL_EXP, GL_EXP2, specifying which equation is used to calculate the blend factor.

See the website for the equations.

Only GL_EXP, GL_EXP2 are possible in Glest with values 0 and 1 respectively, defaulting to GL_EXP2 for any other number. I'm not sure why GL_LINEAR has been left out.

[ChupaReaper]

I found this:
GL_EXP - Basic rendered fog which fogs out all of the screen. It doesn't give much of a fog effect, but gets the job done on older PC's.
GL_EXP2 - Is the next step up from GL_EXP. This will fog out all of the screen, however it will give more depth to the scene.
GL_LINEAR - This is the best fog rendering mode. Objects fade in and out of the fog much better.
From here.

[silnarm]

While that is a good site (and where our freetype font code came from), that info on fog just seems wrong.

Linear is just that, a linear equation, not very realistic and unlikely to give better results than an exponential function... I'd suggest it was left out of Glest because it isn't very good 

NB: I'm no expert on this stuff, maybe despite its simplicity it is best... but I doubt it.

[Omega]

Ok, but then where does the values for the XML come from. ie: the XML's mode is simply "2". Is this GL_EXP2?

[hailstone]

in tileset.h:

Code: [Select]

enum FogMode{
fmExp,
fmExp2
};

tileset->getFogMode() is compared with fmExp which is an enumration with the value 0. If it is 0 then it calls glFogi(GL_FOG_MODE, GL_EXP); . If it isn't 0 then it calls glFogi(GL_FOG_MODE, GL_EXP2);

So to answer the question, 2 is GL_EXP2.