Gamma/Constrast

[Baker]

Just a look at the different methods of doing gamma, contrast and view blends. I'm having a minor but annoying issue so if I document the process I can also fix it But if I don't, I'll continue missing something that is eluding me.

My builds have 5 gamma/contrast methods:

1. WinQuake apply the gamma/contrast to the global palette method
2. GLQuake apply the gamma/contrast to the texture before upload method
3. D3DQuake's d3dSetGammaRamp method
4. The hardware gamma method
5. The render a brightness poly over everything method

Gamma

Building the gamma table from WinQuake. It later gets applied to the palette.

Code: Select all

void BuildGammaTable (float g) // g = gamma
{
   int      i, inf;
   
   if (g == 1.0)
   {
      for (i=0 ; i<256 ; i++)
         gammatable[i] = i;
      return;
   }
   
   for (i=0 ; i<256 ; i++)
   {
      inf = 255 * pow ( (i+0.5)/255.5 , g ) + 0.5;
      if (inf < 0)
         inf = 0;
      if (inf > 255)
         inf = 255;
      gammatable[i] = inf;
   }
}

Enter Contrast

The gamma/contrast table from JoeQuake:

Code: Select all

static void BuildGammaTable2 (float g, float c)
{
   int   i, inf;

   g = bound(0.3, g, 3);
   c = bound(1, c, 3);

   if (g == 1 && c == 1)
   {
      for (i=0 ; i<256 ; i++)
         gammatable[i] = i;
      return;
   }

   for (i=0 ; i<256 ; i++)
   {
      inf = 255 * pow((i + 0.5) / 255.5 * c, g) + 0.5;
      gammatable[i] = bound(0, inf, 255);
   }
}

I'll be stepping through where each of these are done and why as far as the application of the gamma and contrast.

[metlslime]

don't forget idgamma, which causes people to complain that overbright lighting is bad

Note: I think these two are the same:

3. D3DQuake's d3dSetGammaRamp method
4. The hardware gamma method

The only difference being which API you use; d3d or wgl. But they both affect the video card the same way (lookup table in the DAC i believe.)

[Spike]

yeah, setgammaramp is hardware gamma, but the d3d one has less down sides

[Baker]

View Blends

Combined with the gamma [and contrast] the view blends also affect the palette flashes in WinQuake directly:

Code: Select all

typedef struct
{
   int      destcolor[3];
   int      percent;      // 0-256
} cshift_t;

#define   CSHIFT_CONTENTS   0
#define   CSHIFT_DAMAGE   1
#define   CSHIFT_BONUS   2
#define   CSHIFT_POWERUP   3
#define   NUM_CSHIFTS      4

There are 4 chsifts -- I'm guessing the C stands for contrast but it could stand for client. Or maybe contents? Maybe something else (?)

Contents: Empty, Water, Lava, Slime, "Void". Void = no clipping outside the map
Damage: Obvious.
Bonus: Item pickups. "bf"
PowerUP: Quad, Pent, Ring, Suit

The cshift constants ... red, green, blue, intensity percent.

Code: Select all

cshift_t   cshift_empty = { {130,80,50}, 0 };
cshift_t   cshift_water = { {130,80,50}, 128 };
cshift_t   cshift_slime = { {0,25,5}, 150 };
cshift_t   cshift_lava = { {255,80,0}, 150 };

Note: Kurok added an extra one for blue when you go underwater.

Code: Select all

cshift_t   cshift_kwater = { {64,64,128}, 128 }; // Blue water for Kurok

The lifecycle of the CSHIFT begins in R_Render_View_ right after drawing particles.

Code: Select all

void V_SetContentsColor (int contents)
{
   switch (contents)
   {
   case CONTENTS_EMPTY:
   case CONTENTS_SOLID:
      cl.cshifts[CSHIFT_CONTENTS] = cshift_empty;
      break;
   case CONTENTS_LAVA:
      cl.cshifts[CSHIFT_CONTENTS] = cshift_lava;
      break;
   case CONTENTS_SLIME:
      cl.cshifts[CSHIFT_CONTENTS] = cshift_slime;
      break;
   default:
      cl.cshifts[CSHIFT_CONTENTS] = cshift_water;
   }
}

Bonus Flash is actually a command sent over the server ...

Code: Select all

void V_BonusFlash_f (void)
{
   cl.cshifts[CSHIFT_BONUS].destcolor[0] = 215;
   cl.cshifts[CSHIFT_BONUS].destcolor[1] = 186;
   cl.cshifts[CSHIFT_BONUS].destcolor[2] = 69;
   cl.cshifts[CSHIFT_BONUS].percent = 50;
}

It is received in CL_ReadFromServer --> CL_ParseServerMessage and added to the command buffer. So it is probably actually processed 1 frame later.

The damage flash is processed the moment it is received from CL_ParseServerMessage

Code: Select all

      case svc_damage:
         V_ParseDamage ();
         break;

Power up shift is calculated in V_CalcPowerupCShift, which is called by V_UpdatePalette

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/*
=============
V_CalcPowerupCshift
=============
*/
void V_CalcPowerupCshift (void)
{
   if (cl.items & IT_QUAD)
   {
      cl.cshifts[CSHIFT_POWERUP].destcolor[0] = 0;
      cl.cshifts[CSHIFT_POWERUP].destcolor[1] = 0;
      cl.cshifts[CSHIFT_POWERUP].destcolor[2] = 255;
      cl.cshifts[CSHIFT_POWERUP].percent = 30;
   }
   else if (cl.items & IT_SUIT)
   {
      cl.cshifts[CSHIFT_POWERUP].destcolor[0] = 0;
      cl.cshifts[CSHIFT_POWERUP].destcolor[1] = 255;
      cl.cshifts[CSHIFT_POWERUP].destcolor[2] = 0;
      cl.cshifts[CSHIFT_POWERUP].percent = 20;
   }
   else if (cl.items & IT_INVISIBILITY)
   {
      cl.cshifts[CSHIFT_POWERUP].destcolor[0] = 100;
      cl.cshifts[CSHIFT_POWERUP].destcolor[1] = 100;
      cl.cshifts[CSHIFT_POWERUP].destcolor[2] = 100;
      cl.cshifts[CSHIFT_POWERUP].percent = 100;
   }
   else if (cl.items & IT_INVULNERABILITY)
   {
      cl.cshifts[CSHIFT_POWERUP].destcolor[0] = 255;
      cl.cshifts[CSHIFT_POWERUP].destcolor[1] = 255;
      cl.cshifts[CSHIFT_POWERUP].destcolor[2] = 0;
      cl.cshifts[CSHIFT_POWERUP].percent = 30;
   }
   else
      cl.cshifts[CSHIFT_POWERUP].percent = 0;
}

Funny note, apparently the content blend was meant to be cleared in WinQuake if you pulled up the console ...

Code: Select all

/*
===============
SCR_BringDownConsole

Brings the console down and fades the palettes back to normal
================
*/
void SCR_BringDownConsole (void)
{
   int      i;
   
   scr_centertime_off = 0;
   
   for (i=0 ; i<20 && scr_conlines != scr_con_current ; i++)
      SCR_UpdateScreen ();

   cl.cshifts[0].percent = 0;      // no area contents palette on next frame
   VID_SetPalette (host_basepal);
}

It doesn't work.

Probably because SCR_BringDownConsole is never called anywhere in the source and is commented out in cl_main.c

[mh]

"Colour" (or "Color" for those who didn't flunk math and married the prom queen) I would guess.

I don't bother with the D3D gamma ramp and just use the GDI functions instead. My guess is that the D3D version is just a wrapper around the GDI functions anyway (which may or may not work in windowed modes depending on which page of the documentation you read). It does have the ability to do calibration but I've never felt the need for it.

[Baker]

3. D3DQuake's d3dSetGammaRamp method
4. The hardware gamma method

d3dquake's D3DSetGamma only affects the window itself and not the desktop. I noticed that FTEQW 2770 using the D3D render actually uses hardware and contrast, which looks much better.

"Colour"

Baker -1

[Spike]

why d3d's setgammaramps function is better than the windows api:
D3DSGR_NO_CALIBRATION
no stall, no bounds checks, what you send actually goes.

d3d8 only works if its fullscreen. d3d9 works even windowed (affecting the whole screen).

its probably worth creating a d3d9 context just to get ramps working without stalls, even if all rendering is done with opengl.

[mh]

why d3d's setgammaramps function is better than the windows api:
D3DSGR_NO_CALIBRATION
no stall, no bounds checks, what you send actually goes.

d3d8 only works if its fullscreen. d3d9 works even windowed (affecting the whole screen).

its probably worth creating a d3d9 context just to get ramps working without stalls, even if all rendering is done with opengl.

I think I now have the need to use D3D's SGR.

(Although if my theory is correct there should be an API call to disable the crap too).