Quake3 Overbright & Lightmap

OpenGL OpenGL: Advanced Coding
1

I try to render Q3 .BSP files and something seems to be strange.
my rendering procedure is:
vertexcolor * tex0 * lightmap
I use GL_MODULATE environment for Tex0 & Tex1
But everything is really dark (assuming vertexcolor<1.0 texcolor<1.0 and lightmap<1.0.
So my question is:
How to do a Quake3-Like Brightness method that allows RGB color scaling with factor greater than 1?
Thanks.

2

there are 2 things i can think of.
The main thing is probably you should use Vertex color, OR lightmap. I think i recall quake3 still had the option to use vertex colors calculated from the lightmaps as a really low-quality fast option.

The other thing could be the gamma ramp overbrightening that q3 used for a 0-2 dynamic range. You can use win32 Get/SetDeviceGammaRamp to change the gamma ramp to make everything double in brightness like they did. Then the lightmaps or vertex colors need to be adjusted accordingly.

M.

3

from memory quake3 actually changed the brightness of the textures when u loaded them in, the poormans gamma, but guaranteed to work!

4

Yeah like everyone said, you need to boost the brightness of the lightmaps. Here is a function from the DXQuake3 open source engine that does this:

DWORD c_BSP::BrightenColour(U8 r, U8 g, U8 b)
{
	int ir, ig, ib, Gamma, imax;
	float Factor;
	Gamma = 2-DQConsole.OverbrightBits;

	ir = ((int)r)<<Gamma;
	ig = ((int)g)<<Gamma;
	ib = ((int)b)<<Gamma;

	imax = max( ir, max( ig, ib ) );
	if(imax>255) {
		Factor = 255.0f/(float)imax;
		ir = (int)((float)ir*Factor);
		ig = (int)((float)ig*Factor);
		ib = (int)((float)ib*Factor);
	}

	return D3DCOLOR_RGBA( ir, ig, ib, 255 );
}

For more info, google for DXQuake3 and get the source.

-SirKnight

5

You know what, I may as well post a snippet from the function that calls the BrightenColor.

for(i=0;i<NumLightmaps;++i) {

		d3dcheckOK( TempTexture->GetLevelDesc( 0, &desc ) );
		d3dcheckOK( TempTexture->LockRect( 0, &LockedRect, NULL, 0 ) );

		for(u=0;u<128;++u) {
			pixel = (DWORD*)( (BYTE*)LockedRect.pBits+u*LockedRect.Pitch );
			for(v=0;v<128;++v,++pixel) {
				//BGRA (LSB first)
				*pixel = BrightenColour( Lightmap[i].map[u][v][0], Lightmap[i].map[u][v][1], Lightmap[i].map[u][v][2]);
			}
		}

		TempTexture->UnlockRect(0);

		LightmapTextureBuffer[i] = (c_Texture*) DQNewVoid( c_Texture );
		LightmapTextureBuffer[i]->LoadTextureFromSysmemTexture( TempTexture, FALSE, 0 );
	}

I hope that is self explanitory enough.

-SirKnight

6

Thanks everybody :slight_smile:
It’s great.
Boosting brightness of lightmaps is perfect.
And the SetDeviceGammaRamp function allows me to modulate brightness in realtime.
:smiley: