awful awful rendering code

gistfile1.cpp

	float ang_inc = (cam->fov / (float)SCR_WIDTH);
	float ang = -cam->fov / 2.0f - ang_inc;
	for(int i=0; i < SCR_WIDTH; i++)
	{
		ang += ang_inc;
		float cos_corr = cos(ang*D2R);
		float ovx = i - SCR_WIDTH/2;
		float ovy = cam->projDist;
		float mag = sqrt( ovx*ovx + ovy*ovy );
		ovx /= mag;	ovy /= mag;
		float vx = cos_v * ovy - sin_v * ovx;
		float vy = cos_v * ovx + sin_v * ovy;
		if(vx == 0) vx = 0.1f;  // HACK: :(
		bool xhit = false, yhit = false;
		
		float m, b;
		int Hxi, Hyi, Hxs, Hys;
		int Vxi, Vyi, Vxs, Vys;
		m = vy / vx;
		b = cam->y - m * cam->x;
		
		// For horizontal-line intersections
		if(vy > 0) { Hyi = (((int)cam->y/32)*32 + 32.1f) * 65536; Hys = 32 << 16; }
		else { Hyi = (((int)cam->y/32)*32-0.001f) * 65536; Hys = -32 << 16; }
		Hxi = 65536 * (((Hyi>>16) - b) / m);
		Hxs = 65536 * ((vx > 0 ? 32.0f : -32.0f) / absf(m));
		
		// For vertical-line intersections
		if(vx > 0) { Vxi = (((int)cam->x/32)*32 + 32.1f) * 65536; Vxs = 32 << 16; }
		else { Vxi = (((int)cam->x/32)*32-0.001f) * 65536; Vxs = -32 << 16; }
		Vyi = 65536 * (m * (Vxi>>16) + b);
		Vys = 65536 * ((vy > 0 ? 32.0f : -32.0f) * absf(m));
		
		bool noobX=true, noobY=true;
		while((noobX && !xhit) || (noobY && !yhit))
		{
			noobX = !((Hxi>>16) < 0 || (Hyi>>16) < 0 || (Hxi>>16) >= mapWidth*32 || (Hyi>>16) >= mapHeight*32);
			noobY = !((Vxi>>16) < 0 || (Vyi>>16) < 0 || (Vxi>>16) >= mapWidth*32 || (Vyi>>16) >= mapHeight*32);
			
			if(noobX && mapdata[Hxi>>21][Hyi>>21].solid)
				xhit = true;
			else if(noobX && !xhit)
			{
				Hxi += Hxs; Hyi += Hys;
			}
			
			if(noobY && mapdata[Vxi>>21][Vyi>>21].solid)
				yhit = true;
			else if(noobY && !yhit)
			{
				Vxi += Vxs; Vyi += Vys;
			}
		}

		float HxiF = ((float)Hxi) / 65536.0f, HyiF = ((float)Hyi) / 65536.0f;
		float VxiF = ((float)Vxi) / 65536.0f, VyiF = ((float)Vyi) / 65536.0f;
		float pd1 = xhit ? (HxiF-cam->x)*(HxiF-cam->x) + (HyiF-cam->y)*(HyiF-cam->y) : 10000000;
		float pd2 = yhit ? (VxiF-cam->x)*(VxiF-cam->x) + (VyiF-cam->y)*(VyiF-cam->y) : 10000000;
		if(xhit || yhit)
		{
			float pd;
			int tx, ty;
			int u;
			if(pd1 < pd2)
			{
				pd = 1.0f / (sqrt(pd1) * cos_corr);
				tx = (Hxi >> 21);
				ty = (Hyi >> 21);
				u = (Hxi >> 16) & 31;
			}
			else
			{
				pd = 1.0f / (sqrt(pd2) * cos_corr);
				tx = (Vxi >> 21);
				ty = (Vyi >> 21);
				u = (Vyi >> 16) & 31;
			}
			zbuffer[i] = 1.0f / pd;
			float h = (16.0f * cam->projDist) * pd + 1;
			float sy = (-cam->z * cam->projDist) * pd + SCR_HEIGHT/2 - cam->zRot;
			int topy = sy;
			int boty = sy + 2*h;
			int v_inc = (32 * 65536) / (h*2);
			int v = topy < 0 ? v_inc * -topy : 0;
			float fog_mult = maxf(0.0f, minf(1.0f, (1.0f - (1.0f/pd) / fog_dist)));
			int br = mapdata[tx][ty].brightness * fog_mult;
			if(topy < 0) topy = 0;
			if(boty >= SCR_HEIGHT) boty = SCR_HEIGHT;
			SDL_Surface *tex = textures[ mapdata[tx][ty].wallTex ];
			for(int j=topy; j < boty; j++)
			{
				pixel col = getpixel(tex,u,v>>16);
				byte r = (col >> 16) & 255;
				byte g = (col >> 8) & 255;
				byte b = col & 255;
				r = (r * br) >> 16;
				g = (g * br) >> 16;
				b = (b * br) >> 16;
				col = (r << 16) | (g << 8) | b;
				putpixel(screen,i,j, col);
				v += v_inc;
			}
		}
	}