id's sky code is back (gl_sky_clip 2 when no skybox is loaded). Not as fast

as the black polygons (duh:) and not as nice looking as the sky dome, but also
not as slow (fps when standing in the normal coridor looking at the sky in
start: 26 for skydome, 37 for id skys, 44 for black). Good for when you want
to see sky other than black but your card can't handle the fillrate
requirements of skydome. I'll clean up the sqrt in there soonish.

include/r_shared.h

@@ -139,6 +139,9 @@ extern void SetUpForLineScan(fixed8_t startvertu, fixed8_t startvertv,
 extern int	r_skymade;
 extern void R_MakeSky (void);
 
+extern int solidskytexture;
+extern int alphaskytexture;
+
 extern int	ubasestep, errorterm, erroradjustup, erroradjustdown;
 
 extern double r_realtime;

libs/video/renderer/gl/gl_rsurf.c

@@ -335,10 +335,6 @@ R_TextureAnimation (texture_t *base)
 
 /* BRUSH MODELS */
 
-extern float speedscale;				// for top sky and bottom sky
-extern int   solidskytexture;
-extern int   alphaskytexture;
-
 void
 GL_UploadLightmap (int i, int x, int y, int w, int h)
 {

libs/video/renderer/gl/gl_sky.c

@@ -55,7 +55,6 @@
 #include "r_cvar.h"
 
 char       *suf[6] = { "rt", "bk", "lf", "ft", "up", "dn" };
-float       speedscale;					// for top sky and bottom sky
 int         solidskytexture;
 int         alphaskytexture;
 
@@ -230,6 +229,8 @@ R_DrawSkyLayer (float s)
 void
 R_DrawSkyDome (void)
 {
+	float       speedscale;					// for top sky and bottom sky
+
 	qfglDisable (GL_DEPTH_TEST);
 	qfglDepthRange (gldepthmax, gldepthmax);
 

libs/video/renderer/gl/gl_sky_clip.c

@@ -658,6 +658,38 @@ R_DrawSkyDomePoly (glpoly_t *poly)
 	qfglEnd ();
 }
 
+void
+EmitSkyPolys (float speedscale, msurface_t *fa)
+{
+	glpoly_t   *p;
+	float      *v;
+	int         i;
+	float       s, t;
+	vec3_t      dir;
+	float       length;
+
+	for (p = fa->polys; p; p = p->next) {
+		qfglBegin (GL_POLYGON);
+		for (i = 0, v = p->verts[0]; i < p->numverts; i++, v += VERTEXSIZE) {
+			VectorSubtract (v, r_origin, dir);
+			dir[2] *= 3;	// flatten the sphere
+
+			length = DotProduct (dir, dir);
+			length = 6 * 63 / sqrt (length);
+
+			dir[0] *= length;
+			dir[1] *= length;
+
+			s = (speedscale + dir[0]) * (1.0/128);
+			t = (speedscale + dir[1]) * (1.0/128);
+
+			qfglTexCoord2f (s, t);
+			qfglVertex3fv (v);
+		}
+		qfglEnd ();
+	}
+}
+
 void
 R_DrawSkyChain (msurface_t *sky_chain)
 {
@@ -694,6 +726,30 @@ R_DrawSkyChain (msurface_t *sky_chain)
 			sc = sc->texturechain;
 		}
 		qfglDepthRange (gldepthmin, gldepthmax);
+	} else if (gl_sky_clip->int_val == 2) {
+		float       speedscale;
+
+		speedscale = r_realtime*8;
+		speedscale -= (int)speedscale & ~127 ;
+
+		qfglBindTexture (GL_TEXTURE_2D, solidskytexture);
+		while (sc) {
+			EmitSkyPolys (speedscale, sc);
+			sc = sc->texturechain;
+		}
+
+		if (gl_skymultipass->int_val) {
+			sc = sky_chain;
+
+			speedscale = r_realtime*16;
+			speedscale -= (int)speedscale & ~127 ;
+
+			qfglBindTexture (GL_TEXTURE_2D, alphaskytexture);
+			while (sc) {
+				EmitSkyPolys (speedscale, sc);
+				sc = sc->texturechain;
+			}
+		}
 	} else {
 		// this code is duplicated from above because skydome is not yet
 		// clipped