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1 /*
2 Copyright (C) 1996-1997 Id Software, Inc.
3 
4 This program is free software; you can redistribute it and/or
5 modify it under the terms of the GNU General Public License
6 as published by the Free Software Foundation; either version 2
7 of the License, or (at your option) any later version.
8 
9 This program is distributed in the hope that it will be useful,
10 but WITHOUT ANY WARRANTY; without even the implied warranty of
11 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
12 
13 See the GNU General Public License for more details.
14 
15 You should have received a copy of the GNU General Public License
16 along with this program; if not, write to the Free Software
17 Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA  02111-1307, USA.
18 
19 */
20 // d_sky.c
21 
22 #include "quakedef.h"
23 #include "r_local.h"
24 #include "d_local.h"
25 
26 #define SKY_SPAN_SHIFT	5
27 #define SKY_SPAN_MAX	(1 << SKY_SPAN_SHIFT)
28 
29 
30 /*
31 =================
32 D_Sky_uv_To_st
33 =================
34 */
D_Sky_uv_To_st(int u,int v,fixed16_t * s,fixed16_t * t)35 void D_Sky_uv_To_st (int u, int v, fixed16_t *s, fixed16_t *t)
36 {
37 	float	wu, wv, temp;
38 	vec3_t	end;
39 
40 	if (r_refdef.vrect.width >= r_refdef.vrect.height)
41 		temp = (float)r_refdef.vrect.width;
42 	else
43 		temp = (float)r_refdef.vrect.height;
44 
45 	wu = 8192.0 * (float)(u-((int)vid.width>>1)) / temp;
46 	wv = 8192.0 * (float)(((int)vid.height>>1)-v) / temp;
47 
48 	end[0] = 4096*vpn[0] + wu*vright[0] + wv*vup[0];
49 	end[1] = 4096*vpn[1] + wu*vright[1] + wv*vup[1];
50 	end[2] = 4096*vpn[2] + wu*vright[2] + wv*vup[2];
51 	end[2] *= 3;
52 	VectorNormalize (end);
53 
54 	temp = skytime*skyspeed;	// TODO: add D_SetupFrame & set this there
55 	*s = (int)((temp + 6*(SKYSIZE/2-1)*end[0]) * 0x10000);
56 	*t = (int)((temp + 6*(SKYSIZE/2-1)*end[1]) * 0x10000);
57 }
58 
59 
60 /*
61 =================
62 D_DrawSkyScans8
63 =================
64 */
D_DrawSkyScans8(espan_t * pspan)65 void D_DrawSkyScans8 (espan_t *pspan)
66 {
67 	int				count, spancount, u, v;
68 	unsigned char	*pdest;
69 	fixed16_t		s, t, snext, tnext, sstep, tstep;
70 	int				spancountminus1;
71 
72 	sstep = 0;	// keep compiler happy
73 	tstep = 0;	// ditto
74 
75 	do
76 	{
77 		pdest = (unsigned char *)((byte *)d_viewbuffer +
78 				(screenwidth * pspan->v) + pspan->u);
79 
80 		count = pspan->count;
81 
82 	// calculate the initial s & t
83 		u = pspan->u;
84 		v = pspan->v;
85 		D_Sky_uv_To_st (u, v, &s, &t);
86 
87 		do
88 		{
89 			if (count >= SKY_SPAN_MAX)
90 				spancount = SKY_SPAN_MAX;
91 			else
92 				spancount = count;
93 
94 			count -= spancount;
95 
96 			if (count)
97 			{
98 				u += spancount;
99 
100 			// calculate s and t at far end of span,
101 			// calculate s and t steps across span by shifting
102 				D_Sky_uv_To_st (u, v, &snext, &tnext);
103 
104 				sstep = (snext - s) >> SKY_SPAN_SHIFT;
105 				tstep = (tnext - t) >> SKY_SPAN_SHIFT;
106 			}
107 			else
108 			{
109 			// calculate s and t at last pixel in span,
110 			// calculate s and t steps across span by division
111 				spancountminus1 = (float)(spancount - 1);
112 
113 				if (spancountminus1 > 0)
114 				{
115 					u += spancountminus1;
116 					D_Sky_uv_To_st (u, v, &snext, &tnext);
117 
118 					sstep = (snext - s) / spancountminus1;
119 					tstep = (tnext - t) / spancountminus1;
120 				}
121 			}
122 
123 			do
124 			{
125 				*pdest++ = r_skysource[((t & R_SKY_TMASK) >> 8) +
126 						((s & R_SKY_SMASK) >> 16)];
127 				s += sstep;
128 				t += tstep;
129 			} while (--spancount > 0);
130 
131 			s = snext;
132 			t = tnext;
133 
134 		} while (count > 0);
135 
136 	} while ((pspan = pspan->pnext) != NULL);
137 }
138 
139