1 // sphere.cxx -- build an ssg sphere object
3 // Pulled straight out of MesaGLU/quadratic.c
5 // Original gluSphere code is Copyright (C) 1999-2000 Brian Paul and
6 // licensed under the GPL
8 // This program is free software; you can redistribute it and/or
9 // modify it under the terms of the GNU General Public License as
10 // published by the Free Software Foundation; either version 2 of the
11 // License, or (at your option) any later version.
13 // This program is distributed in the hope that it will be useful, but
14 // WITHOUT ANY WARRANTY; without even the implied warranty of
15 // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
16 // General Public License for more details.
18 // You should have received a copy of the GNU General Public License
19 // along with this program; if not, write to the Free Software
20 // Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
29 #include <simgear/compiler.h>
37 // return a sphere object as an ssgBranch
38 ssgBranch *ssgMakeSphere( ssgSimpleState *state, ssgColourArray *cl,
39 double radius, int slices, int stacks,
40 ssgCallback predraw, ssgCallback postdraw )
42 float rho, drho, theta, dtheta;
47 ssgBranch *sphere = new ssgBranch;
51 drho = SG_PI / (float) stacks;
52 dtheta = 2.0 * SG_PI / (float) slices;
54 /* texturing: s goes from 0.0/0.25/0.5/0.75/1.0 at +y/+x/-y/-x/+y
55 axis t goes from -1.0/+1.0 at z = -radius/+radius (linear along
56 longitudes) cannot use triangle fan on texturing (s coord. at
57 top/bottom tip varies) */
61 t = 1.0; /* because loop now runs from 0 */
65 /* build slices as quad strips */
66 for ( i = imin; i < imax; i++ ) {
67 ssgVertexArray *vl = new ssgVertexArray();
68 ssgNormalArray *nl = new ssgNormalArray();
69 ssgTexCoordArray *tl = new ssgTexCoordArray();
73 for ( j = 0; j <= slices; j++ ) {
74 theta = (j == slices) ? 0.0 : j * dtheta;
75 x = -sin(theta) * sin(rho);
76 y = cos(theta) * sin(rho);
79 // glNormal3f( x*nsign, y*nsign, z*nsign );
80 sgSetVec3( vec3, x*nsign, y*nsign, z*nsign );
81 sgNormalizeVec3( vec3 );
85 sgSetVec2( vec2, s, t );
88 // glVertex3f( x*radius, y*radius, z*radius );
89 sgSetVec3( vec3, x*radius, y*radius, z*radius );
92 x = -sin(theta) * sin(rho+drho);
93 y = cos(theta) * sin(rho+drho);
94 z = nsign * cos(rho+drho);
96 // glNormal3f( x*nsign, y*nsign, z*nsign );
97 sgSetVec3( vec3, x*nsign, y*nsign, z*nsign );
98 sgNormalizeVec3( vec3 );
101 // glTexCoord2f(s,t-dt);
102 sgSetVec2( vec2, s, t-dt );
106 // glVertex3f( x*radius, y*radius, z*radius );
107 sgSetVec3( vec3, x*radius, y*radius, z*radius );
112 new ssgVtxTable ( GL_TRIANGLE_STRIP, vl, nl, tl, cl );
114 if ( vl->getNum() != nl->getNum() ) {
115 cout << "bad sphere1\n";
118 if ( vl->getNum() != tl->getNum() ) {
119 cout << "bad sphere2\n";
122 slice->setState( state );
123 slice->setCallback( SSG_CALLBACK_PREDRAW, predraw );
124 slice->setCallback( SSG_CALLBACK_POSTDRAW, postdraw );
126 sphere->addKid( slice );