109 lines
3.0 KiB
C++
109 lines
3.0 KiB
C++
// sphere.cxx -- build an ssg sphere object
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//
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// Pulled straight out of MesaGLU/quadratic.c
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//
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// Original gluSphere code is Copyright (C) 1999-2000 Brian Paul and
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// licensed under the GPL
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//
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// This program is free software; you can redistribute it and/or
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// modify it under the terms of the GNU General Public License as
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// published by the Free Software Foundation; either version 2 of the
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// License, or (at your option) any later version.
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//
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// This program is distributed in the hope that it will be useful, but
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// WITHOUT ANY WARRANTY; without even the implied warranty of
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// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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// General Public License for more details.
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//
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// You should have received a copy of the GNU General Public License
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// along with this program; if not, write to the Free Software
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// Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
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//
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// $Id$
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#include <plib/ssg.h>
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// return a sphere object as an ssgBranch
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ssgBranch *ssgMakeSphere( ssgSimpleState *state, double radius, int slices,
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int stacks ) {
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float rho, drho, theta, dtheta;
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float x, y, z;
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float s, t, ds, dt;
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int i, j, imin, imax;
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float nsign = 1.0;
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ssgBranch *sphere = new ssgBranch;
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sgVec2 vec2;
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sgVec3 vec3;
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drho = M_PI / (float) stacks;
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dtheta = 2.0 * M_PI / (float) slices;
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/* texturing: s goes from 0.0/0.25/0.5/0.75/1.0 at +y/+x/-y/-x/+y
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axis t goes from -1.0/+1.0 at z = -radius/+radius (linear along
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longitudes) cannot use triangle fan on texturing (s coord. at
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top/bottom tip varies) */
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ds = 1.0 / slices;
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dt = 1.0 / stacks;
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t = 1.0; /* because loop now runs from 0 */
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imin = 0;
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imax = stacks;
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/* build slices as quad strips */
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for ( i = imin; i < imax; i++ ) {
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ssgVertexArray *vl = new ssgVertexArray();
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ssgNormalArray *nl = new ssgNormalArray();
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ssgTexCoordArray *tl = new ssgTexCoordArray();
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rho = i * drho;
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s = 0.0;
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for ( j = 0; j <= slices; j++ ) {
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theta = (j == slices) ? 0.0 : j * dtheta;
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x = -sin(theta) * sin(rho);
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y = cos(theta) * sin(rho);
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z = nsign * cos(rho);
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// glNormal3f( x*nsign, y*nsign, z*nsign );
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sgSetVec3( vec3, x*nsign, y*nsign, z*nsign );
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nl->add( vec3 );
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// glTexCoord2f(s,t);
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sgSetVec2( vec2, 2, t );
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tl->add( vec2 );
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// glVertex3f( x*radius, y*radius, z*radius );
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sgSetVec3( vec3, x*radius, y*radius, z*radius );
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vl->add( vec3 );
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x = -sin(theta) * sin(rho+drho);
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y = cos(theta) * sin(rho+drho);
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z = nsign * cos(rho+drho);
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// glNormal3f( x*nsign, y*nsign, z*nsign );
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sgSetVec3( vec3, x*nsign, y*nsign, z*nsign );
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nl->add( vec3 );
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// glTexCoord2f(s,t-dt);
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sgSetVec2( vec2, s, t-dt );
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tl->add( vec2 );
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s += ds;
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// glVertex3f( x*radius, y*radius, z*radius );
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sgSetVec3( vec3, x*radius, y*radius, z*radius );
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vl->add( vec3 );
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}
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ssgLeaf *slice =
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new ssgVtxTable ( GL_TRIANGLE_STRIP, vl, nl, tl, NULL );
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slice->setState( state );
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sphere->addKid( slice );
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t -= dt;
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}
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return sphere;
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}
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