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gears.c
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/* gears.c */
/*
* 3-D gear wheels. This program is in the public domain.
*
* Brian Paul
*/
#include <math.h>
#include <stdlib.h>
#include <stdio.h>
#include <string.h>
#include <GL/gl.h>
#include "ui.h"
#ifndef M_PI
# define M_PI 3.14159265
#endif
/*
* Draw a gear wheel. You'll probably want to call this function when
* building a display list since we do a lot of trig here.
*
* Input: inner_radius - radius of hole at center
* outer_radius - radius at center of teeth
* width - width of gear
* teeth - number of teeth
* tooth_depth - depth of tooth
*/
static void gear( GLfloat inner_radius, GLfloat outer_radius, GLfloat width,
GLint teeth, GLfloat tooth_depth )
{
GLint i;
GLfloat r0, r1, r2;
GLfloat angle, da;
GLfloat u, v, len;
r0 = inner_radius;
r1 = outer_radius - tooth_depth/2.0;
r2 = outer_radius + tooth_depth/2.0;
da = 2.0*M_PI / teeth / 4.0;
glShadeModel( GL_FLAT );
glNormal3f( 0.0, 0.0, 1.0 );
/* draw front face */
glBegin( GL_QUAD_STRIP );
for (i=0;i<=teeth;i++) {
angle = i * 2.0*M_PI / teeth;
glVertex3f( r0*cos(angle), r0*sin(angle), width*0.5 );
glVertex3f( r1*cos(angle), r1*sin(angle), width*0.5 );
glVertex3f( r0*cos(angle), r0*sin(angle), width*0.5 );
glVertex3f( r1*cos(angle+3*da), r1*sin(angle+3*da), width*0.5 );
}
glEnd();
/* draw front sides of teeth */
glBegin( GL_QUADS );
da = 2.0*M_PI / teeth / 4.0;
for (i=0;i<teeth;i++) {
angle = i * 2.0*M_PI / teeth;
glVertex3f( r1*cos(angle), r1*sin(angle), width*0.5 );
glVertex3f( r2*cos(angle+da), r2*sin(angle+da), width*0.5 );
glVertex3f( r2*cos(angle+2*da), r2*sin(angle+2*da), width*0.5 );
glVertex3f( r1*cos(angle+3*da), r1*sin(angle+3*da), width*0.5 );
}
glEnd();
glNormal3f( 0.0, 0.0, -1.0 );
/* draw back face */
glBegin( GL_QUAD_STRIP );
for (i=0;i<=teeth;i++) {
angle = i * 2.0*M_PI / teeth;
glVertex3f( r1*cos(angle), r1*sin(angle), -width*0.5 );
glVertex3f( r0*cos(angle), r0*sin(angle), -width*0.5 );
glVertex3f( r1*cos(angle+3*da), r1*sin(angle+3*da), -width*0.5 );
glVertex3f( r0*cos(angle), r0*sin(angle), -width*0.5 );
}
glEnd();
/* draw back sides of teeth */
glBegin( GL_QUADS );
da = 2.0*M_PI / teeth / 4.0;
for (i=0;i<teeth;i++) {
angle = i * 2.0*M_PI / teeth;
glVertex3f( r1*cos(angle+3*da), r1*sin(angle+3*da), -width*0.5 );
glVertex3f( r2*cos(angle+2*da), r2*sin(angle+2*da), -width*0.5 );
glVertex3f( r2*cos(angle+da), r2*sin(angle+da), -width*0.5 );
glVertex3f( r1*cos(angle), r1*sin(angle), -width*0.5 );
}
glEnd();
/* draw outward faces of teeth */
glBegin( GL_QUAD_STRIP );
for (i=0;i<teeth;i++) {
angle = i * 2.0*M_PI / teeth;
glVertex3f( r1*cos(angle), r1*sin(angle), width*0.5 );
glVertex3f( r1*cos(angle), r1*sin(angle), -width*0.5 );
u = r2*cos(angle+da) - r1*cos(angle);
v = r2*sin(angle+da) - r1*sin(angle);
len = sqrt( u*u + v*v );
u /= len;
v /= len;
glNormal3f( v, -u, 0.0 );
glVertex3f( r2*cos(angle+da), r2*sin(angle+da), width*0.5 );
glVertex3f( r2*cos(angle+da), r2*sin(angle+da), -width*0.5 );
glNormal3f( cos(angle), sin(angle), 0.0 );
glVertex3f( r2*cos(angle+2*da), r2*sin(angle+2*da), width*0.5 );
glVertex3f( r2*cos(angle+2*da), r2*sin(angle+2*da), -width*0.5 );
u = r1*cos(angle+3*da) - r2*cos(angle+2*da);
v = r1*sin(angle+3*da) - r2*sin(angle+2*da);
glNormal3f( v, -u, 0.0 );
glVertex3f( r1*cos(angle+3*da), r1*sin(angle+3*da), width*0.5 );
glVertex3f( r1*cos(angle+3*da), r1*sin(angle+3*da), -width*0.5 );
glNormal3f( cos(angle), sin(angle), 0.0 );
}
glVertex3f( r1*cos(0), r1*sin(0), width*0.5 );
glVertex3f( r1*cos(0), r1*sin(0), -width*0.5 );
glEnd();
glShadeModel( GL_SMOOTH );
/* draw inside radius cylinder */
glBegin( GL_QUAD_STRIP );
for (i=0;i<=teeth;i++) {
angle = i * 2.0*M_PI / teeth;
glNormal3f( -cos(angle), -sin(angle), 0.0 );
glVertex3f( r0*cos(angle), r0*sin(angle), -width*0.5 );
glVertex3f( r0*cos(angle), r0*sin(angle), width*0.5 );
}
glEnd();
}
static GLfloat view_rotx=20.0, view_roty=30.0, view_rotz=0.0;
static GLint gear1, gear2, gear3;
static GLfloat angle = 0.0;
static GLuint limit;
static GLuint count = 1;
void draw( void )
{
glClear( GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT );
glPushMatrix();
glRotatef( view_rotx, 1.0, 0.0, 0.0 );
glRotatef( view_roty, 0.0, 1.0, 0.0 );
glRotatef( view_rotz, 0.0, 0.0, 1.0 );
glPushMatrix();
glTranslatef( -3.0, -2.0, 0.0 );
glRotatef( angle, 0.0, 0.0, 1.0 );
glCallList(gear1);
glPopMatrix();
glPushMatrix();
glTranslatef( 3.1, -2.0, 0.0 );
glRotatef( -2.0*angle-9.0, 0.0, 0.0, 1.0 );
glCallList(gear2);
glPopMatrix();
glPushMatrix();
glTranslatef( -3.1, 4.2, 0.0 );
glRotatef( -2.0*angle-25.0, 0.0, 0.0, 1.0 );
glCallList(gear3);
glPopMatrix();
glPopMatrix();
swap_buffers();
count++;
if (count==limit) {
exit(0);
}
}
void idle( void )
{
angle += 2.0;
draw();
}
/* change view angle, exit upon ESC */
GLenum key(int k)
{
switch (k) {
case KEY_UP:
view_rotx += 5.0;
return GL_TRUE;
case KEY_DOWN:
view_rotx -= 5.0;
return GL_TRUE;
case KEY_LEFT:
view_roty += 5.0;
return GL_TRUE;
case KEY_RIGHT:
view_roty -= 5.0;
return GL_TRUE;
case 'z':
view_rotz += 5.0;
return GL_TRUE;
case 'Z':
view_rotz -= 5.0;
return GL_TRUE;
case KEY_ESCAPE:
exit(0);
}
return GL_FALSE;
}
/* new window size or exposure */
void reshape( int width, int height )
{
GLfloat h = (GLfloat) height / (GLfloat) width;
glViewport(0, 0, (GLint)width, (GLint)height);
glMatrixMode(GL_PROJECTION);
glLoadIdentity();
glFrustum( -1.0, 1.0, -h, h, 5.0, 60.0 );
glMatrixMode(GL_MODELVIEW);
glLoadIdentity();
glTranslatef( 0.0, 0.0, -40.0 );
glClear( GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT );
}
void init( void )
{
static GLfloat pos[4] = {5.0, 5.0, 10.0, 0.0 };
static GLfloat red[4] = {0.8, 0.1, 0.0, 1.0 };
static GLfloat green[4] = {0.0, 0.8, 0.2, 1.0 };
static GLfloat blue[4] = {0.2, 0.2, 1.0, 1.0 };
glLightfv( GL_LIGHT0, GL_POSITION, pos );
glEnable( GL_CULL_FACE );
glEnable( GL_LIGHTING );
glEnable( GL_LIGHT0 );
glEnable( GL_DEPTH_TEST );
/* make the gears */
gear1 = glGenLists(1);
glNewList(gear1, GL_COMPILE);
glMaterialfv( GL_FRONT, GL_AMBIENT_AND_DIFFUSE, red );
gear( 1.0, 4.0, 1.0, 20, 0.7 );
glEndList();
gear2 = glGenLists(1);
glNewList(gear2, GL_COMPILE);
glMaterialfv( GL_FRONT, GL_AMBIENT_AND_DIFFUSE, green );
gear( 0.5, 2.0, 2.0, 10, 0.7 );
glEndList();
gear3 = glGenLists(1);
glNewList(gear3, GL_COMPILE);
glMaterialfv( GL_FRONT, GL_AMBIENT_AND_DIFFUSE, blue );
gear( 1.3, 2.0, 0.5, 10, 0.7 );
glEndList();
glEnable( GL_NORMALIZE );
}
int main(int argc, char **argv)
{
return ui_loop(argc, argv, "gears");
}