Next,
please look to the screenshot of the corrupted moving bounce
provided by the code:
#include
#include
#include
#define COS(X) cos( (X) * 3.14159/180.0 )
#define SIN(X) sin( (X) * 3.14159/180.0 )
#define RED 1
#define WHITE 2
#define CYAN 3
GLuint Ball;
GLenum Mode;
GLfloat Zrot = 0.0, Zstep = 6.0;
GLfloat Xpos = 0.0, Ypos = 1.0;
GLfloat Xvel = 0.2, Yvel = 0.0;
GLfloat Xmin = -4.0, Xmax = 4.0;
GLfloat Ymin = -3.8, Ymax = 4.0;
GLfloat G = -0.1;
static GLuint
make_ball(void)
{
GLuint list;
GLfloat a, b;
GLfloat da = 18.0, db = 18.0;
GLfloat radius = 1.0;
GLuint color;
GLfloat x, y, z;
list = glGenLists(1);
glNewList(list, GL_COMPILE);
color = 0;
for (a = -90.0; a + da <= 90.0; a += da) {
glBegin(GL_QUAD_STRIP);
for (b = 0.0; b <= 360.0; b += db) {
if (color) {
glIndexi(RED);
} else {
glIndexi(WHITE);
}
x = COS(b) * COS(a);
y = SIN(b) * COS(a);
z = SIN(a);
glVertex3f(x, y, z);
x = radius * COS(b) * COS(a + da);
y = radius * SIN(b) * COS(a + da);
z = radius * SIN(a + da);
glVertex3f(x, y, z);
color = 1 - color;
}
glEnd();
}
glEndList();
return list;
}
static void
reshape(int width, int height)
{
glViewport(0, 0, (GLint) width, (GLint) height);
glMatrixMode(GL_PROJECTION);
glLoadIdentity();
glOrtho(-6.0, 6.0, -6.0, 6.0, -6.0, 6.0);
glMatrixMode(GL_MODELVIEW);
}
/* ARGSUSED1 */
static void
key(unsigned char k, int x, int y)
{
switch (k) {
case 27: /* Escape */
exit(0);
}
}
static void
draw(void)
{
GLint i;
glClear(GL_COLOR_BUFFER_BIT);
glIndexi(CYAN);
glBegin(GL_LINES);
for (i = -5; i <= 5; i++) {
glVertex2i(i, -5);
glVertex2i(i, 5);
}
for (i = -5; i <= 5; i++) {
glVertex2i(-5, i);
glVertex2i(5, i);
}
for (i = -5; i <= 5; i++) {
glVertex2i(i, -5);
glVertex2f(i * 1.15, -5.9);
}
glVertex2f(-5.3, -5.35);
glVertex2f(5.3, -5.35);
glVertex2f(-5.75, -5.9);
glVertex2f(5.75, -5.9);
glEnd();
glPushMatrix();
glTranslatef(Xpos, Ypos, 0.0);
glScalef(2.0, 2.0, 2.0);
glRotatef(8.0, 0.0, 0.0, 1.0);
glRotatef(90.0, 1.0, 0.0, 0.0);
glRotatef(Zrot, 0.0, 0.0, 1.0);
glCallList(Ball);
glPopMatrix();
glFlush();
glutSwapBuffers();
}
static void
idle(void)
{
static float vel0 = -100.0;
Zrot += Zstep;
Xpos += Xvel;
if (Xpos >= Xmax) {
Xpos = Xmax;
Xvel = -Xvel;
Zstep = -Zstep;
}
if (Xpos <= Xmin) {
Xpos = Xmin;
Xvel = -Xvel;
Zstep = -Zstep;
}
Ypos += Yvel;
Yvel += G;
if (Ypos < Ymin) {
Ypos = Ymin;
if (vel0 == -100.0)
vel0 = fabs(Yvel);
Yvel = vel0;
}
glutPostRedisplay();
}
void
visible(int vis)
{
if (vis == GLUT_VISIBLE)
glutIdleFunc(idle);
else
glutIdleFunc(NULL);
}
main(int argc, char *argv[])
{
glutInit(&argc, argv);
glutInitDisplayMode(GLUT_RGBA|/*GLUT_INDEX|*/ GLUT_SINGLE);
glutCreateWindow("Bounce");
Ball = make_ball();
glCullFace(GL_BACK);
glEnable(GL_CULL_FACE);
glDisable(GL_DITHER);
glShadeModel(GL_FLAT);
glutDisplayFunc(draw);
glutReshapeFunc(reshape);
glutVisibilityFunc(visible);
glutKeyboardFunc(key);
glutSetColor(RED, 1.0, 0.0, 0.0);
glutSetColor(WHITE, 1.0, 1.0, 1.0);
glutSetColor(CYAN, 0.0, 1.0, 1.0);
glutMainLoop();
return 0; /* ANSI C requires main to return int. */
}
