USING C++ AND OPEN GL: Write a program that displays a cylinder of fixed height
ID: 3861873 • Letter: U
Question
USING C++ AND OPEN GL:
Write a program that displays a cylinder of fixed height and radius at world coordinate origin and allows the user to adjust the number of longitude and latitude lines used to approximate the cylinder's surface as a quadrilateral mesh. The user should also be able to switch between solid and wire-frame views of the cylinder. Vary the resolution of the mesh approximation and observe the visual appearance of the cylinder in the both solid and wire-frame mode. You may use cin to get data from the user.
Explanation / Answer
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <math.h>
#include <GL/glut.h>
#ifndef M_PI
#define M_PI 3.14159265
#endif
int win, win2;
int needsLightUpdate = GL_TRUE;
int useLighting = GL_TRUE;
int useSpecularTexture = GL_FALSE;
int useTexture = GL_FALSE;
int useHighRes = GL_FALSE;
int usePattern = GL_FALSE;
int moveLight = GL_FALSE;
int moveObject = GL_FALSE;
int drawObj = 0, maxObj = 2;
GLfloat lightRotX, lightRotY;
GLfloat objectRotX, objectRotY;
int curx, cury, width, h;
void
drawCylinder(int nummaj, int nummin, float h, float r)
{
double maj = h / nummaj;
double min = 2.0 * M_PI / nummin;
int i, j;
for (i = 0; i < nummaj; ++i) {
GLfloat z0 = 0.5 * h - i * maj;
GLfloat z1 = z0 - maj;
glBegin(GL_TRIANGLE_STRIP);
for (j = 0; j <= nummin; ++j) {
double a = j * min;
GLfloat x = r * cos(a);
GLfloat y = r * sin(a);
glNormal3f(x / r, y / r, 0.0);
glTexCoord2f(j / (GLfloat) nummin, i / (GLfloat) nummaj);
glVertex3f(x, y, z0);
glNormal3f(x / r, y / r, 0.0);
glTexCoord2f(j / (GLfloat) nummin, (i + 1) / (GLfloat) nummaj);
glVertex3f(x, y, z1);
}
glEnd();
}
}
void
initialize(void)
{
glMatrixMode(GL_PROJECTION);
glFrustum(-0.50, 0.50, -0.50, 0.50, 1.0, 3.0);
glMatrixMode(GL_MODELVIEW);
glTranslatef(0.0, 0.0, -2.0);
glDepthFunc(GL_LEQUAL);
glLightModeli(GL_LIGHT_MODEL_LOCAL_VIEWER, GL_TRUE);
}
void
redraw(void)
{
glClearColor(0.1, 0.1, 0.1, 1.0);
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
glBegin(GL_QUADS);
glColor3f(0.0, 0.3, 7.0);
glVertex3f(-2.0, -2.0, -1.0);
glColor3f(0.0, 0.3, 7.0);
glVertex3f(2.0, -2.0, -1.0);
glColor3f(0.0, 0.3, 0.7);
glVertex3f(2.0, 2.0, -1.0);
glColor3f(0.0, 0.3, 0.7);
glVertex3f(-2.0, 2.0, -1.0);
glEnd();
glEnable(GL_DEPTH_TEST);
if (useLighting) {
glEnable(GL_LIGHTING);
glPushMatrix();
glRotatef(lightRotY, 0, 1, 0);
glRotatef(lightRotX, 1, 0, 0);
glPopMatrix();
} else {
glColor3f(0.2, 0.2, 0.2);
}
if (useTexture || useSpecularTexture) {
glEnable(GL_TEXTURE_2D);
}
if (useSpecularTexture) {
/* pass one */
glEnable(GL_BLEND);
glBlendFunc(GL_ONE, GL_ZERO);
}
glPushMatrix();
glRotatef(objectRotY, 0, 1, 0);
glRotatef(objectRotX, 1, 0, 0);
drawCylinder(6, 16, 1.0, 0.4);
glPopMatrix();
if (useSpecularTexture) {
/* pass two */
if (!useLighting) {
glColor3f(1.0, 1.0, 1.0);
}
glBlendFunc(GL_ONE, GL_ONE);
glEnable(GL_TEXTURE_GEN_S);
glEnable(GL_TEXTURE_GEN_T);
glTexGeni(GL_S, GL_TEXTURE_GEN_MODE, GL_SPHERE_MAP);
glTexGeni(GL_T, GL_TEXTURE_GEN_MODE, GL_SPHERE_MAP);
glPushMatrix();
glRotatef(objectRotY, 0, 1, 0);
glRotatef(objectRotX, 1, 0, 0);
drawCylinder(6, 16, 1.0, 0.4);
glPopMatrix();
}
glDisable(GL_DEPTH_TEST);
glDisable(GL_LIGHTING);
glDisable(GL_TEXTURE_2D);
glDisable(GL_BLEND);
glDisable(GL_TEXTURE_GEN_S);
glDisable(GL_TEXTURE_GEN_T);
}
void
motion(int x, int y)
{
if (moveLight || moveObject) {
GLfloat dx = (y - cury) * 360.0 / h;
GLfloat dy = (x - curx) * 360.0 / width;
if (moveLight) {
lightRotX += dx;
if (lightRotX > 360)
lightRotX -= 360;
if (lightRotX < 0)
lightRotX += 360;
lightRotY += dy;
if (lightRotY > 360)
lightRotY -= 360;
if (lightRotY < 0)
lightRotY += 360;
needsLightUpdate = GL_TRUE;
} else if (moveObject) {
objectRotX += dx;
if (objectRotX > 360)
objectRotX -= 360;
if (objectRotX < 0)
objectRotX += 360;
objectRotY += dy;
if (objectRotY > 360)
objectRotY -= 360;
if (objectRotY < 0)
objectRotY += 360;
}
curx = x;
cury = y;
}
glutPostRedisplay();
}
void
mouse(int button, int state, int x, int y)
{
if (state == GLUT_DOWN) {
switch (button) {
case GLUT_LEFT_BUTTON:
moveObject = GL_TRUE;
motion(curx = x, cury = y);
break;
case GLUT_MIDDLE_BUTTON:
moveLight = GL_TRUE;
motion(curx = x, cury = y);
break;
}
} else if (state == GLUT_UP) {
switch (button) {
case GLUT_LEFT_BUTTON:
moveObject = GL_FALSE;
break;
case GLUT_MIDDLE_BUTTON:
moveLight = GL_FALSE;
break;
}
}
}
void
display(void)
{
redraw();
glFlush();
glutSwapBuffers();
}
int main (int argc, char **argv)
{
int i;
glutInit(&argc, argv);
glutInitWindowSize(width = 500, h = 500);
glutInitDisplayMode(GLUT_RGBA | GLUT_DEPTH | GLUT_DOUBLE);
for (i = 1; i < argc; ++i) {
exit(1);
}
win = glutCreateWindow("envphong");
glutDisplayFunc(display);
glutMouseFunc(mouse);
glutMotionFunc(motion);
initialize();
glutMainLoop();
return 0;
}
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