Write an OpenGL program that draws a 3D drone (use your imagination, the geometr

Question

Write an OpenGL program that draws a 3D drone (use your imagination, the geometry can be as simple as you like) that uses shaders (no credit will be given to immediate mode coded projects). You are free to implement any sort of drone you wish. The constraint is that the data points that are the model for the drone must be meaningful in 3D (i.e. non-planar). You can choose how to connect them, etc. You are NOT required to implement hidden surface removal for this project. You can choose to draw objects using a wireframe approach or filled in.

Explanation / Answer

#include <stdio.h>

#include <stdlib.h>

#include <string.h>

#include <GL/glut.h>

static int stencilOn = 1;

/* function declarations */

void

drawScene(void), setMatrix(void), animation(void), resize(int w, int h),

keyboard(unsigned char c, int x, int y), menu(int choice), drawWireframe(int face),

drawFilled(int face);

/* global variables */

float ax, ay, az;       /* angles for animation */

/* coords of a cube */

static GLfloat cube[8][3] =

{0.0, 0.0, 0.0,

1.0, 0.0, 0.0,

1.0, 0.0, 1.0,

0.0, 0.0, 1.0,

1.0, 1.0, 0.0,

1.0, 1.0, 1.0,

0.0, 1.0, 1.0,

0.0, 1.0, 0.0};

static int faceIndex[6][4] =

{0, 1, 2, 3,

1, 4, 5, 2,

4, 7, 6, 5,

7, 0, 3, 6,

3, 2, 5, 6,

7, 4, 1, 0};

int

main(int argc, char **argv)

{

glutInit(&argc, argv);

glutInitWindowSize(400, 400);

glutInitDisplayMode(GLUT_RGB | GLUT_STENCIL | GLUT_DOUBLE | GLUT_DEPTH);

glutCreateWindow("Stenciled hidden surface removal");

ax = 10.0;

ay = -10.0;

az = 0.0;

glutDisplayFunc(drawScene);

glutReshapeFunc(resize);

glutCreateMenu(menu);

glutAddMenuEntry("Motion", 3);

glutAddMenuEntry("Stencil on", 1);

glutAddMenuEntry("Stencil off", 2);

glutAttachMenu(GLUT_RIGHT_BUTTON);

glutKeyboardFunc(keyboard);

glutMainLoop();

return 0;             /* ANSI C requires main to return int. */

}

void

drawWireframe(int face)

{

int i;

glBegin(GL_LINE_LOOP);

for (i = 0; i < 4; i++)

    glVertex3fv((GLfloat *) cube[faceIndex[face][i]]);

glEnd();

}

void

drawFilled(int face)

{

int i;

glBegin(GL_POLYGON);

for (i = 0; i < 4; i++)

    glVertex3fv((GLfloat *) cube[faceIndex[face][i]]);

glEnd();

}

void

drawScene(void)

{

int i;

glEnable(GL_DEPTH_TEST);

glDepthFunc(GL_LEQUAL);

glClearColor(0.0, 0.0, 0.0, 0.0);

glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);

glPushMatrix();

glRotatef(ax, 1.0, 0.0, 0.0);

glRotatef(-ay, 0.0, 1.0, 0.0);

/* all the good stuff follows */

if (stencilOn) {

    glEnable(GL_STENCIL_TEST);

    glClear(GL_STENCIL_BUFFER_BIT);

    glStencilMask(1);

    glStencilFunc(GL_ALWAYS, 0, 1);

    glStencilOp(GL_INVERT, GL_INVERT, GL_INVERT);

}

glColor3f(1.0, 1.0, 0.0);

for (i = 0; i < 6; i++) {

    drawWireframe(i);

    if (stencilOn) {

     glStencilFunc(GL_EQUAL, 0, 1);

      glStencilOp(GL_KEEP, GL_KEEP, GL_KEEP);

    }

    glColor3f(0.0, 0.0, 0.0);

    drawFilled(i);

    glColor3f(1.0, 1.0, 0.0);

    if (stencilOn) {

      glStencilFunc(GL_ALWAYS, 0, 1);

      glStencilOp(GL_INVERT, GL_INVERT, GL_INVERT);

    }

    glColor3f(1.0, 1.0, 0.0);

    drawWireframe(i);

}

glPopMatrix();

if (stencilOn)

    glDisable(GL_STENCIL_TEST);

/* end of good stuff */

glutSwapBuffers();

}

void

setMatrix(void)

{

glMatrixMode(GL_PROJECTION);

glLoadIdentity();

glOrtho(-2.0, 2.0, -2.0, 2.0, -2.0, 2.0);

glMatrixMode(GL_MODELVIEW);

glLoadIdentity();

}

int count = 0;

void

animation(void)

{

/* animate the cone */

ax += 5.0;

ay -= 2.0;

az += 5.0;

if (ax >= 360)

    ax = 0.0;

if (ay <= -360)

    ay = 0.0;

if (az >= 360)

    az = 0.0;

glutPostRedisplay();

count++;

if (count >= 60)

    glutIdleFunc(NULL);

}

void

menu(int choice)

{

switch (choice) {

case 3:

    count = 0;

    glutIdleFunc(animation);

    break;

case 2:

    stencilOn = 0;

    glutSetWindowTitle("Stencil Disabled");

    glutPostRedisplay();

    break;

case 1:

    stencilOn = 1;

    glutSetWindowTitle("Stencil Enabled");

    glutPostRedisplay();

    break;

}

}

/* ARGSUSED1 */

void

keyboard(unsigned char c, int x, int y)

{

switch (c) {

case 27:

    exit(0);

    break;

default:

    break;

}

}

void

resize(int w, int h)

{

glViewport(0, 0, w, h);

setMatrix();

}

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