Source Code

main.cpp:

// Alexandri Zavodny
// CSE 40166: Computer Graphics, Fall 2010
// Example: simple vehicle with hierarchical matrix structure


#include <math.h>
#include <GL/glut.h>
#include <stdio.h>
#include <stdlib.h>

#include "point.h"

#define WHEEL_UP 3
#define WHEEL_DOWN 4

// GLOBAL VARIABLES ////////////////////////////////////////////////////////////

static size_t windowWidth = 640;
static size_t windowHeight = 480;
static float aspectRatio;


GLint leftMouseButton, 
        rightMouseButton,
        midMouseButton;                     //status of the mouse buttons
int mouseX = 0, mouseY = 0;                 //last known X and Y of the mouse

Point cameraTPR, cameraXYZ;                 //camera position in spherical and 
                                            //cartesian coordinates

GLUquadric *quad = NULL;                    //allocate this once at the start
                                            //of the program and re-use it!

bool arrowKeyStates[4] = {false};           //boolean vector which determines
                                            //whether an arrow key has been 
                                            //held down.  [0-3] = [left, right, up, down]

Point carPosition;
float carTheta;
float carAnimationValue = 0.0f;             //this value changes whenever the car gets moved, etc.
                                            //and the amount that it changes is based on distance moved.
                                            //we save one value and use it to rotate wheels and such
                                            //just so we don't have to save the rotation of each component
                                            //of the car.

int lastTime = 0;                           //update this each frame with glutGet(GLUT_ELAPSED_TIME),
                                            //and compare it against the current result of glutGet(GLUT_ELAPSED_TIME)
                                            //to see how much time has passed between frame renderings.


// recomputeOrientation() //////////////////////////////////////////////////////
//
// This function updates the camera's position in cartesian coordinates based 
//  on its position in spherical coordinates. Should be called every time 
//  cameraTPR.x, cameraTPR.y, or cameraTPR.z is updated. 
//
////////////////////////////////////////////////////////////////////////////////
void recomputeOrientation()
{
    cameraXYZ.x = cameraTPR.z *  sinf(cameraTPR.x)*sinf(cameraTPR.y);
    cameraXYZ.z = cameraTPR.z * -cosf(cameraTPR.x)*sinf(cameraTPR.y);
    cameraXYZ.y = cameraTPR.z * -cosf(cameraTPR.y);

    glutPostRedisplay();
}

// resizeWindow() //////////////////////////////////////////////////////////////
//
//  GLUT callback for window resizing. Resets GL_PROJECTION matrix and viewport.
//
////////////////////////////////////////////////////////////////////////////////
void resizeWindow(int w, int h)
{
    aspectRatio = w / (float)h;

    windowWidth = w;
    windowHeight = h;

    //update the viewport to fill the window
    glViewport(0, 0, w, h);

    //update the projection matrix with the new window properties
    glMatrixMode(GL_PROJECTION);
    glLoadIdentity();
    gluPerspective(45.0,aspectRatio,0.1,100000);
}

// drawGrid() //////////////////////////////////////////////////////////////////
//
//  Draws a 10x10 grid around the origin in the XZ plane. Just to give the scene
//      a sense of scale.
//
////////////////////////////////////////////////////////////////////////////////
void drawGrid()
{
    glPushAttrib(GL_LIGHTING_BIT);
    glDisable(GL_LIGHTING);


    for(int k = 0; k < 2; k++)
    {
        for(int i = -5; i < 6; i++)
        {
            glBegin(GL_LINE_STRIP);
            for(int j = -5; j < 6; j++)
                glVertex3f(k==0?i:j, 0, k==0?j:i);
            glEnd();
        }
    }

    glPopAttrib();
}


// drawSolidBox() //////////////////////////////////////////////////////////////
//
//  Draws a solid box of the specified dimensions at the current point.
//  Uses glutSolidCube to draw something that has appropriate normals, texture
//      coordinates, etc., but since glutSolidCube can only draw a cube, we push
//      and pop a scale matrix so that the cube gets drawn as a box with 
//      specified dimensions. We do this instead in a function just so that
//      we don't have to worry about glScalef affecting our other matrices later.
//
////////////////////////////////////////////////////////////////////////////////
void drawSolidBox(float xSize, float ySize, float zSize)
{
    glPushMatrix();
        glScalef(xSize, ySize, zSize);
        glutSolidCube(1.0f);
    glPopMatrix();
}


// drawCylinder() //////////////////////////////////////////////////////////////
//
//  Because we have to use a gluQuadric object to draw a cylinder, and that's
//      less than pretty -- AND, because we have to draw the caps on the ends
//      of the cylinder ourself, put all that code in its own function.
//
////////////////////////////////////////////////////////////////////////////////
void drawCylinder(float outerRadius, float innerRadius, float wheelDepth, int resolution)
{
    gluQuadricOrientation(quad, GLU_OUTSIDE);   //ensure that winding order is appropriate
    gluCylinder(quad, outerRadius, outerRadius, wheelDepth, resolution, 1);
    glPushMatrix();
        glTranslatef(0,0,wheelDepth);
        gluDisk(quad, innerRadius, outerRadius, resolution, 1);
    glPopMatrix();

    gluQuadricOrientation(quad, GLU_INSIDE);
    gluCylinder(quad, innerRadius, innerRadius, wheelDepth, resolution, 1);
    //gluCylinder sets the left side of the cylinder at the current Z
    //position, so no need to translate now
    gluDisk(quad, innerRadius, outerRadius, resolution, 1);

    gluQuadricOrientation(quad, GLU_OUTSIDE);   //ensure that winding order is appropriate
}

// drawWheel() /////////////////////////////////////////////////////////////////
//
//  Draws a wheel at the current OpenGL location. We have this code in its own
//      function because we're going to be drawing 4 wheels for the car and
//      they're all going to be the same. 
//
////////////////////////////////////////////////////////////////////////////////
void drawWheel()
{
    //the cylinder is most of the wheel! no lie.
    drawCylinder(0.5f, 0.4f, 0.1f, 16);

    //draw some spokes
    glPushMatrix();
        glTranslatef(0,0,0.05f);

        for(int i = 0; i < 8; i++)
        {
            glPushMatrix();
            glRotatef(45*i, 0,0,-1);
            glTranslatef(0,0.25,0);

            drawSolidBox(0.1,0.4,0.1);
            glPopMatrix();
        }
    glPopMatrix();
}

// drawCar() ///////////////////////////////////////////////////////////////////
//
//  Draws our car! ... at the specified position, and pointing in the direction
//      of carTheta. Also uses the global variable carAnimation to control
//      how much its parts should move.
//
////////////////////////////////////////////////////////////////////////////////
void drawCar(float x, float y, float z, float carTheta)
{
    glPushMatrix();

    glTranslatef(x,y,z);
    glRotatef(carTheta*180/M_PI, 0, -1 ,0);

    //draw the body of the car
    drawSolidBox(2,1,1);

    //and the, uh, cockpit?
    glPushMatrix();
        glTranslatef(-0.5,0.75,0);
        drawSolidBox(1,0.5,1);

        //and, like, a helicopter blade.
        float heliSpeed = 15;              //heheh it's moving "heli fast"
        glPushMatrix();
            glTranslatef(0,0.5,0);
            glRotatef(carAnimationValue*heliSpeed, 0, 1, 0);

            drawSolidBox(0.1,1,0.1);
            
            //move on top of the rotor...
            glTranslatef(0,0.5,0);

            drawSolidBox(1.5,0.1,0.1);
            drawSolidBox(0.1,0.1,1.5);
        glPopMatrix();

    glPopMatrix();


    float wheelSpeed = 5.0f;
    //all four wheels...
    //wheel one...
    glPushMatrix();
        glTranslatef(-0.75, 0, 0.5);
        glRotatef(carAnimationValue*wheelSpeed, 0, 0, -1);
        drawWheel();
    glPopMatrix();

    //wheel two...
    glPushMatrix();
        glTranslatef(0.75, 0, 0.5);
        glRotatef(carAnimationValue*wheelSpeed, 0, 0, -1);
        drawWheel();
    glPopMatrix();
    
    //wheel three....
    glPushMatrix();
        glTranslatef(-0.75, 0, -0.6);
        glRotatef(carAnimationValue*wheelSpeed, 0, 0, -1);
        drawWheel();
    glPopMatrix();

    //wheel the fourth
    glPushMatrix();
        glTranslatef(0.75, 0, -0.6);
        //this one is the gimp wheel so it rotates 3/4s the speed
        glRotatef(carAnimationValue*wheelSpeed*0.75, 0, 0, -1);
        drawWheel();
    glPopMatrix();

    //and because we're awesome we're gonna do some freaking sparkle.. things... off the back
    float tailSpeed = 2.0f;
    glPushMatrix();
        glTranslatef(-1.0f, 0.25, 0);
        
        glPushMatrix();
            glRotatef(15*cosf(carAnimationValue*tailSpeed/2.0),0,1,0);
            glTranslatef(-0.5f,0,0);

            //the first tail segment!
            drawSolidBox(1,0.125,0.125);

            glTranslatef(-0.5,0,0);
            glRotatef(15*cosf(carAnimationValue*tailSpeed/2.0),0,1,0);
            glTranslatef(-0.25,0,0);

            //the second tail segment!
            drawSolidBox(0.5,0.10,0.10);

            glTranslatef(-0.3,0,0);
            glRotatef(15*cosf(carAnimationValue*tailSpeed/2.0), 0, 1, 0);
            glTranslatef(-0.1,0,0);

            //the final tail segment!
            drawSolidBox(0.3, 0.1, 0.1);
        glPopMatrix();
    glPopMatrix();


    glPopMatrix();
}


// mouseCallback() /////////////////////////////////////////////////////////////
//
//  GLUT callback for mouse clicks. We save the state of the mouse button
//      when this is called so that we can check the status of the mouse
//      buttons inside the motion callback (whether they are up or down).
//
////////////////////////////////////////////////////////////////////////////////
void mouseCallback(int button, int state, int thisX, int thisY)
{
    //update the left and right mouse button states, if applicable
    if(button == GLUT_LEFT_BUTTON)
        leftMouseButton = state;
    else if(button == GLUT_RIGHT_BUTTON)
        rightMouseButton = state;
    else if(button == GLUT_MIDDLE_BUTTON)
        midMouseButton = state;

    if(button == WHEEL_UP)
    {
        cameraTPR.z += 0.05;
        recomputeOrientation();
    }

    if(button == WHEEL_DOWN)
    {
        cameraTPR.z -= 0.05;
        recomputeOrientation();
    }

    //and update the last seen X and Y coordinates of the mouse
    mouseX = thisX;
    mouseY = thisY;
}

// mouseMotion() ///////////////////////////////////////////////////////////////
//
//  GLUT callback for mouse movement. We update cameraTPR.y, cameraTPR.x, and/or
//      cameraTPR.z based on how much the user has moved the mouse in the
//      X or Y directions (in screen space) and whether they have held down
//      the left or right mouse buttons. If the user hasn't held down any
//      buttons, the function just updates the last seen mouse X and Y coords.
//
////////////////////////////////////////////////////////////////////////////////
void mouseMotion(int x, int y)
{
    if(leftMouseButton == GLUT_DOWN)
    {
        cameraTPR.x += (x - mouseX)*0.005;
        cameraTPR.y += (y - mouseY)*0.005;

        // make sure that phi stays within the range (0, M_PI)
        if(cameraTPR.y <= 0)
            cameraTPR.y = 0+0.001;
        if(cameraTPR.y >= M_PI)
            cameraTPR.y = M_PI-0.001;
        
        
        recomputeOrientation();     //update camera (x,y,z) based on (radius,theta,phi)
    } else if(rightMouseButton == GLUT_DOWN || midMouseButton == GLUT_DOWN) {
        double totalChangeSq = (x - mouseX) + (y - mouseY);
        
        cameraTPR.z += totalChangeSq*0.01;
        
        //limit the camera radius to some reasonable values so the user can't get lost
        if(cameraTPR.z < 1.0) 
            cameraTPR.z = 1.0;
        if(cameraTPR.z > 40.0) 
            cameraTPR.z = 40.0;

        recomputeOrientation();     //update camera (x,y,z) based on (radius,theta,phi)
    }
    mouseX = x;
    mouseY = y;
}



// initScene() /////////////////////////////////////////////////////////////////
//
//  A basic scene initialization function; should be called once after the
//      OpenGL context has been created. Doesn't need to be called further.
//
////////////////////////////////////////////////////////////////////////////////
void initScene() 
{
    glEnable(GL_DEPTH_TEST);

    float lightCol[4] = { 1, 1, 1, 1};
    float ambientCol[4] = {0.3, 0.3, 0.3, 1.0};
    glLightfv(GL_LIGHT0,GL_DIFFUSE,lightCol);
    glLightfv(GL_LIGHT0, GL_AMBIENT, ambientCol);
    glEnable(GL_LIGHTING);
    glEnable(GL_LIGHT0);


    glShadeModel(GL_SMOOTH);
    //glShadeModel(GL_FLAT);
}


// doUpdateLogic() /////////////////////////////////////////////////////////////
//
//  This function, which should get called once per preframe, updates the position
//      of objects in the scene based on what keys the user has held down, if any.
//
////////////////////////////////////////////////////////////////////////////////
void doUpdateLogic(float secondsElapsed)
{
    //check the key states
    float movementConstant = secondsElapsed*2;
    if(arrowKeyStates[2])
    {
        float xMovement = cosf(carTheta)*movementConstant;
        float zMovement = sinf(carTheta)*movementConstant;
        carPosition.x += xMovement;
        carPosition.z += zMovement;
    }

    if(arrowKeyStates[3])
    {
        float xMovement = cosf(carTheta)*movementConstant;
        float zMovement = sinf(carTheta)*movementConstant;
        carPosition.x -= xMovement;
        carPosition.z -= zMovement;
    }

    if(arrowKeyStates[0])
        carTheta += movementConstant;

    if(arrowKeyStates[1])
        carTheta -= movementConstant;

    //update the car's animation value! and speed it up a bit cause.. why not.
    carAnimationValue += (arrowKeyStates[2] ^ arrowKeyStates[3]) ? 0.005f : 0.0f;
}

// renderScene() ///////////////////////////////////////////////////////////////
//
//  GLUT callback for scene rendering. Sets up the modelview matrix, renders
//      a teapot to the back buffer, and switches the back buffer with the
//      front buffer (what the user sees).
//
////////////////////////////////////////////////////////////////////////////////
void renderScene(void) 
{
    int currentTime = glutGet(GLUT_ELAPSED_TIME);
    float timeDifference = (currentTime - lastTime) / 1000.0f;
    lastTime = currentTime;
    doUpdateLogic(timeDifference);

    //update the modelview matrix based on the camera's position
    glMatrixMode(GL_MODELVIEW);         //make sure we aren't changing the projection matrix!
    glLoadIdentity();
    gluLookAt(cameraXYZ.x, cameraXYZ.y, cameraXYZ.z,    //camera is located at (x,y,z)
                0, 0, 0,                                //camera is looking at (0,0,0)
                0.0f,1.0f,0.0f);                        //up vector is (0,1,0) (positive Y)

    float lPosition[4] = { 10, 10, 10, 1 };
    glLightfv(GL_LIGHT0,GL_POSITION,lPosition);

    //clear the render buffer
    glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);

    glEnable(GL_NORMALIZE);
    drawCar(carPosition.x, carPosition.y, carPosition.z, carTheta);

    drawGrid();


    //push the back buffer to the screen
    glutSwapBuffers();
}


// normalKeys() ////////////////////////////////////////////////////////////////
//
//  GLUT keyboard callback.
//
////////////////////////////////////////////////////////////////////////////////
void normalKeys(unsigned char key, int x, int y) 
{
    if(key == 'q' || key == 'Q')
        exit(0);
}


// specialKeys() ///////////////////////////////////////////////////////////////
//
//  The GLUT callback for when arrow keys are pressed. Updates the status
//      array appropriately.
//
////////////////////////////////////////////////////////////////////////////////
void specialKeys(int key, int x, int y)
{
    if(key == GLUT_KEY_LEFT)
        arrowKeyStates[0] = true;

    if(key == GLUT_KEY_RIGHT)
        arrowKeyStates[1] = true;

    if(key == GLUT_KEY_UP)
        arrowKeyStates[2] = true;

    if(key == GLUT_KEY_DOWN)
        arrowKeyStates[3] = true;

    glutPostRedisplay();
}

// specialKeysUp() /////////////////////////////////////////////////////////////
//
//  The GLUT callback for when arrow keys are released. Updates the status
//      array appropriately.
//
////////////////////////////////////////////////////////////////////////////////
void specialKeysUp(int key, int x, int y)
{
    if(key == GLUT_KEY_LEFT)
        arrowKeyStates[0] = false;

    if(key == GLUT_KEY_RIGHT)
        arrowKeyStates[1] = false;

    if(key == GLUT_KEY_UP)
        arrowKeyStates[2] = false;

    if(key == GLUT_KEY_DOWN)
        arrowKeyStates[3] = false;
}


// main() //////////////////////////////////////////////////////////////////////
//
//  Program entry point. Does not process command line arguments.
//
////////////////////////////////////////////////////////////////////////////////
int main(int argc, char **argv)
{
    //create a double-buffered GLUT window at (50,50) with predefined windowsize
    glutInit(&argc, argv);
    glutInitDisplayMode(GLUT_DEPTH | GLUT_DOUBLE | GLUT_RGBA);
    glutInitWindowPosition(50,50);
    glutInitWindowSize(windowWidth,windowHeight);
    glutCreateWindow("beep beep! it's not a jeep.");

    //give the camera a 'pretty' starting point!
    cameraTPR.z = 10.0f;
    cameraTPR.x = 2.80;
    cameraTPR.y = 2.0;
    recomputeOrientation();

    carPosition = Point(0,0.5,0);
    carTheta = 0.0f;
    quad = gluNewQuadric();

    //register callback functions...
    glutKeyboardFunc(normalKeys);
    glutSpecialFunc(specialKeys);
    glutSpecialUpFunc(specialKeysUp);
    glutDisplayFunc(renderScene);
    glutIdleFunc(renderScene);
    glutReshapeFunc(resizeWindow);
    glutMouseFunc(mouseCallback);
    glutMotionFunc(mouseMotion);

    //do some basic OpenGL setup
    initScene();

    //and enter the GLUT loop, never to exit.
    glutMainLoop();

    return(0);
}

Files

• Makefile
• main.cpp
• point.cpp
• point.h