Source Code

main.cpp:

// Alexandri Zavodny
// CSE 40166: Computer Graphics, Fall 2010
// Example: bezier curve interpolation


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

#include "point.h"

using namespace std;

#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

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

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.

vector<Point> controlPoints;
int bezierResolution = 20;
int selectedControlPoint = -1;
const size_t SELECTBUF_SIZE = 512;
GLuint selectBuf[SELECTBUF_SIZE];

float viewportWidth, viewportHeight;

// 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);

    viewportWidth = 20*aspectRatio;
    viewportHeight = 20;

    //update the projection matrix with the new window properties
    glMatrixMode(GL_PROJECTION);
    glLoadIdentity();
    gluOrtho2D(-viewportWidth/2.0, viewportWidth/2.0, -viewportHeight/2.0, viewportHeight/2.0);
}

// 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, k==0?j:i, 0);
            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();
}



// 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;

    //add a new control point if the user has clicked with the right mouse button
    if(button == GLUT_RIGHT_BUTTON && state == GLUT_DOWN)
    {
        float xp = thisX / (float)windowWidth;
        float yp = thisY / (float)windowHeight;
        controlPoints.push_back(Point(xp*viewportWidth - viewportWidth/2.0, viewportHeight/2.0 - yp*viewportHeight, 0));
    }

    
    //if the user has clicked with the left moust button, see if there's a 
    //control point within range and set it as selected if there is!
    if(button == GLUT_LEFT_BUTTON && state == GLUT_DOWN)
    {
        int viewport[4];
        
        //tell OpenGL about our hit buffer and set the rendering mode appropriately
        glSelectBuffer(SELECTBUF_SIZE, selectBuf);
        glRenderMode(GL_SELECT);

        //create a new projection matrix, same as before, but preface it with a call to glutPickMatrix.
        //what this really does is only render a small (5x5 pixel) area around the cursor -- and whatever
        //gets rendered gets added to the hit buffer. 
        glMatrixMode(GL_PROJECTION);
        glPushMatrix();
        glLoadIdentity();
        glGetIntegerv(GL_VIEWPORT,viewport);
        gluPickMatrix(thisX, viewport[3]-thisY, 5, 5, viewport);
        gluOrtho2D(-viewportWidth/2.0, viewportWidth/2.0, -viewportHeight/2.0, viewportHeight/2.0);

        
        glMatrixMode(GL_MODELVIEW);
        glInitNames();

        //ok so render the things now
        //protip: this should really be in a separate function which also gets called during the normal
        //rendering pass, but with a different flag (say, not to push/pop names). that way we know that
        //we're actually intersecting with what gets rendered. here it's simple enough that we just
        //duplicate the drawing code.
        for(size_t i = 0; i < controlPoints.size(); i++)
        {
            glPushName(i);
            glPushMatrix();
                glTranslatef(controlPoints.at(i).x, controlPoints.at(i).y, controlPoints.at(i).z);
                glutSolidSphere(0.5, 32, 32);
            glPopMatrix();
            glPopName();
        }

        //ensure that the scene gets rendered
        glFlush();

        //reset the rendering mode -- and since we're returning from GL_SELECT, this function
        //returns the number of hits we had. see the man page for glRenderMode for more info.
        int hits = glRenderMode(GL_RENDER);
        if(hits >= 1)
        {
            //just grab the closest hit -- assuming it has a name (and it should!)
            if(selectBuf[0] == 0)
            {
                printf("Warning -- hit doesn't have a name!\n");
                selectedControlPoint = -1;
            } else {
                //see http://www.lighthouse3d.com/opengl/picking/index.php?openglway3 for more 
                //information about the structure of the selection buffer. since we know we have
                //at least one hit, and it has a name, selectBuf[1] will contain the minimum depth
                //for the first hit, selectBuf[2] will contain the max depth for the first hit,
                //and selectBuf[3] will contain the actual name that we want. note that there may
                //be more, but for simplicity we're just grabbing the first one.
                selectedControlPoint = selectBuf[3];
           }
        } else {
            //if the user clicked blank space, deselect!
            selectedControlPoint = -1;
        }

        //reset the projection matrix
        glMatrixMode(GL_PROJECTION);
        glPopMatrix();
    } else if(button == GLUT_LEFT_BUTTON && state == GLUT_UP) {
        //if the user's lifted up the left mouse button, don't allow them to keep
        //dragging a control point!
        selectedControlPoint = -1;
    }


    //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 && selectedControlPoint >= 0)
    {
        Point *p = &controlPoints.at(selectedControlPoint);
        float xp = x / (float)windowWidth;
        float yp = y / (float)windowHeight;

        p->x = xp*viewportWidth - viewportWidth/2.0f;
        p->y = viewportHeight/2.0f - yp*viewportHeight;
    }

    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);
}


// 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);
    lastTime = currentTime;

    //the modelview matrix is empty because our 2D orthographic
    //projection matrix says it all.
    glMatrixMode(GL_MODELVIEW);         //make sure we aren't changing the projection matrix!
    glLoadIdentity();

    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);

    //draw a grid in the background, because it's, uh, pretty?
    glColor3f(0.75f, 0.75f, 0.75f);
    glLineWidth(1.0f);
    drawGrid();

    //make sure that we can set the current color just using glColor3f
    glEnable(GL_COLOR_MATERIAL);
    glColorMaterial(GL_FRONT_AND_BACK, GL_AMBIENT_AND_DIFFUSE);

    //draw a sphere for each of the control points!
    glEnable(GL_LIGHTING);
    for(size_t i = 0; i < controlPoints.size(); i++)
    {
        glPushMatrix();

        glTranslatef(controlPoints.at(i).x, controlPoints.at(i).y, controlPoints.at(i).z);
        if(selectedControlPoint == (int)i)
            glColor3f(1.0, 0.3, 0.3);
        else 
            glColor3f(0.0f,0.2f,1.0f);
        glutSolidSphere(0.5, 32, 32);

        glPopMatrix();
    }

    //draw the cage for the bezier curve -- just a set of lines
    //between consecutive control points
    glDisable(GL_LIGHTING);
    glColor3f(1,1,0.3);
    glLineWidth(2.0f);
    glBegin(GL_LINE_STRIP);
    for(size_t i = 0; i < controlPoints.size(); i++)
        glVertex3f(controlPoints.at(i).x, controlPoints.at(i).y, controlPoints.at(i).z);
    glEnd();


    //draw the bezier curve!
    glColor3f(1,1,1);
    glLineWidth(2.0f);

    //special case 3 points; 1 point has no lines 
    //and 2 points is just the straight line of the cage...
    if(controlPoints.size() == 3)
    {
        //just use the quadratic form of Bezier interpolation
        Point p0 = controlPoints.at(0);
        Point p1 = controlPoints.at(1);
        Point p2 = controlPoints.at(2);

        glBegin(GL_LINE_STRIP);
        for(int i = 0; i < bezierResolution; i++)
        {
            float t = i / (float)(bezierResolution-1);
            Point location = powf(1.0f - t, 2) * p0 +
                                2*(1.0f - t)*t * p1 +
                                powf(t, 2)*p2;
            glVertex3f(location.x, location.y, location.z);
        }

        glEnd();
    } else if(controlPoints.size() > 3) {
        //create the line!
        //create a separate Bezier curve for each set of 4 points
        for(size_t startingIndex = 0; startingIndex < controlPoints.size()-3; startingIndex+=3)
        {
            glBegin(GL_LINE_STRIP);
            for(int i = 0; i < bezierResolution; i++)
            {
                float t = i / (float)(bezierResolution-1);
                Point p0 = controlPoints.at(startingIndex+0);
                Point p1 = controlPoints.at(startingIndex+1);
                Point p2 = controlPoints.at(startingIndex+2);
                Point p3 = controlPoints.at(startingIndex+3);

                //plug and chug using the cubic form of bezier interpolation!
                Point location = powf((1.0-t), 3.0f)*p0 +
                                3*(1.0f-t)*(1.0f-t)*t*p1 +
                                3*(1.0f-t)*t*t*p2 +
                                t*t*t*p3;

                glVertex3f(location.x, location.y, location.z);
            }
            glEnd();
        }
    }


    //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("clicky clicky");

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

    //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