如何在OpenGL/C++

Question

的窗口周圍拖動圖形是目前的代碼，我的問題在於拖動窗口周圍的圖形？我似乎無法做到這一點？任何提示給我的人？我想要的是，當你點擊並按住鼠標左鍵時，你應該可以在窗口周圍拖動圖形？

#include <GL/glut.h> 
#include <stdlib.h> 
#include <math.h> 
#if !defined(GLUT_WHEEL_UP) 
# define GLUT_WHEEL_UP 

# define GLUT_WHEEL_DOWN 4 
#endif 


/* Set initial size of the display window. */ 
GLsizei winWidth = 600, winHeight = 600; 

/* Set size of world-coordinate clipping window. */ 
GLfloat xwcMin = -50.0, xwcMax = 50.0; 
GLfloat ywcMin = -50.0, ywcMax = 50.0; 
bool leftButton; 
int downX, downY; 

class wcPt3D { 
    public: 
     GLfloat x, y, z; 
}; 

void init (void) {  
    /* Set color of display window to white. */ 
    glClearColor (1.0, 1.0, 1.0, 0.0); 
} 

void plotPoint (wcPt3D bezCurvePt) { 
    glBegin (GL_POINTS); 
    glVertex2f (bezCurvePt.x, bezCurvePt.y); 
    glEnd (); 
} 

/* Compute binomial coefficients C for given value of n. */ 
void binomialCoeffs (GLint n, GLint * C) {  
    GLint k, j; 

    for (k = 0; k <= n; k++) { 
     /* Compute n!/(k!(n - k)!). */ 
     C [k] = 1; 
     for (j = n; j >= k + 1; j--) 
     C [k] *= j; 
     for (j = n - k; j >= 2; j--) 
     C [k] /= j; 
    } 
} 

void computeBezPt (GLfloat t, wcPt3D * bezPt, GLint nCtrlPts, 
        wcPt3D * ctrlPts, GLint * C) { 
    GLint k, n = nCtrlPts - 1; 
    GLfloat bezBlendFcn; 

    bezPt->x = bezPt->y = bezPt->z = 0.0; 

    /* Compute blending functions and blend control points. */ 
    for (k = 0; k < nCtrlPts; k++) { 
     bezBlendFcn = C [k] * pow (t, k) * pow (1 - t, n - k); 
     bezPt->x += ctrlPts [k].x * bezBlendFcn; 
     bezPt->y += ctrlPts [k].y * bezBlendFcn; 
     bezPt->z += ctrlPts [k].z * bezBlendFcn; 
    } 
} 

void bezier (wcPt3D * ctrlPts, GLint nCtrlPts, GLint nBezCurvePts) { 
    wcPt3D bezCurvePt; 
    GLfloat t; 
    GLint *C; 

    /* Allocate space for binomial coefficients */ 
    C = new GLint [nCtrlPts]; 

    binomialCoeffs (nCtrlPts - 1, C); 
    for (int i = 0; i <= nBezCurvePts; i++) { 
     t = GLfloat (i)/GLfloat (nBezCurvePts); 
     computeBezPt (t, &bezCurvePt, nCtrlPts, ctrlPts, C); 
     plotPoint (bezCurvePt); 
    } 
    delete [ ] C; 
} 

void displayFcn (void) { 
    glClear (GL_COLOR_BUFFER_BIT); // Clear display window. 

    /* Set example number of control points and number of 
    * curve positions to be plotted along the Bezier curve. 
    */ GLint nCtrlPts = 4, nBezCurvePts = 1000; 

    wcPt3D ctrlPts [4] = { {-40.0, -40.0, 0.0}, {-10.0, 200.0, 0.0}, 
          {10.0, -200.0, 0.0}, {40.0, 40.0, 0.0} }; 

    glPointSize (4); 
    glColor3f (1.0, 0.0, 0.0);  // Set point color to red. 

    bezier (ctrlPts, nCtrlPts, nBezCurvePts); 
    glutSwapBuffers(); 
} 

void winReshapeFcn (GLint newWidth, GLint newHeight) { 
    /* Maintain an aspect ratio of 1.0. */ 
    glViewport (0, 0, xwcMin, ywcMin); 

    glMatrixMode (GL_PROJECTION); 
    glLoadIdentity (); 

    gluOrtho2D (xwcMin, xwcMax, ywcMin, ywcMax); 

    glutPostRedisplay(); 
} 

void MouseCallback(int button, int state, int x, int y) { 
    downX = x; 
    downY = y; 
    leftButton = ((button == GLUT_LEFT_BUTTON) && (state == GLUT_DOWN)); 
    glutPostRedisplay(); 
} 

void MotionCallback(int x, int y) { 
    if (leftButton){ 
     downX=downX+x; 
     downY=downY+y; 
     gluOrtho2D (xwcMin, xwcMax, ywcMin, ywcMax); 
    } 

    downX = x; 
    downY = y; 
    glutPostRedisplay(); 
} 
/* 
    void MouseCallback(int button, int state, int x, int y) { 
     if (button == GLUT_WHEEL_UP && glutGetModifiers()==GLUT_ACTIVE_CTRL) { 
     }else if (button == GLUT_WHEEL_DOWN) 
      glutPostRedisplay(); 
     } 
*/ 

int main (int argc, char** argv) { 
    glutInit (&argc, argv); 
    glutInitDisplayMode (GLUT_DOUBLE | GLUT_RGB); 
    glutInitWindowPosition (50, 50); 
    glutInitWindowSize (winWidth, winHeight); 
    glutCreateWindow ("Bezier Curve"); 

    init (); 
    glutDisplayFunc (displayFcn); 
    glutReshapeFunc (winReshapeFcn); 
    glutMouseFunc(MouseCallback); 
    glutMotionFunc(MotionCallback); 
    glutMainLoop (); 
} 

Answer 1

試試這個：

#include <GL/glut.h> 
#include <cmath> 

// Compute binomial coefficients C for given value of n. 
void binomialCoeffs 
    (
    GLint n, 
    GLint* C 
    ) 
{  
    for (GLint k = 0; k <= n; k++) 
    { 
     // Compute n!/(k!(n - k)!). 
     C [k] = 1; 
     for (GLint j = n; j >= k + 1; j--) 
      C [k] *= j; 
     for (GLint j = n - k; j >= 2; j--) 
      C [k] /= j; 
    } 
} 

struct wcPt3D 
{ 
    GLfloat x, y, z; 
}; 

void computeBezPt 
    (
    GLfloat t, 
    wcPt3D* bezPt, 
    GLint nCtrlPts, 
    wcPt3D* ctrlPts, 
    GLint* C 
    ) 
{ 
    GLint n = nCtrlPts - 1; 
    GLfloat bezBlendFcn; 

    bezPt->x = bezPt->y = bezPt->z = 0.0; 

    // Compute blending functions and blend control points. 
    for (GLint k = 0; k < nCtrlPts; k++) 
    { 
     bezBlendFcn = C [k] * pow (t, k) * pow (1 - t, n - k); 
     bezPt->x += ctrlPts [k].x * bezBlendFcn; 
     bezPt->y += ctrlPts [k].y * bezBlendFcn; 
     bezPt->z += ctrlPts [k].z * bezBlendFcn; 
    } 
} 

void bezier 
    (
    wcPt3D* ctrlPts, 
    GLint nCtrlPts, 
    GLint nBezCurvePts 
    ) 
{ 
    // Allocate space for binomial coefficients 
    GLint* C = new GLint [nCtrlPts]; 

    binomialCoeffs (nCtrlPts - 1, C); 
    glBegin (GL_POINTS); 
    for (int i = 0; i <= nBezCurvePts; i++) 
    { 
     GLfloat t = GLfloat (i)/GLfloat (nBezCurvePts); 
     wcPt3D bezCurvePt; 
     computeBezPt (t, &bezCurvePt, nCtrlPts, ctrlPts, C); 
     glVertex2f (bezCurvePt.x, bezCurvePt.y); 
    } 
    glEnd(); 
    delete [ ] C; 
} 

int btn; 
int startMouseX = 0; 
int startMouseY = 0; 
int startTransX = 0; 
int startTransY = 0; 
int curTransX = 0; 
int curTransY = 0; 
void MouseCallback(int button, int state, int x, int y) 
{ 
    btn = button; 
    if(button == GLUT_LEFT_BUTTON && state == GLUT_DOWN) 
    { 
     startMouseX = x; 
     startMouseY = glutGet(GLUT_WINDOW_HEIGHT) - y; 
     startTransX = curTransX; 
     startTransY = curTransY; 
    } 
    glutPostRedisplay(); 
} 

void MotionCallback(int x, int y) 
{ 
    int curMouseX = x; 
    int curMouseY = glutGet(GLUT_WINDOW_HEIGHT) - y; 
    if (btn == GLUT_LEFT_BUTTON) 
    { 
     curTransX = startTransX + (curMouseX - startMouseX); 
     curTransY = startTransY + (curMouseY - startMouseY); 
    } 

    glutPostRedisplay(); 
} 

// Set size of world-coordinate clipping window. 
GLfloat xwcMin = -50.0, xwcMax = 50.0; 
GLfloat ywcMin = -50.0, ywcMax = 50.0; 
void displayFcn() 
{ 
    // Clear display window. 
    glClearColor (1.0, 1.0, 1.0, 0.0); 
    glClear (GL_COLOR_BUFFER_BIT); 

    glMatrixMode (GL_PROJECTION); 
    glLoadIdentity (); 
    double w = glutGet(GLUT_WINDOW_WIDTH); 
    double h = glutGet(GLUT_WINDOW_HEIGHT); 
    glTranslatef(curTransX/w * 2, curTransY/h * 2, 0); 
    gluOrtho2D (xwcMin, xwcMax, ywcMin, ywcMax); 

    glMatrixMode (GL_MODELVIEW); 
    glLoadIdentity(); 

    // Set example number of control points and number of 
    // curve positions to be plotted along the Bezier curve. 
    GLint nCtrlPts = 4, nBezCurvePts = 1000; 
    wcPt3D ctrlPts [4] = 
    { 
     {-40.0, -40.0, 0.0}, 
     {-10.0, 200.0, 0.0}, 
     {10.0, -200.0, 0.0}, 
     {40.0, 40.0, 0.0} 
    }; 

    // Set point color to red. 
    glPointSize (4); 
    glColor3f (1.0, 0.0, 0.0);  

    bezier (ctrlPts, nCtrlPts, nBezCurvePts); 
    glutSwapBuffers(); 
} 

int main (int argc, char** argv) 
{ 
    glutInit (&argc, argv); 
    glutInitDisplayMode (GLUT_DOUBLE | GLUT_RGB); 
    glutInitWindowPosition (50, 50); 
    glutInitWindowSize (600, 600); 
    glutCreateWindow ("Bezier Curve"); 

    glutDisplayFunc (displayFcn); 
    glutMouseFunc(MouseCallback); 
    glutMotionFunc(MotionCallback); 
    glutMainLoop (); 
} 

從我的回答here改編。

編輯：最小（-ish）差異版本：

#include <GL/glut.h> 
#include <stdlib.h> 
#include <math.h> 
#if !defined(GLUT_WHEEL_UP) 
# define GLUT_WHEEL_UP 

# define GLUT_WHEEL_DOWN 4 
#endif 


/* Set initial size of the display window. */ 
GLsizei winWidth = 600, winHeight = 600; 

/* Set size of world-coordinate clipping window. */ 
GLfloat xwcMin = -50.0, xwcMax = 50.0; 
GLfloat ywcMin = -50.0, ywcMax = 50.0; 

class wcPt3D { 
    public: 
     GLfloat x, y, z; 
}; 

void init (void) {  
    /* Set color of display window to white. */ 
    glClearColor (1.0, 1.0, 1.0, 0.0); 
} 

void plotPoint (wcPt3D bezCurvePt) { 
    glBegin (GL_POINTS); 
    glVertex2f (bezCurvePt.x, bezCurvePt.y); 
    glEnd (); 
} 

/* Compute binomial coefficients C for given value of n. */ 
void binomialCoeffs (GLint n, GLint * C) {  
    GLint k, j; 

    for (k = 0; k <= n; k++) { 
     /* Compute n!/(k!(n - k)!). */ 
     C [k] = 1; 
     for (j = n; j >= k + 1; j--) 
     C [k] *= j; 
     for (j = n - k; j >= 2; j--) 
     C [k] /= j; 
    } 
} 

void computeBezPt (GLfloat t, wcPt3D * bezPt, GLint nCtrlPts, 
        wcPt3D * ctrlPts, GLint * C) { 
    GLint k, n = nCtrlPts - 1; 
    GLfloat bezBlendFcn; 

    bezPt->x = bezPt->y = bezPt->z = 0.0; 

    /* Compute blending functions and blend control points. */ 
    for (k = 0; k < nCtrlPts; k++) { 
     bezBlendFcn = C [k] * pow (t, k) * pow (1 - t, n - k); 
     bezPt->x += ctrlPts [k].x * bezBlendFcn; 
     bezPt->y += ctrlPts [k].y * bezBlendFcn; 
     bezPt->z += ctrlPts [k].z * bezBlendFcn; 
    } 
} 

void bezier (wcPt3D * ctrlPts, GLint nCtrlPts, GLint nBezCurvePts) { 
    wcPt3D bezCurvePt; 
    GLfloat t; 
    GLint *C; 

    /* Allocate space for binomial coefficients */ 
    C = new GLint [nCtrlPts]; 

    binomialCoeffs (nCtrlPts - 1, C); 
    for (int i = 0; i <= nBezCurvePts; i++) { 
     t = GLfloat (i)/GLfloat (nBezCurvePts); 
     computeBezPt (t, &bezCurvePt, nCtrlPts, ctrlPts, C); 
     plotPoint (bezCurvePt); 
    } 
    delete [ ] C; 
} 

int curTransX = 0; 
int curTransY = 0; 
void displayFcn (void) { 
    glClear (GL_COLOR_BUFFER_BIT); // Clear display window. 

    glMatrixMode (GL_PROJECTION); 
    glLoadIdentity (); 
    double w = glutGet(GLUT_WINDOW_WIDTH); 
    double h = glutGet(GLUT_WINDOW_HEIGHT); 
    glTranslatef(curTransX/w * 2, curTransY/h * 2, 0); 
    gluOrtho2D (xwcMin, xwcMax, ywcMin, ywcMax); 

    glMatrixMode (GL_MODELVIEW); 
    glLoadIdentity(); 

    /* Set example number of control points and number of 
    * curve positions to be plotted along the Bezier curve. 
    */ GLint nCtrlPts = 4, nBezCurvePts = 1000; 

    wcPt3D ctrlPts [4] = { {-40.0, -40.0, 0.0}, {-10.0, 200.0, 0.0}, 
          {10.0, -200.0, 0.0}, {40.0, 40.0, 0.0} }; 

    glPointSize (4); 
    glColor3f (1.0, 0.0, 0.0);  // Set point color to red. 

    bezier (ctrlPts, nCtrlPts, nBezCurvePts); 
    glutSwapBuffers(); 
} 

int btn; 
int startMouseX = 0; 
int startMouseY = 0; 
int startTransX = 0; 
int startTransY = 0; 
void MouseCallback(int button, int state, int x, int y) { 
    btn = button; 
    if(button == GLUT_LEFT_BUTTON && state == GLUT_DOWN) 
    { 
     startMouseX = x; 
     startMouseY = glutGet(GLUT_WINDOW_HEIGHT) - y; 
     startTransX = curTransX; 
     startTransY = curTransY; 
    } 
    glutPostRedisplay(); 
} 

void MotionCallback(int x, int y) { 
    int curMouseX = x; 
    int curMouseY = glutGet(GLUT_WINDOW_HEIGHT) - y; 
    if (btn == GLUT_LEFT_BUTTON) 
    { 
     curTransX = startTransX + (curMouseX - startMouseX); 
     curTransY = startTransY + (curMouseY - startMouseY); 
    } 
    glutPostRedisplay(); 
} 
/* 
    void MouseCallback(int button, int state, int x, int y) { 
     if (button == GLUT_WHEEL_UP && glutGetModifiers()==GLUT_ACTIVE_CTRL) { 
     }else if (button == GLUT_WHEEL_DOWN) 
      glutPostRedisplay(); 
     } 
*/ 

int main (int argc, char** argv) { 
    glutInit (&argc, argv); 
    glutInitDisplayMode (GLUT_DOUBLE | GLUT_RGB); 
    glutInitWindowPosition (50, 50); 
    glutInitWindowSize (winWidth, winHeight); 
    glutCreateWindow ("Bezier Curve"); 

    init (); 
    glutDisplayFunc (displayFcn); 
    glutMouseFunc(MouseCallback); 
    glutMotionFunc(MotionCallback); 
    glutMainLoop (); 
}