ÈÓã Çááå ÇáÑÍãä ÇáÑÍíã æ ÇáÓáÇã Úáíßã

ÌÇÑí åÐÇ ÇáãæÖæÚ Íæá ãÌÇáÇÊ ÇáÊÍßã Ýí ÚÇáã ÇáÃæÈä Ìí Ãá , áÑÈãÇ ßäÊ ÏÇÆãÇ ÊÍÇæá ÑÈØ ãÄÔÑ ÇáÝÃÑÉ ÈÚÇáã ÇáÃæÈä Ìí Ãá ÇáËáÇËí ÇáÃÈÚÇÏ , åÐÇ ÇáãæÖæÚ ßÊÈÊå ÎÕíÕÇ áÐáß æ ÓÃÊØÑÞ Åáì ßá ÔíÁ ÈÅÐä Çááå ÊÚÇáì.
ÇáÊÍÏíÏ
åäÇß ãäåÇÌ íÏÚì ÈÇáÊÍÏíÏ Ãí selection æ åæ æÓíáÉ ÊãßääÇ ãä ãÚÑÝÉ ÇáßÇÆä Ãæ ÇáãÌÓã ÇáãÊãæÖÚ Ýí ÚÇáã ÇáÃæÈä Ìí Ãá ÈÕæÑÉ ÃÎÑì ÓÃÔÑÍ ãÇ íÏæÑ ÎáÝ ßæÇáíÓ ÇáÊÍÏíÏ Ýí ÚÇáã ÇáÃæÈä Ìí Ãá:
Ýí ÇáÈÏÇíÉ äÞæã ÈÑÓã ÇáãÔåÏ æ ÈØÈíÚÉ ÇáÍÇá Óíßæä Ýí ÐÇßÑÉ ÇáÅíØÇÑ framebuffer æ ÈÚÏåÇ äÌÚá ÇáÊØÈíÞ Ãí ÇáÈÑäÇãÌ íÞÝÒ ãä ÇáäãØ ÇáÍÇáí ÇáÊÕíÑ render æ åæ ÇáÅÝÊÑÇÖí Åáì äãØ ÂÎÑ æ åæ ÇááÊÍÏíÏ selection æãä Ëã äÚÑÖ ÇáãÔåÏ , åá ÝåãÊ ãÇ ÃÞÕÏ , Ãí Ãä ÚãáíÉ ÇáÊÍÏíÏ áä ÊÍÕá ÅáÇ Ýí äãØ ÇáÊÍÏíÏ mode selection , ãä ÇáãäØÞí ÃáÇ íÊÛíÑ ãÍÊæì ÐÇßÑÉ ÇáÅíØÇÑ ÍíÊ íÊã ÇáÎÑæÌ ãä äãØ ÇáÊÍÏíÏ æ ÇáÅäÊÞÇá Åáì äãØ ÇáÊÕííÑ render , ÚäÏåÇ ÓíÑÌÚ ÇáÓíÏ ÃæÈä Ìí Ãá ÞÇÆãÉ ÊÍÊæí Úáì ÈíÇäÇÊ äÇÊÌÉ Úä ÊÞÇØÚ ÇáßÇÆäÇÊ Ãæ ÇáãÌÓãÇÊ ÇáãÊãæÖÚÉ Ýí ÚÇáã ÇáÃæÈä Ìí Ãá ãÚ ÍÌã ÇáÑÄíÉ ÇáãÍÏÏ viewing folume ( ÍÌã ÇáÑÄíÉ åæ Ïáíá äÍÏÏå äÍä æåæ ãÚÑÝ ÈæÇÓØÉ äãØ ÇáÑÄíÉ ÇáÍÇáí æ ãÕÝæÝÉ ÇáÅÓÞÇØ æ Ãí ÅÖÇÝÇÊ ÎÇÕÉ ÈãÓØÍÇÊ ÇáÞÕ ),ßá Ôßá íÊÞÇØÚ ãÚ ÍÌã ÇáÑÄíÉ ÓíæáÏ ÊÏÇÎá hit (ÚãæãÇ ÃÚÊãÏ Ýí ÊÑÌãÉ ÇáãÑÇÏÝÇÊ ÍÓÈ ÇáÎÇÕíÉ æ áíÓ ÇáãÚäì)æ ÈÚÏ Ðáß íÞæã ÇáÓíÏ ÃæÈä Ìí Ãá ÈÊãÑíÑ ÇáãÚÑÝÇÊ ÇáÎÇÕÉ Èßá ãÌÓã Ýí ãÕÝæÝÉ ãä äæÚ integer ÊÏÚì Êáß ÇáãÚÑÝÇÊ ÈÇáÃÓãÇÁ names æ ÈÚÖ ÇáÈíÇäÇÊ ÇáãÑÇÝÞÉ áåÇ .
åÐå ÇáãÑÇÍá ÊãËá ãíßÇäíÒãÉ ÇáÊÍÏíÏ íÑÌì ÇáÊÞíÏ ÈåÇ:
1- ÊÎÕíÕ ãÕÝæÝÉ áÊÍÊÝÙ ÈÇáÊÏÇÎáÇÊ æ ÈíÇäÇÊåÇ æ íÊã ÅäÔÇÁ åÐå ÇáãÕÝæÝÉ Úä ØÑíÞ ÅÓÊÏÚÇÁ ÇáÏÇáÉ glSelectBuffer .
2- ÇáãÑæÑ Åáì äãØ ÇáÊÍÏíÏ Úä ØÑíÞ ÊãÑíÑ ÇáÏáíá GL_SELECT Åáì ÇáÏÇáÉ glRenderMode .
3- ÅÚÏÇÏ ÇáãßÏÓ æ ÊåíÆÊå ÈÃæá ÅÓã íÍÊá ÇáÞÇÆãÉ ÈÇáÏÇáÉ glInitNames Ëã äÞæã ÈÍÌÒ ÅÓã áßá Ôßá Ãæ ãÌÓã Ýí ÇáãßÏÓ Úä ØÑíÞ ÇáÏÇáÉ glPushName .
4- ÊÚÑíÝ ÍÌã ÑÄíÉ ãäÇÓÈ æ ÍÌÒ æ ÊÍÑíÑ ãÕÝæÝÇÊ ÇáÊÍæíá ÇáÍÇáíÉ ÈÅÓÊÚãÇá ÇáÏÇáÊÇä glPushMatrix æ glPopMatrix .
5- ÅÚÏÇÏ ÇáÃÔßÇá æ ÇáãÌÓãÇÊ ÇáÊí ÊÑÛÈ Ýí ÊÍÏíÏåÇ áÍÙÉ ÊäÝíÐß ááÈÑäÇãÌ.
6- ÇáÎÑæÌ ãä äãØ ÇáÊÍÏíÏ æ ÇáÚæÏÉ Åáì äãØ ÇáÊÕíÑ ááÞíÇã ÈãÚÇáÌÉ ÇáÈíÇäÇÊ ÇáÊí ÃÑÌÚåÇ ÇáÓíÏ ÃæÈä Ìí Ãá hit record .

 void glSelectBuffer(GLsizei size, GLuint *buffer);

GLint glRenderMode(GLenum mode);

glInitNames();
glPushName(0);
glPushMatrix(); /* ÍÌÒ ÇáÊÍæíá ÇáÍÇáí  */
/* åäÇ ÞÏ ääÔÆ ÍÌã ÇáÑÄíÉ ÇáãÑÛæÈ Ýíå */
glLoadName(1);
drawSomeObject();
glLoadName(2);
drawAnotherObject();
glLoadName(3);
drawYetAnotherObject();
drawJustOneMoreObject();
glPopMatrix(); /* ÊÍÑíÑ ÇáÊÍæíá ÇáãÍÌæÒ*/

void glInitNames(void);

void glPushName(GLuint name);

void glPopName(void);

void glLoadName(GLuint name);

åÐå ÇáÏÇáÉ ÊÚíÏ ÇáÞíãÉ Åáì ÞãÉ ãßÏÓ ÇáÅÓã ãÚ ÇáÅÓã name , ÞÏ ÊÍÏË ÇáÏÇáÉ glLoadName ÇáÎØà GL_INVALID_OPERATION ÅÐÇ ãÇ ßÇä ãßÏÓ ÇáÅÓã ÝÇÑÛÇ ÈÚÏ ÅÓÊÏÚÇÁ ÇáÏÇáÉ glInitNames .

Åä ÅÓÊÏÚÇÁ ÃÍÏ ÇáÏæÇá ÇáËáÇËÉ glPushName æ glPopName æglLoadName Êßæä ÛíÑ ÝÚÇáÉ Ýí ÍÇáÉ ßÇä ÇáÊØÈíÞ áíÓ Ýí äãØ ÇáÊÍÏíÏ .
ÇáÊÏÇÎáÇÊ hit records
ÈÚÏ ÎÑæÌ ÇáÊØÈíÞ ãä äãØ ÇáÊÍÏíÏ æ ÇáÏÎæá Åáì äãØ ÇáÊÕííÑ íÞæã ÇáÓíÏ ÃæÈä Ìí Ãá ÈÅÑÌÇÚ ÚÏÏ ÇáÊÏÇÎáÇÊ æ ÈÚÖ ÇáÈíÇäÇÊ Ýí ÇáãÕÝæÝÉ ÇáãÍÏÏ ÈÇáÏÇáÉ glSelectBuffer ãä ÇáÙÇåÑ Ãä áÏì åÐÇ ÇáäæÚ ãä ÇáÈíÇäÇÊ ÐÇßÑÉ ÎÇÕÉ Èå . æ íÊßæä ßá ÊÏÇÎá ãä ÃÑÈÚ ÈíÇäÇÊ æ ÈÇáÊÑÊíÈ ÇáÊÇáí:
1- ÚÏÏ ÇáÃÓãÇÁ Ýí ãßÏÓ ÇáÅÓã Ãíä ÙåÑ ÇáÊÏÇÎá.
2- ßáÇ ãä ÞíãÊÇ ÅÍÏÇËíÇÊ ÇáäÇÝÐÉ á z ÇáÞÕæì zmax æ ÇáÏäíÇ zmin áÐáß ÇáÊÏÇÎá .
3- ÞÇÆãÉ áÃÓãÇÁ ÇáßÇÆäÇÊ Ãæ ÇáÃÔßÇá Ãíä ÍÏË ÇáÊÍÏíÏ Ãæ ÇáäÞÑ ÚáíåÇ ( ÓíÃÊí ãæÖæÚ ÇáäÞÑ ).
æ ÈÍíË Ãä ÇáÊØÈíÞ íÏÎá Ýí ßá ãÑÉ äãØ ÇáÊÍÏíÏ ÓíÞæã ÇáÃæÈä Ìí Ãá ÈÅÚÏÇÏ ÇáãÄÔÑ äÍæ ÈÏÇíÉ ÇáãÕÝæÝÉ æ åÐÇ ßá ãÇ ÊßÊÈ ÈíÇäÇÊ ÇáÊÏÇÎá Ýí ÇáãÕÝæÝÉ Ãí ÈãÚäì ÂÎÑ íÊã ÊÍÏíË ÇáãÄÔÑ.





ãËÇá Úä ÇáÊÍÏíÏ

void drawTriangle(GLfloat x1, GLfloat y1, GLfloat x2,
GLfloat y2, GLfloat x3, GLfloat y3, GLfloat z)
  {
      glBegin(GL_TRIANGLES);
           glVertex3f(x1, y1, z);
           glVertex3f(x2, y2, z);
           glVertex3f(x3, y3, z);
      glEnd();
}
void drawViewVolume(GLfloat x1, GLfloat x2, GLfloat y1,
GLfloat y2, GLfloat z1, GLfloat z2)
{
     glColor3f(1.0, 1.0, 1.0);
     glBegin(GL_LINE_LOOP);
          glVertex3f(x1, y1, -z1);
          glVertex3f(x2, y1, -z1);
          glVertex3f(x2, y2, -z1);
          glVertex3f(x1, y2, -z1);
     glEnd();
    glBegin(GL_LINE_LOOP);
         glVertex3f(x1, y1, -z2);
         glVertex3f(x2, y1, -z2);
         glVertex3f(x2, y2, -z2);
         glVertex3f(x1, y2, -z2);
     glEnd();
     glBegin(GL_LINES); /* 4 lines */
         glVertex3f(x1, y1, -z1);
         glVertex3f(x1, y1, -z2);
         glVertex3f(x1, y2, -z1);
         glVertex3f(x1, y2, -z2);
         glVertex3f(x2, y1, -z1);
         glVertex3f(x2, y1, -z2);
         glVertex3f(x2, y2, -z1);
         glVertex3f(x2, y2, -z2);
     glEnd();
}
void drawScene(void)
{
     glMatrixMode(GL_PROJECTION);
     glLoadIdentity();
     gluPerspective(40.0, 4.0/3.0, 1.0, 100.0);
     glMatrixMode(GL_MODELVIEW);
     glLoadIdentity();
     gluLookAt(7.5, 7.5, 12.5, 2.5, 2.5, -5.0, 0.0, 1.0, 0.0);
     glColor3f(0.0, 1.0, 0.0); /* green triangle */
          drawTriangle(2.0, 2.0, 3.0, 2.0, 2.5, 3.0, -5.0);
     glColor3f(1.0, 0.0, 0.0); /* red triangle */
          drawTriangle(2.0, 7.0, 3.0, 7.0, 2.5, 8.0, -5.0);
     glColor3f(1.0, 1.0, 0.0); /* yellow triangles */
          drawTriangle(2.0, 2.0, 3.0, 2.0, 2.5, 3.0, 0.0);
          drawTriangle(2.0, 2.0, 3.0, 2.0, 2.5, 3.0, -10.0);
          drawViewVolume(0.0, 5.0, 0.0, 5.0, 0.0, 10.0);
}
void processHits(GLint hits, GLuint buffer[])
{
    unsigned int i, j;
    GLuint names, *ptr;
    printf(“hits = %d\n”, hits);
    ptr = (GLuint *) buffer;
    for (i = 0; i < hits; i++) 
          { /* for each hit */
                  names = *ptr;
                  printf(“ number of names for hit = %d\n”, names); ptr++;
                  printf(“ z1 is %g;”, (float) *ptr/0x7fffffff); ptr++;
                  printf(“ z2 is %g\n”, (float) *ptr/0x7fffffff); ptr++;
                  printf(“ the name is “);
                  for (j = 0; j < names; j++) 
                           { /* for each name */
                                     printf(“%d “, *ptr); ptr++;
                           }
                  printf(“\n”);
          }
}

#define BUFSIZE 512

void selectObjects(void)
{
    GLuint selectBuf[BUFSIZE];
    GLint hits;
    glSelectBuffer(BUFSIZE, selectBuf);
    (void) glRenderMode(GL_SELECT);
    glInitNames();
    glPushName(0);
         glPushMatrix();
               glMatrixMode(GL_PROJECTION);
               glLoadIdentity();
               glOrtho(0.0, 5.0, 0.0, 5.0, 0.0, 10.0);
               glMatrixMode(GL_MODELVIEW);
               glLoadIdentity();
               glLoadName(1);
                   drawTriangle(2.0, 2.0, 3.0, 2.0, 2.5, 3.0, -5.0);
               glLoadName(2);
                   drawTriangle(2.0, 7.0, 3.0, 7.0, 2.5, 8.0, -5.0);
               glLoadName(3);
                   drawTriangle(2.0, 2.0, 3.0, 2.0, 2.5, 3.0, 0.0);
                   drawTriangle(2.0, 2.0, 3.0, 2.0, 2.5, 3.0, -10.0);
           glPopMatrix();
           glFlush();
           hits = glRenderMode(GL_RENDER);
           processHits(hits, selectBuf);
}
void init(void)
{
     glEnable(GL_DEPTH_TEST);
     glShadeModel(GL_FLAT);
}
void display(void)
{
    glClearColor(0.0, 0.0, 0.0, 0.0);
    glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
      drawScene();
    selectObjects();
    glFlush();
}
int main(int argc, char** argv)
{
    glutInit(&argc, argv);
    glutInitDisplayMode(GLUT_SINGLE | GLUT_RGB | GLUT_DEPTH);
    glutInitWindowSize(200, 200);
    glutInitWindowPosition(100, 100);
    glutCreateWindow(argv[0]);
    init();
    glutDisplayFunc(display);
    glutMainLoop();
    return 0;
}

Resized to 85% (was 768 x 614) - Click image to enlarge

glMatrixMode(GL_PROJECTION);
 glPushMatrix();
glLoadIdentity();
gluPickMatrix(...);
gluPerspective, glOrtho, gluOrtho2D, or glFrustum
/* ... draw scene for picking ; perform picking ... */
glPopMatrix();

void gluPickMatrix(GLdouble x, GLdouble y, GLdouble width,GLdouble height, GLint viewport[4]);

glGetIntegerv(GL_VIEWPORT, GLint *viewport);

void init(void)
{
glClearColor(0.0, 0.0, 0.0, 0.0);
glEnable(GL_DEPTH_TEST);
glShadeModel(GL_FLAT);
glDepthRange(0.0, 1.0); /* The default z mapping */
}
void drawRects(GLenum mode)
{
if (mode == GL_SELECT)
glLoadName(1);
glBegin(GL_QUADS);
glColor3f(1.0, 1.0, 0.0);
glVertex3i(2, 0, 0);
glVertex3i(2, 6, 0);
glVertex3i(6, 6, 0);
glVertex3i(6, 0, 0);
glEnd();
if (mode == GL_SELECT)
glLoadName(2);
glBegin(GL_QUADS);
glColor3f(0.0, 1.0, 1.0);
glVertex3i(3, 2, -1);
glVertex3i(3, 8, -1);
glVertex3i(8, 8, -1);
glVertex3i(8, 2, -1);
glEnd();
if (mode == GL_SELECT)
glLoadName(3);
glBegin(GL_QUADS);
glColor3f(1.0, 0.0, 1.0);
glVertex3i(0, 2, -2);
glVertex3i(0, 7, -2);
glVertex3i(5, 7, -2);
glVertex3i(5, 2, -2);
glEnd();
}
void processHits(GLint hits, GLuint buffer[])
{
unsigned int i, j;
GLuint names, *ptr;
printf(“hits = %d\n”, hits);
ptr = (GLuint *) buffer;
for (i = 0; i < hits; i++) { /* for each hit */
names = *ptr;
printf(“ number of names for hit = %d\n”, names); ptr++;
printf(“ z1 is %g;”, (float) *ptr/0x7fffffff); ptr++;
printf(“ z2 is %g\n”, (float) *ptr/0x7fffffff); ptr++;
printf(“ the name is “);
for (j = 0; j < names; j++) { /* for each name */
printf(“%d “, *ptr); ptr++;
}
printf(“\n”);
}
}
#define BUFSIZE 512
void pickRects(int button, int state, int x, int y)
{
GLuint selectBuf[BUFSIZE];
GLint hits;
GLint viewport[4];
if (button != GLUT_LEFT_BUTTON || state != GLUT_DOWN)
return;
glGetIntegerv(GL_VIEWPORT, viewport);
glSelectBuffer(BUFSIZE, selectBuf);
(void) glRenderMode(GL_SELECT);
glInitNames();
glPushName(0);
glMatrixMode(GL_PROJECTION);
glPushMatrix();
glLoadIdentity();
/* create 5x5 pixel picking region near cursor location */
gluPickMatrix((GLdouble) x, (GLdouble) (viewport[3] - y),
5.0, 5.0, viewport);
glOrtho(0.0, 8.0, 0.0, 8.0, -0.5, 2.5);
drawRects(GL_SELECT);
glPopMatrix();
glFlush();
hits = glRenderMode(GL_RENDER);
processHits(hits, selectBuf);
}
void display(void)
{
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
drawRects(GL_RENDER);
glFlush();
}
void reshape(int w, int h)
{
glViewport(0, 0, (GLsizei) w, (GLsizei) h);
glMatrixMode(GL_PROJECTION);
glLoadIdentity();
glOrtho(0.0, 8.0, 0.0, 8.0, -0.5, 2.5);
glMatrixMode(GL_MODELVIEW);
glLoadIdentity();
}
int main(int argc, char **argv)
{
glutInit(&argc, argv);
glutInitDisplayMode(GLUT_SINGLE | GLUT_RGB | GLUT_DEPTH);
glutInitWindowSize(200, 200);
glutInitWindowPosition(100, 100);
glutCreateWindow(argv[0]);
init();
glutMouseFunc(pickRects);
glutReshapeFunc(reshape);
glutDisplayFunc(display);
glutMainLoop();
return 0;
}

Resized to 85% (was 768 x 614) - Click image to enlarge

void gluLookAt(GLdouble eyex, GLdouble eyey, GLdouble eyez,
GLdouble centerx, GLdouble centery, GLdouble centerz,
GLdouble upx, GLdouble upy, GLdouble upz);

int gluUnProject(GLdouble winx, GLdouble winy, GLdouble winz,
const GLdouble modelMatrix[16],
const GLdouble projMatrix[16],
const GLint viewport[4],
GLdouble *objx, GLdouble *objy, GLdouble *objz);

Resized to 85% (was 768 x 614) - Click image to enlarge

#include <windows.h>
#include <GL/glut.h>
#include <stdio.h>
#define RED 1
GLdouble wx, wy, wz, Mx, My, Mz, Ax, Ay, Az, t, tab[10][3];
int ss = 0;
void display(void)
{
   glClear(GL_COLOR_BUFFER_BIT);
   glColor3f(1.,1.,1.);
           glPushMatrix();
        glTranslatef(0.,0.,-0.2);
         glutSolidSphere(0.1,10,10);
    glPopMatrix();
   
    glPushMatrix();
         glTranslatef((float)Mx,(float)My,(float)Mz);
         if (ss == 1)    glColor3f(0.,0.,1.);
                        glutSolidSphere(0.01,10,10);
                       glColor3f(1.,1.,1.);
                         glPopMatrix();
    glFlush();
}

void reshape(int w, int h)
{
   glViewport (0, 0, (GLsizei) w, (GLsizei) h);
   glMatrixMode(GL_PROJECTION);
   glLoadIdentity();
   glFrustum(-0.5, 0.5, -0.5, 0.5,1,10);
   glMatrixMode(GL_MODELVIEW);
   glLoadIdentity();
   gluLookAt (Ax, Ay, Az, 0.0, 0.0, 0.0, 0.0, 1.0, 0.0);

}

void mouse(int button, int state, int x, int y)
{
   GLint viewport[4];
   GLdouble mvmatrix[16], projmatrix[16];
   GLfloat realy;
      switch (button) {
      case GLUT_LEFT_BUTTON:
         if (state == GLUT_DOWN) {
            glGetIntegerv (GL_VIEWPORT, viewport);
            glGetDoublev (GL_MODELVIEW_MATRIX, mvmatrix);
            glGetDoublev (GL_PROJECTION_MATRIX, projmatrix);
            realy = viewport[3] - (GLint) y ;
            printf ("Coordinates at cursor are (%4d, %4d)\n", x, (int)realy);
                gluUnProject ((GLdouble) x, (GLdouble) realy, (GLdouble) 0,
mvmatrix, projmatrix, viewport, &wx, &wy, &wz);
            t=3; // fix t to 3
            Mx = t*(wx-Ax)+Ax; //we calacul position of m with t
                My = t *(wy-Ay) +Ay;
            Mz =t*(wz-Az)+Az ;
               printf ("Coordinates at cursor are (%4f, %4f,%4f)\n", (float)Mx, (float)My, (float)Mz);
               glutPostRedisplay();

         }
         break;
      case GLUT_RIGHT_BUTTON:
         if (state == GLUT_DOWN)
            exit(0);
         break;
      default:
         break;
   }
}

void keyboard(unsigned char key, int x, int y)
{
   switch (key) {
      case 27:
         exit(0);
         break;
   }
}

void processMenuEvents(int option) {
switch (option) {
case RED :
ss=1;
 break;
}
glutPostRedisplay();
}

 int main(int argc, char** argv)
{
     wx=0; wy=0; wz=0;
     Ax=2; Ay=2; Az=5.0;
   glutInit(&argc, argv);
   glutInitDisplayMode (GLUT_SINGLE | GLUT_RGB);
   glutInitWindowSize (500, 500);
   glutInitWindowPosition (100, 500);
   glutCreateWindow (argv[0]);
   int menu = glutCreateMenu(processMenuEvents);
   glutAddMenuEntry("Red",RED);
   glutAttachMenu(GLUT_RIGHT_BUTTON);
   glutDisplayFunc(display);
   glutReshapeFunc(reshape);
   glutKeyboardFunc (keyboard);
   glutMouseFunc(mouse);
   glutMainLoop();
   return 0;
}