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infinitecmdz
11-22-2005, 07:26 PM
hey guys,

I have a problem in picking. I read the tutorials at lighthouse website and i did exactly what they had taught. Well heres my code :

My renderScene code :


GLvoid RenderScene()
{
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT) ;
glLoadIdentity() ;

gluLookAt(CameraObj.mPosition.x , CameraObj.mPosition.y , CameraObj.mPosition.z ,
CameraObj.mView.x , CameraObj.mView.y , CameraObj.mView.z ,
CameraObj.mUp.x , CameraObj.mUp.y , CameraObj.mUp.z) ;


//Draw the x , y , z Axis and the grid initially.
DrawAxis() ;
Draw3DGrid() ;

DrawGrid(GL_RENDER) ;

glScalef(0.030f , 0.030f , 0.030f) ;

glRotatef(180.0 , 0.0f , 1.0f , 0.0f) ;

DrawObject() ;

glFlush() ;

glutSwapBuffers() ;
}Heres my DrawGrid code. This is made of points which I must pick...


GLvoid DrawGrid(int mode)
{
if(mode == GL_SELECT)
{
glInitNames();
//glPushName(0);
}

int i , j ;
glDisable(GL_LIGHTING) ;
glPointSize(6.0f) ;


//Draw the line segments
glColor3f(1.0f , 1.0f , 0.0f) ;
for(i = 0 ; i < 8 ; i++)
{
for(j = 0 ; j < 8 ; j++)
{
glBegin(GL_LINE_STRIP) ;

glVertex3f(ControlPoints[i][j][0] , ControlPoints[i][j][1] , ControlPoints[i][j][2]) ;
glVertex3f(ControlPoints[i + 1][j][0] , ControlPoints[i + 1][j][1] , ControlPoints[i + 1][j][2]) ;
glVertex3f(ControlPoints[i + 1][j + 1][0] , ControlPoints[i + 1][j + 1][1] , ControlPoints[i + 1][j + 1][2]) ;
glVertex3f(ControlPoints[i][j + 1][0] , ControlPoints[i][j + 1][1] , ControlPoints[i][j + 1][2]) ;
glVertex3f(ControlPoints[i][j][0] , ControlPoints[i][j][1] , ControlPoints[i][j][2]) ;
glEnd() ;

}
}

//Draw the control vertices.
glColor3f(0.0f , 1.0f , 0.0f) ;

int k = 1 ;
for(i = 0 ; i < 10 ; i++)
{
if(mode == GL_SELECT)
glPushName(i) ;

for(j = 0 ; j < 10 ; j++)
{
if(mode == GL_SELECT)
glPushName(j);

glBegin(GL_POINTS) ;
glVertex3f(ControlPoints[i][j][0] , ControlPoints[i][j][1] , ControlPoints[i][j][2]) ;
glEnd() ;

glPopName() ;
}
glPopName() ;
}


glLineWidth(1.0f) ;
glEnable(GL_LIGHTING) ;

}and heres the code to initialize the selection mode:


GLvoid MouseFunc(int Button , int State , int x , int y)
{
int Viewport[4] , Hits ;

if(Button == GLUT_LEFT_BUTTON &amp;&amp; State == GLUT_DOWN)
{
glGetIntegerv(GL_VIEWPORT , Viewport) ;

glSelectBuffer(512 , ObjectList) ;

glRenderMode(GL_SELECT) ;

//Enter the projection mode, save the matrix and then load the identity.
glMatrixMode(GL_PROJECTION) ;

glPushMatrix() ;

glLoadIdentity() ;

gluPickMatrix((GLdouble)x , (GLdouble)(Viewport[3] - y) , 4 , 4 , Viewport) ;
glOrtho(-6.0f , 6.0f , -6.0f , 6.0f , -400.0f , 400.0f) ;

glMatrixMode(GL_MODELVIEW) ;

DrawGrid(GL_SELECT) ;

//After drawing , pop back the projection matrix and reset to the modelview matrix.
glMatrixMode(GL_PROJECTION) ;
glPopMatrix() ;
glMatrixMode(GL_MODELVIEW) ;
glFlush() ;

Hits = glRenderMode(GL_RENDER) ;
processHits(Hits , ObjectList) ;
glutPostRedisplay() ;
}
}I cant figure out whats wrong..everytime i click on a vertex i get that the no. of hits is zero.

Plz plz help me out...

Thanx

Yours

Siddharth`

infinitecmdz
11-22-2005, 07:58 PM
And hey another thing is , I tried to debug it by not changing the viewing voluma after gluPickMatrix(), just to see what is being rendered. The particular vertex is being rendered within the scene but i have a doubt. I have kept my point size as 4 and my viewing volume also as 4 by 4. I see that even in a smaller viewing volume, the point size is the same as it were in a bigger viewing volume. Is this supposed to happen or shoudl the point fill up the entire space in the smaller viewing volume?

I still cant figure out why the vertices are not getting a hit record as they definitely fall within the smaller viewing volume..

Plz help.

Yours

Siddharth