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Picking 3D models


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3 replies to this topic

#1 GottiJay   Members   -  Reputation: 100

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Posted 04 July 2011 - 03:09 PM

Guys i really need your help, any ideas on how i could get picking working in my program...i have 6 models rendered. i tried to implement picking but what happens is that, it only gets a hit when certain parts in the scene are clicked (but does not record a hit when the models are clicked). please what could be the problem.


thank you.

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#2 GottiJay   Members   -  Reputation: 100

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Posted 05 July 2011 - 01:19 AM

Guys i really need your help, any ideas on how i could get picking working in my program...i have 6 models rendered. i tried to implement picking but what happens is that, it only gets a hit when certain parts in the scene are clicked (but does not record a hit when the models are clicked). please what could be the problem.


thank you.

Please can someone help???i have read every article on picking and still cant get my program to pick properly....just a look at what i may be doing wrong will be fine thank you

void selection(int x, int y)
 {
 	GLuint buff[64] = {0};
 	GLint hits, view[4];
 		
 		
 	
 	glSelectBuffer(64, buff);    //This chooses the buffer where store the values for the selection data
  	
 	glGetIntegerv(GL_VIEWPORT, view); //This retrieve info about the viewport
  	
 	glRenderMode(GL_SELECT);	//	Switching in selecton mode
  	
 	glInitNames();// Clearing the name's stack
 
 	glPushName(0); //filling the stack with one element
 
 	 	
 	glMatrixMode(GL_PROJECTION);	// Now modify the vieving volume, restricting selection area around the cursor
 	glPushMatrix();
 	glLoadIdentity();
 
 		
		gluPickMatrix((GLdouble)x,(GLdouble) (view[3] - y),1.0,1.0, view);		//restrict the draw to an area around the cursor
 		gluPerspective(45.0f,(GLfloat)screen_width/(GLfloat)screen_height,10.0f,10000.0f);
 
 		glMatrixMode(GL_MODELVIEW);	//	Draw the objects onto the screen
 
 		glutSwapBuffers(); //draw only the names in the stack, and fill the array
 		
		drawReflector(GL_SELECT);
		//drawMast(GL_SELECT);
		drawReflector(GL_SELECT);
 
 	glMatrixMode(GL_PROJECTION);
 	glPopMatrix();
 
 	/*
 		this will help us get the number of objects drawed in that area
 		and return to render mode
 	*/
 	hits = glRenderMode(GL_RENDER);
  	
 	list_hits(hits, buff); // Print a list of the objects
 
 	
 	//selectAll(hits, buff);
 	
  	glMatrixMode(GL_MODELVIEW);
 }



#3 anttoo   Members   -  Reputation: 210

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Posted 10 July 2011 - 03:47 PM


Guys i really need your help, any ideas on how i could get picking working in my program...i have 6 models rendered. i tried to implement picking but what happens is that, it only gets a hit when certain parts in the scene are clicked (but does not record a hit when the models are clicked). please what could be the problem.


thank you.

Please can someone help???i have read every article on picking and still cant get my program to pick properly....just a look at what i may be doing wrong will be fine thank you

void selection(int x, int y)
{
    GLuint buff[64] = {0};
    GLint hits, view[4];
        
        
    
    glSelectBuffer(64, buff);    //This chooses the buffer where store the values for the selection data
      
    glGetIntegerv(GL_VIEWPORT, view); //This retrieve info about the viewport
      
    glRenderMode(GL_SELECT);    //    Switching in selecton mode
      
    glInitNames();// Clearing the name's stack

    glPushName(0); //filling the stack with one element

         
    glMatrixMode(GL_PROJECTION);    // Now modify the vieving volume, restricting selection area around the cursor
    glPushMatrix();
    glLoadIdentity();

        
        gluPickMatrix((GLdouble)x,(GLdouble) (view[3] - y),1.0,1.0, view);        //restrict the draw to an area around the cursor
        gluPerspective(45.0f,(GLfloat)screen_width/(GLfloat)screen_height,10.0f,10000.0f);

        glMatrixMode(GL_MODELVIEW);    //    Draw the objects onto the screen

        glutSwapBuffers(); //draw only the names in the stack, and fill the array
        
        drawReflector(GL_SELECT);
        //drawMast(GL_SELECT);
        drawReflector(GL_SELECT);

    glMatrixMode(GL_PROJECTION);
    glPopMatrix();

    /*
        this will help us get the number of objects drawed in that area
        and return to render mode
    */
    hits = glRenderMode(GL_RENDER);
      
    list_hits(hits, buff); // Print a list of the objects

    
    //selectAll(hits, buff);
    
      glMatrixMode(GL_MODELVIEW);
}


Try and reduce your far plane, from what I understand the picking will only differentiate between things more than (10000.0f /65,000) = about 0.2?. Perhaps that will help.


Here is my picking code if that helps
const int pickBufferSize = 1000;
 
 unsigned int pickBuffer[pickBufferSize];
 
 for ( int i = 0; i < pickBufferSize; ++i)
  pickBuffer[i] = 0;

 int viewport[4];

 //setup selection buffer
 glSelectBuffer(pickBufferSize, pickBuffer);
 
 glRenderMode(GL_SELECT);

 //This is currently test code:
 glInitNames();
 glPushName(6666666); //evil!

 //Set the picking matrix
 glGetIntegerv(GL_VIEWPORT,viewport);
 glMatrixMode(GL_PROJECTION);
 glPushMatrix();
 glLoadIdentity();
 gluPickMatrix(GameCore::App()->MouseX(),viewport[3]-GameCore::App()->MouseY(),
  1,1,viewport);

 //Normal render
 this->Render();

 int nHits = glRenderMode(GL_RENDER);
  
 glMatrixMode(GL_PROJECTION);
 glPopMatrix();
 glLoadIdentity();




#4 GottiJay   Members   -  Reputation: 100

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Posted 10 July 2011 - 03:59 PM



Guys i really need your help, any ideas on how i could get picking working in my program...i have 6 models rendered. i tried to implement picking but what happens is that, it only gets a hit when certain parts in the scene are clicked (but does not record a hit when the models are clicked). please what could be the problem.


thank you.

Please can someone help???i have read every article on picking and still cant get my program to pick properly....just a look at what i may be doing wrong will be fine thank you

void selection(int x, int y)
{
    GLuint buff[64] = {0};
    GLint hits, view[4];
        
        
    
    glSelectBuffer(64, buff);    //This chooses the buffer where store the values for the selection data
      
    glGetIntegerv(GL_VIEWPORT, view); //This retrieve info about the viewport
      
    glRenderMode(GL_SELECT);    //    Switching in selecton mode
      
    glInitNames();// Clearing the name's stack

    glPushName(0); //filling the stack with one element

     	
    glMatrixMode(GL_PROJECTION);    // Now modify the vieving volume, restricting selection area around the cursor
    glPushMatrix();
    glLoadIdentity();

        
        gluPickMatrix((GLdouble)x,(GLdouble) (view[3] - y),1.0,1.0, view);        //restrict the draw to an area around the cursor
        gluPerspective(45.0f,(GLfloat)screen_width/(GLfloat)screen_height,10.0f,10000.0f);

        glMatrixMode(GL_MODELVIEW);    //    Draw the objects onto the screen

        glutSwapBuffers(); //draw only the names in the stack, and fill the array
        
        drawReflector(GL_SELECT);
        //drawMast(GL_SELECT);
        drawReflector(GL_SELECT);

    glMatrixMode(GL_PROJECTION);
    glPopMatrix();

    /*
        this will help us get the number of objects drawed in that area
        and return to render mode
    */
    hits = glRenderMode(GL_RENDER);
      
    list_hits(hits, buff); // Print a list of the objects

    
    //selectAll(hits, buff);
    
      glMatrixMode(GL_MODELVIEW);
}


Try and reduce your far plane, from what I understand the picking will only differentiate between things more than (10000.0f /65,000) = about 0.2?. Perhaps that will help.


Here is my picking code if that helps
const int pickBufferSize = 1000;
 
 unsigned int pickBuffer[pickBufferSize];
 
 for ( int i = 0; i < pickBufferSize; ++i)
  pickBuffer[i] = 0;

 int viewport[4];

 //setup selection buffer
 glSelectBuffer(pickBufferSize, pickBuffer);
 
 glRenderMode(GL_SELECT);

 //This is currently test code:
 glInitNames();
 glPushName(6666666); //evil!

 //Set the picking matrix
 glGetIntegerv(GL_VIEWPORT,viewport);
 glMatrixMode(GL_PROJECTION);
 glPushMatrix();
 glLoadIdentity();
 gluPickMatrix(GameCore::App()->MouseX(),viewport[3]-GameCore::App()->MouseY(),
  1,1,viewport);

 //Normal render
 this->Render();

 int nHits = glRenderMode(GL_RENDER);
  
 glMatrixMode(GL_PROJECTION);
 glPopMatrix();
 glLoadIdentity();



thanks antoo for trying to help...i managed to get it working some days back....i appreciate
not to be greedy or anything i do need your help in some other context,i have been trying drag the models i pick in x,y and z axis, could you please explain to me how you did do this in your program...or you could give an idea how i could do this.....

thank you







Old topic!
Guest, the last post of this topic is over 60 days old and at this point you may not reply in this topic. If you wish to continue this conversation start a new topic.



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