gluUnProject issue
Post: #1
Hello,
I am having a problem with gluUnProject.
I drew a Cube with gluPerspective and rotate it on the Y axis when dragged by mouse. Now I need to place a small sphere on the face of the cube depending on my mouse click (presently if I press P and then click mouse left button then convert the window position to object position).
Everything works fine , if I dont rotate the cube(ie I am able to place the
small sphere on the cube where I click). Now If I rotate the cube , then click on the cube (ie P + mouse) the sphere is not placed where I click. It behaves weirdly. I am new to opengl, please help.
I am having a problem with gluUnProject.
I drew a Cube with gluPerspective and rotate it on the Y axis when dragged by mouse. Now I need to place a small sphere on the face of the cube depending on my mouse click (presently if I press P and then click mouse left button then convert the window position to object position).
Everything works fine , if I dont rotate the cube(ie I am able to place the
small sphere on the cube where I click). Now If I rotate the cube , then click on the cube (ie P + mouse) the sphere is not placed where I click. It behaves weirdly. I am new to opengl, please help.
Post: #3
Below is the code...My intention here is to place the small sphere on the tetrahedron at the position specified by the mouse. It does not work when I rotate the tetrahedron. Hope this gives insight to my problem
Code:
#include <GL/glut.h>
#include <iostream>
#include <stdlib.h>
#include <stdio.h>
void Display();
void Reshape(int w,int h);
static float _angle = 0.0f;
static int stop = 0;
static int rotate = 0;
static int lastx = 0;
static int lasty = 0;
static float rotation_angle = 0.0f;
static bool edit_poly = false;;
static bool second_point = false;
static double object_coord_start[3];
void mouseMovement(int x, int y) {
if(rotate == 1)
{
int diffx=x-lastx; //check the difference between the current x and the last x position
int diffy=y-lasty; //check the difference between the current y and the last y position
lastx=x; //set lastx to the current x position
lasty=y; //set lasty to the current y position
_angle = _angle + (float)diffx;
glutPostRedisplay(); //Tell GLUT that the display has changed
}
else
{
lastx = 0;
lasty = 0;
}
}
void keyboard (unsigned char key, int x, int y) {
/* Called when a key is pressed */
if (key == 27) exit (0); /* 27 is the Escape key */
if(key == 'p')
{
edit_poly = true;
}
}
void mouseEvent(int button, int state, int x, int y)
{
if (button == GLUT_LEFT_BUTTON)
{
if (state == GLUT_DOWN)
{
rotate = 1;
lastx = x;
lasty = y;
if ( edit_poly == true)
{
GLint viewport[4];
GLdouble projection[16],modelview[16];
GLfloat wx=x,wy,wz;
glGetIntegerv(GL_VIEWPORT,viewport);
y=viewport[3]-y;
wy=y;
glGetDoublev(GL_MODELVIEW_MATRIX,modelview);
glGetDoublev(GL_PROJECTION_MATRIX,projection);
glReadPixels(x,y,1,1,GL_DEPTH_COMPONENT,GL_FLOAT,&wz);
GLU_FALSE == gluUnProject(wx,wy,wz,modelview,projection,viewport,&object_coord_start[0],&object_coord_start[1],&object_coord_start[2]);
glutPostRedisplay();
}
}
else if (state == GLUT_UP)
{
rotate = 0;
if ( edit_poly == true)
{
edit_poly = false;
}
}
}
}
int main(int argc,char **argv) {
glutInit(&argc,argv);
glutInitDisplayMode(GLUT_DOUBLE|GLUT_RGB|GLUT_DEPTH);
glutInitWindowSize(500,500);
glutInitWindowPosition(100,100);
glutCreateWindow("ex");
glEnable(GL_DEPTH_TEST);
glEnable(GL_COLOR_MATERIAL);
glutDisplayFunc(Display);
glutReshapeFunc(Reshape);
glutKeyboardFunc (keyboard); /* Register the "keyboard" function */
glutMotionFunc(mouseMovement); //check for mouse movement
glutMouseFunc(mouseEvent);
glutMainLoop();
return 0;
}
GLdouble ox=0.0,oy=0.0,oz=0.0;
void Display() {
glClear(GL_COLOR_BUFFER_BIT|GL_DEPTH_BUFFER_BIT);
glLoadIdentity();
//gluLookAt(10.0,0.0,20.0,0.0,0.0,0.0,0.0,1.0,0.0);
gluLookAt (0.0, 0.0, 6.0, 0.0, 0.0, 0.0, 0.0, 1.0, 0.0);
glPushMatrix();
glRotatef(_angle, 0.0f, 1.0f, 0.0f);
//glRotatef(45,1.0,0.0,0.0);
glColor3f(1,0,0);
glBegin(GL_POLYGON);
glVertex3f(0.0, 0.0, 0.0);
glVertex3f(2.0, 0.0, 0.0);
glVertex3f(1.0,2.0,0.0);
glVertex3f(0.0, 0.0, 0.0);
//glVertex3f(1.0, 1.0, 2.0);
glEnd();
glColor3f(0,1,0);
glBegin(GL_POLYGON);
glVertex3f(0.0, 0.0, 0.0);
glVertex3f(1.0, 2.0, 0.0);
glVertex3f(1.0,1.0,2.0);
glVertex3f(0.0, 0.0, 0.0);
glEnd();
glColor3f(1,1,0);
glBegin(GL_POLYGON);
glVertex3f(2.0,0.0, 0.0);
glVertex3f(1.0,2.0,0.0);
glVertex3f(1.0, 1.0, 2.0);
glVertex3f(2.0, 0.0, 0.0);
glEnd();
glColor3f(0,0,1);
glBegin(GL_POLYGON);
glVertex3f(0.0, 0.0, 0.0);
glVertex3f(2.0,0.0, 0.0);
glVertex3f(1.0,1.0,2.0);
glVertex3f(0.0, 0.0, 0.0);
glEnd();
//glPopMatrix();
glPushMatrix();
glColor3f(0,1,1);
glDepthMask(GL_FALSE);
glTranslated(object_coord_start[0],object_coord_start[1],object_coord_start[2]);
glutSolidSphere(0.1,15,15);
glDepthMask(GL_TRUE);
glPopMatrix();
glutSwapBuffers();
}
void Reshape(int w,int h) {
glViewport(0,0,w,h);
glMatrixMode(GL_PROJECTION);
glLoadIdentity();
gluPerspective (60, (GLfloat)w / (GLfloat)h, 1.0, 100.0);
glMatrixMode(GL_MODELVIEW);
}
Post: #4
The way you do it, it won't work because the matrices you retrieve in mouseEvent() aren't the matrices that were used to draw the cube because of push/pop. You need to store those when drawing or computing them, then use them with unProject() later.
