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[isugamedev-devel] Re: Problem
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From: Chad A. <ae...@vr...> - 2003-05-26 08:01:00
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Ian Overton wants to convert screen coordinates to coordinates on a grid that he
has drawn (with perspective). I've never used gluUnProject before... Can
someone help him?
Thanks,
Chad
Ian Overton wrote:
> Alright I want to figure out how to take the mouse coords and convert them to
> something on the x z plane. I have made a grid and I want to be able to click
> on the grid and know exactly where that click was on that grid, so I will be
> able to make a wall. Problem is I have no idea how to do it, cause of the
> prespective and I've looked everywhere and they don't seem to know either. My
> code is in the broken_metal file.
>
> I have also found something that does kind of what I want, but when I try and
> do it to the grid it always gives huge numbers and it seems it does that on
> that unproject to, but yet it works. I don't know, can check it out and see if
> you can figure it out?
>
> I believe
> 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);
> gluUnProject(wx,wy,wz,modelview,projection,viewport,&ox,&oy,&oz);
>
> is the meat and patatos I don't really need to use glreadpixel, because I only
> need two of the three coords. The y coord is -10
>
>
>
> ------------------------------------------------------------------------
>
> // GLRect.c
> // The Drawing a simple 3D rectangle program with GLUT
> // OpenGL SuperBible, 2nd Edition
> // Richard S. Wright Jr.
>
> #include <windows.h>
> #include <gl/glut.h>
> #include <vector>
> #include <math.h>
>
> #define DEGTORAD(x) ((x)*0.017453292519943296)
>
> std::vector<int> walls;
> bool gofast=0;
> int window_width=0;
> int window_hieght=0;
>
> struct CAMERA
> {
> float position[3];
> float orientation[3];
> } cameraData;
>
> CAMERA pCamera;
> // Called to draw scene
> void RenderScene(void)
> {
> // Clear the window with current clearing color
> glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
>
> // Save matrix state and do the rotation
> glPushMatrix();
> glRotatef(pCamera.orientation[0], 1.0f, 0.0f, 0.0f);//turn and move the camera to the rigth place
> glRotatef(pCamera.orientation[1], 0.0f, 1.0f, 0.0f);
> glRotatef(pCamera.orientation[2], 0.0f, 0.0f, 1.0f);
> glTranslatef(-pCamera.position[0],pCamera.position[1],pCamera.position[2]);
>
> glBegin(GL_LINES);
> glColor3f(0.0f, 1.0f, 1.0f);
>
> for(int y=-500; y<=500; y+=5) //make a grid
> {
> glVertex3i(y,-10,-500);
> glVertex3i(y,-10,500);
> glVertex3i(-500,-10,y);
> glVertex3i(500,-10,y);
> }
>
> glLoadIdentity();
> glColor3f(1.0f, 1.0f, 1.0f);
> if(!walls.empty())
> {
> for(y=0; y<walls.size(); y+=4)//plot my points I made with the mouse
> {
> glVertex3i(walls[y],-1,walls[y+1]);
> glVertex3i(walls[y+2],-1,walls[y+3]);
> }
> }
> glEnd();
>
> // Restore transformations
> glPopMatrix();
>
> glutSwapBuffers();
> }
>
> void Keys(unsigned char key, int x, int y)
> {
> float fAngularVelocityX,fAngle;
> if(key == 'a')
> fAngularVelocityX = -5.0f; //look up
>
> if(key == 'z')
> fAngularVelocityX = 5.0f; //look down
>
> if(key == 0x1b)//esc quit
> exit(0);
>
> if(key == 'r' && !gofast) //run
> gofast=1;
> else
> gofast=0;
>
>
> if(key == 'a' || key == 'z') //update the camera
> {
> // Update Rotation angles (clamp the X rotation)
> fAngle = fAngularVelocityX + pCamera.orientation[0];
>
> if((fAngle < 90.0f) && (fAngle > -90.0f))
> pCamera.orientation[0] = fAngle;
>
> // Refresh the Window
> glutPostRedisplay();
> }
> }
>
> void SpecialKeys(int key, int x, int y)
> {
> float fLinearVelocity=1;
> float fAngularVelocityY=0;
> int speed;
> if(gofast)
> speed=10;
> else
> speed=1;
> if(key == GLUT_KEY_UP) //go forward
> fLinearVelocity= 5.0f*speed;
>
> if(key == GLUT_KEY_DOWN) //go backward
> fLinearVelocity= -5.0f*speed;
>
> if(key == GLUT_KEY_LEFT) //turn to the left
> fAngularVelocityY = -5.0f*speed;
>
> if(key == GLUT_KEY_RIGHT) //turn to the right
> fAngularVelocityY = 5.0f*speed;
>
> pCamera.orientation[1] += fAngularVelocityY;
>
> // Update linear position
> pCamera.position[0] = fLinearVelocity * (float)(sin(DEGTORAD(pCamera.orientation[1]))) + pCamera.position[0];
> pCamera.position[2] = fLinearVelocity * (float)(cos(DEGTORAD(pCamera.orientation[1]))) + pCamera.position[2];
>
> // Refresh the Window
> glutPostRedisplay();
> }
>
> // Setup the rendering state
> void SetupRC(void)
> {
> glEnable(GL_DEPTH_TEST); // Hidden surface removal
>
> // Set clear color to blue
> glClearColor(0.0f, 0.0f, 1.0f, 1.0f);
>
> // Camera initial position and orientation
> // Initially at Origin
> cameraData.position[0] = 0.0f;
> cameraData.position[1] = 0.0f;
> cameraData.position[2] = 0.0f;
>
> // Looking down negative Z Axis (North). Positive X is to the right
> cameraData.orientation[0] = 0.0f;
> cameraData.orientation[1] = 0.0f;
> cameraData.orientation[2] = 0.0f;
> }
>
> /*void moving_mouse (int x, int y)
> {
> int tempx,tempy;
> tempx=-x/(window_width/20) + window_width/20;
> tempy=(window_hieght-y);
> }*/
>
> void MouseHandler(int button, int state, int x, int y) //if they clicked somewhere start making a new wall or finish a wall
> {
> int tempx,tempy;
> if(button == GLUT_LEFT && state == GLUT_DOWN)
> {
> tempx=-sin(DEGTORAD(x))*(window_hieght);
> tempy=cos(DEGTORAD(y))*(window_width);
> walls.push_back(tempx);
> walls.push_back(tempy);
> if(walls.size()%4==0)
> glutPostRedisplay();
> glutMouseFunc(MouseHandler);
> }
> }
>
> void motion(int x, int y) //does the same thing as mousehandler, but it changes the current point they are doing, and if nothing has been clicked it marks the first click as the first point and then after as the finial point.
> {
> int tempx,tempy;
> tempx=-sin(DEGTORAD(x))*(window_hieght);
> tempy=cos(DEGTORAD(y))*(window_width);
>
> if(walls.size()%4==0)
> {
> walls[walls.size()-2]=tempx;
> walls[walls.size()-1]=tempy;
> glutPostRedisplay();
> }
> else
> {
> walls.push_back(tempx);
> walls.push_back(tempy);
> }
> }
>
> // Called by GLUT library when the window has chanaged size
> void ChangeSize(GLsizei w, GLsizei h)
> {
> float fAspect;
>
> window_width=w;
> window_hieght=h;
> // Prevent a divide by zero
> if(h == 0)
> h = 1;
>
> // Set Viewport to window dimensions
> glViewport(0, 0, w, h);
>
> // Reset coordinate system
> glMatrixMode(GL_PROJECTION);
> glLoadIdentity();
>
> fAspect = (float)w/(float)h;
> gluPerspective(45.0,fAspect, 1.0, 500.0);
> glMatrixMode(GL_MODELVIEW);
> glLoadIdentity();
> }
>
> // Main program entry point
> void main(void)
> {
> glutInitDisplayMode(GLUT_DOUBLE | GLUT_RGB | GLUT_DEPTH);
> glutCreateWindow("Broken Metal");
> glutDisplayFunc(RenderScene);
> //glutFullScreen();
> glutKeyboardFunc(Keys);
> glutSpecialFunc(SpecialKeys);
> glutReshapeFunc(ChangeSize);
> glutMotionFunc(motion);
> glutMouseFunc(MouseHandler);
> glutPassiveMotionFunc(moving_mouse);
>
> SetupRC();
>
> glutMainLoop();
> }
>
>
>
> ------------------------------------------------------------------------
>
> /*
> gcc -Wall -lglut -lGLU -lGL unproject.c -o unproject
> */
>
> #include <GL/glut.h>
>
> void Display();
> void Reshape(int w,int h);
> void Mouse(int button,int state,int x,int y);
>
> int main(int argc,char **argv) {
> glutInit(&argc,argv);
> glutInitDisplayMode(GLUT_SINGLE|GLUT_RGB);
> glutInitWindowSize(500,500);
> glutInitWindowPosition(100,100);
> glutCreateWindow(argv[0]);
> glutDisplayFunc(Display);
> glutReshapeFunc(Reshape);
> glutMouseFunc(Mouse);
>
> glEnable(GL_LIGHTING);
> glEnable(GL_LIGHT0);
> glEnable(GL_DEPTH_TEST);
>
> 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);
>
> glPushMatrix();
> glRotatef(45,1.0,0.0,0.0);
> glutSolidTorus(4.0,5.0,20,20);
> glPopMatrix();
>
> glPushMatrix();
> glDepthMask(GL_FALSE);
> glTranslated(ox,oy,oz);
> glutSolidSphere(0.5,15,15);
> glDepthMask(GL_TRUE);
> glPopMatrix();
>
> glFlush();
> }
>
> void Reshape(int w,int h) {
> glViewport(0,0,w,h);
> glMatrixMode(GL_PROJECTION);
> glLoadIdentity();
> gluPerspective(45.0,(float)w/(float)h,5.0,30.0);
> glMatrixMode(GL_MODELVIEW);
> }
>
> void Mouse(int button,int state,int x,int y) {
> GLint viewport[4];
> GLdouble modelview[16],projection[16];
> GLfloat wx=x,wy,wz;
>
> if(state!=GLUT_DOWN)
> return;
> if(button==GLUT_RIGHT_BUTTON)
> exit(0);
> 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);
> gluUnProject(wx,wy,wz,modelview,projection,viewport,&ox,&oy,&oz);
> glutPostRedisplay();
> }
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