Question

我遇到了将3D坐标转换为屏幕坐标的问题。我必须将球体的中心转换为屏幕坐标。我的代码在这里：

//  OpenGL problem

#ifdef __APPLE__
#  include <GLUT/glut.h>
#else
#  include <GL/glut.h>
#endif

void passive(int,int);
void reshape(int,int);
void init(void);
void display(void);
void camera(void);

int cursorX,cursorY,width,height;
double centerX,centerY,centerZ;
//GLfloat modelviewMatrix[16],projectionMatrix[16];
GLdouble modelviewMatrix[16],projectionMatrix[16];
GLint viewport[4];

int main (int argc,char **argv) {
    glutInit (&argc,argv);
    glutInitDisplayMode(GLUT_DOUBLE | GLUT_DEPTH | GLUT_RGBA);
    glutInitWindowSize(1364,689);
    glutInitWindowPosition(0,0);
    glutCreateWindow("Sample");
    init();
    glutDisplayFunc(display);
    glutIdleFunc(display);
    glutPassiveMotionFunc(passive);
    glutReshapeFunc(reshape);
    glutMainLoop();
    return 0;
}

void display() {
    glClearColor (0.0,0.0,0.0,1.0);
    glClear (GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);

    //  Render 3D content
    glMatrixMode(GL_PROJECTION);
    glLoadIdentity();
    gluPerspective(60,(GLfloat)width/(GLfloat)height,1.0,100.0);    // create 3D perspective projection matrix
    glMatrixMode(GL_MODELVIEW);
    glPushMatrix();
    camera();
    glTranslatef(-6,-2,0);
    glColor3f(1,0,0);
    glutSolidSphere(5,50,50);
    glPopMatrix();

    glGetDoublev(GL_MODELVIEW_MATRIX, modelviewMatrix);
    glGetDoublev(GL_PROJECTION_MATRIX, projectionMatrix);
    glGetIntegerv(GL_VIEWPORT, viewport);
    // get 3D coordinates based on window coordinates  
    gluProject(-6, -2, 0, modelviewMatrix, projectionMatrix, viewport, &centerX, &centerY, &centerZ);

    // Render 2D content
    glMatrixMode(GL_PROJECTION);
    glLoadIdentity();
    gluOrtho2D(0, width,height, 0);                 // create 2D orthographic projection matrix
    glMatrixMode(GL_MODELVIEW);
    glColor3f(1,1,1);
    glBegin(GL_LINES);
        glVertex2f( centerX,centerY );          // coordinate of center of the sphere in orthographic projection
        glVertex2f( cursorX,cursorY );
    glEnd();

    glutSwapBuffers();
}

void camera(void) {
    glRotatef(0.0,1.0,0.0,0.0);
    glRotatef(0.0,0.0,1.0,0.0);
    glTranslated(0,0,-20);
}

void init(void) {
    glEnable (GL_DEPTH_TEST);
    glEnable (GL_BLEND);
    glBlendFunc (GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);
    glEnable(GL_COLOR_MATERIAL);
}

void reshape(int w, int h) {
    width=w; height=h;
}

void passive(int x1,int y1) {
    cursorX=x1; cursorY=y1;
}

在我的代码中，centerX和centerY坐标离开了屏幕。我必须在球体的中心和鼠标指针之间画一条线。对代码进行任何修改以使其正常工作？

Answer 1

通常我用来在3D / 2D坐标之间切换的功能。看看它是否适合你。

void toggle2DMode(bool flag, GLint Width, GLint Height) const
{
        if(flag)
        {
                glMatrixMode(GL_PROJECTION);
                glPushMatrix();
                glLoadIdentity();

                glOrtho(0.0, Width, Height, 0.0, -1.0f, 1.0f);
                glMatrixMode(GL_MODELVIEW);
                glPushMatrix();
                glLoadIdentity();
                glDisable(GL_DEPTH_TEST);
                glEnable(GL_BLEND);
        }
        else
        {
                glMatrixMode(GL_PROJECTION);
                glPopMatrix();
                glMatrixMode(GL_MODELVIEW);
                glPopMatrix();
                glEnable(GL_DEPTH_TEST);
                glDisable(GL_BLEND);
        }
}

Answer 2

我检查四元组分辨率的功能

void WINDOW_TEXT::calcResolution( GLshort & x , GLshort & y )
{
    GLdouble tx, ty, ttx, tty, z; // target 2d coords (z is 'unused')

    GLdouble model_view[16];
    glGetDoublev(GL_MODELVIEW_MATRIX, model_view);

    GLdouble projection[16];
    glGetDoublev(GL_PROJECTION_MATRIX, projection);

    GLint viewport[4];
    glGetIntegerv(GL_VIEWPORT, viewport);

    // get window coords based on 3D coordinates
    gluProject( up_right.x, up_right.y, up_right.z,
                model_view, projection, viewport,
                &tx, &ty, &z);

    gluProject( down_left.x, down_left.y, down_left.z,
                model_view, projection, viewport,
                &ttx, &tty, &z);

    x = (GLshort)(tx-ttx);
    y = (GLshort)(tty-ty);
};

“z”被忽略，你得到的纯分辨率存储在x和y

中

在OpenGL中将3D坐标转换为屏幕坐标

2 个答案: