我有一个这样的视图设置:
glMatrixMode(GL_MODELVIEW); //Switch to the drawing perspective
glLoadIdentity(); //Reset the drawing perspective
我从鼠标点击中获得了屏幕位置(sx,sy)。
给定z的值,如何从sx和sy计算出三维空间中的x和y?
gluUnProject
:GLdouble modelMatrix[16];
GLdouble projMatrix[16];
GLint viewport[4];
glGetIntegerv(GL_VIEWPORT, viewport);
glGetDoublev(GL_MODELVIEW_MATRIX, modelMatrix);
glGetDoublev(GL_PROJECTION_MATRIX, projMatrix);
GLdouble x, y, z;
gluUnProject(sx, viewport[1] + viewport[3] - sy, 0, modelMatrix, projMatrix, viewport, &x, &y, &z);
// replace the above gluUnProject call with
gluUnProject(sx, viewport[1] + viewport[3] - sy, 1, modelMatrix, projMatrix, viewport, &x, &y, &z);
现在你已经得到了一个世界坐标系中的线,它跟踪了所有可能点击的点。现在你只需要进行插值:假设你已经知道了z坐标:
GLfloat nearv[3], farv[3]; // already computed as above
if(nearv[2] == farv[2]) // this means we have no solutions
return;
GLfloat t = (nearv[2] - z) / (nearv[2] - farv[2]);
// so here are the desired (x, y) coordinates
GLfloat x = nearv[0] + (farv[0] - nearv[0]) * t,
y = nearv[1] + (farv[1] - nearv[1]) * t;