Opengl鼠标点击物体上的交点坐标

// 渲染
void CmfcView::RenderScene()
{
	glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);	// Clear Screen And Depth Buffer

	glLoadIdentity();									// Reset The Current Modelview Matrix
	glTranslatef(0,0.0f,-10.0f);						// Move Right 1.5 Units And Into The Screen 7.0
	//glRotatef(45,0.0f,1.0f,0.0f);					// Rotate The Quad On The X axis ( NEW )
	//glRotatef(180,0.0f,0.0f,1.0f);					// Rotate The Quad On The X axis ( NEW )
	glBegin(GL_QUADS);									// Draw A Quad
	glColor3f(0.0f,1.0f,0.0f);						// Set The Color To Green
	glVertex3f(0, 0, 2);					// Top Right Of The Quad (Top)
	glVertex3f(1, 0, 2);					// Top Left Of The Quad (Top)
	glVertex3f(1, 1, 2);					// Bottom Left Of The Quad (Top)
	glVertex3f(0, 1, 2);					// Bottom Right Of The Quad (Top)
	glEnd();
}

/****************************************/
/*	功能：计算直线和平面交点
/*	param[in]: planePoint--平面上的一个点
/*	param[in]: planeVector--平面的法向量
/*	param[in]: linePoint1--直线的点1
/*	param[in]: linePoint2--直线的点2
/*  return: 交点坐标
/***************************************/
float* CmfcView::CalPlaneLineIntersectPoint(float* planePoint, float* planeVector, float* linePoint1, float* linePoint2)
{
	float *res = new float[3];	// 交点坐标
	//float planeVector[3] = {0, 0, 1};
	float lineVector[3];		// 直线向量
	lineVector[0] = linePoint2[0] - linePoint1[0];
	lineVector[1] = linePoint2[1] - linePoint1[1];
	lineVector[2] = linePoint2[2] - linePoint1[2];

	float vp1, vp2, vp3, n1, n2, n3, v1, v2, v3, m1, m2, m3, t,vpt;
	vp1 = planeVector[0];
	vp2 = planeVector[1];
	vp3 = planeVector[2];
	n1 = planePoint[0];
	n2 = planePoint[1];
	n3 = planePoint[2];
	v1 = lineVector[0];
	v2 = lineVector[1];
	v3 = lineVector[2];
	m1 = linePoint1[0];
	m2 = linePoint1[1];
	m3 = linePoint1[2];
	vpt = v1 * vp1 + v2 * vp2 + v3 * vp3;
	//首先判断直线是否与平面平行
	if (vpt == 0)
	{
		res = NULL;
	}
	else
	{
		t = ((n1 - m1) * vp1 + (n2 - m2) * vp2 + (n3 - m3) * vp3) / vpt;
		res[0] = m1 + v1 * t;
		res[1] = (m2 + v2 * t);
		res[2] = m3 + v3 * t;
	}
	return res;
}

float* CmfcView::CrossPoint(CPoint pt)
{
	float *crsPt;
	GLdouble x1, y1, z1;
	GLdouble x2, y2, z2;

	GLdouble    modelview[16];
	GLdouble    projection[16];
	GLint       viewport[4];
	glGetDoublev (GL_MODELVIEW_MATRIX, modelview);
	glGetDoublev (GL_PROJECTION_MATRIX, projection);
	glGetIntegerv (GL_VIEWPORT, viewport);

	GLdouble world_x1, world_y1, world_z1;  
	GLdouble world_x2, world_y2, world_z2; 

	// 获取近裁剪面上的交点
	gluUnProject( (GLdouble) pt.x, (GLdouble)(viewport[3] - pt.y - 1), 0.0, 
		modelview, projection, viewport, 
		&world_x1, &world_y1, &world_z1); 

	// 获取远裁剪面上的交点
	gluUnProject( (GLdouble) pt.x, (GLdouble)(viewport[3] - pt.y - 1), 1.0, 
		modelview, projection, viewport, 
		&world_x2, &world_y2, &world_z2); 

	float planePoint[3] = {10, 13, 2};		 // 平面上一点
	float linePoint1[3];
	float linePoint2[3];
	linePoint1[0] = world_x1;
	linePoint1[1] = world_y1;
	linePoint1[2] = world_z1;
	linePoint2[0] = world_x2;
	linePoint2[1] = world_y2;
	linePoint2[2] = world_z2;

	float planeVector[3] = {0, 0, 1};	// 平面向量（根据实际情况计算)

	crsPt = CalPlaneLineIntersectPoint(planePoint, planeVector, linePoint1, linePoint2);
	return crsPt;
}

void CmfcView::OnLButtonDown(UINT nFlags, CPoint point)
{
	// TODO: 在此添加消息处理程序代码和/或调用默认值

	float *crossPoint;
	crossPoint = CrossPoint(point);

	CView::OnLButtonDown(nFlags, point);
}