OpenGL Picking 拾取

[michael2988]

我在代码中用到了glOrtho 和 gluLookAt
在选取模式时要怎样设置：
我的Selection函数

void Selection( int x, int y )
{
	GLuint buffer[512];
	GLint hits;

	GLint viewport[4];
	glGetIntegerv(GL_VIEWPORT, viewport);
	glSelectBuffer(512, buffer);

	(void)glRenderMode(GL_SELECT);

	glInitNames();
	glPushName(0);

	glMatrixMode(GL_PROJECTION);
	glPushMatrix();
	glLoadIdentity();

	GLdouble w = (double)m_ClientRect.Width();
	GLdouble h = (double)m_ClientRect.Height();
	gluPickMatrix((GLdouble)x, (GLdouble)(viewport[3] - y), 500, 500, viewport);
	glOrtho(-w / 2, w / 2, -h / 2, h / 2, -1000000.0, 100000.0);
	glMatrixMode(GL_MODELVIEW);
	DrawBuffer();
	glMatrixMode(GL_PROJECTION);
	glPopMatrix();
	glMatrixMode(GL_MODELVIEW);
	hits = glRenderMode(GL_RENDER);

	if (hits > 0)
	{
		TRACE(_T("%d %d %d %d %d\n"), hits, buffer[0], buffer[1], buffer[2], buffer[3]);
	}
}

可是没有效果，还有如果我使用glDrawArrays来绘制的话，怎样为每个元素调用glLoadName