This is my thought, first get the screen coordinats of the 3d vextex, then check the touch screen point is in the shadow of the object on the screen。 To to this, we need to get the projected coordinate of a 3d point on the screen.

And I encountered a problem.

In opengl, this is simple:

glGetIntegerv(GL_VIEWPORT, viewport);

glGetDoublev(GL_MODELVIEW_MATRIX, modelview);

glGetDoublev(GL_PROJECTION_MATRIX, projection);

gluProject(x1, y1, 0, modelview, projection, viewport, &winX, &winY, &winZ);

But in opengl es，there is no fuction “glGetDoublev”， So how can I get the matrix of modelview and projection?