Subversion Repositories gelsvn

    bool depth_pick(int x, int y, float& depth)

    {

        float new_depth;

        // Get the minimum and maximum depth values.

        float minmax_depth[2];

        glGetFloatv(GL_DEPTH_RANGE, minmax_depth);

        glPushAttrib(GL_PIXEL_MODE_BIT);

        glReadBuffer(GL_FRONT);

        // Read a single pixel at the position of the mouse cursor.

        glReadPixels(x, y, 1,1, GL_DEPTH_COMPONENT,

                     GL_FLOAT, (void*) &new_depth);

        glPopAttrib();

        // If the depth corresponds to the far plane, we clicked on the

        // background.

        if(new_depth == minmax_depth[1])

            return false;

        depth = new_depth;

        return true;

    }

    Vec3d screen2world(int x, int y, float depth)

    {

        // Enquire about the viewport dimensions

        GLint viewport[4];

        glGetIntegerv(GL_VIEWPORT, viewport);

        // Copy modelview matrix.

        double mvmat[16];

        glGetDoublev(GL_MODELVIEW_MATRIX, mvmat);

        // Copy the projection matrix. We assume it is unchanged.

        double prjmat[16];

        glGetDoublev(GL_PROJECTION_MATRIX, prjmat);

        // Now unproject the point from screen to world coordinates.

        double ox, oy, oz;

        gluUnProject(x, y,depth,

                     mvmat,prjmat,viewport,

                     &ox, &oy, &oz);

        return Vec3d(ox,oy,oz);

    }