在Tikz中绘制一个表面的身份

I want to draw an identity across a surface plot. This identity should start at the bottom left, and end at the top right (from tip to tip). With the axis I've given (see below), the v_1=2(v_2-20). This becomes y=2(x-20) given the way the axes are defined. I've tried plotting this in various ways, but it does not seem to work on top of the 3d surface.I want to draw an identity across a surface plo