Question: How do I transform a plot with plot3d

Hi, here is my question.


plot3d(test,u=0..1-v, v=0..1);

How can I  transform this plot in the right triangle into an equilateral triangle? 

So that the three edges of the plot are the same length.

I wanna, squish it, or shear?

any tools i can use? Or can I do it using some tricks to change the function?