How to graph the properties of steam? I need to render this graph in Unity:

I'm using this as a resource: http://www.iapws.org/ 
I've found various implementations of IAPWS (95, 97, etc...) in various languages (python, c++, fortran, etc...).
My problem is that I'm not certain of the methods understood to wrangle this data.
(This is NOT a programming question: I'm interested in the standards of the thermodynamics community)
For example:


*

*I've found that this graph is Log10 on all axis.

*I've found one implementation of IAPWS97 that lets me query v with a known p and t

*The graph generated using this method leaves a giant gap where the "liquid and vapor" dome resides (makes sense, given that it's essentially vertical from the perspective of sampling p and t)

*I've found one implementation of IAPWS95 that lets me query p with a known v and t

*The graph generated using this method looks NOTHING like the illustration below or the previous graph (should I chalk this up to a faulty implementation? or is there some other understanding of this graph I should be looking out for?)

*Is there a known standard way that allows me to query any value (p, v, or t) given the other 2, that specifically corresponds to this graph? Or is this question a category error?

*Note: I am a programmer, NOT a scientist

 A: 
  
*
  
*The graph generated using this method leaves a giant gap where the "liquid and vapor" dome resides (makes sense, given that it's
  essentially vertical from the perspective of sampling p and t)
  

Since you didn't provide your graph showing the "gap" I'm  not exactly sure what the gap is. The possibility that comes to mind is that under the "liquid and vapor dome" pressure and temperature are not independent variables. In order to find or specify a point in this area you need two independent variables: (1) The temperature (or pressure since there is only one corresponding to each temperature, and vice versa, under the dome) and (2) the "quality" of the steam, that is, the percentage of the liquid + vapor that is vapor. Without knowing the quality, you would have a gap for a location between the curves that represent saturated vapor and saturated liquid.
To help you visualize this, I have shown your diagram below to indicate the points where you have a quality of 1 (100 % vapor) and a quality of 0 (100% liquid) on the dome. Everything in between will vary from 0 to 1. Halfway, it is 0.5 or 50 % vapor and 50% liquid. The dotted line connecting the two is both constant temperature and constant pressure. To know where you are, you need to know the quality of the  mixture. 
Hope this helps.

