I have been using TikZ a lot but only for 2D plots. I was hoping I could use the 3D package for plotting regions on the (x,y,z) plane given by linear inequalities (currently I'm using Mathematica for these 3D plots but I wanted to have more control over the plot options) but it seems that this is not the case.
Is there any alternative to TikZ-3D that is able to plot set of points (x,y,z) such that 0 is less or equal than min(x,0)+min(x,y,0)+z ? By that I mean: 1) Can it plot 3D level sets? and 2) If the function is a binary function: 1 in a set similar to the one described above and zero elsewhere, will it be able to do the level sets plot in minutes (say less than one hour)?
EDIT: "tikz-3dplot does not, in general, consider polygons, surfaces, or object opac- ity" so I'm changing the question to allow for gnuplot, PStricks or Asymptote (I'm not familiar with both of these packages) or any tool that allow me to control the plots specifications with greater detail.
I'm attaching a 3D plot I did with Mathematica: