place to make a 3D chart with a formula?

i believe the forum that fits this question the most is here, i'd like to know a site that allows me to put a formula, determine range of variables, and then it spits out a 3D chart, a quick example would be:

formula:

x+y+z=20

x= numbers from 0 to 10
y= numbers from 10 to 20
z= numbers from 0 to 20.

and then it would display a chart that showed it ._. anyone has any clue? i know excel does 3D charts, but i'd need to put every single point of data in it and that's too much wasted time with big numbers. (unless someone knows an easy way to do it?)

http://www.dpgraph.com/ ?

http://www.dpgraph.com/ ?

that's pretty much what i need, looks... complicated, and i need to pay? if so i can't get access to it then ._.

that's pretty much what i need, looks... complicated, and i need to pay? if so i can't get access to it then ._.

The viewer itself (http://www.dpgraph.com/graph-viewer.html) is actually free. It isn't that complex to use, but if you want you can use Wolfram|Alpha or Mathematica to produce the charts as well (albeit the latter costs money).

The viewer itself (http://www.dpgraph.com/graph-viewer.html) is actually free. It isn't that complex to use, but if you want you can use Wolfram|Alpha or Mathematica to produce the charts as well (albeit the latter costs money).

i tried using the viewer, but when trying to change stuff in it it told me that i needed to pay for the other version to be able to change formulas.

and i tried wolfram, couldn't get it to work, aaaargh, i feel like giving up ._.

just as example, the chart i'm trying to make would end up looking kinda like this:

 Spoiler

checking the site from which i got that picture, might have found it, dunno