This is something of an aside - I don't know what I'm doing yet, well enough to implement this via jhs, but here's an ellipsoid:
https://www.shadertoy.com/view/XtlGDX You can tweak the a, b, and c radius values near the top of the script (which should display on the right side of the screen) and hit the play button to see the change. Thanks, -- Raul On Fri, Mar 6, 2015 at 10:38 PM, Skip Cave <s...@caveconsulting.com> wrote: > Looking a bit better, but no cigar: > > a=:3[b=:3[c=:3 > > X=:4 :0 > > a*(cos x)*cos y > > ) > > Y=:4 :0 > > b*(cos x)*sin y > > ) > > Z=:3 :0 > > c*(sin y) > > ) > > steps=: 3 : 'a+(w)*(i.n+1)%n[w=.z-a[''a z n''=.y' > > draw=:3 :0 > > angles=: steps _1p1 1p1 100 > > uangles =: steps _1.5708 1.5708 100 > > x=. uangles X"0 _ angles > > y=. uangles Y"0 _ angles > > z=. Z uangles > > 'surface' plot x;y;z > > ) > > draw'' > > > output at: http://bit.ly/1wNlQe3 > > > Skip Cave > Cave Consulting LLC > > On Fri, Mar 6, 2015 at 9:18 PM, Raul Miller <rauldmil...@gmail.com> wrote: > >> steps=: 3 : 'a+(w)*(i.n+1)%n[w=.z-a[''a z n''=.y' >> >> Thanks, >> >> -- >> Raul >> >> On Fri, Mar 6, 2015 at 10:08 PM, Skip Cave <s...@caveconsulting.com> >> wrote: >> > Here's what I got whaen I ran Jon's code: >> > >> > a=:3[b=:3[c=:3 >> > >> > X=:4 :0 >> > >> > a*(cos x)*cos y >> > >> > ) >> > >> > Y=:4 :0 >> > >> > b*(cos x)*sin y >> > >> > ) >> > >> > Z=:3 :0 >> > >> > c*(sin y) >> > >> > ) >> > >> > draw=:3 :0 >> > >> > angles=: steps _1p1 1p1 100 >> > >> > uangles =: steps _1.5708 1.5708 100 >> > >> > x=. uangles X"0 _ angles >> > >> > y=. uangles Y"0 _ angles >> > >> > z=. Z uangles >> > >> > 'surface' plot x;y;z >> > >> > ) >> > >> > draw'' >> > >> > |value error: steps >> > >> > | angles=: steps _3.14159 3.14159 100 >> > >> > >> > Skip Cave >> > Cave Consulting LLC >> > >> > On Fri, Mar 6, 2015 at 8:56 PM, Jon Hough <jgho...@outlook.com> wrote: >> > >> >> >> >> I butchered Raul's script slightly. But the resulting graph is still >> >> weird. Not sure if it's an improvement. >> >> >> >> >> >> a=:3[b=:3[c=:3 >> >> >> >> >> >> >> >> X=:4 :0 >> >> >> >> >> >> >> >> a*(cos x)*cos y >> >> >> >> >> >> >> >> ) >> >> >> >> >> >> >> >> >> >> >> >> >> >> Y=:4 :0 >> >> >> >> >> >> >> >> b*(cos x)*sin y >> >> >> >> >> >> >> >> ) >> >> >> >> >> >> >> >> >> >> >> >> >> >> Z=:3 :0 >> >> >> >> >> >> >> >> c*(sin y) >> >> >> >> >> >> >> >> ) >> >> >> >> >> >> >> >> >> >> >> >> >> >> draw=:3 :0 >> >> >> >> >> >> >> >> angles=: steps _1p1 1p1 100 >> >> >> >> >> >> >> >> uangles =: steps _1.5708 1.5708 100 >> >> >> >> >> >> >> >> x=. uangles X"0 _ angles >> >> >> >> >> >> >> >> y=. uangles Y"0 _ angles >> >> >> >> >> >> >> >> >> >> >> >> z=. Z uangles >> >> >> >> >> >> >> >> 'surface' plot x;y;z >> >> >> >> >> >> >> >> ) >> >> >> >> >> >> >> >> >> >> draw'' >> >> >> >> > From: jgho...@outlook.com >> >> > To: programm...@jsoftware.com >> >> > Date: Sat, 7 Mar 2015 02:46:35 +0000 >> >> > Subject: Re: [Jprogramming] Plotting a 3D Ellipse >> >> > >> >> > It seems you are using [-pi,pi] as the range of all your angles.I >> think >> >> you need to use [-pi/2,pi/2] as the range for the u argument (in the >> >> wikipedia page). >> >> > >> >> > > From: rauldmil...@gmail.com >> >> > > Date: Fri, 6 Mar 2015 21:35:37 -0500 >> >> > > To: programm...@jsoftware.com >> >> > > Subject: Re: [Jprogramming] Plotting a 3D Ellipse >> >> > > >> >> > > Hmm... >> >> > > >> >> > > I notice that load'graph' no longer provides the steps verb >> mentioned >> >> > > in http://www.jsoftware.com/books/pdf/expmath.pdf >> >> > > >> >> > > So here's a workalike: >> >> > > steps=: 3 : 'a+(w)*(i.n+1)%n[w=.z-a[''a z n''=.y' >> >> > > >> >> > > and that gives us an example of a surface plot. >> >> > > >> >> > > Next, we need a parametric representation of the ellipse, and >> >> > > http://en.wikipedia.org/wiki/Ellipsoid#Parameterization looks like >> a >> >> > > plausible approach there. >> >> > > >> >> > > Using that, and http://www.jsoftware.com/help/jforc/graphics.htm >> as a >> >> > > starting point, it seems to me that I ought to be able to draw an >> >> > > ellipse like this: >> >> > > >> >> > > a=:3[b=:4[c=:5 >> >> > > >> >> > > X=:4 :0~ >> >> > > a*(cos x)*/cos y >> >> > > ) >> >> > > >> >> > > Y=:4 :0~ >> >> > > b*(cos x)*/sin y >> >> > > ) >> >> > > >> >> > > Z=:4 :0~ >> >> > > c*(sin x)*/1: y >> >> > > ) >> >> > > >> >> > > draw=:3 :0 >> >> > > angles=: steps _1p1 1p1 100 >> >> > > x=. X angles >> >> > > y=. Y angles >> >> > > z=. Z angles >> >> > > 'surface' plot x;y;z >> >> > > ) >> >> > > >> >> > > draw'' >> >> > > >> >> > > Sadly, that's not an ellipse. >> >> > > >> >> > > But I do not have enough familiarity with plot to know whether I've >> >> > > screwed up my math or if there's a defect in plot -- I don't know >> how >> >> > > to isolate the problem. >> >> > > >> >> > > That said, a quick test with a 3d model of a cube: >> >> > > >> >> > > 'surface' plot ;/|:#:i.8 >> >> > > |NaN error: ncile >> >> > > >> >> > > ...suggests that plot isn't really designed to represent 3d solids. >> >> > > >> >> > > Still, that does not eliminate any potential errors on my part. >> >> > > >> >> > > On the other hand, maybe the right approach would be to use jhs and >> >> > > generate a distance field renderer along the lines of what you see >> at >> >> > > shadertoy.com. >> >> > > >> >> > > I'll have to think a bit to see if I can pull off something like >> that. >> >> > > (I think that that would only work for people who have adequate >> >> > > graphics hardware support. But I think you have a suitable graphics >> >> > > card?) >> >> > > >> >> > > Thanks, >> >> > > >> >> > > -- >> >> > > Raul >> >> > > >> >> > > >> >> > > On Fri, Mar 6, 2015 at 7:10 PM, Skip Cave <s...@caveconsulting.com> >> >> wrote: >> >> > > > I want to plot a 3D ellipse (ellipsoid) and then be able to change >> >> the >> >> > > > lengths of the three axes. The equation of an ellipse with axis >> >> lengths of >> >> > > > a, b, & c is: >> >> > > > >> >> > > > ((x^2)%(a^2)) + ((y^2)%(b^2)) + ((z^2)%(c^2)) = 1 >> >> > > > >> >> > > > How can I arrange this so it can be plotted in a 3-D plot in J, >> and >> >> then be >> >> > > > able to experiment with the lengths of the axes? >> >> > > > >> >> > > > Skip >> >> > > > >> >> > > > Skip Cave >> >> > > > Cave Consulting LLC >> >> > > > >> >> ---------------------------------------------------------------------- >> >> > > > For information about J forums see >> >> http://www.jsoftware.com/forums.htm >> >> > > >> ---------------------------------------------------------------------- >> >> > > For information about J forums see >> http://www.jsoftware.com/forums.htm >> >> > >> >> > ---------------------------------------------------------------------- >> >> > For information about J forums see >> http://www.jsoftware.com/forums.htm >> >> >> >> ---------------------------------------------------------------------- >> >> For information about J forums see http://www.jsoftware.com/forums.htm >> >> >> > ---------------------------------------------------------------------- >> > For information about J forums see http://www.jsoftware.com/forums.htm >> ---------------------------------------------------------------------- >> For information about J forums see http://www.jsoftware.com/forums.htm >> > ---------------------------------------------------------------------- > For information about J forums see http://www.jsoftware.com/forums.htm ---------------------------------------------------------------------- For information about J forums see http://www.jsoftware.com/forums.htm
