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 <[email protected]> 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 <[email protected]> > 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 <[email protected]> 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: [email protected] > >> > To: [email protected] > >> > 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: [email protected] > >> > > Date: Fri, 6 Mar 2015 21:35:37 -0500 > >> > > To: [email protected] > >> > > 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 <[email protected]> > >> 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
