Ok now I'm confused. Nowhere do I see where we set the length of the three axes a, b, and c. Also the step verb has lots of variables in it, like a, w, n, and z that I don't see defined anywhere. steps=: 3 : 'a+(w)*(i.n+1)%n[w=.z-a[''a z n''=.y'
How do I change the lengths of the axes a, b,and c? Skip Cave Cave Consulting LLC On Fri, Mar 6, 2015 at 10:25 PM, Joe Bogner <[email protected]> wrote: > I don't know what I'm doing other than copy/pasting, but the example from > the plot demo looks pretty close: > > load 'plot' > pd 'clear' > steps=: 3 : 'a+(w)*(i.n+1)%n[w=.z-a[''a z n''=.y' > P=. steps 0 1p1 30 > T=. steps 0 2p1 40 > X=. ((sin P) */ cos T) > Y=. ((sin P) */ sin T) > Z=. ((cos P) +/ T*0)%2 > > pd 'backcolor blue' > pd 'new 0 0 1000 1000' > > pd 'type surface' > pd 'viewpoint 2 2 2;color grayscale' > pd X;Y;Z > pd 'show' > > > > On Fri, Mar 6, 2015 at 11:18 PM, Raul Miller <[email protected]> > wrote: > > > 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 <[email protected]> > > 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 <[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 > > ---------------------------------------------------------------------- > > 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
