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Hi Mike,

Last things first:

Last question: Is the above question the sort of thing that I should be asking in this forum?

As I understand it, this kind of question is precisely what this site was created for.

Now for the Tachyon questions: I don't know how to get to the Tachyon object directly; it looks like tachyon_repr from parametric surface plots could be on the right track. I believe it returns the string representation of the corresponding Tachyon object. I don't see a function for building a Tachyon object from a string, but it must be easy.

In any case, I'm working on a project where I decided Tachyon is definitely the viewer I want, so I started constructing the Tachyon objects directly (as below). I've used parametric_plot happily, and wasn't aware of problems with plot until you pointed them out. As a workaround until someone gives a better answer, you could simply switch your plots to parametric_plots.

As for plot, I noticed 3 problems:

1. syntax error in your original question: `t.show('verbose='true')` should be `t.show(verbose=True)`
2. errors in documentation examples: When pasted to a sage prompt, the following example produces an error because the `def` line needs to be followed by a blank line:

   sage: t = Tachyon(xres=512,yres=512, camera_center=(4,-4,3),viewdir=(-4,4,-3), raydepth=4)
   sage: t.light((4.4,-4.4,4.4), 0.2, (1,1,1))
   sage: def f(x,y): return float(sin(x*y))
   sage: t.texture('t0', ambient=0.1, diffuse=0.9, specular=0.1,  opacity=1.0, color=(1.0,0,0))
   sage: t.plot(f,(-4,4),(-4,4),"t0",max_depth=5,initial_depth=3, num_colors=60)  # increase min_depth for better picture
   sage: t.show()
   

3. t.show() doesn't work for me. If you (or others) are having the same problem, I'll open a trac ticket for this. Here are the details of what works and what doesn't:

For me, the following works fine (pink curve on a black background):

sage: f = lambda t: (t,t^2,t^3)
sage: t = Tachyon(camera_center=(5,0,4))
sage: t.texture('t')
sage: t.light((-20,-20,40), 0.2, (1,1,1))
sage: t.parametric_plot(f,-5,5,'t',min_depth=6)
sage: t.show(verbose=True)

On the other hand, the following seems to be broken (but not because of def--note that I've changed that to a lambda function); my guess is that the data file Tachyon is attempting to show is not formatted quite right:

sage: t = Tachyon(xres=512,yres=512, camera_center=(4,-4,3),viewdir=(-4,4,-3), raydepth=4)
sage: t.light((4.4,-4.4,4.4), 0.2, (1,1,1))
sage: f = lambda x,y : float(sin(x*y))
sage: t.texture('t0', ambient=0.1, diffuse=0.9, specular=0.1,  opacity=1.0, color=(1.0,0,0))
sage: t.plot(f,(-4,4),(-4,4),"t0",max_depth=5,initial_depth=3, num_colors=60)
sage: t.show(verbose=True)
tachyon /Users/niles/.sage//temp/soho.local/502//tmp_48.dat  -format PNG  -o /Users/niles/.sage//temp/soho.local/502//tmp_47.png   ; rm -f "/Users/niles/.sage//temp/soho.local/502//tmp_48.dat"
Tachyon Parallel/Multiprocessor Ray Tracer   Version 0.98   
Copyright 1994-2007,    John E. Stone <johns@megapixel.com> 
----------------------------------------------------------- 
Parse Error:
   Encountered a syntax error in file /Users/niles/.sage//temp/soho.local/502//tmp_48.dat
   Expected to find an object or other declaration
   Actually found: (-3.8101867407915408,
   Error occured at or prior to file offset 13733, line 326
   Error position is only approximate, but should be close

Parser failed due to an input file syntax error.
Aborting render.