I'm trying to draw a picture of a "volume" with pic. Basically, it
should be an ellipse at the top, straight vertical sides, and the
front of an ellipse at the bottom.
Two things stop me from doing this:
1. I can't do only part of an ellipse, or at least that's the way I
read both the documentation and the code.
2. I can't get an arc to start at the bottom of the left hand side.
If I write the code the way it should be, it starts too far to the
left. If I gradually move the start to the right, it suddenly
jumps past the reference point and leaves a gap. This behaviour
has been there for several years now.
I'm attaching the source code and the resultant PostScript output from
the following command:
groff -p pic1.mm > pic1.ps
Questions (yes, the sequence is deliberate):
2. This is a bug, right? Any idea how to fix it?
1. Am I correct in my assumption that I can draw only whole ellipses?
Is there any other way to draw the correct partial ellipse? It
seems that it would be nice to have a feature in pic to draw
arbitrary curves (specified by a formula), but I can't quite see
how to do it. If it's not there, and people think it's a good
idea, I'm prepared to have a crack at it some time. In that case,
can anybody give me an idea how to go about it? I've had a look
in the code, and it doesn't look impossibly difficult or
convoluted.
Greg
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------------------------------------------------------------------------
.PS
T: ellipse ht .3i wid 4i
line from T.e down 4i
line from T.w down 4i
B: arc from T.w+(0,-4) rad 10i to T.e+(0,-4)
.PE