Following up on my own report after poking through things this
morning. In the src/preproc/pic directory, in file object.cpp, in the
routine declared as "linear_object *object_spec::make_arc", lines 1833
and 1834 have the statement
while (radius < d)
radius *= 2.0;
In my example, in some cases the test (radius < d) was satisfied, but
the difference in the two values was on the order of 1e-10. Since
radius was 0.1, doubling the radius leads to the fairly gross error
that I was encountering. For the time being, my workaround is to
replace that statement with
if (radius < d)
radius = d;
which fixed my problem. The original code appears to have been
intended to deal with the situation when radius is orders of magnitude
less than d. My replacement code simply assigns radius the smallest
value that avoids problems with the floating point code/libraries
further on in the routine.
On Aug 26, 2009, at 9:41 AM, Michael Cain wrote:
I'm having the following problem with drawing a series of arcs in
gpic. I'm running version 1.20.1, compiled from sources on Mac OS X
version 10.5.8. The following code draws a sequence of connected
arcs, alternating in size, from top to bottom:
.PS
arc cw rad 0.075 to Here+(0,-0.15)
arc ccw rad 0.025 to Here+(0,-0.05)
arc cw rad 0.075 to Here+(0,-0.15)
arc ccw rad 0.025 to Here+(0,-0.05)
arc cw rad 0.075 to Here+(0,-0.15)
arc ccw rad 0.025 to Here+(0,-0.05)
arc cw rad 0.075 to Here+(0,-0.15)
arc ccw rad 0.025 to Here+(0,-0.05)
arc cw rad 0.075 to Here+(0,-0.15)
arc ccw rad 0.025 to Here+(0,-0.05)
arc cw rad 0.075 to Here+(0,-0.15)
arc ccw rad 0.025 to Here+(0,-0.05)
arc cw rad 0.075 to Here+(0,-0.15)
arc ccw rad 0.025 to Here+(0,-0.05)
arc cw rad 0.075 to Here+(0,-0.15)
arc ccw rad 0.025 to Here+(0,-0.05)
.PE
Part way through the sequence, the radius for the arcs gets messed
up. This happens in the output from gpic alone, shown here. I
tried the same experiment on an Ubuntu Linux box, also with gpic
version 1.20.1, and got the same result.
.lf 1 foo.mm
.lf 1
.PS 1.600i 0.100i
.\" -0.025 -1.6 0.075 0
.\" 0.000i 1.600i 0.100i 0.000i
.nr 00 \n(.u
.nf
.nr 0x 1
\h'0.100i'
.sp -1
\D't -1.000p'\h'1.000p'
.sp -1
\h'0.025i'\v'0.150i'\D'a 0.000i -0.075i -0.000i -0.075i'
.sp -1
\h'0.025i'\v'0.150i'\D'a 0.000i 0.025i -0.000i 0.025i'
.sp -1
\h'0.025i'\v'0.350i'\D'a 0.000i -0.075i -0.000i -0.075i'
.sp -1
\h'0.025i'\v'0.350i'\D'a 0.000i 0.025i -0.000i 0.025i'
.sp -1
\h'0.025i'\v'0.550i'\D'a 0.000i -0.075i -0.000i -0.075i'
.sp -1
\h'0.025i'\v'0.550i'\D'a 0.043i 0.025i -0.043i 0.025i'
.sp -1
\h'0.025i'\v'0.750i'\D'a 0.000i -0.075i -0.000i -0.075i'
.sp -1
\h'0.025i'\v'0.750i'\D'a 0.043i 0.025i -0.043i 0.025i'
.sp -1
\h'0.025i'\v'0.950i'\D'a 0.000i -0.075i -0.000i -0.075i'
.sp -1
\h'0.025i'\v'0.950i'\D'a 0.043i 0.025i -0.043i 0.025i'
.sp -1
\h'0.025i'\v'1.150i'\D'a -0.130i -0.075i 0.130i -0.075i'
.sp -1
\h'0.025i'\v'1.150i'\D'a 0.043i 0.025i -0.043i 0.025i'
.sp -1
\h'0.025i'\v'1.350i'\D'a -0.130i -0.075i 0.130i -0.075i'
.sp -1
\h'0.025i'\v'1.350i'\D'a 0.043i 0.025i -0.043i 0.025i'
.sp -1
\h'0.025i'\v'1.550i'\D'a -0.130i -0.075i 0.130i -0.075i'
.sp -1
\h'0.025i'\v'1.550i'\D'a 0.043i 0.025i -0.043i 0.025i'
.sp -1
.sp 1.600i+1
.if \n(00 .fi
.br
.nr 0x 0
.lf 18
.PE
.lf 19
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