Hi,
brlcad has left the following comment at Investigate and fix source of
rounding error
https://www.google-melange.com/gci/task/view/google/gci2014/5880145319559168:
reassuring
This is very reassuring! Looking at the values, most are either identical,
or matching within double-floating point precision (probably 1ulp off) at
15 digits after the decimal.
As this was an issue you had to investigate in detail, that implies a
comment is warranted to document and warn others about the sensitivity
issue. You do have a comment that says calculating the angle is
complicated, but you don't explain what that means in lay terms. Basically,
there needs to be some warning that says these calculations are sensitive
to trigonometric accuracy so care must be taken to ensure calculated rays
do not have or accumulate error.
Looking at the line counts, this does increase the counts by about 20 lines
which is pretty minor and probably okay to commit now that the results are
matching. However, the data remarshalling does make me think that returning
an xrays list is not the best approach. in fact, ideally the _gen_
functions shouldn't be allocating memory dynamically too, giving the user
the option of creating memory dynamic or on the stack and passing that in
to be used.
Greetings,
The Google Open Source Programs Team
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and fix source of rounding error.
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