Re: How to "reverse" the arc, when creating a shape?

2015-08-23 14:45 GMT+02:00 Otfried Cheong <[email protected]>:
>
>
> On Sun, Aug 23, 2015, at 17:56, Wojciech Zabolotny wrote:
>> Is there any way to generate the arc covering the right range of
>> angles but in reversed direction?
>
> An arc is always counter-clockwise on its supporting unit circle.  To
> get a clockwise arc, you need to change the matrix so that it mirrors
> this circle.  (E.g. negate the change the first element.)
>

Thanks, I've modified my source accordingly (see attached kolka9.lua script),
and now the objects are generated correctly.

Thanks, Wojtek

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doc=ipe.Document()
page=doc[1] ; -- Get the first page
l=page:layers()[1] -- Get the first layer
p = ipe.Direction((90.0-35.0)*math.pi/180.0)
q = ipe.Direction((90.0+35.0)*math.pi/180.0)
for i=5,10 do
 f1=(i-0.2)*5.0
 f2=(i+0.2)*5.0
 m1=ipe.Matrix(f1,0,0,f1)
 m2=ipe.Matrix(-f2,0,0,f2)
 ps={}
 ps["stroke"]="black"
 shape={}
 arc1 = { type="arc", arc=ipe.Arc(m1, p, q), m1*p, m1*q }
 seg1 = { type="segment", m1*q, m2*p}
 arc2 = { type="arc", arc=ipe.Arc(m2, p, q), m2*p, m2*q }
 seg2 = { type="segment", m2*q, m1*p}
 subpath = { type="curve", closed=true, arc1, seg1, arc2, seg2}
 shape = { subpath }
 obj = ipe.Path(ps, shape)
 page:insert(nil,obj,nil,l)  
end
doc:save("test.pdf")