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Le 28/06/2015 09:58, clipka a écrit :
> Overhauling the POV-Ray codebase, I've stumbled across something
> surprising (to me) in the implementation of the fractal currently
> implemented via the `HypercomplexFunctionFractalRules` type. Can
> someone with a bit of "fractal fu" please help me and test this
> out?
>
> In SDL parlance, that should be any fractal using:
>
> julia_fractal { ... hypercomplex FUNCTION ... }
>
> where FUNCTION is any of:
>
> acos acosh asin asinh atan atanh cosh cos exp ln pwr(FLOAT,FLOAT)
> sin sinh tan tanh
>
> Please tell me whether you think the results are ok or bogus.
>
> For reference, the following values of FUNCTION should be fine:
>
> cube sqr reciprocal
>
> The oddity in the code is as old as POV-Ray 3.6.1, maybe even
> older.
The same code seems to be already in 3.1g
Checking exp, the computation seems ok (in regard to >
http://mathworld.wolfram.com/ExponentialFunction.html
)
At least hcmpl.c / hcmpl.cpp code seems ok
exp(z) = exp(x).(cos y + i.sin y) with z = x+i.y (x and y in R)
That is for the complex (in C) operations.
Hypercomplex is a waste family (see
> http://mathworld.wolfram.com/HypercomplexNumber.html
)
The hypercomplex of povray seems to match the Davenport's type
Now, for something interesting in Normal_Calc_HCompl_Func (from
hcmplx.c in 3.1g, it uses global (from fractal.h ) to perform
computation, as input...
how did it handle more than one object at once ?
(Sx, Sy, Sz and Sw)
What I do not like either, in 3.7 now, is the conflict of name between
IStack (as type) and IStack[4] (array of pointer to array of DBL)
(IStack[] replaces the Sx, Sy, Sz, Sw; I have yet to find where it is
filled)
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