Mike Williams nous apporta ses lumieres en ce 2007/11/13 15:01:
> Wasn't it Woody who wrote:
>> I'm trying to create two macros for use with Iso-surfaces
>> they are
>>
>> #macro mac_1()
>>    #if(abs(x)+abs(y)<=0.05)
>>          0
>>    #else
>>          1
>>    #end
>> #end
>>
>> #macro mac_2(a,b,c)
>>   abs(a)+abs(b)
>> #end
>>
>>
>> they are called from the isosurface as
>>
>> isosurface{
>> function{ mac_1() }
>>
>> }
>>
>> isosurface{
>> function { mac_2(x,y,z) }
>> }
>>
>> both produce 'float expected vector identifier found instead' errors.
>>
>> anybody got any ideas
> 
> Macros are evaluated once, at parse time. Isosurface functions need to
> be evaluated for many possible x,y,z values at run time. So you have to
> rewrite your expressions as functions, not macros.
> 
> The second one is easy to write:
>   function { abs(x)+abs(y) }
> 
> The problem is that the expression is >=0 everywhere. It's only zero
> along an infinitely thin line along the z axis, and you see nothing.
It's only a problem if your treshold is zero. If you increase the treshold, it 
gets whider and whider.
> 
> 


-- 
Alain
-------------------------------------------------
I find that the harder I work, the more luck I seem to have.
Thomas Jefferson

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