> Alain<aze### [at] qwertyorg>  wrote:
>
>>
>> That macro is not self contained.
>> First : It create a spline that follows a circular path. For that, it
>> use an externaly created variable: Blockwall_Radius.
>> It also use 2 passed parameters: A value in degrees and a reference
>> value defining what kind of blocks to use.
>>
>> Then, once the spline is constructed, it use another macro
>> (Blockwall_FollowSpline) to place blocks along that spline, surely
>> binded in an union so that you can place the result anywhere you need it.
>>
>> What this macro _DON'T DO_: Create a prism.
>> It /DOES/ use CSG as an union of numerous blocks.
>>
>>
>>
>> Alain
>
> I suspected that. OK, is there a way to create a spline path that can be used to
> draw a prism of a particular radius or diameter. I can do trial and error and
> end up with an approximation but I was wondering if there is a way to get a
> mathematically precise method that can generate values for any radius or
> diameter.
>
>

Quick and dirty:
- Remove the call to the other macro.
- Start your prism.
- Call the macro twice: once with the inside radius of your wall and 
travel it to create the iner part of the prism. (use a loop)
- SAVE the first point!
- Call the macro a second time with the outside radius and travel the 
spline backward to create the outside of the prism.
- Close the prism by adding the last point equal to the first one.
- Add any needed transformation and texturing.
- Finish the prism.

That's for a prism using a linear_spline interpolation.
If you want to use a cubic_spline interpolation, then the last TWO 
points must repeat the first two points. The first and last points are 
controls, the second and secont to last are real points.


Alain

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