On 05/25/2016 04:28 PM, Le_Forgeron wrote:
> Le 25/05/2016 21:50, William F Pokorny a écrit :
>>
>> (1) - Taking the barrel/ogive to be the improved ovus less the two end spheres ?
>>
>> Bill P.
>>
>
> It is a bit more complex than that.
>
> lemon is not an ovus without spheres, or rather, to use a manual lemon with
additional spheres to make an ovus, the computation is not simple. (no, you do not
just put the sphere at the vertex of lemon).
>   ( And you get coincident surfaces problem too, and internal surfaces, useless
computations... things that are better handled in code than later in SDL. )
>
> The same way that putting spheres at the ends of a conical frustum does not make a
nice segment of linear sphere_sweep.
> It's easy with a cylinder, but become more subtle when the radius are different.
>
> lemon is similar to cone, even a bit better: you can get a true lemon (mathematical
object), or a frustum of lemon. With SDL cone, you get a false mathematical cone or a
conical frustum (because a true cone would be infinite along its axis, both ways, and
povray's cone is
> actually only a right circular cone, not all cones)
>

Thanks for the detailed explanation.

If we will then have both an improved ovus and a new lemon/barrel/ogive 
object in 3.7.1, I would suggest adding the two new arguments for the 
ovus in the same order the equivalent information is given to the lemon 
in your mercurial "Hg-povray" code. Namely:

ovus { Bottom_radius, Top_radius [, sphere_to_sphere, inner_radius ] }

Bill P.

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