Am 18.05.2016 um 20:25 schrieb LanuHum:
> clipka <ano### [at] anonymousorg> wrote:
>> Am 12.05.2016 um 20:06 schrieb LanuHum:
>>
>>> But, in the Blender the lemon is unprofitable to be used.
>>> Any this form is created by lathe.
>>
>> You can't create this exact shape with lathe.
> 
> I won't argue. Accuracy of computation of Bezier curves has enough for creation
> of a body of the car.

I doubt the designers of car bodies use Bezier splines -- their weapon
of choice are NURBS (non-uniform rational B-splines); AFAIK those do
have the capacity to precisely represent circular arcs.

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clipka <ano### [at] anonymousorg> wrote:

>
> I doubt the designers of car bodies use Bezier splines -- their weapon
> of choice are NURBS (non-uniform rational B-splines); AFAIK those do
> have the capacity to precisely represent circular arcs.

https://en.wikipedia.org/wiki/B%C3%A9zier_curve


ity to graphics was not realized for


> Renault. The study of these curves was however first developed in 1959 by
> mathematician Paul de Casteljau using de Casteljau's algorithm, a numerically

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Am 19.05.2016 um 16:10 schrieb LanuHum:
> clipka <ano### [at] anonymousorg> wrote:
> 
>>
>> I doubt the designers of car bodies use Bezier splines -- their weapon
>> of choice are NURBS (non-uniform rational B-splines); AFAIK those do
>> have the capacity to precisely represent circular arcs.
> 
> https://en.wikipedia.org/wiki/B%C3%A9zier_curve
> 
[quote from Wikipedia, not clipka]

>> known since 1912, but its applicability to graphics was not realized for


>> Renault. The study of these curves was however first developed in 1959 by
>> mathematician Paul de Casteljau using de Casteljau's algorithm, a numerically


Yes, the /invention/ of Bezier curves was driven by the French
automotive industry.

But as the article also notes, that was around _1960_.

Car body quality requirements have increased quite a lot since then.

Note how the "Applications" section in that article lists computer
graphics, animation and fonts, but /not/ [contemporary] automotive design.

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clipka <ano### [at] anonymousorg> wrote:

>
> Yes, the /invention/ of Bezier curves was driven by the French
> automotive industry.
>
> But as the article also notes, that was around _1960_.
>
> Car body quality requirements have increased quite a lot since then.
>
> Note how the "Applications" section in that article lists computer
> graphics, animation and fonts, but /not/ [contemporary] automotive design.

We distracted, but the task remained unresolved.
Task:
To place five spheres so that centers of spheres lay on a lemon surface.
difference{
lemon{}
sphere{??}
sphere{??}
sphere{??}
sphere{??}
sphere{??}
}

http://news.povray.org/povray.binaries.images/attachment/%3Cweb.573cb381370a969c7a3e03fe0%40news.povray.org%3E/lemon.jp
g

WRITTEN_FOR="LANUHUM"
use_bezier_lathe = False
use_lemon = True
#macro Calculate_points_coords_lemon_surface(number_x,number_y,number_z)
//bla-bla-bla...
replace, please, //bla-bla-bla... with the working source code
If it isn't in documentation, then I don't know how to the rocket to attach
wings
:))))))

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On 05/19/2016 11:46 AM, LanuHum wrote:
> clipka <ano### [at] anonymousorg> wrote:
>
>>
>> Yes, the /invention/ of Bezier curves was driven by the French
>> automotive industry.
>>
>> But as the article also notes, that was around _1960_.
>>
>> Car body quality requirements have increased quite a lot since then.
>>
>> Note how the "Applications" section in that article lists computer
>> graphics, animation and fonts, but /not/ [contemporary] automotive design.
>
> We distracted, but the task remained unresolved.
> Task:
> To place five spheres so that centers of spheres lay on a lemon surface.
> difference{
> lemon{}
> sphere{??}
> sphere{??}
> sphere{??}
> sphere{??}
> sphere{??}
> }
>
>
http://news.povray.org/povray.binaries.images/attachment/%3Cweb.573cb381370a969c7a3e03fe0%40news.povray.org%3E/lemon.jp
> g
>
> WRITTEN_FOR="LANUHUM"
> use_bezier_lathe = False
> use_lemon = True
> #macro Calculate_points_coords_lemon_surface(number_x,number_y,number_z)
> //bla-bla-bla...
> replace, please, //bla-bla-bla... with the working source code
> If it isn't in documentation, then I don't know how to the rocket to attach
> wings
> :))))))
>
>
>
>
>

The code below uses the new spindle torus & not the lemon, but is 
something like this what you are after?

#declare Torus00=torus { 0.25, 0.5 intersection scale <1,2,1> }
#declare Norm=<0,0,0>;
difference {
     object { Torus00 }
     sphere { trace(Torus00, <1,0,0>,    <-1,0,0>, Norm) , 0.15 }
     sphere { trace(Torus00, <1,0.5,0>,  <-1,0,0>, Norm) , 0.15 }
     sphere { trace(Torus00, <1,-0.5,0>, <-1,0,0>, Norm) , 0.15 }
     pigment { color Niagara }
}

Bill P.

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Le 19/05/2016 17:46, LanuHum a écrit :
> clipka <ano### [at] anonymousorg> wrote:
> 
>>
>> Yes, the /invention/ of Bezier curves was driven by the French
>> automotive industry.
>>
>> But as the article also notes, that was around _1960_.
>>
>> Car body quality requirements have increased quite a lot since then.
>>
>> Note how the "Applications" section in that article lists computer
>> graphics, animation and fonts, but /not/ [contemporary] automotive design.
> 
> We distracted, but the task remained unresolved.
> Task:
> To place five spheres so that centers of spheres lay on a lemon surface.
> difference{
> lemon{}
> sphere{??}
> sphere{??}
> sphere{??}
> sphere{??}
> sphere{??}
> }

For lemon { 0, 0, H*y, 0, R }

The 2D circle (of radius R) of the lemon is centred at <-V, H/2>, with
V^2 = R^2 - ((H^2)/4)

easily solved as V = sqrt( R^2 - ((H^2)/4) ).

Assuming you want the spheres in the z=0,x+ demi plane, you just have to satisfy for 
< A, B, C> as the centre:

C = 0

R^2 = (B-(H/2))^2 + (A+V)^2

0 <= B <= H

As I'm tired of equations solving, I let it to wolframalpha solver :

A is sqrt(-2 B^2+2 B H-H^2+4 R^2+sqrt(H^2-4 R^2) sqrt(4 B^2-4 B H+H^2-4 R^2))/sqrt(2)


Have a nice sleep.

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On 05/08/2016 03:33 PM, Le_Forgeron wrote:
> For the time being, only available in hgpovray.
>
> lemon { P1, R1, P2, R2, R3 ... }
>
> similar to cone { P1, R1, P2, R2 ...} but connected with a lemon (inner circle of a
torus) of radius R3.
>
> Options includes : uv_mapping, open and sturm.
>
> All Rx must be positive or null, and there is a complain with error when R3 is too
small.
> The complain gives the minimal value that can be used.
>
> And now that I can sleep a bit, I'm returning to the extension of the ovus.
>

In working with this new object I came across this case:

// P1, R1, P2, R2, R3
#declare LemonLeft  = lemon {
    <-1.2,-0.5,0>, 0.0, <-1.2,0.5,0>, 0.0, 0.499999
}
#declare LemonCenter = lemon {
    <0,-0.5,0>, 0.0, <0,0.5,0>, 0.0, 0.50
}
#declare LemonRight  = lemon {
    <1.2,-0.5,0>, 0.0, <1.2,0.5,0>, 0.0, 0.500001
}

Where the LemonLeft generates this warning message:

File 'lemon.pov' line 176: Possible Parse Error: Inner (last) radius of 
lemon is too small. Minimal would be 0.5. Subtituing a sphere to lemon

recommending the code used in LemonCenter. However the result for 
LemonCenter is quite noisy. An 'epsilon' above is OK.

See attached image.

Bill P.

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Attachments:
Download 'lemonissue.jpg' (75 KB)

Preview of image 'lemonissue.jpg'

Le 26/05/2016 à 13:31, William F Pokorny a écrit :
> In working with this new object I came across this case:
>
> // P1, R1, P2, R2, R3
> #declare LemonLeft  = lemon {
>    <-1.2,-0.5,0>, 0.0, <-1.2,0.5,0>, 0.0, 0.499999
> }
> #declare LemonCenter = lemon {
>    <0,-0.5,0>, 0.0, <0,0.5,0>, 0.0, 0.50
> }
> #declare LemonRight  = lemon {
>    <1.2,-0.5,0>, 0.0, <1.2,0.5,0>, 0.0, 0.500001
> }
>
> Where the LemonLeft generates this warning message:
>
> File 'lemon.pov' line 176: Possible Parse Error: Inner (last) radius of
> lemon is too small. Minimal would be 0.5. Subtituing a sphere to lemon
>
> recommending the code used in LemonCenter. However the result for
> LemonCenter is quite noisy. An 'epsilon' above is OK.
>
> See attached image.
>
> Bill P.

can you try to add "sturm" to LemonCenter ? (I'm away from my hgpovray)

#declare LemonCenter = lemon {
     <0,-0.5,0>, 0.0, <0,0.5,0>, 0.0, 0.50 sturm
}

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On 05/26/2016 07:50 AM, Le_Forgeron wrote:
> Le 26/05/2016 à 13:31, William F Pokorny a écrit :
>
> can you try to add "sturm" to LemonCenter ? (I'm away from my hgpovray)
>
> #declare LemonCenter = lemon {
>      <0,-0.5,0>, 0.0, <0,0.5,0>, 0.0, 0.50 sturm
> }
>

Using sturm as follows is less noisy, but still noisy :

#declare LemonLeft  = lemon {
    <-1.2,-0.5,0>, 0.0, <-1.2,0.5,0>, 0.0, 0.499999
}
#declare LemonCenter = lemon {
    <0,-0.5,0>, 0.0, <0,0.5,0>, 0.0, 0.50 sturm
}
#declare LemonRight  = lemon {
    <1.2,-0.5,0>, 0.0, <1.2,0.5,0>, 0.0, 0.500001 sturm
}

On my first attempt I did the following:

#declare LemonLeft  = lemon {
    <-1.2,-0.5,0>, 0.0, <-1.2,0.5,0>, 0.0, 0.499999 sturm
}
#declare LemonCenter = lemon {
    <0,-0.5,0>, 0.0, <0,0.5,0>, 0.0, 0.50 sturm
}
#declare LemonRight  = lemon {
    <1.2,-0.5,0>, 0.0, <1.2,0.5,0>, 0.0, 0.500001 sturm
}

which gave me this parse error :

File 'lemon.pov' line 175: Parse Error: Keyword 'sturm' cannot be used 
with this object.

So, I assumed you'd not yet set sturm up for the lemon! Wondering now if 
the code creating the inner radius warning for LemonLeft is itself 
creating the error for sturm use in that case?

Bill P.

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Le 26/05/2016 à 15:24, William F Pokorny a écrit :

> File 'lemon.pov' line 175: Parse Error: Keyword 'sturm' cannot be used
> with this object.
>
> So, I assumed you'd not yet set sturm up for the lemon! Wondering now if
> the code creating the inner radius warning for LemonLeft is itself
> creating the error for sturm use in that case?
>
> Bill P.

On LemonLeft, parsing occurs up to the inner radius, then the message is 
written and the object so far get replaced with a sphere.
Then parsing continue and find sturm, which is not supported by a sphere.

Notice that the same issue would occurs with current ovus (when the top 
radius is more than twice the bottom radius).

For lemon, I could replace with another object which would support 
sturm, but is it really needed ? or even wanted ?

(My first approach was to stop with an error instead of a warning, was 
it better ?)

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