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From: xslittlegrass
Subject: Why my lathe object is broken?
Date: 24 May 2014 00:40:01
Message: <web.538021778197fb3f4277cb5c0@news.povray.org>
I'm a beginner of Pov-Ray and I'm trying to create a lathe object in Pov-Ray,
and it looks broken somehow. Could someone give me some suggestion on how to fix
it?
The problem is indicated on this image:

http://i.stack.imgur.com/8cerL.png

Any suggestions or comments are appreciated.


Here is the code I used to create the scene:



#include "colors.inc"

global_settings {
  max_trace_level 5
  assumed_gamma 1.0
  radiosity {
    pretrace_start 0.08
    pretrace_end   0.01
    count 35
    nearest_count 5
    error_bound 1.8
    recursion_limit 2
    low_error_factor .5
    gray_threshold 0.0
    minimum_reuse 0.015
    brightness 1
    adc_bailout 0.01/2
  }
}

#default {
  texture {
    pigment {rgb 1}
    finish {
      ambient 0.0
      diffuse 0.6
      specular 0.6 roughness 0.001
      reflection { 0.0 1.0 fresnel on }
      conserve_energy
    }
  }
}

light_source { <050,250,250> 1 }
background { rgb <0,.25,.5> }

camera{
    location <250,250,250>
    look_at <0,100,0>

    }

lathe{
quadratic_spline
38,
<32.8000,284.0000>,
<37.8000,276.0000>,
<43.3000,267.0000>,
<49.3000,257.0000>,
<53.8000,248.0000>,
<58.3000,236.0000>,
<61.8000,224.0000>,
<64.3000,212.0000>,
<65.3000,199.0000>,
<64.3000,186.0000>,
<61.8000,174.0000>,
<58.3000,166.0000>,
<53.3000,157.0000>,
<46.3000,149.0000>,
<38.8000,144.0000>,
<30.3000,140.0000>,
<23.3000,137.0000>,
<17.8000,135.0000>,
<13.8000,135.0000>,
<13.8000,129.0000>,
<10.3000,127.0000>,
<7.2500,122.0000>,
<5.7500,116.0000>,
<4.7500,109.0000>,
<4.2500,101.0000>,
<3.7500,88.2000>,
<3.7500,70.3000>,
<3.7500,53.8000>,
<4.7500,39.8000>,
<6.7500,25.8000>,
<8.2500,20.3000>,
<11.3000,16.8000>,
<17.3000,14.3000>,
<25.3000,11.3000>,
<33.8000,9.2500>,
<41.3000,7.7500>,
<48.3000,5.7500>,
<48.8000,0.2500>
texture{
       pigment{color White}
       finish { phong 0.5}}
  }


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From: Stephen
Subject: Re: Why my lathe object is broken?
Date: 24 May 2014 01:56:24
Message: <53803488@news.povray.org>
On 24/05/2014 05:35, xslittlegrass wrote:
> Any suggestions or comments are appreciated.

You need to use the sturm keyword in the lathe



-- 

Regards
     Stephen


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From: xslittlegrass
Subject: Re: Why my lathe object is broken?
Date: 24 May 2014 10:35:01
Message: <web.5380ad05952f32a84277cb5c0@news.povray.org>
Hi Stephen,

It works , thanks a lot!
But there is still one broken part remains. I created a zoom in of the
broken part here

http://imgur.com/j1ys4Nb

Do you know why that happens?

The 2d plot of the data I used in the lathe object is shown here

http://i.stack.imgur.com/rrF7B.png


Thanks a lot for your help.

Stephen <mca### [at] aolcom> wrote:
> On 24/05/2014 05:35, xslittlegrass wrote:
> > Any suggestions or comments are appreciated.
>
> You need to use the sturm keyword in the lathe
>
>
>
> --
>
> Regards
>      Stephen


Post a reply to this message

From: Stephen
Subject: Re: Why my lathe object is broken?
Date: 24 May 2014 12:44:49
Message: <5380cc81$1@news.povray.org>
On 24/05/2014 15:33, xslittlegrass wrote:
 > Hi Stephen,
 >
 > It works , thanks a lot!
 > But there is still one broken part remains. I created a zoom in of the
 > broken part here
 >
 > http://imgur.com/j1ys4Nb
 >
 > Do you know why that happens?
 >

Not really but I suspect that it may have something to do with the 
spacing of the plotted points.
Have you tried a cubic curve?
And less points. Remember that the curve does not necessary pass through 
the points. They are control points.

-- 

Regards
     Stephen

-- 

Regards
     Stephen


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From: xslittlegrass
Subject: Re: Why my lathe object is broken?
Date: 24 May 2014 14:35:00
Message: <web.5380e5ca952f32a81e36f4d20@news.povray.org>
I tried a cubic curve and it does look better. I agree that the "broken" may
caused by the data points.

Thanks a lot for your help :)


Stephen <mca### [at] aolcom> wrote:
> On 24/05/2014 15:33, xslittlegrass wrote:
>  > Hi Stephen,
>  >
>  > It works , thanks a lot!
>  > But there is still one broken part remains. I created a zoom in of the
>  > broken part here
>  >
>  > http://imgur.com/j1ys4Nb
>  >
>  > Do you know why that happens?
>  >
>
> Not really but I suspect that it may have something to do with the
> spacing of the plotted points.
> Have you tried a cubic curve?
> And less points. Remember that the curve does not necessary pass through
> the points. They are control points.
>
> --
>
> Regards
>      Stephen
>
> --
>
> Regards
>      Stephen


Post a reply to this message

From: Stephen
Subject: Re: Why my lathe object is broken?
Date: 24 May 2014 16:18:05
Message: <5380fe7d@news.povray.org>
On 24/05/2014 19:32, xslittlegrass wrote:
> I tried a cubic curve and it does look better. I agree that the "broken" may
> caused by the data points.
>
> Thanks a lot for your help :)
>
>

It is a pleasure. :-D
I have posted a couple of screenshots in p.b.images along with the lathe 
code I modified, a bit. As an example to show what I did.


-- 

Regards
     Stephen


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From: Alain
Subject: Re: Why my lathe object is broken?
Date: 27 May 2014 19:32:32
Message: <53852090$1@news.povray.org>

> On 24/05/2014 15:33, xslittlegrass wrote:
>  > Hi Stephen,
>  >
>  > It works , thanks a lot!
>  > But there is still one broken part remains. I created a zoom in of the
>  > broken part here
>  >
>  > http://imgur.com/j1ys4Nb
>  >
>  > Do you know why that happens?
>  >
>
> Not really but I suspect that it may have something to do with the
> spacing of the plotted points.
> Have you tried a cubic curve?
> And less points. Remember that the curve does not necessary pass through
> the points. They are control points.
>

For a quadratic_spline, the FIRST  point is a controll point, all others 
are actual points that are actualy used and, also, serve as controll 
points for the next point but not for the previous one. The curve is 
controlled from the second to third point but not from the third to 
second points.

In most cases, using the cubic_spline gives beter results.
In your case, it will shorten the object by one interval.

In some cases, using less points can help.


Alain


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From: xslittlegrass
Subject: Re: Why my lathe object is broken?
Date: 28 May 2014 22:20:00
Message: <web.5386983c952f32a81e36f4d20@news.povray.org>
Stephen <mca### [at] aolcom> wrote:
> On 24/05/2014 19:32, xslittlegrass wrote:
> > I tried a cubic curve and it does look better. I agree that the "broken" may
> > caused by the data points.
> >
> > Thanks a lot for your help :)
> >
> >
>
> It is a pleasure. :-D
> I have posted a couple of screenshots in p.b.images along with the lathe
> code I modified, a bit. As an example to show what I did.
>
>
> --
>
> Regards
>      Stephen

What is p.b.images?

Best,
xslittlegrass


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From: Stephen
Subject: Re: Why my lathe object is broken?
Date: 29 May 2014 01:51:45
Message: <5386caf1@news.povray.org>
On 29/05/2014 03:15, xslittlegrass wrote:
> Stephen <mca### [at] aolcom> wrote:
>> On 24/05/2014 19:32, xslittlegrass wrote:
>>> I tried a cubic curve and it does look better. I agree that the "broken" may
>>> caused by the data points.
>>>
>>> Thanks a lot for your help :)
>>>
>>>
>>
>> It is a pleasure. :-D
>> I have posted a couple of screenshots in p.b.images along with the lathe
>> code I modified, a bit. As an example to show what I did.
>>
>>
>> --
>>
>> Regards
>>       Stephen
>
> What is p.b.images?
>
> Best,
> xslittlegrass
>
>

Sorry, povray.binaries.images on this newsgroup.

http://www.povray.org/resources/newsgroups/

->
http://news.povray.org/povray.binaries.images/

->

http://news.povray.org/povray.binaries.images/thread/%3C5380fd72%40news.povray.org%3E/


If I remember correctly. Bishop3D's trial allows you to save scenes with 
up to 4 objects. That would allow you to work on a lathe and save it.

You would need to install PovRay 3.6 to get an immage but you can 
inspect the code and copy and past into your 3.7 scene.

-- 

Regards
     Stephen


Post a reply to this message

From: Alain
Subject: Re: Why my lathe object is broken?
Date: 29 May 2014 17:32:46
Message: <5387a77e$1@news.povray.org>

> On 29/05/2014 03:15, xslittlegrass wrote:
>> Stephen <mca### [at] aolcom> wrote:
>>> On 24/05/2014 19:32, xslittlegrass wrote:
>>>> I tried a cubic curve and it does look better. I agree that the
>>>> "broken" may
>>>> caused by the data points.
>>>>
>>>> Thanks a lot for your help :)
>>>>
>>>>
>>>
>>> It is a pleasure. :-D
>>> I have posted a couple of screenshots in p.b.images along with the lathe
>>> code I modified, a bit. As an example to show what I did.
>>>
>>>
>>> --
>>>
>>> Regards
>>>       Stephen
>>
>> What is p.b.images?
>>
>> Best,
>> xslittlegrass
>>
>>
>
> Sorry, povray.binaries.images on this newsgroup.
>
> http://www.povray.org/resources/newsgroups/
>
> ->
> http://news.povray.org/povray.binaries.images/
>
> ->
>
>
http://news.povray.org/povray.binaries.images/thread/%3C5380fd72%40news.povray.org%3E/
>
>
>
> If I remember correctly. Bishop3D's trial allows you to save scenes with
> up to 4 objects. That would allow you to work on a lathe and save it.
>
> You would need to install PovRay 3.6 to get an immage but you can
> inspect the code and copy and past into your 3.7 scene.
>

Use version 3.7. Version 3.6.x is obsolete.
Next, it's just a mather of refering the correct path.


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