povray

Broken lathe object

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?

enter image description here

The code I used to create is 

#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}}
  }
Solution

  • This seems to be caused by inaccuracies in quadratic_spline's calculations. Using cubic_spline as a more precise method should solve the issue.