Reference:Lemon

New to version 3.8 the lemon object has been added. It is similar to the cone in that it's basically described the same way but with these differences: end points are connected along their axis via the revolution surface that's generated by the circular arc of the Inner_Radius for the minimal value of Inner_Radius the surface is a spherical segment where the center of the arc lies along the end points axis with larger values for Inner_Radius the surface is the inner part of a self intersecting torus or frustum if the given Inner_Radius is too small the minimal value is used instead and a warning is issued both or either of the end points radii can be zero

example lemon objects

Note: The minimal Inner_Radius value is defined as: sqrt ( Radius² + ( DistanceBetweenEndPoints/2 )² )

The syntax is as follows:

lemon { 
    <Base_Point>, Base_Radius, <Cap_Point>, Cap_Radius, Inner_Radius
    [LEMON_MODIFIERS]
  }

LEMON_MODIFIERS:
  sturm | open | OBJECT_MODIFIER

The following example produced the above image:

#version 3.8;
global_settings { assumed_gamma 1.0 }

camera {
  location -560*z
  direction z
  up y
  rotate x*20
  right image_width*x/image_height
  angle 5
  }

#include "colors.inc"

#macro LightSource (LightColor)
  light_source { <0,0,-200>, LightColor area_light x*15, z*15 20,20 adaptive 1 jitter orient circular }
#end

background { White }
plane { y,-20 pigment { White } }

object { LightSource (1.0) rotate x*40 }
object { LightSource (0.8) rotate x*-40 rotate y*330 }
object { LightSource (1.2) rotate x*80 rotate y*210 }

lemon { <0,-20,0>, 0, <0,20,0>, 0, 30
  texture { pigment { color srgb <1,0,0> }}
  translate x*-12
  sturm
  }
  
lemon { <0,0,0>, 5, <0,-20,0>, 0, 15
  texture { pigment { color srgb <0,1,0> }}
  translate y*10
  translate <3,-10,-10>
  sturm
  }
  
lemon { <0,0,0>, 5, <0,-20,0>, 5, 15
  open
  texture { pigment { color srgb <0,0,1> }}
  interior_texture { pigment { srgb <1,1,0> }}
  translate y*10
  translate <12,2,12>
  sturm
  }

If additional accuracy is required you can add the sturm object modifier.

See also the cone object.