Reference:Lemon

New to version 3.7.1 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 minimal Inner_Radius is a spherical segment where the center of the arc lies on 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 minimal Inner_Radius is defined as sqrt (radius2 + (distance/2)2) both or either of the end points radii can be zero

example lemon objects

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 3.7.1;
global_settings { assumed_gamma 1.0 }

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

#include "colors.inc"

lemon { -18*y-10*x, 0, 18*y-10*x, 0, 30 texture { pigment { color CH2RGB(30) filter 0.45 } } }
lemon { +10*x+1*y, 5, 18*y+10*x, 0, 15 texture { pigment { color CH2RGB(100) filter 0.45 } } }
lemon { -1*y+10*x, 5, -18*y+10*x, 5, 15 texture { pigment { color CH2RGB(150) filter 0.45 } } }

box { 10*z-20*x-20*y, 10*z+20*x+20*y texture { pigment { color White }}}

light_source { 10*<0,0,-20>, 0.9 }
light_source { 10*<-5,10,-50>, 0.9 }
light_source { 10*<-10,10,-50>, 0.9 }
light_source { 10*<5,10,-50>, 0.9 }
light_source { 10*<10,10,-50>, 0.9 }

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

See also the cone object.