In the scene below I get a bicubic patch object where many triangles are
missing. I really don't think that the patch object is very small, or that
any other elements in my scene are particularly small. How comes the
precision errors in this case appears at a scale that is so far from being
extreme?

I get the problem in both POV-Ray 3.1 and 3.5.

#declare M = 0.4; // 0.4=broken, 0.6=ok

camera {
   location <0.9,0.3,-1.5>*M
   angle 32
   look_at 0
   translate <-0.54,-0.36,0>*M
}
light_source {<0,1,-2>*10*M, color 1.2}
background {color rgb 1}

bicubic_patch {
   type 1 u_steps 4 v_steps 4
   <  0.2204, -0.0904, -1.0329>
   <  0.2125, -0.1580, -1.0308>
   <  0.1594, -0.1118, -1.0336>
   <  0.1447, -0.1788, -1.0142>
   <  0.1659, -0.0932, -1.0648>
   <  0.1600, -0.1595, -1.0614>
   <  0.1177, -0.1174, -1.0527>
   <  0.1068, -0.1819, -1.0314>
   <  0.0600, -0.0967, -1.1058>
   <  0.0581, -0.1598, -1.1010>
   <  0.0366, -0.1248, -1.0771>
   <  0.0400, -0.1858, -1.0537>
   <  0.0000, -0.0967, -1.1058>
   <  0.0000, -0.1607, -1.1009>
   <  0.0000, -0.1255, -1.0768>
   <  0.0000, -0.1858, -1.0537>
   texture {pigment {color rgb 1}}
   scale M
}

Rune
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