Let me guess the reason for this: When povray calculates the ray-hf
itersection, it returns the normal inverted if the regular normal was at
an angle <90 degrees with respect to the incoming ray.
  There might be some archaic reason for this and it doesn't matter with
non-smooth heightfields, but it causes a misbehaviour when a smooth triangle
is oriented so that it faces the camera but some of its normal vectors are
pointing away from it.

-- 
#macro N(D)#if(D>99)cylinder{M()#local D=div(D,104);M().5,2pigment{rgb M()}}
N(D)#end#end#macro M()<mod(D,13)-6mod(div(D,13)8)-3,10>#end blob{
N(11117333955)N(4254934330)N(3900569407)N(7382340)N(3358)N(970)}//  - Warp -

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