On 3/8/2016 11:17 AM, Stephen wrote:
>> OK - back to interpolating the control points for my 3x3 bicubic patch
>> model.
>> 16 data points, 128 interpolated control points, 144 control points
>> altogether.
>>   :D
>
> Good luck. :-)
> IIRC Moray had a way of joining bicubic patchs.

I don't know if this will help you. This is a couple of bicubic patches 
that make a cylinder of radius 1. Note that the Y value is 4/3 and in 
Moray, Z is up. (Please don't restart the Maths Vs Engineering, flame 
war. ;-) )



union { // BezPtch001
   object {
     bicubic_patch { type 1 flatness 0.0100 u_steps 3 v_steps 3,
       <-1.000000, 0.000000, 0.000000>, <-1.000000, -1.333333, 
0.000000>, <1.000000, -1.333333, 0.000000>, <1.000000, 0.000000, 0.000000>,
       <-1.000000, 0.000000, 2.000000>, <-1.000000, -1.333333, 
2.000000>, <1.000000, -1.333333, 2.000000>, <1.000000, 0.000000, 2.000000>,
       <-1.000000, 0.000000, 4.000000>, <-1.000000, -1.333333, 
4.000000>, <1.000000, -1.333333, 4.000000>, <1.000000, 0.000000, 4.000000>,
       <-1.000000, 0.000000, 6.000000>, <-1.000000, -1.333333, 
6.000000>, <1.000000, -1.333333, 6.000000>, <1.000000, 0.000000, 6.000000>
     }
   }
   object {
     bicubic_patch { type 1 flatness 0.0100 u_steps 3 v_steps 3,
       <1.000000, 0.000000, 0.000000>, <1.000000, 1.333333, 0.000000>, 
<-1.000000, 1.333330, 0.000000>, <-1.000000, 0.000000, 0.000000>,
       <1.000000, 0.000000, 2.000000>, <1.000000, 1.333333, 2.000000>, 
<-1.000000, 1.333330, 2.000000>, <-1.000000, 0.000000, 2.000000>,
       <1.000000, 0.000000, 4.000000>, <1.000000, 1.333333, 4.000000>, 
<-1.000000, 1.333330, 4.000000>, <-1.000000, 0.000000, 4.000000>,
       <1.000000, 0.000000, 6.000000>, <1.000000, 1.333333, 6.000000>, 
<-1.000000, 1.333330, 6.000000>, <-1.000000, 0.000000, 6.000000>
     }
   }

}


-- 

Regards
     Stephen

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