I've got a problem here, I have a mechanism modeled, sort of a door that is
opened by an arm-type thing.  Point 1 and 2 are stationary, the second half
of the arm must be the same length throughout its rotation, from point 3 to
4.  At clock=0 and clock=1 there is no problem.  However, in between...  If
anyone could help me with making sure the second arm is always the same
length, while still connecting the two points, I would appreciate it.

Here is the important code for what I have so far:

#local d = 18.4349488229220106484278062795076;
#local m = 3.162277660168379331998893544432;
#local s1 = sin(radians(d+((68-d)*R)))*m;
#local c1 = cos(radians(d+((68-d)*R)))*m;
#local s2 = sin(radians(65*R))*4;
#local c2 = cos(radians(65*R))*4;
union {
  union {
    box {<-1.25, -.1, -7.5>, <1.25, 0, 0>}
    cylinder {<0, -.4, -4>, <0, 0, -4>, .025 pigment {red 1} finish {ambient
1}}
    rotate <R*65, 0, 0>
  }
  cylinder {<-.4, -2, -4>, <-.4, -2+s1, -4+c1>, .1 pigment {red .7} finish
{ambient 1}}
  cylinder {<-.4, -2+s1, -4+c1>, <-.4, -.1+s2, -c2>, .1 pigment {blue .7}
finish {ambient 1}}
}

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Attachments:
Download '1.jpg' (12 KB) Download '2.jpg' (12 KB) Download '3.jpg' (12 KB)

Preview of image '1.jpg'

Preview of image '2.jpg'

Preview of image '3.jpg'

Hi Ben,

I did something similar a while back. The problem is the same as finding
the intersection points of two circles in the plane. Paul Bourke's 
answer is given at

http://www.swin.edu.au/astronomy/pbourke/geometry/2circle/

I'll post the source for the image at the bottom of this reply in
p.t.s-f, just to show my implementation of this answer.

Bye for now,
	Mike Andrews.

Ben Lauritzen wrote:
> 
> I've got a problem here, I have a mechanism modeled, sort of a door that is
> opened by an arm-type thing.  Point 1 and 2 are stationary, the second half
> of the arm must be the same length throughout its rotation, from point 3 to
> 4.  At clock=0 and clock=1 there is no problem.  However, in between...  If
> anyone could help me with making sure the second arm is always the same
> length, while still connecting the two points, I would appreciate it.
> 
> Here is the important code for what I have so far:
> 
> #local d = 18.4349488229220106484278062795076;
> #local m = 3.162277660168379331998893544432;
> #local s1 = sin(radians(d+((68-d)*R)))*m;
> #local c1 = cos(radians(d+((68-d)*R)))*m;
> #local s2 = sin(radians(65*R))*4;
> #local c2 = cos(radians(65*R))*4;
> union {
>   union {
>     box {<-1.25, -.1, -7.5>, <1.25, 0, 0>}
>     cylinder {<0, -.4, -4>, <0, 0, -4>, .025 pigment {red 1} finish {ambient
> 1}}
>     rotate <R*65, 0, 0>
>   }
>   cylinder {<-.4, -2, -4>, <-.4, -2+s1, -4+c1>, .1 pigment {red .7} finish
> {ambient 1}}
>   cylinder {<-.4, -2+s1, -4+c1>, <-.4, -.1+s2, -c2>, .1 pigment {blue .7}
> finish {ambient 1}}
> }
> 
>  [Image]
> 
>  [Image]
> 
>  [Image]

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