ulp function wanted:distance from point to smd pad edge

Morten Leikvoll wrote on Wed, 16 December 2009 03:52

I need a function that returns the distance between a point and the

edge of

a smd pad. If the point is inside the pad, I'd want it to return 0.

Anyone tried doing that? I want the roundness of the smd to be a part

of the

function too.

That's going to be a little tricky since you have to mimic the Eagle SMD

roundness algorithm.  The UL_SMD structure only gives you the rectangular

size and roundness as a separate parameter.  There are various ways the

roundess parameter could be used to blend between a rectangle and a elipse,

and I don't remember seeing documentation on how exactly Eagle does it.

On the other hand, maybe it doesn't need to be that accurate and you can

probably get a good idea of their method with a little experimentation.

Once you know how to compute the pad shape, the brute force way to do what

you ask would be to turn it into a polygon and perform a normal in/out

function.  At least you know the polygon will be convex.

However, it still sounds like you're stuck in a rut having made the wrong

choice several layers up and now requiring ever more elaborate schemes to

work around the problem, when the right answer is to not be in this

situation in the first place.  Step back and explain the original problem

you are trying to solve.

--

Browser access to CadSoft Support Forums at http://www.eaglecentral.ca

"Olin Lathrop" <eagle@embedinc.com> wrote in message

news:hgap4t$8a5$1@cheetah.cadsoft.de...

That's going to be a little tricky since you have to mimic the Eagle SMD

roundness algorithm.  The UL_SMD structure only gives you the rectangular

size and roundness as a separate parameter.  There are various ways the

roundess parameter could be used to blend between a rectangle and a

elipse,

and I don't remember seeing documentation on how exactly Eagle does it.

 

On the other hand, maybe it doesn't need to be that accurate and you can

probably get a good idea of their method with a little experimentation.

Once you know how to compute the pad shape, the brute force way to do what

you ask would be to turn it into a polygon and perform a normal in/out

function.  At least you know the polygon will be convex.

 

However, it still sounds like you're stuck in a rut having made the wrong

choice several layers up and now requiring ever more elaborate schemes to

work around the problem, when the right answer is to not be in this

situation in the first place.  Step back and explain the original problem

you are trying to solve.

I know I can do it (gimme a day or two), that is not the problem. I just

didnt want to if anyone else has done it and wanted to share it before I

spend my valuable time.

"Morten Leikvoll" <mleikvol@yahoo.nospam> wrote in message

news:hga74q$qco$1@cheetah.cadsoft.de...

I need a function that returns the distance between a point and the edge of

a smd pad. If the point is inside the pad, I'd want it to return 0.

Anyone tried doing that? I want the roundness of the smd to be a part of

the function too.

If any interest, here is one way of doing it (with printf's for debugging

commented out).

It basicaly turns a SMD into an octacon and 4 corner circles, checks the

distance to each side + circles, then picks the smallest.

Of course I can not guarantee that it will work for all types of smds, but

it should work for the basic ones. It will not detect wether you are inside

the smd or not, just the smallest distance to the smd edge.

-

int Point2PointDistance(real x1, real y1, real x2, real y2)

{

    return floor(sqrt( ((x1 - x2) * (x1 - x2)) + ((y1 - y2) * (y1 - y2))));

}

int Point2WireDistance(int x, int y, int x1, int y1,int x2,int y2)

{

int Ux = x - x1;

int Uy = y - y1;

int Vx = x2 - x1;

int Vy = y2 - y1;

real dot = 1.0 * Ux * Vx + 1.0 * Uy * Vy;

real len_sq = 1.0 * Vx * Vx + 1.0 * Vy * Vy;

if(len_sq==0) return 0; //line len is 0

real param = dot / len_sq;

if(param<0) param=0;

if(param>1) param=1;

    real xx = round(paramVx + 1.0x1);

    real yy = round(paramVy + 1.0y1);

return Point2PointDistance(x,y,xx,yy);

}

int smddist(int x,int y,UL_CONTACT C)

{

int dist,t,t1;

int x1,y1,x2,y2;

int xs,ys,ang;

xs=round(C.smd.dx/2);

ys=round(C.smd.dy/2);

ang=C.smd.angle;

int edg=(xs<ys)?xs:ys;//smallest edge

edg=edg-round(1.0edgC.smd.roundness/100);//radius of corner circles

//printf("Checking point (%f %f) distance to smd at (%f

%f)\n",u2mm(x),u2mm(y),u2mm(C.x),u2mm(C.y));

x1=C.x+round(cos(PIang/180)(xs-edg)-sin(PIang/180)ys); //find dist to

upper wire

y1=C.yround(sin(PIang/180)(xs-edg)cos(PIang/180)ys);

x2=C.xround(cos(PIang/180)(-xsedg)-sin(PIang/180)ys);

y2=C.yround(sin(PIang/180)(-xsedg)+cos(PIang/180)ys);

t1=Point2WireDistance(x,y,x1,y1,x2,y2);

dist=t1;

//printf("\tDist to upper wire (%f %f) (%f

%f):%f\n",u2mm(x1),u2mm(y1),u2mm(x2),u2mm(y2),u2mm(t1));

x1=C.x+round(cos(PIang/180)(xs-edg)-sin(PIang/180)(-ys)); //find dist

to lower wire

y1=C.yround(sin(PIang/180)(xs-edg)cos(PIang/180)(-ys));

x2=C.xround(cos(PIang/180)(-xsedg)-sin(PIang/180)(-ys));

y2=C.yround(sin(PIang/180)(-xsedg)+cos(PIang/180)(-ys));

t1=Point2WireDistance(x,y,x1,y1,x2,y2);

if(t1<dist) dist=t1;

//printf("\tDist to lower wire (%f %f) (%f

%f):%f\n",u2mm(x1),u2mm(y1),u2mm(x2),u2mm(y2),u2mm(t1));

x1=C.x+round(cos(PIang/180)(-xs)-sin(PIang/180)(ys-edg)); //find dist

to left wire

y1=C.yround(sin(PIang/180)(-xs)cos(PIang/180)(ys-edg));

x2=C.xround(cos(PIang/180)(-xs)-sin(PIang/180)(-ysedg));

y2=C.yround(sin(PIang/180)(-xs)cos(PIang/180)(-ys+edg));

t1=Point2WireDistance(x,y,x1,y1,x2,y2);

if(t1<dist) dist=t1;

//printf("\tDist to left wire (%f %f) (%f

%f):%f\n",u2mm(x1),u2mm(y1),u2mm(x2),u2mm(y2),u2mm(t1));

x1=C.x+round(cos(PIang/180)(xs)-sin(PIang/180)(ys-edg)); //find dist to

right wire

y1=C.yround(sin(PIang/180)(xs)cos(PIang/180)(ys-edg));

x2=C.xround(cos(PIang/180)(xs)-sin(PIang/180)(-ysedg));

y2=C.yround(sin(PIang/180)(xs)cos(PIang/180)(-ys+edg));

t1=Point2WireDistance(x,y,x1,y1,x2,y2);

if(t1<dist) dist=t1;

//printf("\tDist to right wire (%f %f) (%f

%f):%f\n",u2mm(x1),u2mm(y1),u2mm(x2),u2mm(y2),u2mm(t1));

if(edg)

{

  x1=C.x+round(cos(PIang/180)(xs-edg)-sin(PIang/180)(ys-edg)); //circle

in upper right corner

  y1=C.yround(sin(PIang/180)(xs-edg)cos(PIang/180)(ys-edg));

  t=Point2PointDistance(x,y,x1,y1)-edg; // check dist to circle in upper

right corner

//printf("\tDist to upper right corner circle(%f

%f):%f\n",u2mm(x1),u2mm(y1),u2mm(t));

  if(t<dist) dist=t;

  x1=C.xround(cos(PIang/180)(xs-edg)-sin(PIang/180)(-ysedg)); //circle

in lower right corner

  y1=C.yround(sin(PIang/180)(xs-edg)cos(PIang/180)(-ys+edg));

  t=Point2PointDistance(x,y,x1,y1)-edg; // check dist to circle in lower

right corner

//printf("\tDist to lower right corner circle(%f

%f):%f\n",u2mm(x1),u2mm(y1),u2mm(t));

  if(t<dist) dist=t;

  x1=C.xround(cos(PIang/180)(-xsedg)-sin(PIang/180)(-ys+edg));

//circle in lower left corner

  y1=C.yround(sin(PIang/180)(-xsedg)cos(PIang/180)(-ysedg));

  t=Point2PointDistance(x,y,x1,y1)-edg; // check dist to circle in lower

left corner

//printf("\tDist to lower left corner circle(%f

%f):%f\n",u2mm(x1),u2mm(y1),u2mm(t));

  if(t<dist) dist=t;

  x1=C.xround(cos(PIang/180)(-xsedg)-sin(PIang/180)(ys-edg)); //circle

in upper left corner

  y1=C.yround(sin(PIang/180)(-xsedg)+cos(PIang/180)(ys-edg));

  t=Point2PointDistance(x,y,x1,y1)-edg; // check dist to circle in upper

left corner

//printf("\tDist to upper left corner circle(%f

%f):%f\n",u2mm(x1),u2mm(y1),u2mm(t));

  if(t<dist) dist=t;

}

//printf("\tDistance=%f\n",u2mm(dist));

return dist;

}

I should post this bug warning.  The position of the corner circles may be

wrong. They should probably be positioned at xs±edg/2,ys±edg/2 instead of

xs±edg,ys±edg.

"Morten Leikvoll" <mleikvol@yahoo.nospam> wrote in message

news:hh9qlp$6ok$1@cheetah.cadsoft.de...

"Morten Leikvoll" <mleikvol@yahoo.nospam> wrote in message

news:hga74q$qco$1@cheetah.cadsoft.de...

I need a function that returns the distance between a point and the edge

of a smd pad. If the point is inside the pad, I'd want it to return 0.

Anyone tried doing that? I want the roundness of the smd to be a part of

the function too.

 

If any interest, here is one way of doing it (with printf's for debugging

commented out).

It basicaly turns a SMD into an octacon and 4 corner circles, checks the

distance to each side + circles, then picks the smallest.

Of course I can not guarantee that it will work for all types of smds, but

it should work for the basic ones. It will not detect wether you are

inside the smd or not, just the smallest distance to the smd edge.

--------------

 

int Point2PointDistance(real x1, real y1, real x2, real y2)

{

   return floor(sqrt( ((x1 - x2) * (x1 - x2)) + ((y1 - y2) * (y1 - y2))));

}

 

int Point2WireDistance(int x, int y, int x1, int y1,int x2,int y2)

{

int Ux = x - x1;

int Uy = y - y1;

int Vx = x2 - x1;

int Vy = y2 - y1;

 

real dot = 1.0 * Ux * Vx + 1.0 * Uy * Vy;

real len_sq = 1.0 * Vx * Vx + 1.0 * Vy * Vy;

 

if(len_sq==0) return 0; //line len is 0

 

real param = dot / len_sq;

if(param<0) param=0;

if(param>1) param=1;

   real xx = round(paramVx + 1.0x1);

   real yy = round(paramVy + 1.0y1);

 

return Point2PointDistance(x,y,xx,yy);

}

 

int smddist(int x,int y,UL_CONTACT C)

{

int dist,t,t1;

int x1,y1,x2,y2;

int xs,ys,ang;

 

xs=round(C.smd.dx/2);

ys=round(C.smd.dy/2);

ang=C.smd.angle;

 

int edg=(xs<ys)?xs:ys;//smallest edge

edg=edg-round(1.0edgC.smd.roundness/100);//radius of corner circles

 

//printf("Checking point (%f %f) distance to smd at (%f

%f)\n",u2mm(x),u2mm(y),u2mm(C.x),u2mm(C.y));

 

x1=C.x+round(cos(PIang/180)(xs-edg)-sin(PIang/180)ys); //find dist to

upper wire

y1=C.yround(sin(PIang/180)(xs-edg)cos(PIang/180)ys);

x2=C.xround(cos(PIang/180)(-xsedg)-sin(PIang/180)ys);

y2=C.yround(sin(PIang/180)(-xsedg)+cos(PIang/180)ys);

t1=Point2WireDistance(x,y,x1,y1,x2,y2);

dist=t1;

//printf("\tDist to upper wire (%f %f) (%f

%f):%f\n",u2mm(x1),u2mm(y1),u2mm(x2),u2mm(y2),u2mm(t1));

 

x1=C.x+round(cos(PIang/180)(xs-edg)-sin(PIang/180)(-ys)); //find dist

to lower wire

y1=C.yround(sin(PIang/180)(xs-edg)cos(PIang/180)(-ys));

x2=C.xround(cos(PIang/180)(-xsedg)-sin(PIang/180)(-ys));

y2=C.yround(sin(PIang/180)(-xsedg)+cos(PIang/180)(-ys));

t1=Point2WireDistance(x,y,x1,y1,x2,y2);

if(t1<dist) dist=t1;

//printf("\tDist to lower wire (%f %f) (%f

%f):%f\n",u2mm(x1),u2mm(y1),u2mm(x2),u2mm(y2),u2mm(t1));

 

x1=C.x+round(cos(PIang/180)(-xs)-sin(PIang/180)(ys-edg)); //find dist

to left wire

y1=C.yround(sin(PIang/180)(-xs)cos(PIang/180)(ys-edg));

x2=C.xround(cos(PIang/180)(-xs)-sin(PIang/180)(-ysedg));

y2=C.yround(sin(PIang/180)(-xs)cos(PIang/180)(-ys+edg));

t1=Point2WireDistance(x,y,x1,y1,x2,y2);

if(t1<dist) dist=t1;

//printf("\tDist to left wire (%f %f) (%f

%f):%f\n",u2mm(x1),u2mm(y1),u2mm(x2),u2mm(y2),u2mm(t1));

 

x1=C.x+round(cos(PIang/180)(xs)-sin(PIang/180)(ys-edg)); //find dist

to right wire

y1=C.yround(sin(PIang/180)(xs)cos(PIang/180)(ys-edg));

x2=C.xround(cos(PIang/180)(xs)-sin(PIang/180)(-ysedg));

y2=C.yround(sin(PIang/180)(xs)cos(PIang/180)(-ys+edg));

t1=Point2WireDistance(x,y,x1,y1,x2,y2);

if(t1<dist) dist=t1;

//printf("\tDist to right wire (%f %f) (%f

%f):%f\n",u2mm(x1),u2mm(y1),u2mm(x2),u2mm(y2),u2mm(t1));

 

if(edg)

{

x1=C.x+round(cos(PIang/180)(xs-edg)-sin(PIang/180)(ys-edg)); //circle

in upper right corner

y1=C.yround(sin(PIang/180)(xs-edg)cos(PIang/180)(ys-edg));

t=Point2PointDistance(x,y,x1,y1)-edg; // check dist to circle in upper

right corner

//printf("\tDist to upper right corner circle(%f

%f):%f\n",u2mm(x1),u2mm(y1),u2mm(t));

if(t<dist) dist=t;

 

x1=C.xround(cos(PIang/180)(xs-edg)-sin(PIang/180)(-ysedg));

//circle in lower right corner

y1=C.yround(sin(PIang/180)(xs-edg)cos(PIang/180)(-ys+edg));

t=Point2PointDistance(x,y,x1,y1)-edg; // check dist to circle in lower

right corner

//printf("\tDist to lower right corner circle(%f

%f):%f\n",u2mm(x1),u2mm(y1),u2mm(t));

if(t<dist) dist=t;

x1=C.xround(cos(PIang/180)(-xsedg)-sin(PIang/180)(-ys+edg));

//circle in lower left corner

y1=C.yround(sin(PIang/180)(-xsedg)cos(PIang/180)(-ysedg));

t=Point2PointDistance(x,y,x1,y1)-edg; // check dist to circle in lower

left corner

//printf("\tDist to lower left corner circle(%f

%f):%f\n",u2mm(x1),u2mm(y1),u2mm(t));

if(t<dist) dist=t;

x1=C.xround(cos(PIang/180)(-xsedg)-sin(PIang/180)(ys-edg));

//circle in upper left corner

y1=C.yround(sin(PIang/180)(-xsedg)+cos(PIang/180)(ys-edg));

t=Point2PointDistance(x,y,x1,y1)-edg; // check dist to circle in upper

left corner

//printf("\tDist to upper left corner circle(%f

%f):%f\n",u2mm(x1),u2mm(y1),u2mm(t));

if(t<dist) dist=t;

}

//printf("\tDistance=%f\n",u2mm(dist));

 

return dist;

}

 

 

"Morten Leikvoll" <mleikvol@yahoo.nospam> wrote in message

news:hh9u0b$hnr$1@cheetah.cadsoft.de...

I should post this bug warning.  The position of the corner circles may be

wrong. They should probably be positioned at xs±edg/2,ys±edg/2 instead of

xs±edg,ys±edg.

This was false alarm. I just had my hand written sketch drawn wrong.. The

original function was correct.