Script to replicate hull and minkoswki for CSG export/import into FreeCAD
Hi, long time OpenSCAD user, first time poster.
I want to export a model I've designed in OpenSCAD in a form that I can
import into a more 'feature rich' CAD package, so I can do some nice renders
of it. I've looked at Blender OpenSCAD import scripts, but these seem to be
rather limited, and the only other apparent way to export the model, and
retain geometry (rather than export as STL), seems to be to export as CSG,
and import into FreeCAD - the only tool I've found that can cope with
OpenSCAD CSG files.
FreeCAD's CSG import doesn't support OpenSCAD functions such as 'hull' and
'minkowski', which I've used to give my design nice rounded edges.
Fortunately, most of my parts are 2D extrusions, as I plan to lasercut most
of it, and it's relatively easy to reduce minkowski and hull functions to
squares, circles and polygons.
However, FreeCAD (on Mac OS X at least) doesn't seem to like unions of lots
of circles, squares and polygons, and drops geometry, creating holes from
overlapping parts when I import them. Also, some shapes are difficult to
translate into circles and squares alone. So I've come up a script that, to
some extent, replicates 2D hull and minkowski with just circles and a
polygon. With an input of the points of the shape, it draws a circle of a
given radius at each point, then calculates the tangents that connect all
the circles, and creates a polygon. With a linear extrusion, FreeCAD seems
happy with this. Here's my code so far:
radius = 5;
shape = [ 10,10 , 0,40 , 40,80 , 100,80 , 50,0];
x1 = shape[0];
y1 = shape[1];
x2 = shape[2];
y2 = shape[3];
x3 = shape[4];
y3 = shape[5];
x4 = shape[6];
y4 = shape[7];
x5 = shape[8];
y5 = shape[9];
linear_extrude (height=5)
union () {
translate ([x1,y1]) circle (r=radius);
translate ([x2,y2]) circle (r=radius);
translate ([x3,y3]) circle (r=radius);
translate ([x4,y4]) circle (r=radius);
translate ([x5,y5]) circle (r=radius);
polygon ([
tangent_1 (x1,y1,x2,y2,radius),
tangent_2 (x1,y1,x2,y2,radius),
tangent_1 (x2,y2,x3,y3,radius),
tangent_2 (x2,y2,x3,y3,radius),
tangent_1 (x3,y3,x4,y4,radius),
tangent_2 (x3,y3,x4,y4,radius),
tangent_1 (x4,y4,x5,y5,radius),
tangent_2 (x4,y4,x5,y5,radius),
tangent_1 (x5,y5,x1,y1,radius),
tangent_2 (x5,y5,x1,y1,radius),
]);
}
function tangent_1 (x_1, y_1, x_2, y_2, rad) =
let (
x_delta = x_2-x_1,
y_delta = y_2-y_1,
theta = atan2(y_delta,x_delta)+360,
xa = x_1+(cos(90+theta)*rad),
ya = y_1+(sin(90+theta)*rad),
xb = xa+x_delta,
yb = ya+y_delta
)
[xa,ya];
function tangent_2 (x_1,y_1,x_2,y_2,rad) =
let (
x_delta = x_2-x_1,
y_delta = y_2-y_1,
theta = atan2(y_delta,x_delta),
xa = x_1+(cos(90+theta)*rad),
ya = y_1+(sin(90+theta)*rad),
xb = xa+x_delta,
yb = ya+y_delta
)
[xb,yb];
This seems to produce a valid CSG shape, that I can import into FreeCAD,
displays correctly, and can be exported as a STEP file to bring into other
CAD programs with better rendering engines (Blender/Fusion360 are the ones
I've briefly tested).
I'm nearly at my limit of maths/programming, so I'm having difficulty with a
few things:
- I'd really like to be able to put as few (minimum 3) or as many points in
for the shape (currently 5), but I can't work out the way of iterating the
function through all the points, and then back to the first again. - Having a different radius for each point would be nice too (eg shape = [
[x1,y1,r1] , [x2,y2r2], ... ] ), but I think that needs some extra trig to
calculate the tangents. - Finally, it's not a million miles away from another 'hull' requested
feature (I've seen it asked about on the forum before); that of have a point
outside the hull, to create an indent into the shape. If you change the
shape to:
shape = [ 50,50 , 0,40 , 40,80 , 100,80 , 50,0];
You can see it attempts to draw the indentation, but it gets the tangent
wrong, because it needs to use inner tangent lines, rather than outer
tangent lines. I think it would be possible to create a script that deals
with these (the maths is here:
http://www.ambrsoft.com/TrigoCalc/Circles2/Circles2Tangent_.htm ), and
points outside the hull could be identified by using '-r', perhaps, then the
'-r' circles differenced from the polygon shape, rather than unioned. I
could probably use conditional operators (
https://en.wikibooks.org/wiki/OpenSCAD_User_Manual/The_OpenSCAD_Language#Conditional_Operator
) or some kind of recursive function (
https://en.wikibooks.org/wiki/OpenSCAD_User_Manual/The_OpenSCAD_Language#Recursive_functions
). But then I'm really at the limits of my maths/programming!
Unless you know of any other way of getting a model out of OpenSCAD, while
maintaining the geometry, any pointers/help with this script would be
greatly appreciated!
Ian S.
--
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Sent from the OpenSCAD mailing list archive at Nabble.com.
Nice job so far Ian. I am hoping to do similar for my printer parts, will read with interest...
Tapped on my mobile phone.
On 18 Mar 2016, at 10:13, droftarts ginjaian@hotmail.com wrote:
Hi, long time OpenSCAD user, first time poster.
I want to export a model I've designed in OpenSCAD in a form that I can
import into a more 'feature rich' CAD package, so I can do some nice renders
of it. I've looked at Blender OpenSCAD import scripts, but these seem to be
rather limited, and the only other apparent way to export the model, and
retain geometry (rather than export as STL), seems to be to export as CSG,
and import into FreeCAD - the only tool I've found that can cope with
OpenSCAD CSG files.
FreeCAD's CSG import doesn't support OpenSCAD functions such as 'hull' and
'minkowski', which I've used to give my design nice rounded edges.
Fortunately, most of my parts are 2D extrusions, as I plan to lasercut most
of it, and it's relatively easy to reduce minkowski and hull functions to
squares, circles and polygons.
However, FreeCAD (on Mac OS X at least) doesn't seem to like unions of lots
of circles, squares and polygons, and drops geometry, creating holes from
overlapping parts when I import them. Also, some shapes are difficult to
translate into circles and squares alone. So I've come up a script that, to
some extent, replicates 2D hull and minkowski with just circles and a
polygon. With an input of the points of the shape, it draws a circle of a
given radius at each point, then calculates the tangents that connect all
the circles, and creates a polygon. With a linear extrusion, FreeCAD seems
happy with this. Here's my code so far:
radius = 5;
shape = [ 10,10 , 0,40 , 40,80 , 100,80 , 50,0];
x1 = shape[0];
y1 = shape[1];
x2 = shape[2];
y2 = shape[3];
x3 = shape[4];
y3 = shape[5];
x4 = shape[6];
y4 = shape[7];
x5 = shape[8];
y5 = shape[9];
linear_extrude (height=5)
union () {
translate ([x1,y1]) circle (r=radius);
translate ([x2,y2]) circle (r=radius);
translate ([x3,y3]) circle (r=radius);
translate ([x4,y4]) circle (r=radius);
translate ([x5,y5]) circle (r=radius);
polygon ([
tangent_1 (x1,y1,x2,y2,radius),
tangent_2 (x1,y1,x2,y2,radius),
tangent_1 (x2,y2,x3,y3,radius),
tangent_2 (x2,y2,x3,y3,radius),
tangent_1 (x3,y3,x4,y4,radius),
tangent_2 (x3,y3,x4,y4,radius),
tangent_1 (x4,y4,x5,y5,radius),
tangent_2 (x4,y4,x5,y5,radius),
tangent_1 (x5,y5,x1,y1,radius),
tangent_2 (x5,y5,x1,y1,radius),
]);
}
function tangent_1 (x_1, y_1, x_2, y_2, rad) =
let (
x_delta = x_2-x_1,
y_delta = y_2-y_1,
theta = atan2(y_delta,x_delta)+360,
xa = x_1+(cos(90+theta)*rad),
ya = y_1+(sin(90+theta)*rad),
xb = xa+x_delta,
yb = ya+y_delta
)
[xa,ya];
function tangent_2 (x_1,y_1,x_2,y_2,rad) =
let (
x_delta = x_2-x_1,
y_delta = y_2-y_1,
theta = atan2(y_delta,x_delta),
xa = x_1+(cos(90+theta)*rad),
ya = y_1+(sin(90+theta)*rad),
xb = xa+x_delta,
yb = ya+y_delta
)
[xb,yb];
This seems to produce a valid CSG shape, that I can import into FreeCAD,
displays correctly, and can be exported as a STEP file to bring into other
CAD programs with better rendering engines (Blender/Fusion360 are the ones
I've briefly tested).
I'm nearly at my limit of maths/programming, so I'm having difficulty with a
few things:
- I'd really like to be able to put as few (minimum 3) or as many points in
for the shape (currently 5), but I can't work out the way of iterating the
function through all the points, and then back to the first again. - Having a different radius for each point would be nice too (eg shape = [
[x1,y1,r1] , [x2,y2r2], ... ] ), but I think that needs some extra trig to
calculate the tangents. - Finally, it's not a million miles away from another 'hull' requested
feature (I've seen it asked about on the forum before); that of have a point
outside the hull, to create an indent into the shape. If you change the
shape to:
shape = [ 50,50 , 0,40 , 40,80 , 100,80 , 50,0];
You can see it attempts to draw the indentation, but it gets the tangent
wrong, because it needs to use inner tangent lines, rather than outer
tangent lines. I think it would be possible to create a script that deals
with these (the maths is here:
http://www.ambrsoft.com/TrigoCalc/Circles2/Circles2Tangent_.htm ), and
points outside the hull could be identified by using '-r', perhaps, then the
'-r' circles differenced from the polygon shape, rather than unioned. I
could probably use conditional operators (
https://en.wikibooks.org/wiki/OpenSCAD_User_Manual/The_OpenSCAD_Language#Conditional_Operator
) or some kind of recursive function (
https://en.wikibooks.org/wiki/OpenSCAD_User_Manual/The_OpenSCAD_Language#Recursive_functions
). But then I'm really at the limits of my maths/programming!
Unless you know of any other way of getting a model out of OpenSCAD, while
maintaining the geometry, any pointers/help with this script would be
greatly appreciated!
Ian S.
--
View this message in context: http://forum.openscad.org/Script-to-replicate-hull-and-minkoswki-for-CSG-export-import-into-FreeCAD-tp16537.html
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OpenSCAD mailing list
Discuss@lists.openscad.org
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Just a quick side note - especially for 2D extrusions, the double
offset() command can do an awesome job of rounding corners.
example: offset (r=+5) offset (r=-5) square(20);
of course, offset isn't supported in FreeCAD either.
On 3/18/2016 6:13 AM, droftarts wrote:
Hi, long time OpenSCAD user, first time poster.
I want to export a model I've designed in OpenSCAD in a form that I can
import into a more 'feature rich' CAD package, so I can do some nice renders
of it. I've looked at Blender OpenSCAD import scripts, but these seem to be
rather limited, and the only other apparent way to export the model, and
retain geometry (rather than export as STL), seems to be to export as CSG,
and import into FreeCAD - the only tool I've found that can cope with
OpenSCAD CSG files.
FreeCAD's CSG import doesn't support OpenSCAD functions such as 'hull' and
'minkowski', which I've used to give my design nice rounded edges.
Fortunately, most of my parts are 2D extrusions, as I plan to lasercut most
of it, and it's relatively easy to reduce minkowski and hull functions to
squares, circles and polygons.
However, FreeCAD (on Mac OS X at least) doesn't seem to like unions of lots
of circles, squares and polygons, and drops geometry, creating holes from
overlapping parts when I import them. Also, some shapes are difficult to
translate into circles and squares alone. So I've come up a script that, to
some extent, replicates 2D hull and minkowski with just circles and a
polygon. With an input of the points of the shape, it draws a circle of a
given radius at each point, then calculates the tangents that connect all
the circles, and creates a polygon. With a linear extrusion, FreeCAD seems
happy with this. Here's my code so far:
radius = 5;
shape = [ 10,10 , 0,40 , 40,80 , 100,80 , 50,0];
x1 = shape[0];
y1 = shape[1];
x2 = shape[2];
y2 = shape[3];
x3 = shape[4];
y3 = shape[5];
x4 = shape[6];
y4 = shape[7];
x5 = shape[8];
y5 = shape[9];
linear_extrude (height=5)
union () {
translate ([x1,y1]) circle (r=radius);
translate ([x2,y2]) circle (r=radius);
translate ([x3,y3]) circle (r=radius);
translate ([x4,y4]) circle (r=radius);
translate ([x5,y5]) circle (r=radius);
polygon ([
tangent_1 (x1,y1,x2,y2,radius),
tangent_2 (x1,y1,x2,y2,radius),
tangent_1 (x2,y2,x3,y3,radius),
tangent_2 (x2,y2,x3,y3,radius),
tangent_1 (x3,y3,x4,y4,radius),
tangent_2 (x3,y3,x4,y4,radius),
tangent_1 (x4,y4,x5,y5,radius),
tangent_2 (x4,y4,x5,y5,radius),
tangent_1 (x5,y5,x1,y1,radius),
tangent_2 (x5,y5,x1,y1,radius),
]);
}
function tangent_1 (x_1, y_1, x_2, y_2, rad) =
let (
x_delta = x_2-x_1,
y_delta = y_2-y_1,
theta = atan2(y_delta,x_delta)+360,
xa = x_1+(cos(90+theta)*rad),
ya = y_1+(sin(90+theta)*rad),
xb = xa+x_delta,
yb = ya+y_delta
)
[xa,ya];
function tangent_2 (x_1,y_1,x_2,y_2,rad) =
let (
x_delta = x_2-x_1,
y_delta = y_2-y_1,
theta = atan2(y_delta,x_delta),
xa = x_1+(cos(90+theta)*rad),
ya = y_1+(sin(90+theta)*rad),
xb = xa+x_delta,
yb = ya+y_delta
)
[xb,yb];
This seems to produce a valid CSG shape, that I can import into FreeCAD,
displays correctly, and can be exported as a STEP file to bring into other
CAD programs with better rendering engines (Blender/Fusion360 are the ones
I've briefly tested).
I'm nearly at my limit of maths/programming, so I'm having difficulty with a
few things:
- I'd really like to be able to put as few (minimum 3) or as many points in
for the shape (currently 5), but I can't work out the way of iterating the
function through all the points, and then back to the first again. - Having a different radius for each point would be nice too (eg shape = [
[x1,y1,r1] , [x2,y2r2], ... ] ), but I think that needs some extra trig to
calculate the tangents. - Finally, it's not a million miles away from another 'hull' requested
feature (I've seen it asked about on the forum before); that of have a point
outside the hull, to create an indent into the shape. If you change the
shape to:
shape = [ 50,50 , 0,40 , 40,80 , 100,80 , 50,0];
You can see it attempts to draw the indentation, but it gets the tangent
wrong, because it needs to use inner tangent lines, rather than outer
tangent lines. I think it would be possible to create a script that deals
with these (the maths is here:
http://www.ambrsoft.com/TrigoCalc/Circles2/Circles2Tangent_.htm ), and
points outside the hull could be identified by using '-r', perhaps, then the
'-r' circles differenced from the polygon shape, rather than unioned. I
could probably use conditional operators (
https://en.wikibooks.org/wiki/OpenSCAD_User_Manual/The_OpenSCAD_Language#Conditional_Operator
) or some kind of recursive function (
https://en.wikibooks.org/wiki/OpenSCAD_User_Manual/The_OpenSCAD_Language#Recursive_functions
). But then I'm really at the limits of my maths/programming!
Unless you know of any other way of getting a model out of OpenSCAD, while
maintaining the geometry, any pointers/help with this script would be
greatly appreciated!
Ian S.
--
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Thanks, Alex!
A note about the current script:
- The points need to be in a clockwise direction, or it draws the polygon on
the wrong side of the circles, as it only calculates the tangent on one side
of the circle (out of a possible four tangents)
I did try another approach, which was to draw a polygon from each point,
draw a circle on each point, then draw a square of width r*2 between each
point, but this caused problems in FreeCAD. As each element (polygon,
circles, squares) is stored in the CSG, there were multiple overlapping
elements, and FreeCAD seemed to randomly put holes in. A 2D (ie no
linear_extrude) output of the above script still doesn't show correctly in
FreeCAD (there are some parts that are not coloured in), but the 3D version
does show correctly.
Ian
--
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Thanks shadowwynd, and I agree, offest is very useful. I'd tried that
approach for this problem, too, before finding it didn't import into FreeCAD
either!
Ian S
--
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Hi Stuart,
Here is a general version that takes a list of points and makes a rounded
polygon.
radius = 5;
shape = [ [10,10] , [0,40] , [40,80] , [100,80] , [50,0] ];
linear_extrude (height=5) rounded_polygon(shape, radius);
function next(i) = (i + 1) % len(shape);
function tangents(i) = [tangent(shape[i], shape[next(i)],radius, 0),
tangent(shape[i], shape[next(i)],radius, 1)];
function flatten(list) = [for(p = list) for(x = p) x];
module rounded_polygon(points, radius)
union () {
for(point = shape)
translate(point)
circle (r = radius);
polygon(flatten([for(i = [0 : len(shape) - 1]) tangents(i)]));
}
function tangent(p1, p2, rad, side) =
let (
x_delta = p2.x - p1.x,
y_delta = p2.y - p1.y,
theta = atan2(y_delta, x_delta),
xa = p1.x +(cos(90 + theta) * rad),
ya = p1.y +(sin(90 + theta) * rad),
xb = xa + x_delta,
yb = ya + y_delta
)
side ? [xb, yb] : [xa, ya];
On 18 March 2016 at 10:51, droftarts ginjaian@hotmail.com wrote:
Thanks shadowwynd, and I agree, offest is very useful. I'd tried that
approach for this problem, too, before finding it didn't import into
FreeCAD
either!
Ian S
--
View this message in context:
http://forum.openscad.org/Script-to-replicate-hull-and-minkoswki-for-CSG-export-import-into-FreeCAD-tp16537p16542.html
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Here's a simpler one:
radius = 5;
shape = [ [10,10] , [0,40] , [40,80] , [100,80] , [50,0] ];
linear_extrude (height=5) rounded_polygon(shape, radius);
function next(i) = (i + 1) % len(shape);
function tangents(i, side) = tangent(shape[i], shape[next(i)],radius, side);
module rounded_polygon(points, radius)
union () {
for(point = shape)
translate(point)
circle (r = radius);
polygon([for(i = [0 : len(shape) - 1]) for(side = [0, 1])
tangents(i, side)]);
}
function tangent(p1, p2, rad, side) =
let (
x_delta = p2.x - p1.x,
y_delta = p2.y - p1.y,
theta = atan2(y_delta, x_delta),
xa = p1.x +(cos(90 + theta) * rad),
ya = p1.y +(sin(90 + theta) * rad),
xb = xa + x_delta,
yb = ya + y_delta
)
side ? [xb, yb] : [xa, ya];
On 18 March 2016 at 11:29, nop head nop.head@gmail.com wrote:
Hi Stuart,
Here is a general version that takes a list of points and makes a
rounded polygon.
radius = 5;
shape = [ [10,10] , [0,40] , [40,80] , [100,80] , [50,0] ];
linear_extrude (height=5) rounded_polygon(shape, radius);
function next(i) = (i + 1) % len(shape);
function tangents(i) = [tangent(shape[i], shape[next(i)],radius, 0),
tangent(shape[i], shape[next(i)],radius, 1)];
function flatten(list) = [for(p = list) for(x = p) x];
module rounded_polygon(points, radius)
union () {
for(point = shape)
translate(point)
circle (r = radius);
polygon(flatten([for(i = [0 : len(shape) - 1]) tangents(i)]));
}
function tangent(p1, p2, rad, side) =
let (
x_delta = p2.x - p1.x,
y_delta = p2.y - p1.y,
theta = atan2(y_delta, x_delta),
xa = p1.x +(cos(90 + theta) * rad),
ya = p1.y +(sin(90 + theta) * rad),
xb = xa + x_delta,
yb = ya + y_delta
)
side ? [xb, yb] : [xa, ya];
On 18 March 2016 at 10:51, droftarts ginjaian@hotmail.com wrote:
Thanks shadowwynd, and I agree, offest is very useful. I'd tried that
approach for this problem, too, before finding it didn't import into
FreeCAD
either!
Ian S
--
View this message in context:
http://forum.openscad.org/Script-to-replicate-hull-and-minkoswki-for-CSG-export-import-into-FreeCAD-tp16537p16542.html
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Hi nophead
Wow! Thanks for the reply, that solves what I need at the moment. I knew
there had to be a way to iterate this, but just couldn't see it. That gives
me plenty to wrap my head around; I'd perhaps like to extend it to allow for
different radii.
I've been spending some time with your Mendel90 OpenSCAD files recently, and
have learnt a huge amount from that!
Ian S
P.S. Who's Stuart?!
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P.S. Who's Stuart?!
No idea, sorry Ian.
I am attempting the different radii case at the moment. No quite right yet.
On 18 March 2016 at 12:26, droftarts ginjaian@hotmail.com wrote:
Hi nophead
Wow! Thanks for the reply, that solves what I need at the moment. I knew
there had to be a way to iterate this, but just couldn't see it. That gives
me plenty to wrap my head around; I'd perhaps like to extend it to allow
for
different radii.
I've been spending some time with your Mendel90 OpenSCAD files recently,
and
have learnt a huge amount from that!
Ian S
P.S. Who's Stuart?!
--
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Here is a multi radii version. It looks right but somebody might want to
check my maths as it is much simpler than the link you provided.
$fn = 100;
shape = [ [10, 10, 8], [0, 40, 3], [40, 80, 5], [100, 80, 10], [50, 0, 20]
];
linear_extrude (height = 5) rounded_polygon(shape);
function next(i) = (i + 1) % len(shape);
function tangents(i, side) = tangent(shape[i], shape[next(i)], side);
module rounded_polygon(points, radius)
union () {
for(i = [0 : len(shape) - 1])
translate([shape[i].x, shape[i].y])
#circle(shape[i][2]);
polygon([for(i = [0 : len(shape) - 1]) for(side = [0, 1])
tangents(i, side)]);
}
function tangent(p1, p2, side) =
let (
r1 = p1[2],
r2 = p2[2],
dx = p2.x - p1.x,
dy = p2.y - p1.y,
d = sqrt(dx * dx + dy * dy),
theta = atan2(dy, dx) + acos((r1 - r2) / d),
xa = p1.x +(cos(theta) * r1),
ya = p1.y +(sin(theta) * r1),
xb = p2.x +(cos(theta) * r2),
yb = p2.y +(sin(theta) * r2)
)
side ? [xb, yb] : [xa, ya];
On 18 March 2016 at 12:35, nop head nop.head@gmail.com wrote:
P.S. Who's Stuart?!
No idea, sorry Ian.
I am attempting the different radii case at the moment. No quite right yet.
On 18 March 2016 at 12:26, droftarts ginjaian@hotmail.com wrote:
Hi nophead
Wow! Thanks for the reply, that solves what I need at the moment. I knew
there had to be a way to iterate this, but just couldn't see it. That
gives
me plenty to wrap my head around; I'd perhaps like to extend it to allow
for
different radii.
I've been spending some time with your Mendel90 OpenSCAD files recently,
and
have learnt a huge amount from that!
Ian S
P.S. Who's Stuart?!
--
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