Hulling a projection

classic Classic list List threaded Threaded
10 messages Options
Reply | Threaded
Open this post in threaded view
|

Hulling a projection

raycewest
This post has NOT been accepted by the mailing list yet.
Hello all,

I'm attempting to make a stand/walls for a union of 3d objects.  It would be helpful if I could hull said union with its xy-plane projection in order to have something it could sit on and fit perfectly, and then go from there.  Anyone know if this is doable?  I can hull a projection itself so that there's no empty space inside of it, but hulling a projection with its parent 3d object doesn't seem to work.  
Reply | Threaded
Open this post in threaded view
|

Re: Hulling a projection

MichaelAtOz
Administrator
Hi Rayce,

Your post is still flagged as "This post has NOT been accepted by the mailing list yet", so nobody gets it unless they look.
You need to subscribe to the mailing list, and CLICK THE LINK in the registration email (check your spam folder).

Re projection, that is a 2D object, try linear extruding it a bit to make it 3D.
Admin - PM me if you need anything,
or if I've done something stupid...

Unless specifically shown otherwise above, my contribution is in the Public Domain; to the extent possible under law, I have waived all copyright and related or neighbouring rights to this work.
Obviously inclusion of works of previous authors is not included in the above.


The TPP is no simple “trade agreement.” Fight it! http://www.ourfairdeal.org/ time is running out!
Reply | Threaded
Open this post in threaded view
|

Re: Hulling a projection

raycewest
This post has NOT been accepted by the mailing list yet.
I think that answers my question!  Thank you - if I may, I think that only leaves me with one more problem:  if the 3d object has concave areas between it and its projection, there will be unwanted concave space on the opposite side (above) filled by the hull.  Have you ever had this issue and do you have any ideas on how to hull the bottom of an object and not the top?

On Sun, Jun 25, 2017 at 5:27 PM, MichaelAtOz [via OpenSCAD] <[hidden email]> wrote:
Hi Rayce,

Your post is still flagged as "This post has NOT been accepted by the mailing list yet", so nobody gets it unless they look.
You need to subscribe to the mailing list, and CLICK THE LINK in the registration email (check your spam folder).

Re projection, that is a 2D object, try linear extruding it a bit to make it 3D.
Admin - PM me if you need anything,
or if I've done something stupid...

Unless specifically shown otherwise above, my contribution is in the Public Domain; to the extent possible under law, I have waived all copyright and related or neighbouring rights to this work.
Obviously inclusion of works of previous authors is not included in the above.


The TPP is no simple “trade agreement.” Fight it! http://www.ourfairdeal.org/ time is running out!



If you reply to this email, your message will be added to the discussion below:
http://forum.openscad.org/Hulling-a-projection-tp21748p21749.html
To unsubscribe from Hulling a projection, click here.
NAML

Reply | Threaded
Open this post in threaded view
|

Re: Hulling a projection

MichaelAtOz
Administrator
(you still need to subscribe to the mailing list)

Maybe I'm not visualising this properly, but when they are union-ed it will fill the space.
Or translate another projection up to whatever level in the top 3D object, hull the two projections and it will be solid.

Perhaps a picture is worth a few words?
Admin - PM me if you need anything,
or if I've done something stupid...

Unless specifically shown otherwise above, my contribution is in the Public Domain; to the extent possible under law, I have waived all copyright and related or neighbouring rights to this work.
Obviously inclusion of works of previous authors is not included in the above.


The TPP is no simple “trade agreement.” Fight it! http://www.ourfairdeal.org/ time is running out!
Reply | Threaded
Open this post in threaded view
|

Re: Hulling a projection

Ronaldo
In reply to this post by raycewest
It is not clear to me what is your intention: Would it be to fill the gap between the union and the xy plane?

To make a stand for the objects you would need something like a negative mould of them. Is that your intent?
Reply | Threaded
Open this post in threaded view
|

Re: Hulling a projection

raycewest
This post has NOT been accepted by the mailing list yet.
Yes that's correct. 

On Sun, Jun 25, 2017 at 7:40 PM, Ronaldo [via OpenSCAD] <[hidden email]> wrote:
It is not clear to me what is your intention: Would it be to fill the gap between the union and the xy plane?

To make a stand for the objects you would need something like a negative mould of them. Is that your intent?


If you reply to this email, your message will be added to the discussion below:
http://forum.openscad.org/Hulling-a-projection-tp21748p21752.html
To unsubscribe from Hulling a projection, click here.
NAML

Reply | Threaded
Open this post in threaded view
|

Re: Hulling a projection

raycewest
This post has NOT been accepted by the mailing list yet.
In reply to this post by Ronaldo
But only in one direction (down).  I could do a hull of said object and a linear extrusion of its projection onto the xy plane, but it would result in unwanted space above the object (concave areas) being filled.  Thoughts?

On Sun, Jun 25, 2017 at 7:57 PM, Rayce West <[hidden email]> wrote:
Yes that's correct. 

On Sun, Jun 25, 2017 at 7:40 PM, Ronaldo [via OpenSCAD] <[hidden email]> wrote:
It is not clear to me what is your intention: Would it be to fill the gap between the union and the xy plane?

To make a stand for the objects you would need something like a negative mould of them. Is that your intent?


If you reply to this email, your message will be added to the discussion below:
http://forum.openscad.org/Hulling-a-projection-tp21748p21752.html
To unsubscribe from Hulling a projection, click here.
NAML


Reply | Threaded
Open this post in threaded view
|

Re: Hulling a projection

MichaelAtOz
Administrator
Rayce,

Your forum posts are being rejected by the mailing-list, as Admin I get them as Discarded messages.
So only people who actually browse the forum get to see them, not the vast majority of people who would get them via the mailing-list. There are two linked parts, the forum & the mailing-list, you need to be known to both.

So, I'll repeat myself.

Your post is still flagged as "This post has NOT been accepted by the mailing list yet",
so nobody gets it unless they look.
YOU NEED TO SUBSCRIBE to the mailing list,
and CLICK THE LINK in the registration email (check your spam folder).

When you have subscribe, please post an image of what you have so far and describe the missing/wrong part. That would be the best way to get community support.
Admin - PM me if you need anything,
or if I've done something stupid...

Unless specifically shown otherwise above, my contribution is in the Public Domain; to the extent possible under law, I have waived all copyright and related or neighbouring rights to this work.
Obviously inclusion of works of previous authors is not included in the above.


The TPP is no simple “trade agreement.” Fight it! http://www.ourfairdeal.org/ time is running out!
Reply | Threaded
Open this post in threaded view
|

Re: Hulling a projection

Ronaldo
In reply to this post by raycewest
raycewest wrote
But only in one direction (down).  I could do a hull of said object and a
linear extrusion of its projection onto the xy plane, but it would result
in unwanted space above the object (concave areas) being filled.  Thoughts?
There are possibly simpler and better way to do it but here you have a starting point:

epsilon = 0.01;

// a test object
translate([30,0,0]) obj();
// its downward extension
extendown() translate([-10,0,0]) obj();

module extendown()
    intersection() {
        minkowski() {
            children();
            mirror([0,0,1])
            pillar() children();
        }
        // cylindrical envelope of children
        minkowski(){
            linear_extrude(height=epsilon)
            projection() children();
            pillar() children();
        }
    }

module obj()
    translate([0,0,5])
    rotate([30,40,0])
    { cube(10);
      translate([10,10,0]) cylinder(10,10);
      translate([15,0,15]) cube(3);}

// a thin pillar on the origin with height equal to
// the highest point of children
module pillar()
    translate([-epsilon/2,-epsilon/2,0])
    rotate([-90,0,0])
    linear_extrude(height=epsilon)
    projection() rotate([0,90,0])
    linear_extrude(height=epsilon)
        intersection() {
            hull()
            projection() rotate([90,0,0])
                children();
            // discard portions of children with negative z
            mirror([0,1,0]) translate([-1/epsilon/epsilon/2,0,0]) square(1/epsilon/epsilon);
        }

Reply | Threaded
Open this post in threaded view
|

Re: Hulling a projection

Ronaldo
The module pillar() as previously defined does not work as expected when children is above the xy plane. The following code corrects that.

// a thin pillar on the origin with height equal to
// the highest point of children
module pillar()
    translate([-epsilon/2,-epsilon/2,0])
    rotate([-90,0,0])
    linear_extrude(height=epsilon)
    hull(){
        square(epsilon,center=true);
        projection() rotate([0,90,0])
        linear_extrude(height=epsilon)
            intersection() {
                hull()
                projection() rotate([90,0,0])
                    children();
                // discard portions of children with negative z
                mirror([0,1,0])
                translate([-1/epsilon/epsilon/2,0,0])
                square(1/epsilon/epsilon);
        }
    }