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Seeing the inside of a shape from the outside using transparency?

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Seeing the inside of a shape from the outside using transparency?

THX11384EB
I am trying to make a shape/model which is comprised of a few other shapes
added and subtracted from each other. When I did this using Fusion 360, I
used a transparency setting which allowed me to visually confirm that I was
achieving my aim. Unfortunately, the alpha setting for the color command
doesn't seem to have the same effect - it doesn't allow me to see the inside
of my shape. Is there some way I can get to see the inside of my shape from
the outside, as I can in other software (e.g. Google Sketchup, Fusion 360
and 123Design)?

<http://forum.openscad.org/file/t2755/openscad.png>
<http://forum.openscad.org/file/t2755/fusion.png>



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Re: Seeing the inside of a shape from the outside using transparency?

MichaelAtOz
Administrator
Not within an object. you have to cut them open, e.g.

module cut(s=10000) {
  difference() {  
    children();
    translate([-s/2,0,0])
    cube(s);
  }
}

cut()
  difference() {
    cylinder(20,20,20,center=true);
    cylinder(16,16,16,center=true);
  }



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Re: Seeing the inside of a shape from the outside using transparency?

JordanBrown
In reply to this post by THX11384EB
On 2/24/2020 11:08 AM, THX11384EB wrote:
Is there some way I can get to see the inside of my shape from
the outside, as I can in other software (e.g. Google Sketchup, Fusion 360
and 123Design)?

<http://forum.openscad.org/file/t2755/openscad.png> 
<http://forum.openscad.org/file/t2755/fusion.png> 

I assume that center part is hollow?

You might be able to see something useful using View/Wireframe.  Looks like that requires an F6 render first.

I'm a little surprised that the # and % modifiers don't help, but they don't.

It's a little surprising that View/Show Edges doesn't combine with an alpha setting to show the edges inside the object, but I wouldn't say it's wrong.


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Re: Seeing the inside of a shape from the outside using transparency?

JordanBrown
On 2/24/2020 2:39 PM, Jordan Brown wrote:
You might be able to see something useful using View/Wireframe.  Looks like that requires an F6 render first.

On further tries, I'm not seeing the requirement for F6 that I thought I saw.


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Re: Seeing the inside of a shape from the outside using transparency?

Parkinbot
In reply to this post by THX11384EB
In OpenSCAD the order of objects plays a role, whether a look inside into a
transparent object (alpha<1) is presented or not. Thus this object must be
evaluated last.

See this codes:

color("yellow",.5)cube (20, center =true);  // transparent only for objects
already displayed
color("green",1)  cube (10, center =true);  // not visible

vs.

color("green",1)  cube (10, center =true);  // visible
color("yellow",.5)cube (20, center =true);  // transparent only objects
already displayed

the problem is, you can't change the order in cases like the following

difference()
{
  color("yellow",.5)cube (20, center =true);
  color("green",1)  cube (10, center =true);
}

my trick to look through all coats in such a case is the temporal
redefinition of difference() into a union having the right order.

cube (5, center =true);
difference()
{
  cube (20, center =true);
  cube (10, center =true);
}

module difference()
  color("green",.3)
  {
    children([1:$children-1]);
    children(0);
  }




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