I try to color one half of an object (in this case a cube) in one color,
and the other half in a different color, like this:

color("red")
difference(){
cube(30,center=true);
translate([15,0,0])
cube([30,31,31],center=true);
}
color("green")
difference(){
cube(30,center=true);
translate([-15,0,0])
cube([30,31,31],center=true);
}

I cut off one half of the object and color it red, and then in the same
way the other half green. If you execute only the first part you get a
red half cube, however, if you execute both parts you get a green full
cube, the red is gone, apparently overruled by the green.

My provisional solution is to slightly reduce the size of the second
part, and this works. But it seems this is an error in OpenSCAD, if you
cut off a part of an object, it should cut off the color too....

color("red")
difference(){
cube(30,center=true);
translate([15,0,0])
cube([30,31,31],center=true);
}
color("green")
difference(){
scale([1,.99,.99])
cube(30,center=true);
translate([-15,0,0])
cube([30,31,31],center=true);
}

I use OpenSCAD 2021.01 on an M2 Mac.

Maurice

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On Apr 8, 2023, at 22:36, Maurice van Peursem openscad@vanpeursem.net wrote:

I try to color one half of an object (in this case a cube) in one color, and the other half in a different color, like this:

color("red")
difference(){
cube(30,center=true);
translate([15,0,0])
cube([30,31,31],center=true);
}
color("green")
difference(){
cube(30,center=true);
translate([-15,0,0])
cube([30,31,31],center=true);
}

I cut off one half of the object and color it red, and then in the same way the other half green. If you execute only the first part you get a red half cube, however, if you execute both parts you get a green full cube, the red is gone, apparently overruled by the green.

My provisional solution is to slightly reduce the size of the second part, and this works. But it seems this is an error in OpenSCAD, if you cut off a part of an object, it should cut off the color too....

color("red")
difference(){
cube(30,center=true);
translate([15,0,0])
cube([30,31,31],center=true);
}
color("green")
difference(){
scale([1,.99,.99])
cube(30,center=true);
translate([-15,0,0])
cube([30,31,31],center=true);
}

I use OpenSCAD 2021.01 on an M2 Mac.

Maurice

OpenSCAD mailing list
To unsubscribe send an email to discuss-leave@lists.openscad.org

color("red") /render() /
        difference(){
                cube(30,center=true);
                translate([15,0,0])
                        cube([30,31,31],center=true);
        }

color("green") /render() /
        difference(){
                cube(30,center=true);
                translate([-15,0,0])
                        cube([30,31,31],center=true);
        }

works after I added the render() for each half in the original
first example. Others can explain why, I just had a hunch after having tried
color("red") sphere(d=50);
color("green") cube(40) ;
and confirmed that colors do not "override" on a join

Msquare

On Sun, 9 Apr 2023 at 04:37, Maurice van Peursem
<openscad@vanpeursem.net mailto:openscad@vanpeursem.net> wrote:

 I try to color one half of an object (in this case a cube) in one
 color,
 and the other half in a different color, like this:

 color("red")
          difference(){
                  cube(30,center=true);
                  translate([15,0,0])
                          cube([30,31,31],center=true);
          }
 color("green")
          difference(){
                  cube(30,center=true);
                  translate([-15,0,0])
                          cube([30,31,31],center=true);
          }

 I cut off one half of the object and color it red, and then in the same
 way the other half green. If you execute only the first part you get a
 red half cube, however, if you execute both parts you get a green full
 cube, the red is gone, apparently overruled by the green.

 My provisional solution is to slightly reduce the size of the second
 part, and this works. But it seems this is an error in OpenSCAD, if you
 cut off a part of an object, it should cut off the color too....

 color("red")
          difference(){
                  cube(30,center=true);
                  translate([15,0,0])
                          cube([30,31,31],center=true);
          }
 color("green")
          difference(){
                  scale([1,.99,.99])
                          cube(30,center=true);
                          translate([-15,0,0])
                                  cube([30,31,31],center=true);
          }

 I use OpenSCAD 2021.01 on an M2 Mac.

 Maurice
 _______________________________________________
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 <mailto:discuss-leave@lists.openscad.org>

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The "strange transparency" may be resolved by using render(convexity=10)
or a slightly higher number

Michael, fra mobilen

søn. 9. apr. 2023 23.59 skrev Maurice van Peursem
<openscad@vanpeursem.net mailto:openscad@vanpeursem.net>:

 Thanks for that! There is no need to use render() on the first part,
 and
 when I did use it I got a strange, transparent looking result (my
 object
 is more complicated than a simple cube). But if you only use
 render() on
 the second part, everything works out perfectly.

 Maurice

 color("red")
       difference(){
           cube(30,center=true);
           translate([15,0,0])
               cube([30,31,31],center=true);
       }
 color("green")
       render()
           difference(){
               cube(30,center=true);
               translate([-15,0,0])
                   cube([30,31,31],center=true);
       }