Re: [OpenSCAD] restrict hull function to one or two dimensions
rav0r wrote
I am trying to modulate an object by not changing it's suface so I
designed a code for it to be sliced and the slices be rearranged after a
custom equation. The problem I have is that if the object is not flat and
has holes that need to be preserved, hull does not help much. As a test,
we place two objects and use the code, the two join. Of course, in a
simplified case, I can cut the object and create a module out of every
cut, but is there a way to automize this for, let's say, 100 modules?
module test() {
cube([200,10,2]);
translate([0,12,0])
cube([200,10,2]);
}
//variables for cut points
ca1=-8.89;
ca2=-8.9;
cb1=-9.89;
cb2=-9.9;
//variables for equation
a=110;
b=125;
c=-250;
//variables for y cut points
yca1=-8.89;
yca2=-8.9;
ycb1=-9.89;
ycb2=-9.9;
//variables for y equation
ya=110;
yb=125;
yc=-250;
module x2() {
for (z = [1:50])
hull() {
translate([0,0,log(z+a)*b+c])
{
difference() {
test();
translate([z+ca1,-10,-1]) cube([300,200,200]);
translate([ca2-300+z,-100,-1]) cube([300,200,200]);
}
}
translate([0,0,log(z+a-1)*b+c])
{
difference() {
test();
translate([z+cb1,-10,-1]) cube([300,200,200]);
translate([-300+cb2+z,-100,-1]) cube([300,200,200]);
}
}
}
}
x2();
bump, as it didn't make it to the mailing list.
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On 2016-03-25 02:41, MichaelAtOz wrote:
rav0r wrote
I am trying to modulate an object by not changing it's suface so I
designed a code for it to be sliced and the slices be rearranged after
a
custom equation. The problem I have is that if the object is not flat
and
has holes that need to be preserved, hull does not help much. As a
test,
we place two objects and use the code, the two join. Of course, in a
simplified case, I can cut the object and create a module out of every
cut, but is there a way to automize this for, let's say, 100 modules?
You could perhaps slice the model by means of many intersection()'s with
a thin+wide cube(), stacked on top of each other. This could be in z,y,z
or some other direction. Then reassemble by modulating the slices as
preferred and scale up the slice thickness slightly. Finally union() the
modulated slices.
This should preserve holes and surface shapes. Not sure if it will work
in practice, but you could try.
Carsten Arnholm
Do you mean something like that:
module test2() {
translate([100,0,0])
difference(){
cylinder(r=100,h=10,center=true);
cylinder(r=50,h=12,center=true);
}
}
module slice(x,d) {
intersection(){
children();
translate([x,0,0])
cube([d,1000,1000],center=true);
}
}
function shear_transf(x1,x2,d) = let( r=d/(x2-x1) )
[ [1,0,0,0], [0,1,0,0], [r,0,1,-r*x1], [0,0,0,1] ];
module shear(x1,x2,d) {
multmatrix(shear_transf(x1,x2,d)) children();
}
function f(x,a,b,c) = axx+b*x+c;
module modulate(a,b,c,x1,x2,d){
for(x=[x1:d:x2]) {
translate([0,0,f(x,a,b,c)])
shear(x,x+d,f(x+d,a,b,c)-f(x,a,b,c)) slice(x,d) children();
}
}
modulate(-0.01, 1.5, 10, 0, 200, 2) test2();
translate([0,0,-200]) test2();
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I love it!
Jon
On 3/25/2016 9:38 AM, Ronaldo wrote:
module test2() {
translate([100,0,0])
difference(){
cylinder(r=100,h=10,center=true);
cylinder(r=50,h=12,center=true);
}
}
module slice(x,d) {
intersection(){
children();
translate([x,0,0])
cube([d,1000,1000],center=true);
}
}
function shear_transf(x1,x2,d) = let( r=d/(x2-x1) )
[ [1,0,0,0], [0,1,0,0], [r,0,1,-r*x1], [0,0,0,1] ];
module shear(x1,x2,d) {
multmatrix(shear_transf(x1,x2,d)) children();
}
function f(x,a,b,c) = axx+b*x+c;
module modulate(a,b,c,x1,x2,d){
for(x=[x1:d:x2]) {
translate([0,0,f(x,a,b,c)])
shear(x,x+d,f(x+d,a,b,c)-f(x,a,b,c)) slice(x,d) children();
}
}
modulate(-0.01, 1.5, 10, 0, 200, 2) test2();
translate([0,0,-200]) test2();
@ Ronaldo: Very good example usage of multmatrix. Thx for sharing.
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There was a mistake in the definition of module modulate. The correct one
would be:
module modulate(a,b,c,x1,x2,dx){
for(x=[x1:dx:x2]) {
translate([0,0,f(x+dx/2,a,b,c)])
shear(x,x+dx,f(x+dx,a,b,c)-f(x,a,b,c)) slice(x,dx) children();
}
}
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It did work, I came up with this idea, but it takes days to render. Will try
out the other versions.
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All depends on the complexity of your starting model and the slice width.
If you could share your model we could suggest other alternatives. For
instance, if your model has only vertical throughout holes, you would get a
little time gain doing the differences after modulation. Anyway, please
share your final solution. I am interested in it.
2016-04-04 17:09 GMT-03:00 rav0r coltoiu.matei@gmail.com:
It did work, I came up with this idea, but it takes days to render. Will
try
out the other versions.
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http://lists.openscad.org/mailman/listinfo/discuss_lists.openscad.org
It's a frame with a grid, about 250mm long, 80 mm wide and 5 bars
(longtitudinal) plus 3 cross bars. Openscad is the only application that can
work without issues in regard to "full" stl's, not only facets.
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I would take a very different approach for your problem. I would "modulate"
the center lines of each bar, sweep each with the bar section and union
everything. A sweep module may be found in:
https://github.com/openscad/list-comprehension-demos
https://github.com/openscad/list-comprehension-demos
Take the sweep-path.scad as an example. And ask for help if you need.
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