use <dotSCAD/src/loft.scad>;

include <sprabhakar2006/dependencies.scad>

stages =200;

stage_height = 1.25;

rad = 50;

f1 = 25;

f2 = 25;

phase1 = 0;

phase2 = 180;

height_depth=5;

depth1 = 20;

depth2 = 20;

thickness = 2;

bottom_thickness = 3;

myslices = 5;

angle_step=0.1;

// generate outer points

points_base = [for (i = [0:1:stages]) let(f = pow(sin(i/stages * 120),2) * 7 + 1, var = 1 , a=((sin((i/stages*360*f)%360) * 0.5 + 0.5) * (var * height_depth))) [for(j = [0:angle_step:360-angle_step]) [sin(j) * (rad+a+(pauw(sin(j *f1+phase1),0.5)*0.5+0.5)*depth1*i/stages+(pauw(sin(j *f2+phase2),0.5)*0.5+0.5)*depth2*(1-i/stages)), cos(j) *(rad+a+(pauw(sin(j *f1+phase1),0.5)*0.5+0.5)*depth1*i/stages+(pauw(sin(j *f2+phase2),0.5)*0.5+0.5)*depth2*(1-i/stages))]]];

// generate inner points with offset from outer points for hollowing out

points_base_e = [for (i = [0:1:stages]) f_offset(points_base[i],-thickness)];

// points - outside

points = [for (i = [0:1:stages-1]) [for (j = [0:1:(len(points_base[i])-1)]) concat(points_base[i][j][0],points_base[i][j][1],i * stage_height)]];

// points - inside

points_e = [for (i = [0:1:stages]) [for (j = [0:1:(len(points_base_e[i])-1)]) concat(points_base_e[i][j][0],points_base_e[i][j][1],i * stage_height)]];

//echo("points: ", points);

// separate points in packs for stepped extrusion

steps = [for (i = [0:1:stages-1]) points[i]];

steps_e = [for (i = [0:1:stages]) points_e[i]];

// extrusion with dotSCAD's loft function

difference() {

loft(steps,slices = myslices);

difference() {

	loft(steps_e,slices = myslices);

	cylinder(h = bottom_thickness, r = rad \* 2 + 20, center=true);

}

}

//======================== FUNCTIONS

function elbow(i,a,b,c) = lookup(i, [[0,a],[0.5,b],[1,c]]);

function elbow2(i,a,b,c,d) = lookup(i, [[0,a],[0.33333,b],[0.66666,c],[1,d]]);

function pauw(x,p) = sign(x) * pow(abs(x),p);

Sanjeev, here’s the full code using your lib:

use <dotSCAD/src/loft.scad>;

include <sprabhakar2006/dependencies.scad>

stages =200;

stage_height = 1.25;

rad = 50;

f1 = 25;

f2 = 25;

phase1 = 0;

phase2 = 180;

height_depth=5;

depth1 = 20;

depth2 = 20;

thickness = 2;

bottom_thickness = 3;

myslices = 5;

angle_step=0.1;

// generate outer points

points_base = [for (i = [0:1:stages]) let(f = pow(sin(i/stages * 120),2) *
7 + 1, var = 1 , a=((sin((i/stages360f)%360) * 0.5 + 0.5) * (var *
height_depth))) [for(j = [0:angle_step:360-angle_step]) [sin(j) *
(rad+a+(pauw(sin(j *f1+phase1),0.5)*0.5+0.5)depth1i/stages+(pauw(sin(j
*f2+phase2),0.5)*0.5+0.5)depth2(1-i/stages)), cos(j) *(rad+a+(pauw(sin(j
*f1+phase1),0.5)*0.5+0.5)depth1i/stages+(pauw(sin(j
*f2+phase2),0.5)*0.5+0.5)depth2(1-i/stages))]]];

// generate inner points with offset from outer points for hollowing out

points_base_e = [for (i = [0:1:stages])
f_offset(points_base[i],-thickness)];

// points - outside

points = [for (i = [0:1:stages-1]) [for (j =
[0:1:(len(points_base[i])-1)])
concat(points_base[i][j][0],points_base[i][j][1],i * stage_height)]];

// points - inside

points_e = [for (i = [0:1:stages]) [for (j =
[0:1:(len(points_base_e[i])-1)])
concat(points_base_e[i][j][0],points_base_e[i][j][1],i * stage_height)]];

//echo("points: ", points);

// separate points in packs for stepped extrusion

steps = [for (i = [0:1:stages-1]) points[i]];

steps_e = [for (i = [0:1:stages]) points_e[i]];

// extrusion with dotSCAD's loft function

difference() {

loft(steps,slices = myslices);

difference() {

loft(steps_e,slices = myslices);

cylinder(h = bottom_thickness, r = rad * 2 + 20, center=true);

}

}

//======================== FUNCTIONS

function elbow(i,a,b,c) = lookup(i, [[0,a],[0.5,b],[1,c]]);

function elbow2(i,a,b,c,d) = lookup(i,
[[0,a],[0.33333,b],[0.66666,c],[1,d]]);

function pauw(x,p) = sign(x) * pow(abs(x),p);

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This model has
so much symmetry that it really seems like it ought to be possible to
construct one "unit" and then replicate it around the circle, but
someone else can do that.  :)

Thanks Adrian
18 minutes you got with 0.1 step angle?
With 1 degree I got the render in around 4 minutes.
I wonder why there is so much of a difference

On Tue, 12 Apr 2022, 07:08 Adrian Mariano, avm4@cornell.edu wrote:

Sanjeev's version takes 18 minutes to preview for me and 20 minutes to
render with a cube.  I did notice some oddities, though.  The first
image offset1.png shows his offset result in red, with a thickness of
2 next to a 2x2 green square.  It looks like the offset is 1 or less
instead of 2.  Also it's not a very even offset.  The use of offset 1
instead of 2 could potentially make the problem easier to solve.

In BOSL2, offset() can change the number of points: if it adds a
radius curve it increases the point count, and if part of the curve
collapses to a point, the number of points decreases.  In the example
posted, with the offset of 2, the number of points decreases, so the
lists do not have matching point count.  I don't know what loft() does
with that since I use BOSL2 instead, but it is unlikely to be good.
The BOSL2 skin module can actually handle this case---it will line up
mismatched data if you tell it to. But the algorithm is slow (cubic)
so it won't work with such huge inputs as the ones here.

When the mismatched data isn't lined up correctly, I think you get an
invalid VNF, at least in this case.  Certainly both dotSCAD loft() and
BOSL2 skin() produce pretty bad looking, artifact covered results.
Most likely there is some self intersecting patch or other issue as a
result.  (These aren't obvious because they are on the inside of the
model because you have offset inward.)

If you decrease the offset to 1, then it becomes less likely that the
offset collapses to a point.  Certainly for a small enough offset this
will happen.  In that case you can set check_valid=false in BOSL2
offset() and get a result faster, and the points line up.  I did this
with my code and got a preview in 9 minutes using the same settings
Sanjeev used, except offset of 1.  However, the resulting model when
unioned with a cube, failed, showing that somewhere, the offset had a
problem.

How then to solve the problem?  I have seen it happen other times that
someone wants to use offset in a way where the points can be lined up,
so I have written a new option for the BOSL2 offset, so you can write
same_length=true and get a result with the same length.  When several
points collapse in the offset the output repeats the corner point as
many times as necessary.  This output is correctly handled by the
BOSL2 skin().  I have no idea what dotSCAD loft() would do with it.
Using this I have gotten a model that previewed in about an hour with
the angle step set to 0.5.  So here's my code.  You'll need to get
the BOSL2 update that was just posted for this to work.  Note that I
think angle step 1 is a bit too large, but 0.1 is probably
unnecessarily small.  The offset() checks are quadratic, so going from
1 to 0.1 you should expect 100x the run time.  So make sure you have
this as big as you can tolerate.  You can probably also save time with
adaptive spacing of the stages, as some of the model has stages where
there is very little vertical change.  This implementation creates
your object as a single polyhedron without any differences, but I
require the bottom to be a multiple of the number of stages.  (We also
avoid computing the unused offsets for the bottom.)    This model has
so much symmetry that it really seems like it ought to be possible to
construct one "unit" and then replicate it around the circle, but
someone else can do that.  :)

include <BOSL2/std.scad>

stages =200;
stage_height = 1.25;
rad = 50;
f1 = 25;
f2 = 25;
phase1 = 0;
phase2 = 180;
height_depth=5;
depth1 = 20;
depth2 = 20;
thickness = 2;
bottom_stages = 2; //bottom_thickness = 3;
myslices = 0;

// angle_step=0.1;
angle_step=1;

// generate outer points

points_base =
  [for (i = [0:1:stages-1])
    let(f = pow(sin(i/stages * 120),2) * 7 + 1,
        var = 1 ,
        a=((sin((i/stages*360*f)%360) * 0.5 + 0.5) * (var * height_depth))
    )
    [
     for(j = [0:angle_step:360-angle_step])
        let(R=(rad+a+(pauw(sin(j *f1+phase1),0.5)*0.5+0.5)*depth1*i/stages
                        +(pauw(sin(j

*f2+phase2),0.5)0.5+0.5)depth2(1-i/stages)))
R[sin(j),cos(j)]
]
];

points_base_e = [for (i = [bottom_stages:1:stages-1])

offset(points_base[i],delta=-thickness,
closed=true,
quality=1,same_length=false)];

// points - outside
points = [for (i = [0:1:stages-1]) path3d(points_base[i],i*stage_height)];

// points - inside
points_e = [for (i = idx(points_base_e))

path3d(points_base_e[i],(i+bottom_stages)*stage_height)];

skin(concat(points, reverse(points_e)),slices=myslices);  // up

the outside, then down the inside

function pauw(x,p) = sign(x) * pow(abs(x),p);

The attached images show the offset computed by Sanjeev's code (with
the fingers down) next to a 2x2 square.  Offset looks irregular and is
not 2 units wide.  Second picture with fingers up is BOSL2 code with
offset of 2 next to the 2x2 square.  Final picture with fingers
pointing left is BOSL2 offset of 1.

Final picture shows the model computed using the above code with the
angle spacing set to 0.5.
On Mon, Apr 11, 2022 at 1:16 PM Sanjeev Prabhakar
sprabhakar2006@gmail.com wrote:

please try this code:

it took 3 minutes 43 sec to render in my system

include <sprabhakar2006/

dependencies.scad>

stages =200;

stage_height = 1.25;

rad = 50;

f1 = 25;

f2 = 25;

phase1 = 0;

phase2 = 180;

height_depth=5;

depth1 = 20;

depth2 = 20;

thickness = 2;

bottom_thickness = 3;

myslices = 5;

angle_step=1;

// generate outer points

points_base = [for (i = [0:1:stages]) let(f = pow(sin(i/stages * 120),2) * 7 + 1, var = 1 , a=((sin((i/stages360f)%360) * 0.5 + 0.5) * (var * height_depth))) [for(j = [0:angle_step:360-angle_step]) [sin(j) * (rad+a+(pauw(sin(j *f1+phase1),0.5)*0.5+0.5)depth1i/stages+(pauw(sin(j *f2+phase2),0.5)*0.5+0.5)depth2(1-i/stages)), cos(j) *(rad+a+(pauw(sin(j *f1+phase1),0.5)*0.5+0.5)depth1i/stages+(pauw(sin(j *f2+phase2),0.5)0.5+0.5)depth2(1-i/stages)),istage_height]]];

points_base1=[for(p=points_base)offst(c3t2(p),-thickness)];
points_base_e=[for(i=[0:len(points_base1)-1])[for(p=points_base1[i])[p.x,p.y,i*stage_height]]];
//echo(points_base_e);
swp_prism_h(points_base,points_base_e);
//swp(points_base_e);

step angle of 0.1 seems to be an overkill so increased  to 1

On Mon, 11 Apr 2022 at 15:15, roald.baudoux@brutele.be wrote:

Sanjeev, here’s the full code using your lib:

use <dotSCAD/src/loft.scad>;

include <sprabhakar2006/dependencies.scad>

stages =200;

stage_height = 1.25;

rad = 50;

f1 = 25;

f2 = 25;

phase1 = 0;

phase2 = 180;

height_depth=5;

depth1 = 20;

depth2 = 20;

thickness = 2;

bottom_thickness = 3;

myslices = 5;

angle_step=0.1;

// generate outer points

points_base = [for (i = [0:1:stages]) let(f = pow(sin(i/stages * 120),2) * 7 + 1, var = 1 , a=((sin((i/stages360f)%360) * 0.5 + 0.5) * (var * height_depth))) [for(j = [0:angle_step:360-angle_step]) [sin(j) * (rad+a+(pauw(sin(j *f1+phase1),0.5)*0.5+0.5)depth1i/stages+(pauw(sin(j *f2+phase2),0.5)*0.5+0.5)depth2(1-i/stages)), cos(j) *(rad+a+(pauw(sin(j *f1+phase1),0.5)*0.5+0.5)depth1i/stages+(pauw(sin(j *f2+phase2),0.5)*0.5+0.5)depth2(1-i/stages))]]];

// generate inner points with offset from outer points for hollowing out

points_base_e = [for (i = [0:1:stages]) f_offset(points_base[i],-thickness)];

// points - outside

points = [for (i = [0:1:stages-1]) [for (j = [0:1:(len(points_base[i])-1)]) concat(points_base[i][j][0],points_base[i][j][1],i * stage_height)]];

// points - inside

points_e = [for (i = [0:1:stages]) [for (j = [0:1:(len(points_base_e[i])-1)]) concat(points_base_e[i][j][0],points_base_e[i][j][1],i * stage_height)]];

//echo("points: ", points);

// separate points in packs for stepped extrusion

steps = [for (i = [0:1:stages-1]) points[i]];

steps_e = [for (i = [0:1:stages]) points_e[i]];

// extrusion with dotSCAD's loft function

difference() {

loft(steps,slices = myslices);

difference() {

loft(steps_e,slices = myslices);

cylinder(h = bottom_thickness, r = rad * 2 + 20, center=true);

}

}

//======================== FUNCTIONS

function elbow(i,a,b,c) = lookup(i, [[0,a],[0.5,b],[1,c]]);

function elbow2(i,a,b,c,d) = lookup(i, [[0,a],[0.33333,b],[0.66666,c],[1,d]]);

function pauw(x,p) = sign(x) * pow(abs(x),p);

---

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In the definition of R two multiplications were missing.

let(R=(rad+a+(pauw(sin(j *f1+phase1),0.5)0.5+0.5)depth1i/stages
+(pauw(sin(jf2+phase2),0.5)0.5+0.5)depth2(1-i/stages)))

should be:

let(R=(rad+a+(pauw(sin(j *f1+phase1),0.5)0.5+0.5)depth1i/stages
+(pauw(sin(jf2+phase2),0.5)*0.5+0.5)*depth2(1-i/stages)))

I suppose there's also something missing in:

R[sin(j),cos(j)]

because it triggers an error message. But what?

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