Empathy List Archives

NH

nop head

Thu, Jun 13, 2019 3:51 PM

What is the correct convexity for a simple tube?

I ask because I used three and it works on two of my PC but on an old
laptop with Intel graphics it needs to be four.

What is the correct convexity for a simple tube? I ask because I used three and it works on two of my PC but on an old laptop with Intel graphics it needs to be four.

RD

Revar Desmera

Thu, Jun 13, 2019 8:44 PM

A line could possibly pass through a maximum of four walls of a tube, so convexity should be 4.

Revar

On Jun 13, 2019, at 8:51 AM, nop head nop.head@gmail.com wrote:

What is the correct convexity for a simple tube?

I ask because I used three and it works on two of my PC but on an old laptop with Intel graphics it needs to be four.

OpenSCAD mailing list
Discuss@lists.openscad.org
http://lists.openscad.org/mailman/listinfo/discuss_lists.openscad.org

A line could possibly pass through a maximum of four walls of a tube, so convexity should be 4. - Revar > On Jun 13, 2019, at 8:51 AM, nop head <nop.head@gmail.com> wrote: > > What is the correct convexity for a simple tube? > > I ask because I used three and it works on two of my PC but on an old laptop with Intel graphics it needs to be four. > _______________________________________________ > OpenSCAD mailing list > Discuss@lists.openscad.org > http://lists.openscad.org/mailman/listinfo/discuss_lists.openscad.org

NH

nop head

Thu, Jun 13, 2019 8:49 PM

Not sure because convexity defaults to 1 and that is sufficient for a
cylinder.

On Thu, 13 Jun 2019, 21:44 Revar Desmera, revarbat@gmail.com wrote:

A line could possibly pass through a maximum of four walls of a tube, so
convexity should be 4.

Revar

On Jun 13, 2019, at 8:51 AM, nop head nop.head@gmail.com wrote:

What is the correct convexity for a simple tube?

I ask because I used three and it works on two of my PC but on an old

laptop with Intel graphics it needs to be four.

OpenSCAD mailing list
Discuss@lists.openscad.org
http://lists.openscad.org/mailman/listinfo/discuss_lists.openscad.org

Not sure because convexity defaults to 1 and that is sufficient for a cylinder. On Thu, 13 Jun 2019, 21:44 Revar Desmera, <revarbat@gmail.com> wrote: > A line could possibly pass through a maximum of four walls of a tube, so > convexity should be 4. > > - Revar > > > > On Jun 13, 2019, at 8:51 AM, nop head <nop.head@gmail.com> wrote: > > > > What is the correct convexity for a simple tube? > > > > I ask because I used three and it works on two of my PC but on an old > laptop with Intel graphics it needs to be four. > > _______________________________________________ > > OpenSCAD mailing list > > Discuss@lists.openscad.org > > http://lists.openscad.org/mailman/listinfo/discuss_lists.openscad.org > > _______________________________________________ > OpenSCAD mailing list > Discuss@lists.openscad.org > http://lists.openscad.org/mailman/listinfo/discuss_lists.openscad.org >

JB

Jordan Brown

Thu, Jun 13, 2019 8:58 PM

Is there a significant penalty to setting it to a large number, like
10? That's what I usually do when I notice a rendering problem, and I
haven't noticed any performance problems, but maybe I've been working
with simple cases.

Is there a significant penalty to setting it to a large number, like 10? That's what I usually do when I notice a rendering problem, and I haven't noticed any performance problems, but maybe I've been working with simple cases.

NH

nop head

Thu, Jun 13, 2019 9:40 PM

I don't know. I will do some experiments tomorrow. Odd it needs to be one
more on Intel graphics.

On Thu, 13 Jun 2019, 21:58 Jordan Brown, openscad@jordan.maileater.net
wrote:

Is there a significant penalty to setting it to a large number, like 10?
That's what I usually do when I notice a rendering problem, and I haven't
noticed any performance problems, but maybe I've been working with simple
cases.

I don't know. I will do some experiments tomorrow. Odd it needs to be one more on Intel graphics. On Thu, 13 Jun 2019, 21:58 Jordan Brown, <openscad@jordan.maileater.net> wrote: > Is there a significant penalty to setting it to a large number, like 10? > That's what I usually do when I notice a rendering problem, and I haven't > noticed any performance problems, but maybe I've been working with simple > cases. > >

A

adrianv

Thu, Jun 13, 2019 9:55 PM

I hadn't really paid attention to convexity and hadn't realized that there
was a solution to my models having sections that disappear as I rotate them
in preview. I did a test run and found that setting convexity to 10 had no
effect on my run time and it increased the geometry cache by about 10%.
Basically, no obvious penalty.

--
Sent from: http://forum.openscad.org/

I hadn't really paid attention to convexity and hadn't realized that there was a solution to my models having sections that disappear as I rotate them in preview. I did a test run and found that setting convexity to 10 had no effect on my run time and it increased the geometry cache by about 10%. Basically, no obvious penalty. -- Sent from: http://forum.openscad.org/

T

Troberg

Fri, Jun 14, 2019 6:41 AM

RevarBat wrote

A line could possibly pass through a maximum of four walls of a tube, so
convexity should be 4.

I can't see how a straight line could pass through more than two walls. How
would it pass through four???

--
Sent from: http://forum.openscad.org/

RevarBat wrote > A line could possibly pass through a maximum of four walls of a tube, so > convexity should be 4. I can't see how a straight line could pass through more than two walls. How would it pass through four??? -- Sent from: http://forum.openscad.org/

L

lar3ry@sasktel.net

Fri, Jun 14, 2019 6:57 AM

Incredible. I was sort of accepting the idea that previewing objects with parts cut out of them
was going to just give me a mess because that's the way Preview is. Thank You! Now I can
do this sort of thing a WHOLE lot easier.

On 13 Jun 2019 at 14:55, adrianv wrote:

I hadn't really paid attention to convexity and hadn't realized that there
was a solution to my models having sections that disappear as I rotate them
in preview. I did a test run and found that setting convexity to 10 had no
effect on my run time and it increased the geometry cache by about 10%.
Basically, no obvious penalty.

Sent from: http://forum.openscad.org/

OpenSCAD mailing list
Discuss@lists.openscad.org
http://lists.openscad.org/mailman/listinfo/discuss_lists.openscad.org

--
Magic trumps science for most people,
and wishful thinking drives a lot of decision-making.
- Joe Haldeman

Incredible. I was sort of accepting the idea that previewing objects with parts cut out of them was going to just give me a mess because that's the way Preview is. Thank You! Now I can do this sort of thing a WHOLE lot easier. On 13 Jun 2019 at 14:55, adrianv wrote: > I hadn't really paid attention to convexity and hadn't realized that there > was a solution to my models having sections that disappear as I rotate them > in preview. I did a test run and found that setting convexity to 10 had no > effect on my run time and it increased the geometry cache by about 10%. > Basically, no obvious penalty. > -- > Sent from: http://forum.openscad.org/ > > _______________________________________________ > OpenSCAD mailing list > Discuss@lists.openscad.org > http://lists.openscad.org/mailman/listinfo/discuss_lists.openscad.org > -- Magic trumps science for most people, and wishful thinking drives a lot of decision-making. - Joe Haldeman

NH

nop head

Fri, Jun 14, 2019 7:00 AM

This is a distilled version of the code I was having a problem with:

for(c = [1:4])
translate([c * 40, 0])
difference () {
linear_extrude(height = 50, center = true, convexity = c)
difference() {
circle(5);
circle(4);
}

        translate([0, 0, 20])
            cube(20, center = true);

    }

This is how it looks on my old laptop:

[image: image.png]

And this is how it looks on my normal desktop machine, which also has Intel
graphics but it never gives me problems. Goldfeather makes no difference.

[image: image.png]

It seems 2 is sufficient on this machine but the old machine needs 4.

The manual says "Integer number of "inward" curves, ie. expected path
crossings of an arbitrary line through the polygon." in one place and "The
convexity parameter specifies the maximum number of front sides (back
sides) a ray intersecting the object might penetrate" in another.

Neither statement is clear to me. What does " front sides (back sides)"
mean?

If it is simply the maximum number of edges a line can pass through then I
agree it should be 4 for a tube.

On Thu, 13 Jun 2019 at 22:56, adrianv avm4@cornell.edu wrote:

I hadn't really paid attention to convexity and hadn't realized that there
was a solution to my models having sections that disappear as I rotate them
in preview. I did a test run and found that setting convexity to 10 had no
effect on my run time and it increased the geometry cache by about 10%.
Basically, no obvious penalty.

--
Sent from: http://forum.openscad.org/

OpenSCAD mailing list
Discuss@lists.openscad.org
http://lists.openscad.org/mailman/listinfo/discuss_lists.openscad.org

This is a distilled version of the code I was having a problem with: for(c = [1:4]) translate([c * 40, 0]) difference () { linear_extrude(height = 50, center = true, convexity = c) difference() { circle(5); circle(4); } translate([0, 0, 20]) cube(20, center = true); } This is how it looks on my old laptop: [image: image.png] And this is how it looks on my normal desktop machine, which also has Intel graphics but it never gives me problems. Goldfeather makes no difference. [image: image.png] It seems 2 is sufficient on this machine but the old machine needs 4. The manual says "Integer number of "inward" curves, ie. expected path crossings of an arbitrary line through the polygon." in one place and "The convexity parameter specifies the maximum number of front sides (back sides) a ray intersecting the object might penetrate" in another. Neither statement is clear to me. What does " front sides (back sides)" mean? If it is simply the maximum number of edges a line can pass through then I agree it should be 4 for a tube. On Thu, 13 Jun 2019 at 22:56, adrianv <avm4@cornell.edu> wrote: > I hadn't really paid attention to convexity and hadn't realized that there > was a solution to my models having sections that disappear as I rotate them > in preview. I did a test run and found that setting convexity to 10 had no > effect on my run time and it increased the geometry cache by about 10%. > Basically, no obvious penalty. > > > > > -- > Sent from: http://forum.openscad.org/ > > _______________________________________________ > OpenSCAD mailing list > Discuss@lists.openscad.org > http://lists.openscad.org/mailman/listinfo/discuss_lists.openscad.org >

NH

nop head

Fri, Jun 14, 2019 7:04 AM

However if that was the case why doesn't it default to 2, because for a
convex shape 2 in the minimum. And why isn't it called concavity as it is
concave shapes that go wrong?

On Fri, 14 Jun 2019 at 08:00, nop head nop.head@gmail.com wrote:

This is a distilled version of the code I was having a problem with:

for(c = [1:4])
translate([c * 40, 0])
difference () {
linear_extrude(height = 50, center = true, convexity = c)
difference() {
circle(5);
circle(4);
}

         translate([0, 0, 20])
             cube(20, center = true);

     }

This is how it looks on my old laptop:

[image: image.png]

And this is how it looks on my normal desktop machine, which also has
Intel graphics but it never gives me problems. Goldfeather makes no
difference.

[image: image.png]

It seems 2 is sufficient on this machine but the old machine needs 4.

The manual says "Integer number of "inward" curves, ie. expected path
crossings of an arbitrary line through the polygon." in one place and "The
convexity parameter specifies the maximum number of front sides (back
sides) a ray intersecting the object might penetrate" in another.

Neither statement is clear to me. What does " front sides (back sides)"
mean?

If it is simply the maximum number of edges a line can pass through then I
agree it should be 4 for a tube.

On Thu, 13 Jun 2019 at 22:56, adrianv avm4@cornell.edu wrote:

I hadn't really paid attention to convexity and hadn't realized that there
was a solution to my models having sections that disappear as I rotate
them
in preview. I did a test run and found that setting convexity to 10 had
no
effect on my run time and it increased the geometry cache by about 10%.
Basically, no obvious penalty.

--
Sent from: http://forum.openscad.org/

OpenSCAD mailing list
Discuss@lists.openscad.org
http://lists.openscad.org/mailman/listinfo/discuss_lists.openscad.org

However if that was the case why doesn't it default to 2, because for a convex shape 2 in the minimum. And why isn't it called concavity as it is concave shapes that go wrong? On Fri, 14 Jun 2019 at 08:00, nop head <nop.head@gmail.com> wrote: > This is a distilled version of the code I was having a problem with: > > for(c = [1:4]) > translate([c * 40, 0]) > difference () { > linear_extrude(height = 50, center = true, convexity = c) > difference() { > circle(5); > circle(4); > } > > translate([0, 0, 20]) > cube(20, center = true); > > } > > This is how it looks on my old laptop: > > > [image: image.png] > > And this is how it looks on my normal desktop machine, which also has > Intel graphics but it never gives me problems. Goldfeather makes no > difference. > > [image: image.png] > > It seems 2 is sufficient on this machine but the old machine needs 4. > > The manual says "Integer number of "inward" curves, ie. expected path > crossings of an arbitrary line through the polygon." in one place and "The > convexity parameter specifies the maximum number of front sides (back > sides) a ray intersecting the object might penetrate" in another. > > Neither statement is clear to me. What does " front sides (back sides)" > mean? > > If it is simply the maximum number of edges a line can pass through then I > agree it should be 4 for a tube. > > On Thu, 13 Jun 2019 at 22:56, adrianv <avm4@cornell.edu> wrote: > >> I hadn't really paid attention to convexity and hadn't realized that there >> was a solution to my models having sections that disappear as I rotate >> them >> in preview. I did a test run and found that setting convexity to 10 had >> no >> effect on my run time and it increased the geometry cache by about 10%. >> Basically, no obvious penalty. >> >> >> >> >> -- >> Sent from: http://forum.openscad.org/ >> >> _______________________________________________ >> OpenSCAD mailing list >> Discuss@lists.openscad.org >> http://lists.openscad.org/mailman/listinfo/discuss_lists.openscad.org >> >

discuss@lists.openscad.org

Convexity