I suggested this a long time ago On 1/16/2021 1:28 PM, adrianv wrote: > I never remember convexity. I have it set to 10 in all my library functions, > and I've never noticed that this causes any problems or performance issues. > Is there some reason the default couldn't be changed in a future version of > OpenSCAD? Why would anybody need convexity to be low? >

I wonder if once the vbo rendering gets merged the default can be increased. It is something like two orders of magnitude faster drawing OpenSCG scenes. Will that swamp increasing convexity to 10? I have never been able to perceive a higher convexity actually being slower. On Sat, 16 Jan 2021 at 18:42, jon <jon@jonbondy.com> wrote: > I suggested this a long time ago > > On 1/16/2021 1:28 PM, adrianv wrote: > > I never remember convexity. I have it set to 10 in all my library > functions, > > and I've never noticed that this causes any problems or performance > issues. > > Is there some reason the default couldn't be changed in a future version > of > > OpenSCAD? Why would anybody need convexity to be low? > > > > _______________________________________________ > OpenSCAD mailing list > Discuss@lists.openscad.org > http://lists.openscad.org/mailman/listinfo/discuss_lists.openscad.org >

I did a little experimentation using the beveled cylinder as a test case. It appears to display correctly with convexity 2 but wrong with convexity 1. I don't notice any difference in performance with convexity 1 vs convexity 10. With convexity 100 it's still hard to identify a difference. Maybe a very slight degradation? With convexity 1000 the model rotates jerkily and it is hard to control. I increased complexity by making a 10x10 array of beveled cylinders, so 100 objects. In this case a difference is very clear. With convexity 1 it rotates very responsively (with incorrect display). With 2 it is also responsive. With 10 there is a very noticeable lag with jerky rotation---it's hard to rotate the model. With 100 it's unusable. Note that the time to produce the preview is the same regardless of the convexity value. nophead wrote > I wonder if once the vbo rendering gets merged the default can be > increased. It is something like two orders of magnitude faster drawing > OpenSCG scenes. Will that swamp increasing convexity to 10? I have never > been able to perceive a higher convexity actually being slower. > > On Sat, 16 Jan 2021 at 18:42, jon &lt; > jon@ > &gt; wrote: > >> I suggested this a long time ago >> >> On 1/16/2021 1:28 PM, adrianv wrote: >> > I never remember convexity. I have it set to 10 in all my library >> functions, >> > and I've never noticed that this causes any problems or performance >> issues. >> > Is there some reason the default couldn't be changed in a future >> version >> of >> > OpenSCAD? Why would anybody need convexity to be low? >> > >> >> _______________________________________________ >> OpenSCAD mailing list >> > Discuss@.openscad >> http://lists.openscad.org/mailman/listinfo/discuss_lists.openscad.org >> > > _______________________________________________ > OpenSCAD mailing list > Discuss@.openscad > http://lists.openscad.org/mailman/listinfo/discuss_lists.openscad.org -- Sent from: http://forum.openscad.org/

Excellent experiment!   Thank you! I wonder why it gets jerky if the preview time is always the same On 1/16/2021 1:55 PM, adrianv wrote: > I did a little experimentation using the beveled cylinder as a test case. It > appears to display correctly with convexity 2 but wrong with convexity 1. I > don't notice any difference in performance with convexity 1 vs convexity 10. > With convexity 100 it's still hard to identify a difference. Maybe a very > slight degradation? With convexity 1000 the model rotates jerkily and it is > hard to control. > > I increased complexity by making a 10x10 array of beveled cylinders, so 100 > objects. In this case a difference is very clear. With convexity 1 it > rotates very responsively (with incorrect display). With 2 it is also > responsive. With 10 there is a very noticeable lag with jerky > rotation---it's hard to rotate the model. With 100 it's unusable. > > Note that the time to produce the preview is the same regardless of the > convexity value. >

Presumably it has to draw more pixels. On Sat, 16 Jan 2021 at 18:59, jon <jon@jonbondy.com> wrote: > Excellent experiment! Thank you! > > I wonder why it gets jerky if the preview time is always the same > > On 1/16/2021 1:55 PM, adrianv wrote: > > I did a little experimentation using the beveled cylinder as a test > case. It > > appears to display correctly with convexity 2 but wrong with convexity > 1. I > > don't notice any difference in performance with convexity 1 vs convexity > 10. > > With convexity 100 it's still hard to identify a difference. Maybe a > very > > slight degradation? With convexity 1000 the model rotates jerkily and > it is > > hard to control. > > > > I increased complexity by making a 10x10 array of beveled cylinders, so > 100 > > objects. In this case a difference is very clear. With convexity 1 it > > rotates very responsively (with incorrect display). With 2 it is also > > responsive. With 10 there is a very noticeable lag with jerky > > rotation---it's hard to rotate the model. With 100 it's unusable. > > > > Note that the time to produce the preview is the same regardless of the > > convexity value. > > > > _______________________________________________ > OpenSCAD mailing list > Discuss@lists.openscad.org > http://lists.openscad.org/mailman/listinfo/discuss_lists.openscad.org >

Why would higher convexity cause it to draw more pixels? Where would these extra pixels come from? nophead wrote > Presumably it has to draw more pixels. > > On Sat, 16 Jan 2021 at 18:59, jon &lt; > jon@ > &gt; wrote: > >> Excellent experiment! Thank you! >> >> I wonder why it gets jerky if the preview time is always the same >> >> On 1/16/2021 1:55 PM, adrianv wrote: >> > I did a little experimentation using the beveled cylinder as a test >> case. It >> > appears to display correctly with convexity 2 but wrong with convexity >> 1. I >> > don't notice any difference in performance with convexity 1 vs >> convexity >> 10. >> > With convexity 100 it's still hard to identify a difference. Maybe a >> very >> > slight degradation? With convexity 1000 the model rotates jerkily and >> it is >> > hard to control. >> > >> > I increased complexity by making a 10x10 array of beveled cylinders, so >> 100 >> > objects. In this case a difference is very clear. With convexity 1 it >> > rotates very responsively (with incorrect display). With 2 it is also >> > responsive. With 10 there is a very noticeable lag with jerky >> > rotation---it's hard to rotate the model. With 100 it's unusable. >> > >> > Note that the time to produce the preview is the same regardless of the >> > convexity value. >> > >> >> _______________________________________________ >> OpenSCAD mailing list >> > Discuss@.openscad >> http://lists.openscad.org/mailman/listinfo/discuss_lists.openscad.org >> > > _______________________________________________ > OpenSCAD mailing list > Discuss@.openscad > http://lists.openscad.org/mailman/listinfo/discuss_lists.openscad.org -- Sent from: http://forum.openscad.org/

No idea but with a lower convexity some bits are missing, so I assume filling them in involves more drawing and that is why it is slower. On Sat, 16 Jan 2021 at 20:25, adrianv <avm4@cornell.edu> wrote: > Why would higher convexity cause it to draw more pixels? Where would these > extra pixels come from? > > > nophead wrote > > Presumably it has to draw more pixels. > > > > On Sat, 16 Jan 2021 at 18:59, jon &lt; > > > jon@ > > > &gt; wrote: > > > >> Excellent experiment! Thank you! > >> > >> I wonder why it gets jerky if the preview time is always the same > >> > >> On 1/16/2021 1:55 PM, adrianv wrote: > >> > I did a little experimentation using the beveled cylinder as a test > >> case. It > >> > appears to display correctly with convexity 2 but wrong with convexity > >> 1. I > >> > don't notice any difference in performance with convexity 1 vs > >> convexity > >> 10. > >> > With convexity 100 it's still hard to identify a difference. Maybe a > >> very > >> > slight degradation? With convexity 1000 the model rotates jerkily and > >> it is > >> > hard to control. > >> > > >> > I increased complexity by making a 10x10 array of beveled cylinders, > so > >> 100 > >> > objects. In this case a difference is very clear. With convexity 1 > it > >> > rotates very responsively (with incorrect display). With 2 it is also > >> > responsive. With 10 there is a very noticeable lag with jerky > >> > rotation---it's hard to rotate the model. With 100 it's unusable. > >> > > >> > Note that the time to produce the preview is the same regardless of > the > >> > convexity value. > >> > > >> > >> _______________________________________________ > >> OpenSCAD mailing list > >> > > > Discuss@.openscad > > >> http://lists.openscad.org/mailman/listinfo/discuss_lists.openscad.org > >> > > > > _______________________________________________ > > OpenSCAD mailing list > > > Discuss@.openscad > > > http://lists.openscad.org/mailman/listinfo/discuss_lists.openscad.org > > > > > > -- > Sent from: http://forum.openscad.org/ > > _______________________________________________ > OpenSCAD mailing list > Discuss@lists.openscad.org > http://lists.openscad.org/mailman/listinfo/discuss_lists.openscad.org >

With lower convexity some bits are missing...but the missing bits aren't "pixels" they are larger regions. I don't think any conclusion can be drawn about how many pixels are drawn. It seems more like differing computations are done to determine what to draw, and with lower convexity the result is that the wrong stuff is drawn. nophead wrote > No idea but with a lower convexity some bits are missing, so I assume > filling them in involves more drawing and that is why it is slower. > > On Sat, 16 Jan 2021 at 20:25, adrianv &lt; > avm4@ > &gt; wrote: > >> Why would higher convexity cause it to draw more pixels? Where would >> these >> extra pixels come from? >> >> >> nophead wrote >> > Presumably it has to draw more pixels. >> > >> > On Sat, 16 Jan 2021 at 18:59, jon &lt; >> >> > jon@ >> >> > &gt; wrote: >> > >> >> Excellent experiment! Thank you! >> >> >> >> I wonder why it gets jerky if the preview time is always the same >> >> >> >> On 1/16/2021 1:55 PM, adrianv wrote: >> >> > I did a little experimentation using the beveled cylinder as a test >> >> case. It >> >> > appears to display correctly with convexity 2 but wrong with >> convexity >> >> 1. I >> >> > don't notice any difference in performance with convexity 1 vs >> >> convexity >> >> 10. >> >> > With convexity 100 it's still hard to identify a difference. Maybe >> a >> >> very >> >> > slight degradation? With convexity 1000 the model rotates jerkily >> and >> >> it is >> >> > hard to control. >> >> > >> >> > I increased complexity by making a 10x10 array of beveled cylinders, >> so >> >> 100 >> >> > objects. In this case a difference is very clear. With convexity 1 >> it >> >> > rotates very responsively (with incorrect display). With 2 it is >> also >> >> > responsive. With 10 there is a very noticeable lag with jerky >> >> > rotation---it's hard to rotate the model. With 100 it's unusable. >> >> > >> >> > Note that the time to produce the preview is the same regardless of >> the >> >> > convexity value. >> >> > >> >> >> >> _______________________________________________ >> >> OpenSCAD mailing list >> >> >> >> > Discuss@.openscad >> >> >> http://lists.openscad.org/mailman/listinfo/discuss_lists.openscad.org >> >> >> > >> > _______________________________________________ >> > OpenSCAD mailing list >> >> > Discuss@.openscad >> >> > http://lists.openscad.org/mailman/listinfo/discuss_lists.openscad.org >> >> >> >> >> >> -- >> Sent from: http://forum.openscad.org/ >> >> _______________________________________________ >> OpenSCAD mailing list >> > Discuss@.openscad >> http://lists.openscad.org/mailman/listinfo/discuss_lists.openscad.org >> > > _______________________________________________ > OpenSCAD mailing list > Discuss@.openscad > http://lists.openscad.org/mailman/listinfo/discuss_lists.openscad.org -- Sent from: http://forum.openscad.org/

Hi, Thanks to all for the many answers. I'm with version 2019.05 and quite new to OpenSCAD, but as a (retired, if one ever retires from that) programmer, I enjoy the code-like approach of this design tool. I didn't know about the F5/F6 commands, I always use the Render button, that corresponds to F6. My friend printed my STL and notes a small imperfection at the base of the bevel (photo) - perhaps starting the cube left of the cylinder would help, as was suggested. It was easier to start right at the cylinder edge since I readily know what the intercept height should be without further computation. Mirrycle.jpg <http://forum.openscad.org/file/t3095/Mirrycle.jpg> -- Sent from: http://forum.openscad.org/

Looks to me like the slicer that converted the STL into gcode for the 3d printer did something weird with the sharp corner at the bottom edge of the hole. That "missing" part is not missing in the OpenSCAD model. Presumably the solution to this is to round off the edge of the hole, which is kind of tricky to do. lleblanc wrote > Hi, > > Thanks to all for the many answers. > > I'm with version 2019.05 and quite new to OpenSCAD, but as a (retired, if > one ever retires from that) programmer, I enjoy the code-like approach of > this design tool. > > I didn't know about the F5/F6 commands, I always use the Render button, > that > corresponds to F6. > > My friend printed my STL and notes a small imperfection at the base of the > bevel (photo) - perhaps starting the cube left of the cylinder would > help, > as was suggested. It was easier to start right at the cylinder edge since > I > readily know what the intercept height should be without further > computation. > > Mirrycle.jpg &lt;http://forum.openscad.org/file/t3095/Mirrycle.jpg&gt; > > > > -- > Sent from: http://forum.openscad.org/ > > _______________________________________________ > OpenSCAD mailing list > Discuss@.openscad > http://lists.openscad.org/mailman/listinfo/discuss_lists.openscad.org -- Sent from: http://forum.openscad.org/