REAL circles in Sketchup

pilou

arn't they drawn as polygons ?

it's that the magic
To be or not to be

thomthom

Technically, can any CAD software draw circles ?-) Vector programs remember the properties of a circle, but because of our bit-mapped displays, arn't they drawn as polygons ?-)

Yes, but when you zoom in the circle is redrawn to look smooth. And snapping tools snap to the actual circle border, not the faceted one.
But not in Sketchup, you only get faceted circles. No plugin can fix that either. It's a SU core thing.
Closest you get is adding a large number of sides.

Jim

Because circles in SketchUp are not true circles but are regular polygons - 24-gons by default. So even if you wrote a tool that treats the 24-gon as if it were a true circle for calculations, any calculated tangent would practically never lie on any of the actual geometry.

I guess such a tool might be able to redraw the 24-gon and either add segments, or re-orient it so a vertex occurs at the tangent point. Or maybe just adds a Guide Point at the tangent, and lets the user figure it out.

machining

I have issues trying to get a circle with DXF export. Maybe there is a plugin for that??

bigstick

You can't get true circles because SketchUp is a 3d polygonal modeler, not a 3d NURBS one. The purpose of drawing circles is to extrude them (otherwise it would be a 2d package) and when they are extruded, they create a series of polygonal faces. Only NURBS modelers like Rhino or MoI can create extruded true circles I believe.

sketch3d.de

@honoluludesktop said:

Technically, can any CAD software draw circles ?-)

Technically, any CAD software can draw circles.

hth,
Norbert

pilou

Eyes don't see any segments at any zoom with progs like Moi

bigstick

This is what you would expect from a NURBS modeler like MoI.

Zilonx

Well, yes, technically, any CAD software can draw circles.

Maybe Sketchup need to be less a visualization tool and more a CAD tool - circle entities are important, and this deficiency can have significant impact on several kinds of projects. Those kinds of projects need to be made with a true CAD tool - for now.

360 sides does not make a polygon a circle...

pilou

@unknownuser said:

360 sides does not make a polygon a circle

Of course a big zoom on it makes a lot of polygons
But you don't see more a "complete circle" on the screen

sketch3d.de

@zilonx said:

Maybe Sketchup need to be less a visualization tool and more a CAD tool

surely not, the strength of SU is just not to be a typical and complex CAD but an intuitive 3D sketcher, nothing less, nothing more.

if you need a CAD, use a CAD

e.g. ViaCAD:

NURBS modeler
advanced surface modeling
volume modeling incl. bool's
feature based (= edit the feature, don't create it again)
history tree
2D drafting
real dimensions
all common, vector based CAD interfaces as e.g. STEP, IGES, Acis SAT etc.
SU import
Mac/Win
upgrade path to more capable versions
bargain pricing compared with e.g. Rhino and even SUP
production status compared with e.g. Moi

@zilonx said:

360 sides does not make a polygon a circle...

using real, analytic circles for creating 3D stuff based on them is much more complex than the handling of facetted polygons resp. wire frames only and would require to use another 3D kernel as e.g. the commercial products ACIS or Parasolids (= royalties!) or something programmed by Google itstelf.

and CAD is not only the geometric entities but also some further stuff as e.g. associative dimensions and advanced dimension configuring, GD&T, welding symbols, precise printing in scale, high entity support etc.

hth,
Norbert

Gaieus

@sketch3d.de said:

@zilonx said:

Maybe Sketchup need to be less a visualization tool and more a CAD tool

surely not, the strength of SU is just not to be a typical and complex CAD but an intuitive 3D sketcher, nothing less, nothing more.
...
Norbert

True. There are even free CAD applications so SU being a popular (and free) app shouldn't justify that. Let it be what it was meant for: "an intuitive 3D sketcher".

Zilonx

@sketch3d.de said:

@zilonx said:

Maybe Sketchup need to be less a visualization tool and more a CAD tool

surely not, the strength of SU is just not to be a typical and complex CAD but an intuitive 3D sketcher, nothing less, nothing more.

hth,
Norbert

I agree with you about simplicity of use, but I can see a clear "upgrade path" to Sketchup, as the program matures to a more evolving solution. Sketchup can be a very powerful tool with not so many advancements, but great ones. It can have an integrated rendering, a modeling core with more features, as mentioned before. If a Cad tool can do all that for free, or for a few bucks, and a Cad tool can do it for almost 30 years (!), why not Sketchup (for five hundred bucks)? Performance is also a serious problem, it is nonsense with the advanced hardware available today - but discussion here is about modeling features..

Another useful feature would be modeling physics. Google can partner with hardware manufacturers to make great use of the GPUs available today.

TrophyJoe

Thank you solo. With 360 segments, my circles look, well, like circles.