f

#### "Escher" models (was "Modelling Exercise")

```Following Heikki's "Modelling Exercise", I made some more "impossible
geometry" models
They're on http://www.dynabits.com/gallery/escher.htm
The "strange hex nut" is very simple to model once you get the idea from
someone else...
The "Penrose Triangle" is IMHO very challenging.
Took me a long time to model something far from perfect...
Can anyone make it simpler and better ?

This gave me an idea for an enhancement request (or an add-in...) : add a
way do draw and constrain sketches in view coordinates, for example to draw
a triangle that looks equilateral in isometric view... "Convert entities" in
view coordinates could also help. Useful ?
--
Philippe Guglielmetti - www.dynabits.com

```
 0
Philippe
1/29/2004 2:54:11 PM

6 Replies
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```Cool stuff!  How about creating a plane, creating your layout sketch on
it, and then view-perpendicular to plane?  Seems too simple, am I
missing something?

> This gave me an idea for an enhancement request (or an add-in...) : add a
> way do draw and constrain sketches in view coordinates, for example to draw
> a triangle that looks equilateral in isometric view... "Convert entities" in
> view coordinates could also help. Useful ?

--
Posted via Mailgate.ORG Server - http://www.Mailgate.ORG
```
 0
Denny
1/29/2004 7:29:57 PM
```> The "Penrose Triangle" is IMHO very challenging.
> Can anyone make it simpler and better ?

Hmm, In my opinion the penrose triangle was very easy to model. By using
lofts it may be difficult, indeed, and you seem to have an extra "edge" in
the model. I will submit my version later, but I need to remodel it since it
seems to be lost. I'd prefer to use straight extrusions instead of lofts;
for example in your version of the "modelling exercise" you can actually see
the curvature of the spokes in the wooden texture.

-h-

```
 0
Heikki
1/30/2004 7:17:00 AM
```> I will submit my version later, but I need to remodel it since it
> seems to be lost.

And here they are:

http://naakka.dyndns.org/misc/escher_triangle.jpg
http://naakka.dyndns.org/misc/escher_triangle.sldprt

-h-

```
 0
Heikki
1/30/2004 7:57:09 AM
```"Heikki Leivo" wrote:
> http://naakka.dyndns.org/misc/escher_triangle.jpg
> http://naakka.dyndns.org/misc/escher_triangle.sldprt

Argh! your solution is so simple ;-)
I started the same but then missed the point with the cut in ISO-plane...

--
Philippe Guglielmetti - www.dynabits.com

```
 0
Philippe
1/30/2004 10:15:00 AM
```"Denny Trimble" wrote:
> it, and then view-perpendicular to plane?  Seems too simple, am I
> missing something?
it's ok to create the layout sketch on a plane with the desired orientation,
but then you cannot use "Convert Entities" to project them on the "useful"
planes to build the model because "Convert Entities" and other sketch
constraint project entities perpendicularly to the destination sketch (the
one being edited), not to the source sketch as needed here.
Or am I missing something ?

For example if you take Heikki's great Escher triangle and start by
sketching an equilateral triangle on his "ISO-plane", you can't project it
on Face/Top/Right planes and guess that the triangle could be built so
simply...
--
Philippe Guglielmetti - www.dynabits.com

```
 0
Philippe
1/30/2004 10:24:56 AM
```> "Heikki Leivo" wrote:
> > http://naakka.dyndns.org/misc/escher_triangle.jpg
> > http://naakka.dyndns.org/misc/escher_triangle.sldprt
>
> Argh! your solution is so simple ;-)
> I started the same but then missed the point with the cut in ISO-plane...

You could actually model the triangle as sheetmetal, and do a flat pattern.
Then you could cut and bend the triangle eg. from paper. This makes it
possible to take a photograph from somebody holding the impossible triangle;
the viewpoint has to be chosen carefully. I have seen such photos somewhere.

-h-

```
 0
Heikki
1/30/2004 2:24:47 PM

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