I tried a very basic thing- extruding an edge. Here's how I did that:

1 - Created Geometry container, got into that container and deleted teh File Node inside of it.

2. Created a Tube SOP in the Geometry container, changed its type to Polygons and set Rows 4/ Columns 20.

3. Selected an Edge and pressed L in order to select the whole edge.

4. With the edge selected, I pressed TAB whith my mouse over the Viewport and created a PolyExtrude SOP.

5. Now I pulled on the Gnomon in order to extrude the edge in positive Y direction…most parts of the selected edges were following but one part was moving in the completely opposite direction (negative Y).

No matter what I try, this is happening over and over again and I cannot find an explanation…do you?

EDIT:

Ok, polyExtrude works well if I just extrude with the default number of rows, If I put in anything but 10 the extrusion goes nuts. Maybe a bug.

See the image and hopefully this will explain anything.

Can you try local symmetry to normals or average positions to see if it fixes it?

As well, instead of using the handle and local extrusions, remove them and go to the Global folder and try an extrusion in the Y direction by directly manipulating the parameter with the MiddleMouseButton ladder handle or just type in values.

Thanky ou for your advice, extruding in Global mode helps- but in Local mode it is alwys the same trouble. Especially if I touch the Gnomon again and a Local translation of any kind is made everything breaks again.


But there's something I discovered ( one can reproduce this, it is in every new scene I create):

I can extrude an edge of a polygonal Tube if the settings for rows/ columns are set to the default 2/ 10. The extrusion just works as expected.

If I make e.g. 10 extrusions in a row (I am coming from Maya and as you certainly know, extruding over and over again is a common polygonal modelling workflow- if there is a more Houdiniesque way of using extrusions, I am all ears). After those ten extrusions, I decide my Tube should have some more subdivisions from the beginning on- so I change the rows/ columns value in the Tube SOP.

Doing this also breaks the geometry- but from everything I saw from Houdini one can change values in SOPs that on top of the Graph.

Luckily, a Subdivide SOP works without breaking the geometry- but I think one should be able to pick how many rows/ columns a tube can have right at its creation- without having to use the Suvdivide SOP later in the process.

So what is causing this strange behaviour? Am I doing something wrong?

hi ,

my preferred ‘way’ of dealing with these kind of situations ( esp when the silhouette is closed ) is this ;

- select the edge loop
- apply a PolyCap to those
- from there , for me is ‘the usual business’ with That polygon, which acts as a placeholder for those edges …


.cheers

Doing this also breaks the geometry

Hi Phlok,

AFAIK, the reason for this behaviour - breaking geometry after you change something higher up the node tree - is caused by the way H11 deals with interactive mesh edits - it remembers - by numbers - the vertices you applied e.g. an extrusion to. Unfortunately, it is stupid enough that if you add a more divisions up the node tree, it does not realise that the vertex numbers that described a loop, previously, now refer to something else.

If you want to keep the flexibility of your edits, the only way around it that I found is to do as much of geometry selection not interactively, but using some procedural patterns, directly in the node tree, and then apply operations to these. E.g. select only vertices that have PY >= YMAX - .0001 to select just a top row. Whenever you change something up the graph, the selection will be re-evaluated and your edits re-applied appropriately.

Cheers,
Greg

Thank you very much for those valuable hints!

aiworks
Unfortunately, it is stupid enough that if you add a more divisions up the node tree, it does not realise that the vertex numbers that described a loop, previously, now refer to something else.

I would rather describe this behaviour as normal instead of stupid

Dragos

Hi Digitallysane!

I would rather describe this behaviour as normal instead of stupid

Ok, I might have not been gentle enough with my evaluation :-)

Stilll…. I wish there could be a flag in the group tool to keep selected loops/rings alive, with simple topology changes like adding extra additional loops. After all, it's Houdini - so it should be magic 8)

Cheers,
Greg