Option to extrude with keep original poligons?

[tokikake]

When I use extrude tools for modeling mesh (retopo mesh), I feel there seems no way to extrude with keep original faces.

eg

1.  add any 2d primitives then draw  base poligons.

2.  extrude face/verts with normal to make it 3d 

3. with any extrude option, 3d coat extrude faces (or verts) but not remain original base poligons >> everytime I need to cap or add faces for the side to make it as 3d model

Is there any option or smart way to make it work?

Though I know how to add faces or cap, but the more base shape complex the more face it take time.  

I suppose I may duplicate and join etc, but hope to know if there is option which can extrude with keep original poligons . 

(of course, it is case by case that I  remain original or not when extrude, eg if I only need to extrude for retopo along with sculpt mesh, I may need not. but when modeling I may often make 2d face, then extrude.  for that case I usually need to remain base meshes. )

I do not know many other modeling tool,  but usually I can keep original (base) poligons when I extrude faces to convert 2d to 3d.

but can extrude region without add un-necessary faces. 

[digman]

I think this is what you are asking for.

Before extruding the flat polygons do the below: 

Make sure when doing the below you are in Faces Mode. Top tool bar in 3DC.

Under the Selected menu (left tool bar)

Select all the polygons using the Select tool.

 Selected Menu----Select Shell. This will create bottom faces on your model. 

A gizmo will appear so you can do your first extrusion.

Next:

Select the polygon faces on the bottom and use the Separate tool (Selected menu)  This will separate the bottom polygons and place them into their own polygroup.

Flip the separated  bottom faces Selected menu (Flip Faces) 

You now have a original copy on it's own polygroup layer of your flat polygons before extrusion.

Picture shows final result. 

Edit:

If you want to keep the model in-closed and not open on the bottom but have a copy of the bottom polygons, Select Clone after selecting the bottom polygons. Flip the polygon faces. Cloning also creates a new polygroup.

[tokikake]

I means, (in blender , sorry I olny know about blender and do not know other modeling tool)

1. I add plane

2. extrude (face)

3. as you can see, it keep the original plane (under face). (which I put in to scene) + add extrude faces.

4 if I keep extrude, it only extrude region (selected faces)  so do not add new face for each section. (as same as 3d coat)

3d coat exturde remove original face,  but remain extruded faces only. 

I test "Extrude faces, "but it not remain the original plane (so if I extrude plane , it not convert as 3d primitive I need to fill ,the removed face)

I try all extrude  options, but it not remain the original face. so it not change plane as cube by extrude. 

(of course it not matter, if I only extrude such simple plane, but draw 2d +  extrude, then convert as 3d model,  re-fill all faces again,, is annoying )

and yes digman, it is what I means,, (I may follow what you show thanks, but I may hope 3d coat auto remain the face, without remove (as option) ..

when we start extrude for 2d faces. 

Edited August 9, 2021 by tokikake

[tokikake]

Yes thanks Digman,,  the shell tool seems do what I means...  (I did not think to use it for the purpose, but I feel yes it work,, as extrude with keep original mesh)  

only annoying thing, I usually just use transform tool. after select polgion (commit extrude),  so if I hope to keep original, I need to use shell tool first, then slightly extrude change tool as transform tool  (then keep extrude or simply scale , rotate etc)..

 

 

[Gorbatovsky]

The extrude tool does not make the shell.

Use the tool the shell.