How can I define a new polygon using only existing points in an object?

mgarstin

I'm new to Hexagon and DAZ 3D so please bear with me.

I've imported an object from another graphics package (TrueSpace) but the object has concave surfaces that were generated using boolean subtraction (yes, I know all about the issues of migrating booleans from one engine to another).  When I imported the TrueSpace object into Bryce the concave surfaces got covered up, so I saved the object as an .OBJ and then loaded it onto Hexagon.  There I was able to delete the bogus polygons that were covering up the concave surface but the surface covering the edge (rim) of the concave section is now missing leaving me with two seperate surfaces that look like two skins, one inside of the other.

I would like to add new faces to the rim using existing points from either side of the two surfaces (recreating the 'rim' in other words) but I can't seem to get Hexagon to do it.  I may be using the wrong function or simply approaching the problem incorrectly.  If anyone can give me pointers on where to start it would be much appreciated (I'm hoping there's a magic button that I press once and presto, my object is fixed).

(I found a way of doing it by coverting the object to an ASCII file in TrueSpace and then editting in the new faces manually using a text editor but that is painfully slow and torturous, worse than a root canal without anesthesia).

Cheers,

 

Mark

Roygee

By your description it looks like you may be able to use the bridge or target weld tools - I'd like to see a screen capture of the mesh in Hex, in flat solid and edges mode and including the scene tree to be more certain. 

mgarstin

Hi there Roygee.

The first picture is the original imported object.  The concave surface (in this case it's a hole through a cyllinder creating a pipe with grooves on the inside) is covered up by badly formed triangles (you can see the edges traversing the hole).  The second image is how it appears after I have deleted the bad triangles.  I get the inner and outter surfaces but not the rim going around the end of the pipe.  I would like to be able to create the polygons (faces) necessary to cap the ends off.

The third image is a rendering of the object from TrueSpace.  Here I was able to manually edit the object file (there's a backwards way I can do this in TrueSpace) to add in three triangles at the top of the pipe.  It takes a lot of effort to do this (it took me about an hour to create and add in these three trianlges).  But that shows the goal of what I'm attempting to achieve.

This is just one object (the simplest of all my objects) that come out like this.  Once I can figure out a better (faster, easier, more efficient) way of doing this then I will edit all of my other objects.  I could send you the .OBJ file for this object if you would like to look at it yourself.  It is my own creation so there's no copyright issues around it.

 

Cheers,

 

 

Mark

Roygee

Thank you and welcome to the forum.  Yes, bridging would work, but be pretty laborius because the tri's would not allow you to do edge-loop selection, so you would also have to do them one pair of edges at a time.  I'm also not sure whether the number of iner and outer edges match up, which could be a further annoyance.

Here's a more efficient method.  Draw a circle with 36 points in top view.  Extrude inwards, then inwards again.  Hide the curve.  Delete every sixth edge on the inner loop to get the shape shown in my pic, then add depth to get the length required.

I don't know how familiar you are with the Hexagon tools, so please ask if any of these steps are unclear:)

mgarstin

Hi again Roygee,

Sorry for not responding the last couple of days.  I'm in the process of moving from one province to another and I'm in the middle of packing up the house.  My being on-line will be spotty until mid-May (when we actually move).

I found the Bridge function under Vertex modelling.  I can add in faces between the two surfaces with it but, as you suspected, the number of inner and outer edges don't match up and the bridge function appears to want complete edges from both surfaces (I haven't yet figured out how to get the function to create a triangle instead of a quad).  I shall continue to poke around with this.  Perhaps I can convert a quad into two tri's then delete one of the tri's so as to add a quad in its place.  That would work, so long as I can find a function that will do the splitting of the quad into tri's (any hints on that?).

On a different note, how can I change the profile picture that appears with my name in these logs?  You have, what appears to be, an image of Moses.  I've looked around in my account info but haven't found anywhere where one can upload a profile picture.

Cheers,

 

Mark

 

Roygee

Moses - love it:)  That is a likeness of myself made many years ago using an application (FaceWorx) which makes a head mesh of a full-face and profile photos.  Not very good and needs some work to get it right.  Stuck that onto M4 and added some wild hair.  I call him The Wandering Poet; some say he's just a homeless bum!.

I believe you need to go into your account to update your profile - how?  I have no idea of how this new format forum works - hopefully a mod will give some guidance.

To triangulate faces select them, go to the Vertex modelling tab, hit the little down arrow under the sixth icon from the left and select "Triangular tessellation".

Edit:  On second thoughts, this may not be what you are wanting - that tool will split a quad into four tri's.  I do my utmost to avoid tri's, so have never really gone into this - probably the only method to split a quad into two tri's is to select two verts on opposite corners and connect them?

Your mention of moving to another Province - are you possibly located in South Africa?

cdordoni

Mark, here's another way, hopefully this works: http://www.concept-4d.com/samples/hexagon close.html

Roygee

 

Mark, here's another way, hopefully this works: http://www.concept-4d.com/samples/hexagon close.html

Problem is that method gives an n-gon, which makes a real mess when you triangulate.

mgarstin

Hi Roygee,

Alas, I live in Canada and we're moving from Vancouver, British Columbia to Calgary, Alberta.  About 800 kms distance but only 1/10th the way across the country.

cdordoni,

I will give your technique a try.  It looks like what I was looking for.  If it doesn't work (since my inner surface has fewer edges than the outer surface) then I will go back and try splitting quads into tri's using Roygee's approach.

Cheers guy, this has all been extremely helpful and well appreciated.

 

Mark

mgarstin

Roygee,

I found where I can change my profile picture.  Yes, that really is me, dressed up as Moses for a Halloween party.

Cheers,

 

Mark

cdordoni

Roygee said:

 

Problem is that method gives an n-gon, which makes a real mess when you triangulate.

Unfortunately yes, but depending on how the object is used, it could be a non issue.

Roygee

Unfortunately yes, but depending on how the object is used, it could be a non issue.

You are correct - the standard answer to all things topology-wise..."It depends" - definitely to be avaoided if rendering with Daz Studio or Poser:)

Here's some quite fascinating reading (if topology fascinates you!) - these are answers to Blender questions, but apply generally.

http://blender.stackexchange.com/questions/89/when-should-n-gons-be-used-and-when-shouldnt-they

http://blender.stackexchange.com/questions/2931/why-should-triangle-meshes-be-avoided-for-character-animation

http://blender.stackexchange.com/questions/27780/topology-question-regarding-circular-holes

mgarstin

Thanks for the help guys, I'm fixing my objects up nicely now.  Having multiple techniques to solve the same problem is always useful since the "It depends" issue will dictation which technique gets applied under which situation.

Cheers,

 

Mark

de3an

I’m late to this thread, but I wanted to try and see what it would take to reproduce the shape from scratch. Indeed, I believe trying to fix the original model would be much harder.

Roygee had the right idea. Start with a circle and then add thickness.
Here is my process:

Create a 42 vertex circle, extrude inward twice to make two rows of polygons.
Delete every seventh poly from the inner row.

Use the Thickness tool to expand the 2D disk into a 3D shape. This gives you the basic object.

To refine further you’ll want to chamfer the sharp edges. This is where it gets somewhat tedious.
Manually select all of the object’s edges.

Choose Chamfer and select a range of 1, and a radius just large enough to be noticeable.

The result of this chamfer produces 6-sided n-gons at the points shown. Fix them with the surface tesselation tool.

Add smoothing.

And render.

 

Fun exercise.

 

Roygee

Good call, de3an - chamfering adds a nice realistic finish to any hard-body model.:)