Help with the tool Cut and Subdivide

#1

I’m almost giving up because I lost 4 hours of modelling and experimenting, and always I end up with a mess of polys :’(

Then I tried to use the same tools on a simple Cube. The Shift-K, without selecting a poly, cuts through the cube like butter; I press TAB and all looks fine.
But, when I apply the same tool with a single poly (because on some places I need more points to give roundness and to separate volumes), I press TAB and everything is good but that poly where I applied the cut :’(

It happens even when I use Subdivide, Split and such. The polys don’t merge good with the rest of their neighbourghs, and that destroys much of my practice works… Sorry, I’m very sad, because I’m a novice and I recent started with 3D and then I crash against this impediment, wich frustrates a lot my creativity and wishes of carry on with 3D :frowning:

The picture of sample:

I hope someone can point me what I’m doing wrong, because I watched lots of tutorials using the Cut tool, and really I need it for making extra points and edges on precise places.

#2

your using lightwaves native nurb system, so the poly above and below the cut
is known as an N-Gone - a polygon with more than 4 points. In this case they both have 5. they wont smooth properly, so you have 2 choices. 1) use CC
subpatches (if your using LW9 and up ( but they have a few niggling issues.
or use the edge tool to create more cuts so everything connects in 3 point polygons.

Basically this is what you need:

#3

the standard sub-d’s need quads to work correctly, you can also have triangles but it is best to stay with 4-point polygons…that’s the basics of working with sub-d’s…now here’s why that is relevant.

The problem that you’re experiencing is that the polygon that you have cut is not connected in the middle because you have created two extra points. To see what I am trying to explain, select the two points and move them away from the cube…you will see that they are not connected to the polygons above and below.

In order to keep the split and connect the polygons together you would need to add a point to the polygons above and below the split, however, that would make them 5-point polygons and they wouldn’t work with sub-d’s*.

In the image that I have attached, I have shown one solution. It will not give you a nice clean mesh and might cause some problems with pinching but it will give you the split where you want it and allow sub-d’s. You can work on ways to create cleaner meshes after you have mastered the basics.

You will need to create points on the top and bottom polygons (in red) and then split the polygons into triangles (select two points, ctrl+L). Then weld the points together bewteen the polygons.

*Catmull-clark sub-d’s do allow more than 4 point polygons but personally, I think that you’re better to learn good modelling techniques rather than hoping that tools or plugins will make up for your lack of experience.

#4

Select all six points of your polygon. On the ‘create’ tab, click ‘Make Polygon’ or press ‘p’ on your keyboard. and you will have two triangular polygons either side. This approach will avoid problems with pinching further down your loop.

Hope this helps.

#5

Sorry for the late reply. Job takes almost every free time.

Thanks for the replies and tips :slight_smile: I felt comfy making triangles to try to fix the gaps while modelling in unsubpatch mode. Fortunatelly, gaps aren’t now that common as I learn to model properly without using the Knife tool and such.

Either case, I have another question related to subpatch mode. I am modelling from the typical box (commiting mistakes and try to learn from them) but I jumped to model the box directlly from the subpatch mode. I don’t know why it have some “clay” feeling, but at least allows me to use the Symmetric mode tab so I can model easily. My question is if that will affect later to the whole rigging, weight map and UV maps. I’m starting to make some UV for my current model (a little character of mine) piece by piece. I don’t know if I can apply UV maps just only to selected polys (because my character have tons of details and every part have its own texture, either eyes, tongue, fangs, nails…).

Will try to finish the model first before doing the rest of UV maps (just did the dorsal fin because it have a little transparency and I hope Lightwave respects the PNG transparencies if I do them).

Currently the model as for this morning looks like this:
Agh, too big to fit here.

(I know it looks “wonky” on certain places but still I’m trying to realize how to fix the weirdness). I even did the skelegon but I have no idea how to move it or how to apply it to my model (it is on other layer right now). Practicing with everything you see. Thanks for the feedback :slight_smile:

#6

You shouldn’t have any problems using the symmetry tool to build your model at this stage and you should only start weighting your model after you’ve built and rigged it. Rigging your character using the mirror and symetry tool should not pose any problems either. Just make sure you name your hierarchies correctly. It’s also possibe to create a mirror image of your weight maps using the ‘select by map’ and ‘symmetry’ tools withought the need for a plugin.

You might want to read Timothy Albee’s character animation book. This will give you a solid working knowledge of basic character rigging and weight mapping. Worked for me!

#7

If you have EasySplit http://easysplit.trueart.pl
your life would be easier…

It’s cutting through face polygons, traditional Sub-Patch and Catmull-Clark Sub-D, without breaking geometry. It works only in perspective viewport, without perspective distortions. It supports Symmetry and maintain vertex maps and CC edge weighting.

#8

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