Honestly in my opinion, NGons should never be present in a final model. Every artist will have slightly different opinions on this but here is my take.
When NGons are okay
On completely flat surfaces.
Hidden areas of models that will never be seen or used for any reason (but this still sloppy and not desirable)
As a temporary holding surface that will ...
Rather than thinking of limitations with using triangles (I think this is an over simplification of the topic), you need to understand common workflows that take advantage of quad-dominant meshes.
adding and removing edge loops (to increase or remove detail)
using loops to better define features of the mesh (such as facial features, around eyes etc).
One way to reduce mesh density is the decimate modifier, however for the workflow you want (creating a game asset) I think you want Retopology.
This is a workflow which gives your more control over the final result, however it will take longer as it is a manual process.
Some helpful addons and built in functionality for retopologizing your mesh:
While in Edit Mode, select the parts of your mesh you want to convert and use Alt + J or from the Faces special menu with Ctrl + F > Tris to Quads to convert tris to quads or via the 3d view header, use, Mesh > Faces > Tris to Quads.
This tool converts the selected triangles into quads by taking adjacent tris and removes the shared edge to create a quad, ...
The key with shoulder topology is to represent the deltoid muscle well and to separate the arm mesh from the body. The exact topology will depend on your subject. Most of the time every model will have slightly different topology.
For example, a muscular male will need far more dense and defined topology than a slim female.
The general rule of thumb with ...
It looks like while I was composing my answer someone else beat me to the punch. Nonetheless, I will share what I have. I think you get the gist of it already, but there are some slight differences. I hope you'll find it helpful.
Create the edge outline.
Do a spin extrusion.
Make some Loop Cuts.
Scale down with proportional editing enabled. (Sharp ...
Here are some wonderful tools for speeding up the retopology process:
These are paid, but worth every penny as they're really time-saving tools.
If you don't want to buy them you may do a fast retopology using a Bsurfaces addon. Go to User ...
Manual with good topology
To get the topology in your second image. Select the loops you want to delete with Alt RMB , or in Wireframe mode use border select (B). Then press Delete and choose Edge Loops.
Manual with N-gons
To delete all edges and vertices on a face and just be left with a large N-gon. Select all the faces on a plane (example everything ...
This one will work only for external Edge Loop and will give ugly ngon, so it's just for the pure knowledge. Better skip to second one.
Select corner vertex, press CTRL+SHIFT+B, move mouse to get desired angle, use scroll to get more vertices. You can tweak it as well in in Tools Panel.
This is with proper/clean/nice looking ...
If you know that your circle has a even number of vertices, and do not care how the gird is aligned; then select all the vertices in the circle with alt RMB , then ctrl F > grid fill.
Select half of the vertices of the circle. The selection needs to have the same number of vertices along the top and bottom, and the same number unselected on the side.
When people refer to character animation, they often don't include robots with rigid surfaces where, apart from the modelling process, tris for flat surfaces aren't that bad. They refer to human faces or otherwise flexible surfaces.
To simplify controlling the mesh for facial expressions or lipsync, faces of characters are modeled ...
There's a big misunderstanding regarding tris. A lot of people say that you should never use tris, and they're somewhat right. But the main reason behind not using tris, is because they can be harder to work with, and they can cause issues with deformations. Although, before exporting/baking your model for use in games, it's advisable that it's triangulated ...
Build the "curves" and only then simplify them
As your main issue is dealing with the lack of curvature, I would approach the problem from drawing at the very beginning an high poly version of the mesh (it's quite geometrical, so it should not be a big deal) that you said you'll need it anyway, and only after simplify it to get the low poly shape with all ...
Another option is the Remesh modifier. This modifier will result in a mesh that is all quads, regardless of the topology of the input mesh. From the wiki:
The Remesh modifier is a tool for generating new mesh topology based on an input surface. The output follows the surface curvature of the input, but its topology contains only quads.
Note that if the ...
You are merging 2 meshes with very different densities. The circle is about double the subdivision compared to the rest. Your topology should look similar to this:
the 5 green polys (the E pole vertex in the middle) are responsible for the change in edge flow
both marked edgeloops should be nice and even to produce edges with consistent curvature alongside ...
I think this solves the issue with moonbots answer. Use the TinyCAD addon to create vertices at the edge itersections
rotate top face 90 degrees (R, Z, 90)
duplicate (Shift-D) and mirror along any axis (e.g. Ctrl-M, X)
press W and select TinyCAD ⯈ XALL
press F to fill faces
press W and select Remove Doubles
I suggest you use the modifier Edge Split instead.
In Edit mode, select your edges desired to be sharp. Hit Ctrl+E to bring up the Edges menu. Select Mark Sharp. Now add the Edge Split modifier.
Edges are split by the modifier. In Edit mode they are marked cyan. Topology is still fine:
Subsurf does not treat tri, quad and ngon differently:
In each case the result follows exactly the same pattern:
Every edge is subdivided into exactly two edges.
Every face is subdivided into n faces where n = original number of vertices. Every new face is a quad.
A new vertex is created at the centre of the face. Every new face shares this vertex.
An edge loop is a series of directly connected edges:
You can select an edge loop with AltRMB.
An edge ring is a series of edges which are not directly connected, but share faces:
You can select an edge ring with CtrlAltRMB.
As a bonus, you can run the select edge loop or the select edge ring operator on every selected edge ...
I like the topology clean whether it's game model or not - so here are all the caps you will ever need:
If you have more sides, you can downscale these caps into them - the corresponding sub-cap topologies are highlighted (4-side cap, 6-side cap, 8-side cap):
With this you can make very clean any size cap with grid-like topology (which is very good).
This can be done with a base shape, two array modifiers and two simple deform modifiers controlled by two empties:
Modelling from top view, create with a basic shape that is symmetric on both x & Y axes, so that it can be tiled.
(click on the image to enlarge)
Add an array modifier to repeat the base shape on the X axis.
(click on the image to ...
This question is very generic - but you give a very specific example (Subsurf) which happens to treat ngons differently to many triangles (to be clear - differently to a triangulated ngon).
The answer is something like ... it depends: each modifier, tool, export-format and rendering engine can choose to use ngons / quads / triangles - differently. There are ...
You should avoid tris and ngons in your geometry, even if its a game model (its ok for mobile game models though - depends on polycount)
The meshflow is ok, its not good around the nostrils. Here is a good edgeflow that I recommend, its from a Zbrush course:
Source: Zbrush workshop with Ryan Kingslien
Direct Source: Workshops with Ryan Kingslien
In layman terms loop cut will only work on geometry with 'clear edge flow' meaning in most if not all cases you should ideally be able to look at it and tell where the cut will go or it should divide your mesh equally into more sections that can be cut again. So it won't work for triangles (3 vertices) or ngons (mesh with more than 4 vertices), What is non-...
Select the inner Vertices, press W > Smooth and adjust Smooth Vertex settings:
You can also access Smooth Vertex operator settings via F6:
Another way is selecting a whole row or column of vertex and then Scale in X or Y axis to a factor or Zero with S > X + 0
Alternatively place the 3D cursor over the vertex you wish to align to, press . to transform ...
N-Gons with more than 4 sides and Tris are bad because they do not subdivide smoothly and so break up the flow of edges through a model.
Tris are only bad when you need to smooth a mesh ie add subdivisions.
This diagram shows the effect of using quads and the subdividing as you see you still have quads after subdivision, so you could do it again for example.
N-gons are useful and detrimental for various things.
If you're using Blender, they are usually fine.
So long as you always save as a .blend, n-gons are fine, and I've never had issues within Blender from them without having other serious issues with my models.
That said, n-gons have their advantages and disadvantages; you have to consider all the things ...
Ngons can cause trouble with the subsurf modifier. Let's look at two examples:
Ngons with a subsurf result in what I would call megapoles (poles are verts with 3, 5 or more edges connected to them in a surface). They have one vertex in the center and the border is usually star shaped like the object to the left. That results in an uneven transition. The ...
Triangulation can't be controlled directly, it's not even done by Blender in object mode. Instead, it is left to the graphics driver to decide how to triangulate non-planar quads (which differs among drivers for different cards). Behavior may even change with VBO enabled or disabled.
You can use the triangulation modifier to get a bit of control with the ...