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Fundamentals

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Michael Hulse edited this page Sep 5, 2018 · 1 revision

Blender Quick Start

  • Toggle sidebars using T, N and SHIFT + SPACE
  • LMB + CMD to “Rotate View”
  • RMB + CMD to “Move View”
  • Scroll the MMB to “Zoom”
  • F6 for options and numeric control
  • CTRL + F for “Faces” menu
  • On my laptop, FN + 1-0 for view changes. Keypad 5 is ortho view. 7 is top-down. Use CTRL and FN to flip to the opposite side.
  • …

General 3d mesh concepts

Ngons vs. Tris vs. Quads

  • Ngon: Is a face or polygon that is made up of five or more sides or edges connected by five or more vertices. Anything over a quad (4 sides) is considered an ngon.
  • Tri: Is a triangle face that consists of just 3 sides or edges connected by 3 vertices.
  • Quad: Is a face or polygon made up of four sides or edges connected by four vertices.

Quads are most optimal and you should aways strive to output quad-based meshes for your final model.

Tris and ngons can be acceptable if they appear on a totally flat surface (for example) or are used sparingly to end complex geometry (see Example Mesh below).

One area where you might see a lot of ngons and tris is hard-surface modeling:

Hard surface modeling is anything with hard surfaces, i.e. tables, houses, cars, computers, robots and alike. This type of modeling doesn’t typically involve deformations which means you can hide ngons and tris on the flat surfaces. This might be obvious, but the opposite of hard surface modeling would be organic modeling (like humans, animals, fruits, etc.)

Though, for the final mesh, it is advised that you clean it up using quad (where possible) or tri faces.

Example mesh

The above is an example of a mesh, by @caseydedore, that uses both tris and quads to acheive a perfect final mesh with a good balance of detail and simplicity.

The red lines represent areas that could have been turned into quads, but in this case, doing so would have been overkill. Casey states:

I only use them when I need to end a certain level of detail and they aren’t used in a place where deformation is extremely important (i.e., the eyes, mouth, etc.)

Planar, non-planar, coplanar faces/polygons

  • Planar: A polygon face is planar when all of its vertices lie in a certain plane.
  • Non-planar: A polygon face is non-planar when it has more than three vertices, and one or more of those vertices do not lie in the same plane.
  • Coplanar: In a 3D model, coincident or coplanar faces are two or more faces or polygons that occupy the same space and represent the same surface.

Concave and convex faces/polygons

  • Concave: Curved in; the opposite being convex. Means face in which one vert is inside a triangle formed by other vertices of the face.
  • Convex: Means not concave face. Opposite of concave face.

Note: Every polygon is either convex or concave. The difference between convex and concave polygons lies in the measures of their angles. For a polygon to be convex, all of its interior angles must be less than 180 degrees. Otherwise, the polygon is concave.

Non-manifold geometry

  • Non-manifold geometry is essentially geometry which cannot exist in the real world. Examples include:
  1. Disconnected vertices and edges
  2. Internal faces
  3. Areas with no thickness
  4. Overlapping edges

Summary

At its most basic, the rule of thumb is:

  1. Quads = most optimal
  2. Concave = evil.
  3. Convex = good, especially if quad.
  4. Ngon = typically bad.
  5. Tris are to be used sparingly and carefully, especially in areas that are meant to deform.
  6. Non-manifold = co-planer and concave = bad!

Cleaning up your mesh

Keep in mind, quad faces are the best.

  • In edit mode, press A to select all of the vertices; next, press CTRL + N, or SHIFT + CTRL + N, to recalculate the normals so they all point outward.
  • Remove ngons by joining (J key) two verts across the ngon’s face.
  • Convert triangles into quads by selecting two adjoining tris and clicking ALT + J.
  • With auto-weld of verts turned on, if needed, use DD to slide verts into each other thus reducing the number of verts to a face.
  • If needed, use ALT + D to rip a new vert thus adding the number of verts to a face.

For quick conversion to quad faces, apply a subdivision modifier and choose Catmull-Clark SubD.

In Edit mode, go to the Mesh menu and choose any of the options under Clean Up.

Make Planar Faces is super useful. Notice that you can control the number of iterations via the input field in the “Current Tool” options panel (in sidebar, open using the T key):

Also, Vertices > Remove Doubles

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