1.7.8.1. Subdivide

Reference

Mode: Edit Mode
Panel: Tool Shelf ‣ Tools ‣ Mesh Tools ‣ Add: Subdivide
Menu: Mesh ‣ Edges ‣ Subdivide, Specials ‣ Subdivide/Subdivide Smooth

Subdividing splits selected edges and faces by cutting them in half or more, adding necessary vertices, and subdividing accordingly the faces involved, following a few rules, depending on the settings:

  • When only one edge of a face is selected (Triangle mode), triangles are subdivided into two triangles, and quads, into three triangles.
  • When two edges of a face are selected:
    • If the face is a triangle, a new edge is created between the two new vertices, subdividing the triangle in a triangle and a quad.
    • If the face is a quad, and the edges are neighbors, we have three possible behaviors, depending on the setting of Corner Cut Type (the select menu next to the Subdivide button, in Mesh Tools panel) See below for details.
    • If the face is a quad, and the edges are opposite, the quad is just subdivided in two quads by the edge linking the two new vertices.
  • When three edges of a face are selected:
    • If the face is a triangle, this means the whole face is selected and it is then sub-divided in four smaller triangles.
    • If the face is a quad, first the two opposite edges are subdivided as described above. Then, the "middle" edge is subdivided, affecting its new "sub-quad" as described above for only one edge.
  • When four edges of a face (a quad) are selected, the face is subdivided into four smaller quads.

1.7.8.1.1. Options

These options are available in the Tool Panel after running the tool;

Number of Cuts
Specifies the number of cuts per edge to make. By default this is 1, cutting edges in half. A value of 2 will cut it into thirds, and so on.
Smoothness

Displaces subdivisions to maintain approximate curvature, The effect is similar to the way the Subdivision Surface Modifier might deform the mesh.

_images/subdivide-smooth-before.png

Figure 1: Mesh before subdividing.

_images/subdivide-smooth-none.png

Figure 2: Subdivided with no smoothing.

_images/subdivide-smooth-after.png

Figure 3: Subdivided with smoothing of 1.

Quad/Tri Mode
Forces subdivide to create triangles or quads instead of n-gons (see examples below). This mode doesn't allow the use of Straight Cut on quad corners.
Corner Cut Type

This select menu controls the way quads with only two adjacent selected edges are subdivided.

Fan
The quad is sub-divided in a fan of four triangles, the common vertex being the one opposite to the selected edges.
Inner vertices
The selected edges are sub-divided, then an edge is created between the two new vertices, creating a small triangle. This edge is also sub-divided, and the "inner vertex" thus created is linked by another edge to the one opposite to the original selected edges. All this results in a quad sub-divided in a triangle and two quad.
Path
First an edge is created between the two opposite ends of the selected edges, dividing the quad in two triangles. Then, the same goes for the involved triangle as described above.
Straight Cut
_images/subdivide-twoedgesquad-fan2.png

Figure 4: Fan cut type.

_images/subdivide-twoedgesquad-innervert.png

Figure 5: Inner vertices cut type.

_images/subdivide-twoedgesquad-path.png

Figure 6: Path cut type.

Fractal

Displaces the vertices in random directions after the mesh is subdivided.

_images/subdivide-fractal-before.png

Figure 7: Plane before subdivision.

_images/subdivide-fractal-none.png

Figure 8: Regular subdivision.

_images/subdivide-fractal-after1.png

Figure 9: Same mesh with fractal added.

Along Normal

Causes the vertices to move along the their normals, instead of random directions.

_images/subdivide-fractal-alongnormal.png

Figure 10: Along normal set to 1.

Random Seed

Changes the random seed of the Fractal noise function, producing a different result for each seed value.

_images/subdivide-fractal-after2.png

Figure 11: Same mesh with a different seed value.

1.7.8.1.2. Examples

Below are several examples illustrating the various possibilities of the Subdivide and Subdivide Multi tools. Note the selection after subdivision.

_images/subdivide-before.png

Figure 12: The sample mesh.

1.7.8.1.2.1. One Edge

_images/subdivide-oneedge.png

Figure 13: One Edges.

_images/subdivide-oneedge-tri.png

Figure 14: Quad/Tri Mode.

1.7.8.1.2.2. Two Tri Edges

_images/subdivide-twoedgestri.png
_images/subdivide-twoedgestri-tri.png

Figure 16: Quad/Tri Mode.

1.7.8.1.2.3. Two Opposite Quad Edges

_images/subdivide-twoedgesopposite.png
_images/subdivide-twoedgesopposite-tri.png

Figure 18: Quad/Tri Mode.

1.7.8.1.2.4. Two Adjacent Quad Edges

_images/subdivide-twoedgesquad-fan2.png

Figure 19: Fan cut type.

_images/subdivide-twoedgesquad-fan.png

Figure 20: Quad/Tri Mode.

_images/subdivide-twoedgesquad-innervert.png

Figure 21: Innervert cut type.

_images/subdivide-twoedgesquad-innervert-tri.png

Figure 22: Quad/Tri Mode.

_images/subdivide-twoedgesquad-path.png

Figure 23: Path cut type.

_images/subdivide-twoedgesquad-path-tri.png

Figure 24: Quad/Tri Mode.

1.7.8.1.2.5. Three Edges

_images/subdivide-threeedges.png
_images/subdivide-threeedges-tri.png

Figure 26: Quad/Tri Mode.

1.7.8.1.2.6. Tri

_images/subdivide-threeedgestri.png
_images/subdivide-threeedgestri-tri.png

Figure 28: Quad/Tri Mode.

1.7.8.1.2.7. Quad/Four Edges

_images/subdivide-fouredges.png
_images/subdivide-fouredges-tri.png

Figure 30: Quad/Tri Mode.

1.7.8.1.2.8. Multicut

_images/subdivide-tri-multi.png

Figure 31: Tri with two cuts.

_images/subdivide-quad-multi.png

Figure 32: Quad with two cuts

1.7.8.1.3. Un-Subdivide

Reference

Mode: Edit Mode
Menu: Mesh ‣ Edges ‣ Un-Subdivide

Unsubdivide functions as the reverse of subdivide by attempting to remove edges that were the result of a subdivide operation. If additional editing has been done after the subdivide operation, unexpected results may occur.

Iterations
How many subdivisions to remove.