Digital 3D literacy

Vertices, triangles, normals, STL — the grammar of every CAD tool you will touch.

Objectives

Explain what an STL actually stores.
Describe a vertex normal and why smoothing depends on it.
Spot a hole, a non-manifold edge, and a flipped normal.

What an STL stores

Vertices and triangles. No enamel. Thickness is a distance between shells.

Molar · #3 · FDI 16 · 6┘

Wireframe — every triangle the miller will see.
Normals — RGB is the direction the surface faces. Undercut maps use this dot product.
A flipped normal renders black and writes a bad toolpath.

Read this

A scan is not a tooth. It is a mesh.

An STL is a list of triangles. Each triangle has three vertices and a normal. There is no enamel, no pulp, no ‘inside’ unless the triangles close a volume. When a design tool talks about ‘thickness’ it is measuring distance between mesh shells.

Resolution vs. anatomy

Too few triangles and a groove disappears. Too many and the file is noisy — every speck of powder becomes a mountain. Sculpting and CAD both start with the same question: is this vertex anatomy, or is it dirt?

Normals

A normal is the direction the surface faces. Sculpt brushes move along normals. Undercut detection dots the normal against the insertion axis. If a normal is flipped, the tooth renders black and the miller gets a bad toolpath.

Open the practice lab

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