Pretty Poly Editor Documentation
I. PPE Manual - 5. Terminology
- Vertex: Defines a point in 3D-space.
- Vertices: The plural of 'Vertex'.
- Line: Depending on the context, a line may be finite or infinite.
Strictly speaking, a line that merely joins two vertices is called
a 'line segment' - but then most people do not speak strictly!
- Point: What you get when you draw a vertex by itself. Points are
mathematically infinitely small - but in OpenGL, they may be
rendered as a tiny circle of just one or two pixels in diameter.
- Polygon: Defined by three or more vertices lying in a plane. In
the context of PPE, polygons should always be convex.
- Triangle: A Polygon with exactly three vertices. In the end,
every polygon is rendered as a collection of one or more
triangles in OpenGL.
- Quadrilateral: A Polygon with exactly four vertices. (Generally
abbreviated as 'Quad').
- Primitive: A primitive is term we use in PPE to refer to a
single OpenGL entity such as could be rendered between a
glBegin() and a glEnd(). That's not a very useful definition
for an Artist. In OpenGL (and hence PPE) a primitive could contain
either a number of discrete triangles, a strip of triangles
that share their vertices, a 'fan' of triangles organised
around a single point, a collection of quadrilaterals, a
strip of quads that share vertices at their ends, a single
polygon with any number of vertices, a line segment, a loop
made up of lines, a 'strip' of lines connected end-to-end or
a collection of points.
- Leaf node: A leaf node (at the moment) is the structure that
holds a primitive in the underlying "Scene Graph" that PPE
depends upon.
- Branch node: A branch node is a container that can hold a
collection of leaf and/or branch nodes.
Specialised versions of the basic 'branch' can
contain information on how the data in the nodes "below"
should be interpreted.
- Transformations: Operations that can be applied to a or many vertices and change their position in space. For example: Translation, rotation, scaling, shear.
- Renderer: (Part of) Program that displays objects on the screen.