Formal editing semantics

[bvssvni]

Work out editing semantics using https://github.com/PistonDevelopers/piston/issues/736. This is necessary to prove that the API design is sufficient for editing applications.

Question: Will storing texture UV and normal with vertex position affect editing semantics?

[bvssvni]

copy(x) -> x, x' where x = x'

edit(x) -> x'

is_used(x, scene) -> bool

is_used_by(x, y) -> bool

A delete might be cancelled if there are objects using on it.

delete(x, scene) -> scene | scene'

A cascading delete removes all objects that depends on the object being deleted.

delete_cascade(x, scene) -> scene'

One action that is helpful for cleaning up a scene is to delete all unused objects.

delete_unused(scene) -> scene'

[bvssvni]

An naive vertex format containing a position, uv coordinates for a single texture, and a normal:

pos(vertex) -> x, y, z
uv(vertex) -> x, y
normal(vertex) -> x, y, z

Editing:

set_pos(vertex, x, y, z) -> vertex'
set_uv(vertex, x, y) -> vertex'
set_normal(vertex, x, y, z) -> vertex'

Can derive that set_pos, set_uv and set_normal matches editing functions:

d = vertex, x, y, z
d = vertex', x, y, z
set_pos(d) -> d'
edit(d) -> d'
edit(x) -> x'

[bvssvni]

The upper bound on information required to check whether an object is used in hierarchical contiguous arrays is the level where no range includes the object or points to a range that does.

[bvssvni]

In the case where two different geometries share a vertex, there must be some information that tells it is shared to move both vertices. This will happen when two edges of different materials meet.

[bvssvni]

When a triangle get subdivided into smaller triangles, it keeps the same position/uv/normal values for the corner vertices.