### Composite

- brep
  - brp file format
- NURBSmesh
- bezierblob
- CSG
  - intersection
  - subtractunion

#### brep

brep object are described in brp file format.

##### brp file format

The description of a simple file .brp:

{ pbrep

vertices

3

0 0 0

1 0 0

1 1 0

0 1 0

faces

1

{ 1 { 4 0 1 2 3 } }

}

This is a simple object. It is a square in the plane x-y with edge of 1.

Remember this is an open brep, you cannot assume it will be a transparent object.

There are definite four vertices, which we call A for (0,0,0) , B for ( 1,0,0) , C for (1,1,0) , D for (0,1,0) . It is definite one face with one contour. A face can have more than a contour; in this case the first contour is the external contour, while the others are holes in the face.

Every face has a normal versor, which describes the external side of a face. We can tell this to the program with the order we put the vertices in the contour description:

x exit

. enter

ABCD anticlockwise

ADCB clockwise

If you have a hole, the order of the hole contour must be opposite to the external.

#### NURBSmesh

#### bezierblob

5.5.2.4

Blob use only external model. The blob models are stored in .blb format, the same that the program Winblob. You can find it at:

ftp://ftp.povray.org/pub/povray/utilities/general/winblobs.zip

#### CSG

##### intersection

##### subtractunion

5.5.2.5.3