Cubes and cylinders

■ The Cube command

The Cube command in B3D and CSV objects is equivalent to a series of Vertex/AddVertex and Face/AddFace commands.

Given the following code (B3D style):


▶	`Cube x, y, z`

The Cube command corresponds to these instructions (B3D style):


▶	`Vertex x, y, -z Vertex x, -y, -z Vertex -x, -y, -z Vertex -x, y, -z Vertex x, y, z Vertex x, -y, z Vertex -x, -y, z Vertex -x, y, z Face v+0, v+1, v+2, v+3 Face v+0, v+4, v+5, v+1 Face v+0, v+3, v+7, v+4 Face v+6, v+5, v+4, v+7 Face v+6, v+7, v+3, v+2 Face v+6, v+2, v+1, v+5`

where v is the number of vertices that have already been created before the Cube command was used.

If you want to texture the cube, you need to add appropriate Coordinate/SetTextureCoordinate commands manually.

■ The Cylinder command

The Cylinder command in B3D and CSV objects is equivalent to a series of Vertex/AddVertex and Face/AddFace commands.

Given the following code (B3D style):


▶	`Cylinder n, r1, r2, h`

The Cylinder command first corresponds to n pairs of two vertex instructions (B3D style):

▶ Vertex cos[2*pi*0/n]*r1, h/2, sin[2*pi*0/n]*r1 Vertex cos[2*pi*0/n]*r2, -h/2, sin[2*pi*0/n]*r2 Vertex cos[2*pi*1/n]*r1, h/2, sin[2*pi*1/n]*r1 Vertex cos[2*pi*1/n]*r2, -h/2, sin[2*pi*1/n]*r2 Vertex cos[2*pi*2/n]*r1, h/2, sin[2*pi*2/n]*r1 Vertex cos[2*pi*2/n]*r2, -h/2, sin[2*pi*2/n]*r2 ... Vertex cos[2*pi*(n-1)/n]*r1, h/2, sin[2*pi*(n-1)/n]*r1 Vertex cos[2*pi*(n-1)/n]*r2, -h/2, sin[2*pi*(n-1)/n]*r2

Then, n faces are added to form the side walls (B3D style):


▶	`Face 2, 3, 1, 0 Face 4, 5, 3, 2 Face 6, 7, 5, 4 Face 8, 9, 7, 6 ... Face 2n-6, 2n-5, 2n-7, 2n-8 Face 2n-4, 2n-3, 2n-5, 2n-6 Face 2n-2, 2n-1, 2n-3, 2n-4 Face 0, 1, 2n-1, 2n-2`

If r2>0, a lower cap is then added (B3D style):


▶	`Face 2n-2, 2n-4, 2*n-6, ..., 4, 2, 0`

If r1>0, an upper cap is then added (B3D style):


▶	`Face 1, 3, 5, ..., 2n-5, 2n-3, 2*n-1`

If you want to texture the cylinder, you need to add appropriate Coordinate/SetTextureCoordinate commands manually.