B.2.3 Weaving collisions

This perfect weave is not possible in all cases. Let's look at another example:

S=6, J=4:

0 *-----*-----*-----*
1     *-----*-----*-----*
2         *-----*-----*-----*
3             *-----*-----*-----*
4             ^   *-^---*-----*-----*
5             |   ^ | *-^---*-----*-----*
              OUCH!   ^ |   ^
                      |     |

Here we have a collision. Some lines printed in later passes overprint lines printed by earlier passes. We can see why by considering which row number is printed by a given jet number j (numbered from 0) of a given pass, p:

row(p, j) = p*J + j*S

Because J=4 and S=6 have a common factor of 2, jet 2 of pass 0 prints the same row as jet 0 of pass 3:

row(0, 2) = 0*4 + 2*6 = 12
row(3, 0) = 3*4 + 0*6 = 12

In fact, with this particular weave pattern, jets 0 and 1 of pass p+3 always overprint jets 2 and 3 of pass p. We'll represent overprinting rows by a ‘^’ in our diagrams, and correct rows by ‘*’:

S=6 J=4:

0 *-----*-----*-----*
1     *-----*-----*-----*
2         *-----*-----*-----*
3             ^-----^-----*-----*
4                 ^-----^-----*-----*
5                     ^-----^-----*-----*