riders: xmen. plane duplicated and misplaced for very large shrink values

[jotego]

In the intro sequence, the Blackbird (X-men's plane) should appear from the distance. The zoom does not work well as it displays it duplicated for large reduction and it seems to offset it to the left and up/down. Eventually one of the two copies disappears because it seems to fall outside the screen. When the zoom shrinkage is not that aggressive, the ship appears correctly.

two planes

two planes, bottom one visible

two planes (?), top one visible, a bit misplaced

For this shrink level, the position seems correct

[rp-jt]

In jt053246, vzoom/hzoom is obtained with 10 bits, but only 8 of them are considered to take the offset value from the zoffset array. In this case, vzoom/hzoom[9:8] was active, but the offset value taken was from the middle of the array, instead of an offset for large numbers of vzoom/hzoom (reduction). Something similar to what happened in #548. It can be solved in the same way

Examples in scenes 2 and 6

[rp-jt]

The duplication is produced by a large value of yz_add that doesn't trigger the condition if( yz_add[16] ) inzone = 0 Can be fixed by using |yz_add[17:16] and considering larger numbers

Scene 5