Vectrex Programming TOC

Vectors
Vectors in vectrex relation consist of following parts.

- Brightness
- Y position start
- X position start
- length in Y direction
- length in X direction
- scaling factor

Brightness

There are two ways to control brightness. First the 'Intensity', which is a value from 0-\$7f (if the 7th bit is set there is no intensity), 0 means black, \$7f means full brightness. Apart from the intensity you can vary brightness of vectors by drawing vectors more than ones or for dots leaving the vector beam for a longer period of time on the same dot. For the last there is a BIOS variable Vec_Dot_Dwell (\$C828), which sets a counter for how long the vector beam will illuminate the dot.

Positions

The position of vectors are most of the time relative to the last known position. Somtimes the position is not interesting when drawing a vector, since it was set some other time, and now drawing just continues. Positioning with any function is done in relation to the present scaling factor (TIME). The programer must keep track of the position, and should zero it now and than. If the set position is not 'used' within a certain time, the position will drift (my vectrex drifts allways to +,+ (cartesian coordinates), a few centimenters per 10,000 cycles!). Position is given in values from -128 to +127. Most position information is set with first Y than X postion.

Length of vectors / Scale

The length of vectors here means something like the speed with which the beam will travel across the screen. The scaling is something like the time, for how long the travelling will be done. Thus it is easy to see, that travelling with a speed of 10 for a time of 5, which would equal a travelled space of 50, is about the same as travelling with a speed of 50 for a time of 1, which also results in a space of 50 to be covered. The only difference is, that the first will take five times as long as the second! Length is given in values from -128 to +127. Most length information is set with first Y than X length.

Vectrex Programming TOC