afni.nimh.nih.gov

And for extra entertainment, in the expression a*x+b*y+c*z-d,
change '-d' to '-d-25+5*t'. The 't' is a time variable, used when
you "Automate" a sequence of images.

Then click the "Automate" button, set "Frames" equal to 10, set
"DynaDraw", set "Accumulate", and finally, press "Compute".
Note that you will have to re-state the equation in repeat the
automated process.

Enjoy,

- rick