Much simpler, thank you (although it's not libcod-free, it shouldn't be a problem for most people).
Here is the code
PHP Code:
    botdelay 150;
    
extrapolationfactor botdelay 1000;
    
velocity target getVelocity();
    
deltapos = [];
    
    for(
03k++)
    {
        
deltapos[k] = velocity[k] * extrapolationfactor;
    }
    
    
vtarget vectorNormalize((target_mark[0] + deltapos[0], target_mark[1] + deltapos[1], target_mark[2] + deltapos[2]) - eye);