limiting random origin motion

double  RandOrgRange = 1;   // 0 to 2, default is 1
DPOINT  RandOrgBias = {0, 0};   // -.5 to .5, default is 0
double  ofs = (1 - RandOrgRange) / 2;
m_TargetOrg.x = double(rand()) / RAND_MAX
    * RandOrgRange + ofs + RandOrgBias.x;
m_TargetOrg.y = double(rand()) / RAND_MAX
    * RandOrgRange + ofs + RandOrgBias.y;