综上代码

void point_on_line(float* res, float* p, float* q, float lambda)
{
   float tmp = 1 - lambda;
   res[0] = tmp* p[0] + lambda * q[0];
   res[1] = tmp* p[1] + lambda * q[1];
   res[2] = tmp* p[2] + lambda * q[2];
}