Initial (manual) import

TempleOSCD/Apps/Span/SpanDerive.HC

@@ -0,0 +1,47 @@
+U0 MyDerivative(CMathODE *ode,F64,COrder2D3 *,COrder2D3 *)
+{
+//The forces due to springs and drag are
+  //automatically handled by the
+  //ode code.  We can add new forces
+  //here.
+  CTask *task=ode->win_task;
+  F64 d,dd;
+  CD3 p,p2;
+  MyMass *tmpm1,*tmpm2;
+
+  //Collisions
+  tmpm1=ode->next_mass;
+  while (tmpm1!=&ode->next_mass) {
+    tmpm2=tmpm1->next;
+    while (tmpm2!=&ode->next_mass) {
+      D3Sub(&p,&tmpm2->state->x,&tmpm1->state->x);
+      dd=D3NormSqr(&p);
+      if (dd<=Sqr(tmpm1->radius+tmpm2->radius)) {
+	d=Sqrt(dd)+0.0001;
+	dd=10.0*Sqr(Sqr(Sqr(tmpm1->radius+tmpm2->radius)-dd));
+	D3MulEqu(&p,dd/d);
+	D3AddEqu(&tmpm2->DstateDt->DxDt,&p);
+	D3SubEqu(&tmpm1->DstateDt->DxDt,&p);
+      }
+      tmpm2=tmpm2->next;
+    }
+    tmpm1=tmpm1->next;
+  }
+
+  tmpm1=ode->next_mass;
+  while (tmpm1!=&ode->next_mass) {
+    if (!(tmpm1->flags&MSF_FIXED))
+      tmpm1->DstateDt->DyDt+=10.0*tmpm1->mass; //Gravity
+    tmpm1=tmpm1->next;
+  }
+
+  if (cursor_mass) {
+    p2.x=ms.pos.x-task->pix_left-task->scroll_x;
+    p2.y=ms.pos.y-task->pix_top-task->scroll_y;
+    p2.z=0;
+    D3Sub(&p,&p2,&cursor_mass->state->x);
+    d=10.0*D3NormSqr(&p);
+    D3MulEqu(&p,d);
+    D3AddEqu(&cursor_mass->DstateDt->DxDt,&p);
+  }
+}