Update the CannonBall example for the Tutorial. #1097

trick_source/trick_utils/SAIntegrator/examples/CannonBall/CannonBall.cpp

@@ -1,6 +1,5 @@
 #include <math.h>
 #include <stdio.h>
-#include <iostream>
 #include "SAIntegrator.hh"
 
 struct Cannon {
@@ -9,15 +8,13 @@ struct Cannon {
     Cannon(double px, double py, double vx, double vy);
 };
 Cannon::Cannon(double px, double py, double vx, double vy) {
-    pos[0] = px;
+    pos[0] = px;  pos[1] = py;
-    pos[1] = py;
+    vel[0] = vx;  vel[1] = vy;
-    vel[0] = vx;
-    vel[1] = vy;
 }
-void print_header() {
+void CSV_header() {
     printf ("t, cannon.pos[0], cannon.pos[1], cannon.vel[0], cannon.vel[1]\n");
 }
-void print_state( double t, Cannon& cannon) {
+void CSV_state( double t, Cannon& cannon) {
     printf ("%5.3f, %5.10f, %5.10f, %5.10f, %5.10f\n",
     t, cannon.pos[0], cannon.pos[1], cannon.vel[0], cannon.vel[1]);
 }
@@ -27,28 +24,24 @@ void calc_derivs( double t, double state[], double derivs[], void* udata) {
     derivs[2] =   0.0;
     derivs[3] = -9.81;
 }
-double impact( double t, double state[], RootFinder* root_finder, void* udata) {
-    double root_error = root_finder->find_roots(t, state[1]);
-    if (root_error == 0.0) {
-        root_finder->init();
-        state[2] =  0.9 * state[2];
-        state[3] = -0.9 * state[3];
-    }
-    return (root_error);
-}
 int main ( int argc, char* argv[]) {
-    Cannon cannon(0.0, 0.0, 50.0*cos(M_PI/6.0), 50.0*sin(M_PI/6.0));
+    const double muzzle_speed = 50; // m/s
+    const double muzzle_angle = 30; // degrees
+    double vx0 = muzzle_speed * cos(muzzle_angle * M_PI / 180.0);
+    double vy0 = muzzle_speed * sin(muzzle_angle * M_PI / 180.0);
+    Cannon cannon(0.0, 0.0, vx0, vy0);
+
     double* state_var_p[4] = { &(cannon.pos[0]), &(cannon.pos[1]),
                                &(cannon.vel[0]), &(cannon.vel[1]) };
-    double t  = 0.0;
     double dt = 0.01;
-    SA::RK2Integrator integ(dt, 4, state_var_p, state_var_p, calc_derivs, NULL);
+    SA::RK2Integrator integ(dt, 4, state_var_p, calc_derivs, NULL);
-    integ.add_Rootfinder(1.0e-10, Negative, &impact);
+
-    print_header();
+    double t  = 0.0;
-    print_state( t, cannon);
+    CSV_header();
-    while (t < 20.0) {
+    CSV_state( t, cannon);
+    while (t < 5.1) {
         integ.integrate();
         t = integ.getIndyVar();
-        print_state( t, cannon);
+        CSV_state( t, cannon);
     }
 }

trick_source/trick_utils/SAIntegrator/examples/CannonBall/README.md

@@ -1,9 +1,7 @@
 # CannonBall
 
 The CannonBall program is an example of using the SA::RK2Integrator
-to create a simple cannon ball simulation. We also use a rootfinder
+to create a simple cannon ball simulation. 
-with our integrator to detect contact with the ground, and bounce
-the cannonball.
 
 For each numerical integration time-step, the simulation program prints: