init commit

engine/vehicle.cpp

@@ -0,0 +1,21 @@
+#include "vehicle.h"
+
+void Vehicle::step(double dt, double wheel_torque_nm) {
+    double drive_force_n = wheel_torque_nm / kWheelRadiusM;
+    double drag_force_n = kDragCoeff * m_speed_mps * m_speed_mps;
+
+    double net_force_n = drive_force_n - drag_force_n;
+    double accel_mps2 = net_force_n / kMassKg;
+
+    m_speed_mps += accel_mps2 * dt;
+    if (m_speed_mps < 0.0) m_speed_mps = 0.0; // no reverse yet
+}
+
+double Vehicle::speed_mps() const {
+    return m_speed_mps;
+}
+
+double Vehicle::wheel_rpm() const {
+    double wheel_rad_per_s = m_speed_mps / kWheelRadiusM;
+    return wheel_rad_per_s * 60.0 / (2.0 * 3.14159265358979);
+}