init commit

engine/engine.cpp

@@ -0,0 +1,22 @@
+#include "engine.h"
+
+void Engine::step(double dt, double load_torque_nm) {
+    // TODO: replace with real combustion/friction torque model driven
+    // by throttle position and crank angle. For now: seek idle rpm
+    // and just track the applied load so downstream pieces have
+    // something to wire against.
+    m_rpm += (kIdleRpm - m_rpm) * dt;
+    m_torque_nm = -load_torque_nm;
+}
+
+double Engine::rpm() const {
+    return m_rpm;
+}
+
+double Engine::torque_nm() const {
+    return m_torque_nm;
+}
+
+void Engine::reset() {
+    m_rpm = 0;
+}