Commit of work up to day 11 of learnopengl.com.

08-colors-basic-light/src/physics.cpp

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+#include "physics.hpp"
+
+struct BoxTest Box2d_setup(b2World &world) {
+  BoxTest box;
+  float wall_x[4] = {0.0f, 0.0f, -0.99f, 0.99f};
+  float wall_y[4] = {-0.99, 0.99f, 0.0f, 0.0f};
+  float bound_w[4] = {1.0f, 1.0f, 0.1f, 0.1f};
+  float bound_h[4] = {0.1f, 0.1f, 1.0f, 1.0f};
+
+  for(size_t i = 0; i < 4; i++) {
+    b2BodyDef groundBodyDef;
+    groundBodyDef.position.Set(wall_x[i], wall_y[i]);
+    b2Body *groundBody = world.CreateBody(&groundBodyDef);
+
+    b2PolygonShape groundBox;
+    groundBox.SetAsBox(bound_w[i], bound_h[i]);
+    groundBody->CreateFixture(&groundBox, 1.0f);
+
+    box.walls[i] = groundBody;
+  }
+
+  for(size_t i = 0; i < BODY_COUNT; i++) {
+    b2BodyDef bodyDef;
+    bodyDef.type = b2_dynamicBody;
+    bodyDef.position.Set(0.0f, 0.5f);
+    box.bodies[i] = world.CreateBody(&bodyDef);
+
+    b2PolygonShape dynamicBox;
+    dynamicBox.SetAsBox(0.1f, 0.1f);
+    b2FixtureDef fixtureDef;
+    fixtureDef.shape = &dynamicBox;
+
+    fixtureDef.density = 1.0f;
+    fixtureDef.friction = 0.3f;
+
+    box.bodies[i]->CreateFixture(&fixtureDef);
+  }
+
+  return box;
+}
+
+void Box2d_step_world(b2World& world) {
+  float timeStep = 1.0f / 60.0f;
+  int velocityIterations = 6;
+  int positionIterations = 2;
+
+  // step the world
+  world.Step(timeStep, velocityIterations, positionIterations);
+}