add 2D physics (use box2d), fixed some little bugs

ExampleApp/Src/PlayerCube.cs

@@ -0,0 +1,54 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Text;
+using System.Threading.Tasks;
+
+using Prism;
+
+namespace Example
+{
+    class PlayerCube : Entity
+    {
+        public float HorizontalForce = 10.0f;
+        public float VerticalForce = 10.0f;
+
+        private RigidBody2DComponent m_PhysicsBody;
+        private MaterialInstance m_MeshMaterial;
+
+        void OnCreate()
+        {
+            m_PhysicsBody = GetComponent<RigidBody2DComponent>();
+
+            MeshComponent meshComponent = GetComponent<MeshComponent>();
+            m_MeshMaterial = meshComponent.Mesh.GetMaterial(0);
+            m_MeshMaterial.Set("u_Metalness", 0.0f);
+        }
+
+        void OnUpdate(float ts)
+        {
+            if (Input.IsKeyPressed(KeyCode.D))
+                m_PhysicsBody.ApplyLinearImpulse(new Vec2(HorizontalForce, 0), new Vec2(), true);
+            else if (Input.IsKeyPressed(KeyCode.A))
+                m_PhysicsBody.ApplyLinearImpulse(new Vec2(-HorizontalForce, 0), new Vec2(), true);
+
+            if (Input.IsKeyPressed(KeyCode.Space))
+                m_PhysicsBody.ApplyLinearImpulse(new Vec2(0, VerticalForce), new Vec2(0, -10), true);
+
+            Vec3 color = new Vec3(0.8f, 0.8f, 0.8f);
+            if (Input.IsKeyPressed(KeyCode.Q))
+                color = new Vec3(0.0f, 1.0f, 0.0f);
+
+            m_MeshMaterial.Set("u_AlbedoColor", color);
+
+            if (Input.IsKeyPressed(KeyCode.R))
+            {
+                Mat4 transform = GetTransform();
+                transform.Translation = new Vec3(0.0f);
+                SetTransform(transform);
+            }
+
+        }
+
+    }
+}