# Generating Physical Objects (CPP)


We need some geometric primitives that the player can move around the Play Area and shoot at. Let's generate them via code.


A primitive should have a [body](../../../principles/physics/bodies/index.md) and a [shape](../../../principles/physics/shapes/index.md) to collide with the Player Character and be affected by gravity. We have implemented interaction with bullets via [Intersections](../../../code/usage/intersections/index_cpp.md) at the previous step, so we should set the *BulletIntersection* bit for the object's *[Intersection](../../../principles/bit_masking/index.md#intersection_mask)* mask.


When the robot moves fast and the application framerate is low, the character will be teleported each frame and may go through physical objects due to *discrete collision detection*. To avoid this we are going to use [continuous collision detection](../../../principles/physics/collision/index.md#discrete_continuous).


> **Notice:** Continuous collision detection is available for [sphere](../../../principles/physics/shapes/index.md#sphere) and [capsule](../../../principles/physics/shapes/index.md#capsule) shapes only.


1. Create a new *C++ component* in your IDE and call it **ObjectGenerator**. Copy the following code to the corresponding files and save the solution. This component generates the physical objects and places them in the world. <details> <summary>ObjectGenerator.h | Close</summary> ```cpp #include <UnigineComponentSystem.h> #include <UnigineGame.h> #pragma once class ObjectGenerator : public Unigine::ComponentBase { public: COMPONENT_DEFINE(ObjectGenerator, ComponentBase); COMPONENT_INIT(init, 1); // 1st initialization order protected: void init(); }; ``` </details> <details> <summary>ObjectGenerator.cpp | Close</summary> ```cpp #include "ObjectGenerator.h" #include <UniginePrimitives.h> using namespace Unigine; REGISTER_COMPONENT(ObjectGenerator); void ObjectGenerator::init() { // cube ObjectMeshDynamicPtr box = Primitives::createBox(Math::vec3(1.0f)); box->setTriggerInteractionEnabled(1); box->setIntersection(1, 0); box->setIntersectionMask(0x00000080, 0); // check the BulletIntersection bit box->setWorldTransform(translate(Math::Vec3(0.5f, 7.5f, 1.0f))); box->setMaterialFilePath("materials/mesh_base_0.mat", "*"); box->setName("box"); Unigine::BodyRigidPtr bodyBox = BodyRigid::create(box); ShapeBoxPtr shapeBox = ShapeBox::create(bodyBox, Math::vec3(1.0f)); ShapeSphere::create(bodyBox, 0.5f); bodyBox->setShapeBased(0); bodyBox->setMass(2.0f); // sphere ObjectMeshDynamicPtr sphere = Primitives::createSphere(0.5f, 9, 32); sphere->setTriggerInteractionEnabled(1); sphere->setIntersection(1, 0); sphere->setIntersectionMask(0x00000080, 0); // check the BulletIntersection bit sphere->setWorldTransform(translate(Math::Vec3(4.5f, 5.5f, 1.0f))); sphere->setMaterialFilePath("materials/mesh_base_1.mat", "*"); sphere->setName("sphere"); BodyRigidPtr bodySphere = BodyRigid::create(sphere); ShapeSphere::create(bodySphere, 0.5f); bodySphere->setShapeBased(0); bodySphere->setMass(2.0f); // capsule ObjectMeshDynamicPtr capsule = Primitives::createCapsule(0.5f, 1.0f, 9, 32); capsule->setTriggerInteractionEnabled(1); capsule->setIntersection(1, 0); capsule->setIntersectionMask(0x00000080, 0); // check the BulletIntersection bit capsule->setWorldTransform(translate(Math::Vec3(4.5f, 0.5f, 3.0f))); capsule->setMaterialFilePath("materials/mesh_base_2.mat", "*"); capsule->setName("capsule"); BodyRigidPtr bodyCapsule = BodyRigid::create(capsule); ShapeCapsule::create(bodyCapsule, 0.5f, 1.0f); bodyCapsule->setShapeBased(0); bodyCapsule->setMass(2.0f); } ``` </details> > **Notice:** Do not change the size of an object after the creation. The physics doesn't support scaling nodes with *Body* attached.
2. Build and run the solution in your IDE to generate a property file for the component.
3. Switch back to the UnigineEditor and create a new *Dummy Node*, rename it to **"object_generator"**, and place it somewhere in the world.
4. Attach the created *ObjectGenerator* component to the **"object_generator"** node to make it generate physical objects on the initialization.
5. Create **3** new materials in the UnigineEditor: in the *Materials* window, right-click the `mesh_base` material and choose *Create Child*. By default, the created materials are named as specified in the previous code snippet (`mesh_base_*`). Move the materials to the `data/materials` folder of your project (create this folder if it doesn't exist). ![](materials.png)
6. Select materials one by one in the *Materials* window and in the *Parameters* window switch to the *Parameters* tab and click on the color field near **Albedo** to choose different colors for the objects via the color picker. ![](color_picker.png)
7. Save changes to the world via **Ctrl + S**.
8. Run the project in your IDE to see the spawned physical objects in the world.