JoltPhysics/Samples/Tests/General/ConveyorBeltTest.cpp

// Jolt Physics Library (https://github.com/jrouwe/JoltPhysics)
// SPDX-FileCopyrightText: 2023 Jorrit Rouwe
// SPDX-License-Identifier: MIT

#include <TestFramework.h>

#include <Tests/General/ConveyorBeltTest.h>
#include <Jolt/Physics/Collision/Shape/BoxShape.h>
#include <Jolt/Physics/Collision/Shape/CylinderShape.h>
#include <Jolt/Physics/Body/BodyCreationSettings.h>
#include <Layers.h>

JPH_IMPLEMENT_RTTI_VIRTUAL(ConveyorBeltTest)
{
	JPH_ADD_BASE_CLASS(ConveyorBeltTest, Test)
}

void ConveyorBeltTest::Initialize()
{
	// Floor
	CreateFloor();

	// Create conveyor belts
	const float cBeltWidth = 10.0f;
	const float cBeltLength = 50.0f;
	BodyCreationSettings belt_settings(new BoxShape(Vec3(cBeltWidth, 0.1f, cBeltLength)), RVec3::sZero(), Quat::sIdentity(), EMotionType::Static, Layers::NON_MOVING);
	for (int i = 0; i < 4; ++i)
	{
		belt_settings.mFriction = 0.25f * (i + 1);
		belt_settings.mRotation = Quat::sRotation(Vec3::sAxisY(), 0.5f * JPH_PI * i) * Quat::sRotation(Vec3::sAxisX(), DegreesToRadians(1.0f));
		belt_settings.mPosition = RVec3(belt_settings.mRotation * Vec3(cBeltLength, 6.0f, cBeltWidth));
		mLinearBelts.push_back(mBodyInterface->CreateAndAddBody(belt_settings, EActivation::DontActivate));
	}

	// Bodies with decreasing friction
	BodyCreationSettings cargo_settings(new BoxShape(Vec3::sReplicate(2.0f)), RVec3::sZero(), Quat::sIdentity(), EMotionType::Dynamic, Layers::MOVING);
	for (int i = 0; i <= 10; ++i)
	{
		cargo_settings.mPosition = RVec3(-cBeltLength + i * 10.0f, 10.0f, -cBeltLength);
		cargo_settings.mFriction = max(0.0f, 1.0f - 0.1f * i);
		mBodyInterface->CreateAndAddBody(cargo_settings, EActivation::Activate);
	}

	// Create 2 cylinders
	BodyCreationSettings cylinder_settings(new CylinderShape(6.0f, 1.0f), RVec3(-25.0f, 1.0f, -20.0f), Quat::sRotation(Vec3::sAxisZ(), 0.5f * JPH_PI), EMotionType::Dynamic, Layers::MOVING);
	mBodyInterface->CreateAndAddBody(cylinder_settings, EActivation::Activate);
	cylinder_settings.mPosition.SetZ(20.0f);
	mBodyInterface->CreateAndAddBody(cylinder_settings, EActivation::Activate);

	// Let a dynamic belt rest on it
	BodyCreationSettings dynamic_belt(new BoxShape(Vec3(5.0f, 0.1f, 25.0f), 0.0f), RVec3(-25.0f, 3.0f, 0), Quat::sIdentity(), EMotionType::Dynamic, Layers::MOVING);
	mLinearBelts.push_back(mBodyInterface->CreateAndAddBody(dynamic_belt, EActivation::Activate));

	// Create cargo on the dynamic belt
	cargo_settings.mPosition = RVec3(-25.0f, 6.0f, 15.0f);
	cargo_settings.mFriction = 1.0f;
	mBodyInterface->CreateAndAddBody(cargo_settings, EActivation::Activate);

	// Create an angular belt
	BodyCreationSettings angular_belt(new BoxShape(Vec3(20.0f, 0.1f, 20.0f), 0.0f), RVec3(10.0f, 3.0f, 0), Quat::sIdentity(), EMotionType::Static, Layers::NON_MOVING);
	mAngularBelt = mBodyInterface->CreateAndAddBody(angular_belt, EActivation::Activate);

	// Bodies with decreasing friction dropping on the angular belt
	for (int i = 0; i <= 6; ++i)
	{
		cargo_settings.mPosition = RVec3(10.0f, 10.0f, -15.0f + 5.0f * i);
		cargo_settings.mFriction = max(0.0f, 1.0f - 0.1f * i);
		mBodyInterface->CreateAndAddBody(cargo_settings, EActivation::Activate);
	}
}

void ConveyorBeltTest::OnContactAdded(const Body &inBody1, const Body &inBody2, const ContactManifold &inManifold, ContactSettings &ioSettings)
{
	// Linear belts
	bool body1_linear_belt = std::find(mLinearBelts.begin(), mLinearBelts.end(), inBody1.GetID()) != mLinearBelts.end();
	bool body2_linear_belt = std::find(mLinearBelts.begin(), mLinearBelts.end(), inBody2.GetID()) != mLinearBelts.end();
	if (body1_linear_belt || body2_linear_belt)
	{
		// Determine the world space surface velocity of both bodies
		const Vec3 cLocalSpaceVelocity(0, 0, -10.0f);
		Vec3 body1_linear_surface_velocity = body1_linear_belt? inBody1.GetRotation() * cLocalSpaceVelocity : Vec3::sZero();
		Vec3 body2_linear_surface_velocity = body2_linear_belt? inBody2.GetRotation() * cLocalSpaceVelocity : Vec3::sZero();

		// Calculate the relative surface velocity
		ioSettings.mRelativeLinearSurfaceVelocity = body2_linear_surface_velocity - body1_linear_surface_velocity;
	}

	// Angular belt
	bool body1_angular = inBody1.GetID() == mAngularBelt;
	bool body2_angular = inBody2.GetID() == mAngularBelt;
	if (body1_angular || body2_angular)
	{
		// Determine the world space angular surface velocity of both bodies
		const Vec3 cLocalSpaceAngularVelocity(0, DegreesToRadians(10.0f), 0);
		Vec3 body1_angular_surface_velocity = body1_angular? inBody1.GetRotation() * cLocalSpaceAngularVelocity : Vec3::sZero();
		Vec3 body2_angular_surface_velocity = body2_angular? inBody2.GetRotation() * cLocalSpaceAngularVelocity : Vec3::sZero();

		// Note that the angular velocity is the angular velocity around body 1's center of mass, so we need to add the linear velocity of body 2's center of mass
		Vec3 body2_linear_surface_velocity = body2_angular? body2_angular_surface_velocity.Cross(Vec3(inBody1.GetCenterOfMassPosition() - inBody2.GetCenterOfMassPosition())) : Vec3::sZero();

		// Calculate the relative angular surface velocity
		ioSettings.mRelativeLinearSurfaceVelocity = body2_linear_surface_velocity;
		ioSettings.mRelativeAngularSurfaceVelocity = body2_angular_surface_velocity - body1_angular_surface_velocity;
	}
}

void ConveyorBeltTest::OnContactPersisted(const Body &inBody1, const Body &inBody2, const ContactManifold &inManifold, ContactSettings &ioSettings)
{
	// Same behavior as contact added
	OnContactAdded(inBody1, inBody2, inManifold, ioSettings);
}