QuarkPhysics

QuarkPhysics is a 2D physics engine optimized for games. It is designed to simulate a variety of physical entities within a unified environment, including:

• Rigid bodies
• Soft bodies
• Different physics models

A QWorld object manages all physics objects and handles the simulation steps. You must create a world instance first, configure its properties like gravity and iteration count, and then call Update() to progress the simulation.

To configure the world:

• Use SetGravity(QVector) to set the gravity vector.
• Use SetIterationCount(int) to set the number of physics iterations per step.
• Use Update() to advance the simulation.

// Create a world
QWorld *world = new QWorld(); 

// Set the gravity value
world->SetGravity(QVector(0.0f, 0.2f)); 

// Set the iteration count per step of physics in the world
world->SetIterationCount(4); 

// Update the physics simulation of the world as a step
world->Update();

Soft bodies are created similarly to rigid bodies but use the QSoftBody class. A QSoftBody requires a QMesh that defines its shape. For soft bodies, it is often necessary to use gridded meshes to provide internal particle connections and spring networks.

// Create a Soft Body
QSoftBody *body = new QSoftBody();

// Create a Mesh  
QMesh *polygonMesh = QMesh::CreateWithPolygon(radius, sideCount, QVector(centerPosX, centerPosY));

// Add the Mesh to the Soft Body
body->AddMesh(polygonMesh); 

// Set the Body Position
body->SetPosition(QVector(posX, posY));

// Set the Body Rotation
body->SetRotation(radAngle); // or body->SetRotationDegree(degreeAngle)

// Add the Soft Body to the World
world->AddBody(body);

To build the project, ensure you have SFML and CMake installed on your system. You can build using the provided shell scripts.

Standard build: Navigate to the main project folder and run:

./build.sh -r

Fast Linux build: If you are on Linux and want a faster compilation, run:

./run_linux_fast.sh -r

#!/bin/bash
./build.sh -r

Use QJoint to connect two rigid bodies with constraints. You must add the joint to the world using QWorld::AddJoint().

Connecting to a fixed point in space: To connect a body to a specific point in the world (rather than another body), pass nullptr as the second body in the QJoint constructor and provide the world anchor position.

// Connect two bodies
QJoint *joint = new QJoint(bodyA, anchorWorldPositionA, anchorWorldPositionB, bodyB);
world->AddJoint(joint);

// Connect a body to a point in space (e.g., for mouse interaction)
QJoint *mouseJoint = new QJoint(bodyA, anchorWorldPositionA, mousePosition, nullptr);
world->AddJoint(mouseJoint);

To build and run the included examples, you must first install SFML 2.x and CMake on your system.

Using the build script

From the main project folder, run:

./build.sh -r

Fast Linux compilation

If you are on Linux, you can compile the project directly via gcc using:

./run_linux_fast.sh -r

To create a rigid body, follow these steps:

1. Instantiate a QRigidBody object.
2. Create a QMesh to define the shape (e.g., using QMesh::CreateWithRect).
3. Attach the mesh to the body using AddMesh().
4. Set the body's position with SetPosition() and rotation with SetRotation() (radians) or SetRotationDegree() (degrees).
5. Add the body to the world using QWorld::AddBody().

// Create a Rigid Body
QRigidBody *body = new QRigidBody();

// Create a Mesh  
QMesh *rectMesh = QMesh::CreateWithRect(QVector(rectWidth, rectHeight), QVector(centerPosX, centerPosY));

// Add the Mesh to the Rigid Body
body->AddMesh(rectMesh); 

// Set the Body Position
body->SetPosition(QVector(posX, posY));

// Set the Body Rotation
body->SetRotation(radAngle); // or body->SetRotationDegree(degreeAngle)

// Add the Rigid Body to the World
world->AddBody(body);

To give soft bodies structural integrity, use QMesh methods that generate internal spring connections via grid networks.

• Gridded Rectangle: Use QMesh::CreateWithRect and provide gridRowCount and gridColumnCount.
• Gridded Polygon: Use QMesh::CreateWithPolygon and provide a polarGrid value.

// Create a Gridded Rectangle Mesh
int gridColumnCount = 3;
int gridRowCount = 3;
QMesh *griddedRectMesh = QMesh::CreateWithRect(QVector(width, height), QVector(centerX, centerY), QVector(gridRowCount, gridColumnCount));
mySoftBody->AddMesh(griddedRectMesh);

// Create a Gridded Polygon Mesh
int polarGrid = 2;
QMesh *griddedPolyMesh = QMesh::CreateWithPolygon(64, 12, QVector(centerX, centerY), polarGrid);
mySoftBody->AddMesh(griddedPolyMesh);