Hello World

We will now add physics to the scene. We do this by creating a new instance of the World class and adding several rigid bodies to it.

Replace the content of Program.cs with the following code (marked lines indicate the additions to the source code):

using System.Numerics;
using Raylib_cs;
using Jitter2;
using Jitter2.Collision.Shapes;
using Jitter2.Dynamics;
using Jitter2.LinearMath;
using static Raylib_cs.Raylib;

static Matrix4x4 GetRayLibTransformMatrix(RigidBody body)
{
    JMatrix ori = JMatrix.CreateFromQuaternion(body.Orientation);
    JVector pos = body.Position;

    return new Matrix4x4(ori.M11, ori.M12, ori.M13, pos.X,
                         ori.M21, ori.M22, ori.M23, pos.Y,
                         ori.M31, ori.M32, ori.M33, pos.Z,
                         0, 0, 0, 1.0f);
}

static Texture2D GenCheckedTexture(int size, int checks, Color colorA, Color colorB)
{
    Image imageMag = GenImageChecked(size, size, checks, checks, colorA, colorB);
    Texture2D textureMag = LoadTextureFromImage(imageMag);
    UnloadImage(imageMag);
    return textureMag;
}

const int NumberOfBoxes = 12;

// set a hint for anti-aliasing
SetConfigFlags(ConfigFlags.Msaa4xHint);

// initialize a 1200x800 px window with a title
InitWindow(1200, 800, "BoxDrop example");

// dynamically create a plane model
Texture2D texture = GenCheckedTexture(10, 1,  Color.LightGray, Color.Gray);
Model planeModel = LoadModelFromMesh(GenMeshPlane(10, 10, 10, 10));
SetMaterialTexture(ref planeModel, 0, MaterialMapIndex.Diffuse, ref texture);

// dynamically create a box model
texture = GenCheckedTexture(2, 1,  Color.White, Color.Magenta);
Mesh boxMesh = GenMeshCube(1, 1, 1);
Material boxMat = LoadMaterialDefault();
SetMaterialTexture(ref boxMat, MaterialMapIndex.Diffuse, texture);

// initialize the Jitter physics world
World world = new ();
world.SubstepCount = 4;

// add a body representing the plane
RigidBody planeBody = world.CreateRigidBody();
planeBody.AddShape(new BoxShape(10));
planeBody.Position = new JVector(0, -5, 0);
planeBody.IsStatic = true;

// add NumberOfBoxes cubes
for(int i = 0; i < NumberOfBoxes; i++)
{
    RigidBody body = world.CreateRigidBody();
    body.AddShape(new BoxShape(1));
    body.Position = new JVector(0, i * 2 + 0.5f, 0);
}

// create a camera
Camera3D camera = new ()
{
    Position = new Vector3(-20.0f, 8.0f, 10.0f),
    Target = new Vector3(0.0f, 4.0f, 0.0f),
    Up = new Vector3(0.0f, 1.0f, 0.0f),
    FovY = 45.0f,
    Projection = CameraProjection.Perspective
};

// 100 fps target
SetTargetFPS(100);

// simple render loop
while (!WindowShouldClose())
{
    BeginDrawing();
    ClearBackground(Color.Blue);

    BeginMode3D(camera);

    DrawModel(planeModel, Vector3.Zero, 1.0f, Color.White);

    world.Step(1.0f / 100.0f, true);

    foreach(var body in world.RigidBodies)
    {
        if (body == planeBody || body == world.NullBody) continue; // do not draw this
        DrawMesh(boxMesh, boxMat, GetRayLibTransformMatrix(body));
    }

    EndMode3D();
    DrawText($"{GetFPS()} fps", 10, 10, 20, Color.White);

    EndDrawing();
}

CloseWindow();

Running your program, you should now see a few boxes dynamically falling onto the ground.