Babylon.js/Playground/scripts/drag and drop.js

var createScene = function () {
    var scene = new BABYLON.Scene(engine);
    var camera = new BABYLON.ArcRotateCamera("Camera", 0, 0, 10, new BABYLON.Vector3(0, 0, 0), scene);
    camera.setPosition(new BABYLON.Vector3(20, 200, 400));

    camera.lowerBetaLimit = 0.1;
    camera.upperBetaLimit = (Math.PI / 2) * 0.99;
    camera.lowerRadiusLimit = 150;

    scene.clearColor = new BABYLON.Color3(0, 0, 0);

    // Light
    var light = new BABYLON.PointLight("omni", new BABYLON.Vector3(0, 50, 0), scene);

    // Ground
    var ground = BABYLON.Mesh.CreateGround("ground", 1000, 1000, 1, scene, false);
    var groundMaterial = new BABYLON.StandardMaterial("ground", scene);
    groundMaterial.specularColor = BABYLON.Color3.Black();
    ground.material = groundMaterial;

    // Meshes
    var redSphere = BABYLON.Mesh.CreateSphere("red", 32, 20, scene);
    var redMat = new BABYLON.StandardMaterial("ground", scene);
    redMat.diffuseColor = new BABYLON.Color3(0.4, 0.4, 0.4);
    redMat.specularColor = new BABYLON.Color3(0.4, 0.4, 0.4);
    redMat.emissiveColor = BABYLON.Color3.Red();
    redSphere.material = redMat;
    redSphere.position.y = 10;
    redSphere.position.x -= 100;

    var greenBox = BABYLON.Mesh.CreateBox("green", 20, scene);
    var greenMat = new BABYLON.StandardMaterial("ground", scene);
    greenMat.diffuseColor = new BABYLON.Color3(0.4, 0.4, 0.4);
    greenMat.specularColor = new BABYLON.Color3(0.4, 0.4, 0.4);
    greenMat.emissiveColor = BABYLON.Color3.Green();
    greenBox.material = greenMat;
    greenBox.position.z -= 100;
    greenBox.position.y = 10;

    var blueBox = BABYLON.Mesh.CreateBox("blue", 20, scene);
    var blueMat = new BABYLON.StandardMaterial("ground", scene);
    blueMat.diffuseColor = new BABYLON.Color3(0.4, 0.4, 0.4);
    blueMat.specularColor = new BABYLON.Color3(0.4, 0.4, 0.4);
    blueMat.emissiveColor = BABYLON.Color3.Blue();
    blueBox.material = blueMat;
    blueBox.position.x += 100;
    blueBox.position.y = 10;


    var purpleDonut = BABYLON.Mesh.CreateTorus("red", 30, 10, 32, scene);
    var purpleMat = new BABYLON.StandardMaterial("ground", scene);
    purpleMat.diffuseColor = new BABYLON.Color3(0.4, 0.4, 0.4);
    purpleMat.specularColor = new BABYLON.Color3(0.4, 0.4, 0.4);
    purpleMat.emissiveColor = BABYLON.Color3.Purple();
    purpleDonut.material = purpleMat;
    purpleDonut.position.y = 10;
    purpleDonut.position.z += 100;

    // Events
    var canvas = engine.getRenderingCanvas();
    var startingPoint;
    var currentMesh;

    var getGroundPosition = function () {
        // Use a predicate to get position on the ground
        var pickinfo = scene.pick(scene.pointerX, scene.pointerY, function (mesh) { return mesh == ground; });
        if (pickinfo.hit) {
            return pickinfo.pickedPoint;
        }

        return null;
    }

    var onPointerDown = function (evt) {
        if (evt.button !== 0) {
            return;
        }

        // check if we are under a mesh
        var pickInfo = scene.pick(scene.pointerX, scene.pointerY, function (mesh) { return mesh !== ground; });
        if (pickInfo.hit) {
            currentMesh = pickInfo.pickedMesh;
            startingPoint = getGroundPosition(evt);

            if (startingPoint) { // we need to disconnect camera from canvas
                setTimeout(function () {
                    camera.detachControl(canvas);
                }, 0);
            }
        }
    }

    var onPointerUp = function () {
        if (startingPoint) {
            camera.attachControl(canvas, true);
            startingPoint = null;
            return;
        }
    }

    var onPointerMove = function (evt) {
        if (!startingPoint) {
            return;
        }

        var current = getGroundPosition(evt);

        if (!current) {
            return;
        }

        var diff = current.subtract(startingPoint);
        currentMesh.position.addInPlace(diff);

        startingPoint = current;

    }

    canvas.addEventListener("pointerdown", onPointerDown, false);
    canvas.addEventListener("pointerup", onPointerUp, false);
    canvas.addEventListener("pointermove", onPointerMove, false);

    scene.onDispose = function () {
        canvas.removeEventListener("pointerdown", onPointerDown);
        canvas.removeEventListener("pointerup", onPointerUp);
        canvas.removeEventListener("pointermove", onPointerMove);
    }

    return scene;
};