A Beginners Guide

From Croquet Consortium

Introduction

So, you are new to Squeak and Croquet, are excited about what you have learned about this system, and now want to get started creating powerful applications...

The first thing to keep in mind is that it is imprortant not to think of the Croquet SDK as an application in itself - despite the fact that one can use the SDK to enter collaborative environment and do the types of things that you would expect to be provided by applications such as Second Life or ActiveWorlds (Croquet is intended to be used as a way of building simulations and real-time collaborative environments that are far more powerful, capable, and customizable than Second Life and ActiveWorlds).

In its current state of development, Croquet should be thought of as an enabling technology intended for use by software developers to create their own applications or customized OpenGL-based game engines - complete with user interfaces and application-specific features and functionalities. In this way it is more similar to a combination of a virtual machine-programming language-3D game engine "hybrid" than it is to a "level editor" that would be used to create environments that run on an existing game engine. Croquet-based "level editors" are currently being developed by a number of people, however, none has yet been made available as part of the distribution. It is anticipated that these tools will be available within the next year.

Connecting Two Computers

The Croquet SDK (Software Developer Kit) is a software toolkit for building realtime collaborative systems. To really experience Croquet you should create a shared, collaborative space inhabitied by more than one user. You will probably want two computers on a local area network to try this. Here is how:

Drag a Croquet world object out of the green objects bin onto the grey background. A window will appear where you release the mouse button and the system will create a live instance of the Croquet world. Two different ways of establishing shared spaces are described below.

1. Join a common space using Demo (Master) and Demo (Participant)

• On one computer, drag the Demo (Master) object out of the objects bin. Croquet will build an instance of the demo world, and make it available for participants to join. The master is ready to be joined once the clouds in the sky start moving.

• On another computer, drag the Demo (Participant) object out of the objects bin. The participant object will look for a master on the LAN, and when it finds one it will synchronize itself by copying the state of the shared world and then start it running. You will be able to tell you have synchronized with the other user(s) when you see the world and the clouds begin moving.

• Now that you and the other user(s) have joined the common world, you will be able to see each other's avatars, and changes made in the world (such as moving/creating objects) are reflected in everyone's copies of the world. If one of the participants leaves the world, their avatar will disappear, but they or other users can rejoin the world.

2. Establish a connection between two different master spaces using Sailing (Master) and SimpleDemo (Master)

• On one computer, drag the Sailing (Master) object out of the objects bin. Croquet will start an instance of the boating world which will then be available for participants to join.

• On another computer, drag the SImpleDemo (Master) object out of the objects bin. Again, Croquet will start an instance of this world which will be available for participants to join.

• From either of the worlds, go to the Tools menu and select the "Connect to Another World" option. In the Postcard Settings window, select from the popup list of nearby worlds, then click the OK button. This will create a one-way portal to the other world. If you then click in the content area of the portal window to open it, you will synchronize with the other world and will be able to drive your avatar through the portal to enter your friend's world.

• Once you are in the shared world, you and the other avatar(s) can collaboratively update the world. To coordinate your actions, you can use the text or audio chat tools found in the Talk menu.

See also, Getting Started#Connecting to Others.

Programing in Croquet

For basic information on how to approach programming in Croquet, please refer to the Developer's Guide (Please note that these documents do not attempt to teach you how to use the Squeak programming environment, or how to program in OpenGL. There are a number of useful resources available for both of these, including  Squeak: Object-Oriented Design with Multimedia Applications by Mark Guzdial, Prentice-Hall, 2000, and the OpenGL Programming Guide by Mason Woo, Jackie Neider, Tom Davis, and Dave Shreiner, Third Edition. Addison-Wesley. 1999).