Eminent, www.unity3d.com . Its a fully featured game development platform for mac based platforms and windows amongst others.
Quote: "I have, and I used the free version up until I heard about UDK (And got my computer updated). But, how exactly are they different? Sure the way you create the game with them might be a bit different, but in the end you get a game."
Whilst what you are saying is entirely true, I can try and summarize the difference as I understand it.
1. UDK in all likelihood has the more powerful graphics engine behind it
2. Unity3D is a generic development platform, whereas UDK is far more specialised for first person shooter games (Not saying that many types of games are not possible with UDK, but it is not nessecarily designed for this)
3. Unity3D supports web deployment on mac and windows, which allows people to play your game in a browser window
4. Unity3D offers iphone and some console deployment (at extra cost)
5. Unity3D is cheaper than UDK. Its a simple fact in the long run. You buy unity once, make 10 games = $120 per game. UDK is much more expensive when put into these terms.
My point is, if you want to make a first person shooter with lots of epic physics and graphical effects in a development pipeline that is suited to it, then use the UDK, otherwise I would seriously consider unity3D.
To summarize, both are excellent pieces of software and you should make the decision based ultimately on what you wish to achieve in the long term.
The main difference comes in the fact that with Unity3D you have a blank canvas, and a managed engine and scripting environment to work with. Generic things such as meshes, physics, lights, materials, rendering, sound and input are covered, but they are not limited. UDK has much more of the legwork for an FPS already done for you, so you can jump right in and do an FPS quickly in UDK, but it may be quicker to make any other type of game in Unity3D.
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