Transforms Transform

Transcription

1 Transforms The Transform is used to store a GameObject s position, rotation, scale and parenting state and is thus very important. A GameObject will always have a Transform component attached - it is not possible to remove a Transform or to create a GameObject without one.

2 Editing Transforms Transforms are manipulated in 3D space in the X, Y, and Z axes or in 2D space in just X and Y. A transform showing the color-coding of the axes

3 The View, Translate, Rotate, and Scale tools The tools can be used on any object in the scene. When you click on an object, you will see the tool gizmo appear within it. Transform gizmo

4 When you click and drag on one of the three gizmo axes, you will notice that its color changes to yellow. A Transform showing the selected (yellow) X axis

5 Parenting When a GameObject is a Parent of another GameObject, the Child GameObject will move, rotate, and scale exactly as its Parent does. You can think of parenting as being like the relationship between your arms and your body; whenever your body moves, your arms also move along with it. These multiple levels of parent-child relationships form a Transform hierarchy. The object at the very top of a hierarchy (ie, the only object in the hierarchy that doesn t have a parent) is known as the root. You can create a Parent by dragging any GameObject in the Hierarchy View onto another.

6 Example of a Parent-Child hierarchy. GameObjects with foldout arrows to the left of their names are parents.

7 Note that the Transform values in the Inspector for any child GameObject are displayed relative to the Parent s Transform values. These values are referred to as local coordinates.

8 Limitations with Non-Uniform Scaling Non-uniform scaling is when the Scale in a Transform has different values for x, y, and z; for example (2, 4, 2). In contrast, uniform scaling has the same value for x, y, and z; for example (3, 3, 3). Certain components do not fully support non-uniform scaling. For example, some components have a circular or spherical element defined by a radius property, among them Sphere Collider, Capsule Collider, Light and Audio Source. In cases like this the circular shape will not become elliptical under non-uniform scaling as you would expect and will simply remain circular.

9 Importance of Scale The scale of the Transform determines the difference between the size of a mesh in your modeling application and the size of that mesh in Unity. The mesh s size in Unity (and therefore the Transform s scale) is very important, especially during physics simulation. By default, the physics engine assumes that one unit in world space corresponds to one metre. If an object is very large, it can appear to fall in slow motion ; the simulation is actually correct since effectively, you are watching a very large object falling a great distance.

10 There are three factors that can affect the scale of your object: The size of your mesh in your 3D modeling application. The Mesh Scale Factor setting in the object s Import Settings. The Scale values of your Transform Component. Ideally, you should not adjust the Scale of your object in the Transform Component. The best option is to create your models at real-life scale so you won t have to change your Transform s scale. The next best option is to adjust the scale at which your mesh is imported in the Import Settings for your individual mesh.

11 Tips for Working with Transforms When parenting Transforms, it is useful to set the parent s location to <0,0,0> before adding the child Particle Systems are not affected by the Transform s Scale. If you are using Rigidbodies for physics simulation then be sure to read about the Scale property on the Rigidbody component reference page. Changing the Scale affects the position of child transforms. For example scaling the parent to (0,0,0) will position all children at (0,0,0) relative to the parent.

12 Adding Random Gameplay Elements Randomly chosen items or values are important in many games. Choosing a Random Item from an Array Picking an array element at random boils down to choosing a random integer between zero and the array s maximum index value (which is equal to the length of the array minus one). var element = myarray[random.range(0, myarray.length)];

13 Choosing Items with Different Probabilities 50% chance of friendly greeting 25% chance of running away 20% chance of immediate attack 5% chance of offering money as a gift You can visualise these different outcomes as a paper strip divided into sections each of which occupies a fraction of the strip s total length. In the script, the paper strip is actually an array of floats that contain the different probabilities for the items in order.

14 float Choose (float[] probs) { float total = 0; foreach (float elem in probs) { } total += elem; float randompoint = Random.value * total; for (int i= 0; i < probs.length; i++) { if (randompoint < probs[i]) {

15 return i; } } else { randompoint -= probs[i]; } } return probs.length - 1;

16 Shuffling a List A deck of cards is typically shuffled so they are not drawn in a predictable sequence. void Shuffle (int[] deck) { for (int i = 0; i < deck.length; i++) { int temp = deck[i]; int randomindex = Random.Range(0, deck.length); deck[i] = deck[randomindex]; deck[randomindex] = temp; } }

17 Random Points in Space A random point in a cubic volume can be chosen by setting each component of a Vector3 to a value returned by Random.value:- var randvec = Vector3(Random.value, Random.value, Random.value); This gives a point inside a cube with sides one unit long. The cube can be scaled simply by multiplying the X, Y and Z components of the vector by the desired side lengths. When the volume is a sphere, you can use Random.insideUnitSphere multiplied by the desired radius:- var randwithinradius = Random.insideUnitSphere * radius;

18 Rotation and Orientation in Unity Summary Rotations in 3D applications are usually represented in one of two ways, Quaternions or Euler angles. Each has its own uses and drawbacks. Unity uses Quaternions internally, but shows values of the equivalent Euler angles in the inspector to make it easy for you to edit.

19 The Difference Between Euler Angles and Quaternions Euler Angles Euler angles have a simpler representation, that being three angle values for X, Y and Z that are applied sequentially. Benefit: Euler angles have an intuitive human readable format, consisting of three angles. Benefit: Euler angles can represent the rotation from one orientation to another through a turn of more than 180 degrees Limitation: Euler angles suffer from Gimbal Lock. When applying the three rotations in turn, it is possible for the first or second rotation to result in the third axis pointing in the same direction as one of the previous axes.

20 Quaternions Quaternions can be used to represent the orientation or rotation of an object. This representation internally consists of four numbers (referenced in Unity as x, y, z & w) however these numbers don t represent angles or axes and you never normally need to access them directly. Benefit: Quaternion rotations do not suffer from Gimbal Lock. Limitation: A single quaternion cannot represent a rotation exceeding 180 degrees in any direction. Limitation: The numeric representation of a Quaternion is not intuitively understandable.

21 The rotation of a Game Object is displayed and edited as Euler angles in the inspector, but is stored internally as a Quaternion

22 Implications for Scripting When dealing with handling rotations in your scripts, you should use the Quaternion class and its functions to create and modify rotational values. Creating and Manipulating Quaternions Directly Unity s Quaternion class has a number of functions which allow you to create and manipulate rotations without needing to use Euler angles at all. For example: Creating: Quaternion.LookRotation Quaternion.AngleAxis Quaternion.FromToRotation

23 Manipulating: Quaternion.Slerp Quaternion.Inverse Quaternion.RotateTowards Transform.Rotate & Transform.RotateAround Here are some examples of mistakes commonly made using a hypothetical example of trying to rotate an object around the X axis at 10 degrees per second. And here is an example of using Euler angles in script correctly: // rotation scripting with Euler angles correctly. // here we store our Euler angle in a class variable, and only use it to

24 // apply it as a Euler angle, but we never rely on reading the Euler back. float x; void Update () { x += Time.deltaTime * 10; transform.rotation = Quaternion.Euler(x,0,0); }

25 Implications for Animation Many 3D authoring packages, and indeed Unity s own internal animation window, allow you to use Euler angles to specify rotations during an animation. These rotations values can frequently exceed range expressable by quaternions. For example, if an object should rotate 720 degrees in-place, this could be represented by Euler angles X: 0, Y: 720, Z:0. But this is simply not representable by a Quaternion value.

26 Unity s Animation Window Within Unity s own animation window, there are options which allow you to specify how the rotation should be interpolated - using Quaternion or Euler interpolation. By specifying Euler interpolation you are telling Unity that you want the full range of motion specified by the angles. With Quaternion rotation however, you are saying you simply want the rotation to end at a particular orientation, and Unity will use Quaternion interpolation and rotate across the shortest distance to get there.

27 External Animation Sources When importing animation from external sources, these files usually contain rotational keyframe animation in Euler format. Unity s default behaviour is to resample these animations and generate a new Quaternion keyframe for every frame in the animation, in an attempt to avoid any situations where the rotation between keyframes may exceed the Quaternion s valid range. There are still some situations where - even with resampling - the quaternion representation of the imported animation may not match the original closely enough, For this reason, in Unity 5.3 and onwards there is the option to turn off animation resampling, so that you can instead use the original Euler animation keyframes at runtime.

28 Trouble Shooting Script Editing Is there a way to get rid of the welcome page in MonoDevelop? Yes. In the MonoDevelop preferences, go to the Visual Style section, and uncheck Load welcome page on startup. Why does my script open in MonoDevelop when I have selected Visual Studio as my script editor? This happens when VS reports that it failed to open your script. The most common cause for this is an external plugin (e.g. Resharper) popping up a dialog at startup, requesting input from the user - this will cause VS to report that it failed to open.

29 Graphics Slow framerate and/or visual artifacts. This may occur if your video card drivers are not up to date.

30 Shadows Shadows also require certain graphics hardware support. Check if shadows are not completely disabled in Quality Settings. Shadows on Android and ios have these limitations: soft shadows are not available and in forward rendering rendering path only a single directional light can cast shadows. Some of my objects do not cast or receive shadows An object s Renderer must have Receive Shadows enabled for shadows to be rendered onto it. Also, an object must have Cast Shadows enabled in order to cast shadows on other objects (both are on by default).

31 Lights Lights are an essential part of every scene. While meshes and textures define the shape and look of a scene, lights define the color and mood of your 3D environment. You ll likely work with more than one light in each scene. Making them work together requires a little practice but the results can be quite amazing.

32 A simple, two-light setup Lights can be added to your scene from the GameObject- >Light menu.

33 You can add a Light Component to any selected GameObject by using Component->Rendering->Light. Light Component properties in the Inspector By simply changing the Color of a light, you can give a whole different mood to the scene.

34 Bright, sunny lights

35 Dark, medieval lights

36 Spooky night lights

37 Cameras Just as cameras are used in films to display the story to the audience, Cameras in Unity are used to display the game world to the player. You will always have at least one camera in a scene, but you can have more than one. Multiple cameras can give you a two-player splitscreen or create advanced custom effects. You can animate cameras, or control them with physics.

38 Cross-Platform Considerations Most of Unity s API and project structure is identical for all supported platforms and in some cases a project can simply be rebuilt to run on different devices. However, fundamental differences in the hardware and deployment methods mean that some parts of a project may not port between platforms without change.

39 Input The most obvious example of different behaviour between platforms is in the input methods offered by the hardware. Keyboard and joypad The Input.GetAxis function is very convenient on desktop platforms as a way of consolidating keyboard and joypad input. However, this function doesn t make sense for the mobile platforms which rely on touchscreen input. Likewise, the standard desktop keyboard input doesn t port over to mobiles well for anything other than typed text. It is worthwhile to add a layer of abstraction to your input code if you are considering porting to other platforms in the future.

40 // Returns values in the range (== left.. right). function Steering() { } return Input.GetAxis("Horizontal"); // Returns values in the range (== accel.. brake). function Acceleration() { } return Input.GetAxis("Vertical");

41 var currentgear: int; // Returns an integer corresponding to the selected gear. function Gears() { if (Input.GetKeyDown("p")) currentgear++; else if (Input.GetKeyDown("l")) currentgear--; } return currentgear;

42 Touches and clicks The Input.GetMouseButtonXXX functions are designed so that they have a reasonably obvious interpretation on mobile devices even though there is no mouse as such. A single touch on the screen is reported as a left click and the Input.mousePosition property gives the position of the touch as long as the finger is touching the screen. This means that games with simple mouse interaction can often work transparently between the desktop and mobile platforms.

43 Memory, storage and CPU performance Mobile devices inevitably have less storage, memory and CPU power available than desktop machines and so a game may be difficult to port simply because its performance is not acceptable on lower powered hardware. Movie playback Currently, mobile devices are highly reliant on hardware support for movie playback. The result is that playback options are limited and certainly don t give the flexibility that the MovieTexture asset offers on desktop platforms.

44 Storage requirements Video, audio and even textures can use a lot of storage space and you may need to bear this in mind if you want to port your game. Storage space (which often also corresponds to download time) is typically not an issue on desktop machines but this is not the case with mobiles. Furthermore, mobile app stores often impose a limit on the maximum size of a submitted product. It may require some planning to address these concerns during the development of your game.

45 Automatic memory management The recovery of unused memory from dead objects is handled automatically by Unity and often happens imperceptibly on desktop machines. CPU power A game that runs well on a desktop machine may suffer from poor framerate on a mobile device simply because the mobile CPU struggles with the game s complexity.

46 Publishing Builds How to access the Build Settings and how to create different builds of your games. File->Build Settings is the menu item to access the Build Settings window.

47 The Build Settings window

48 Each of your scenes has a different index value. Scene 0 is the first scene that will be loaded when you build the game. When you want to load a new scene, use Application.LoadLevel() inside your scripts. If you ve added more than one scene file and want to rearrange them, simply click and drag the scenes on the list above or below others until you have them in the desired order. Enabling the Development Build checkbox on a player will enable Profiler functionality and also make the Autoconnect Profiler and Script Debugging options available.

49 Building standalone players With Unity you can build standalone applications for Windows, Mac and Linux. It s simply a matter of choosing the build target in the build settings dialog, and hitting the Build button. When building standalone players, the resulting files will vary depending on the build target. For the Windows build target, an executable file (.exe) will be built, along with a Data folder which contains all the resources for your application. Distributing your standalone on Windows you need to provide both the.exe file and the Data folder for others to run it.

50 Inside the build process The building process will place a blank copy of the built game application wherever you specify. Then it will work through the scene list in the build settings, open them in the editor one at a time, optimize them, and integrate them into the application package. Any GameObject in a scene that is tagged with EditorOnly will not be included in the published build. When a new level loads, all the objects in the previous level are destroyed. To prevent this, use DontDestroyOnLoad() on any objects you don t want destroyed. After the loading of a new level is finished, the message: OnLevelWasLoaded() will be sent to all active game objects.

51 Preloading Published builds automatically preload all assets in a scene when the scene loads. The exception to this rule is scene 0. This is because the first scene is usually a splashscreen, which you want to display as quickly as possible. To make sure all your content is preloaded, you can create an empty scene which calls Application.LoadLevel(1). In the build settings make this empty scene s index 0. All subsequent levels will be preloaded.

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