Session 6. Microsoft and The DigiPen Institute of Technology Webcast Series

Transcription

1 Session 6 Microsoft and The DigiPen Institute of Technology Webcast Series

2 HOW TO USE THIS DOCUMENT This e-textbook has been distributed electronically using the Adobe Portable Document Format (PDF) format. More than just a converted text file, this document was designed to take advantage of this medium so that both instructors and participants, using the free Adobe Acrobat Reader version 6.0 or 7.0, can create personalized versions of the document. They can easily search, highlight text, and add comments. This section will cover how to use this document and provides tips on the best practices. On the left side of the document there are tabs. If you click on the bookmark tab, you will see the different chapters of the book in Red. If you click on them they will take you to that part of the book. You can expand the bookmarks by clicking the plus sign next to each bookmark to see the different sections of that particular chapter. Bookmarks The sections are color-coded as follows: BLUE Sub-sections of content for a given chapter. ORANGE Examples are orange. 2

3 Searching the Document This document makes it easy for users to search through the document for specific words or phrases. To access this feature: Press CTRL+F Or Click the Edit in the top menu and click Search. Or Click on the the toolbar. icon on This will open up the search dialogue box on the right side of the screen. Simply type in the word or phrase and choose the options that best fit your search and click Search. To hide the dialogue box, click the Hide button in the top right-hand corner. Commenting One of the most useful functions available to users is the ability to use Adobe Acrobat Reader version 6.0 or 7.0 to highlight important sections of text and to add personal comments to the user s copy of this PDF. Much like how you would use a highlighter or scribble comments in the margin, this function enhances the PDF to be a functional study resource. Click the Commenting icon or in the top menus, click Tools and scroll down to Commenting. In the scroll down menu that appears, select Show Commenting Toolbar. You will notice that there are a few options to choose from. The tools you will be primarily concerned with are the Note Tool and the Highlighter. 3

4 Notes The Note Tool allows you to place sticky notes anywhere you wish in the document. Simply click on this icon and click anywhere in the document. A small text window will open for the user to enter comments. Comment/Notes can be minimized or left open. Minimized notes can be opened again by double clicking the icon of the note you wish to open. In the tabs on the left of the screen is the Comments tab. This allows the user to view all of the comments. This section allows the user to print/import/export the comments. You can use the import/export function to share your notes with other participants. In the top right corner of the Comments window is Options under which selected comments can be imported or exported. 4

5 Highlighting The Highlighter allows a user to highlight sections of text Customizing the Highlighing/Commenting Feature To further customize these features open the Properties Toolbar by either pressing CTRL+E or clicking View in the top menu, scrolling down to Toolbars and click Properties Bar. The Properties Toolbar allows you to choose the color, transparency and icons that appear when you use the commenting tools. To change the properties of a note or highlighted section after it is already placed, right click on the icon or section and select Properties. You will be able to change the color, transparency, the icon, or the Author name. 5

6 Other Functionality Snapshot Tool Another useful tool in this document is the Snapshot Tool. This allows a user to take a picture of a section of the screen and paste it into PowerPoint presentations, Word documents and other programs. To use this tool, click on the Snapshot Tool icon and drag an area select window around the section of the document you wish to put onto the clipboard for pasting into another program. 6

7 BACKGROUND COLLISION Object Movement Using The Grid System In this grid-based game, all the objects are placed using a pre-determined distance from each other. When creating any GameObject that moves on the grid (except the grid itself which is also an object), you pass two integers X and Y as parameters, or a Node object (which in its turn has these two integers X and Y saved by the class variables). public Enemy(Node CurrentNode public Node(int X, int Y, int NewIndex public Cookie(int X, int Y, COOKIETYPE NewType public Player(Node NewSource For example, the cookies are all aligned both vertically and horizontally. Each cookie is equidistant from the previous and the next one. The same idea applies to the nodes. This was achieved by using a mapped coordinates systems. In other words, by creating an object and passing 2, 3 as parameters (X=2 and Y=3), the object is not placed at position (2, 3, 0) in the world, instead, the coordinates are multiplied by a predefined value, in order to get the final position in the 3D world. The Cookie constructor passes the point to the base class (GameObject class) base(new Vector3(-70.0f + X * 15, -60.0f + Y * 15, -3.0f) Using offsets X Axis Position Position.X is equal to -70.0f + X * 15 This equation means that when we pass 0 as X, the object s position on the X axis will be -70. When X is different form 0, its value will be multiplied by 15 and the result is added to -70. For example, if an object has its X value equal to 0, and another object has its X value equal to 1, these objects will be 15 units away from each other in the X axis. Y Axis Position Position.Y is equal to -60.0f + Y * 15 This equation means that when we pass 0 as Y, the object s position on the Y axis will be -60. When Y is different form 0, its value will be multiplied by 15 and the result is added to -60. For example, if an object has its Y value equal to 0, and another object has its Y value equal to 1, these objects will be 15 units away from each other in the Y axis. Z-Axis Position We only pass two integers in the constructors of game objects. X and Y. As explained above, these tow integers will let us determine the position of the game object on the X axis and Y axis. Since all our objects will be placed slightly above the grid, their position on the Z axis is predefined (In the case of Puc the Pirate it is -3, and cannot be assigned to the game object while creating it. You can still create another class derived from the class GameObject, and let its constructor take a real 3D position and pass it to the base class. But it is preferred to stick with the mapped coordinates system for all the objects that should be on the grid, since that it will take much more time to place each object manually in the world. 7

8 Example Node System In Puc the Pirate, all the objects (except the grid and the cookies) are placed on nodes (that is why they take a Node object as parameter). Therefore knowing the nodes positions before creating most of the game objects is a must. The reason we are placing these game objects on the nodes is because they will use those nodes to navigate properly in the grid. When Puc goes directly towards a wall, he stops. It appears that Puc has collided with the wall, and obviously could not go further so he stopped. What really happened is that Puc reached a node and coud not find a new node to go to. Nodes are manually placed at each point where game objects (which are using the nodes in order to navigate) can change their current direction. When we created the nodes, we four boolean values as parameters: public Node( bool UP, bool RIGHT, bool DOWN, bool LEFT) These four boolean values determine if a node has a connection to the respective neighbor that each boolean value represents. If it is set to true, then the AutoAssignNeighbors function will find the closest Node in the specified direction and link it to the current node. The node linking is done by saving a reference to all the neighboring nodes in the array: public Node[] Neighbours = null, null, null, null ; 8

9 Here is an example of how the nodes are linked: The red spheres represent nodes and the thick lines are the links between the respective nodes. Now how does the game, using the input of the player, make Puc navigate the grid using those nodes are the connections between them? These variables control Puc s movement: private Node Source = null; private Node Destination = null; private Vector3 CurrentMove; MOVEDIRECTION CurrentDirection, NextPossibleDirection; float Speed = 0.5f; Source: The node Puc has already reached (or started at the beginning of the level). Destination: The node that Puc is currently heading toward (in the case where Puc is not moving, Destination will be the same as Source). CurrentMove: The current vector Puc is using to go from the Source node to the Destination node. CurrentDirection: A member of the enumeration MOVEDIRECTION UP, DOWN, LEFT, RIGHT, STILL It holds Puc s current direction. In the case where Puc is not moving, the value of this variable will be STILL. NextPossibleDirection: The direction Puc will attempt to go to. This variable is directly affected by the player s input. This is the direct effect that the keyboard input has on Puc s movement: switch (e.keycode) case Keys.Up: NextPossibleDirection = MOVEDIRECTION.UP; case Keys.Down: 9

10 NextPossibleDirection = MOVEDIRECTION.DOWN; case Keys.Left: NextPossibleDirection = MOVEDIRECTION.LEFT; case Keys.Right: NextPossibleDirection = MOVEDIRECTION.RIGHT; The varaible NextPossibleDirection holds the direction that the player wishes to make Puc use. Case 1 (Same): The player input is the same as Puc s current direction. Nothing is done in this case. Case 2 (Opposite): This is the only case where the next possible movement could be used directly (without checking if Puc is currently at a node) when the player turns Puc in the opposite direction. For example, if Puc is moving to the right, and the player presses the left arrow, or if Puc is moving upward, and the player presses the down arrow. Example If Puc is moving to the right, we can be sure that he is moving along a line between two nodes that are aligned, that is why flipping Puc s direction does not require much checking. The same concept is applied vertically. Case 3 (Different): When the player inputs a direction that is totally unrelated to the current direction, nothing is done until the next node (Referenced by the variable Destination) is reached. 10

11 Example The blue arrow represents Puc s current movement direction, which is saved in the variable CurrentDirection, and while moving right, the player presses the Up key. Puc can not move into the desired new direction, so the direction was saved by the variable NextPossibleDirection. At the beginning of Puc s Update function, a function HandleMovement is called. This function handles the possible change in Puc s direction. private void HandleMovement() if (CollisionTwoD(this.Position, Destination.Position)) //Position = Destination.Position; Position.X = Destination.Position.X; Position.Y = Destination.Position.Y; Source = Destination; //trying the new direction if (Game.CurrentLevel.WantToMove(Source.index, NextPossibleDirection, out CurrentMove)) CurrentMove.Normalize(); CurrentDirection = NextPossibleDirection; Destination = Source.Neighbours[(int)NextPossibleDirection]; //trying the old direction if (Game.CurrentLevel.WantToMove(Source.index, CurrentDirection, out CurrentMove)) CurrentMove.Normalize(); Destination = Source.Neighbours[(int)CurrentDirection]; else CurrentDirection = MOVEDIRECTION.STILL; 11

12 This function first checks if Puc reached the node referenced by the variable Destination. A 2D collision was used instead of the spherical 3D collision to take care of the situation where Puc is jumping over a node. Example In the 2D collision, Puc s elevation does not affect whether Puc collides with the destination node or not. To avoid the situation where Puc s current direction is before the node he is reaching for, and the next position is after it (in other words, neither of these two positions collide with the node), a small check is performed before Puc s movement update in each loop: if (Vector2.LengthSq(NewPosition2D - OldPosition2D) >= Vector2.LengthSq(DestinationPosition2D - OldPosition2D)) Position.X = Destination.Position.X; Position.Y = Destination.Position.Y; else Position.X += Speed * CurrentMove.X; Position.Y += Speed * CurrentMove.Y; Here, we are checking Puc s next direction. If it is beyond the destination node, we place him on that destination. If not, we move Puc normally. 12

13 This situation usually arises when we set a relatively high-speed value for the object. The same concept is used for all objects that move using the nodes, enemies for example. When Puc collides (2D collision) with the node referenced by Destination, we must check which node Puc should move towards. The function now checks the direction that was chosen by the player that was saved in NextPossibleDirection. if (Game.CurrentLevel.WantToMove(Source.index, NextPossible- Direction, out CurrentMove)) The WantToMove function takes the node where Puc is currently located (Source), and the direction he will attempt to use. Depending on the neighbors of the source node, WantToMove will return a Boolean value whether this direction is acceptable or not. In this case shown above, Puc reached a node. The direction he will attempt to use is the one pointed by the green arrow (which is saved in the variable NextPossibleDirection). If it is acceptable, it will be taken, if not, the current direction is the one pointed by the blue arrow (saved in the variable CurrentDirection). if (Game.CurrentLevel.WantToMove(Source.index, CurrentDirection, out CurrentMove)) We checked the next possible direction before the current one because the direction saved in the variable NextPossibleDirection represents the player s last input. In other words, it is the direction the player wants to move Puc. If both directions are not acceptable, the current direction is set to STILL, and Puc will stop moving until a new acceptable input is received from the player. 13

14 Here, Puc will attempt to move Right (NextPossibleDirection). This is impossible because of the wall. Puc will then attempt to continue moving in the current direction (CurrentDirection), but this will also be rejected because of the wall. Therefore, in this situation, the only solution for Puc is to stop, which is done by setting the current direction to STILL. CurrentDirection = MOVEDIRECTION.STILL; Adding Background Collision To add background collision, add the highlighted code to each of the tasks below: File Name = Grid.cs Class Name = class Grid Function Name = public Grid(Vector3 newposition, int New- Width, int NewHeight, Meshes newmeshindex) : base(newposition, newmeshindex) Replace the highlighted code: public Grid(Vector3 newposition, int NewWidth, int NewHeight, Meshes newmeshindex) : base(newposition, newmeshindex) Width = NewWidth; Height = NewHeight; int index = 0; GridNodes.Add(new Node(0, 0, index++, Level.LevelMeshHolder.GetMesh("NormalCoin.x"), true, true, false, false)); Update(Matrix.Identity); 14

15 With the following code: public Grid(Vector3 newposition, int NewWidth, int NewHeight, Meshes newmeshindex) : base(newposition, newmeshindex) Width = NewWidth; Height = NewHeight; int index = 0; //Adding all the nodes, setting their mapped positions neighbours, then finding the shortest paths among each others using Dijkstra s algorithm GridNodes.Add(new Node(0, 0, index++, Level.LevelMeshHolder.GetMesh(2), true, true, false, false)); GridNodes.Add(new Node(2, 0, index++, Level.LevelMeshHolder.GetMesh(2), true, true, false, true)); GridNodes.Add(new Node(4, 0, index++, Level.LevelMeshHolder.GetMesh(2), true, true, false, true)); GridNodes.Add(new Node(5, 0, index++, Level.LevelMeshHolder.GetMesh(2), true, true, false, true)); GridNodes.Add(new Node(7, 0, index++, Level.LevelMeshHolder.GetMesh(2), true, true, false, true)); GridNodes.Add(new Node(9, 0, index++, Level.LevelMeshHolder.GetMesh(2), true, false, false, true)); Add also the following nodes, replacing... with index++, Level.LevelMeshHolder.GetMesh(2) (1, 1,...,true,false,false, false)); (2, 1,..., false, true, true, false)); (3, 1,..., true, false, false, true)); (4, 1,..., true, true, true, false)); (5, 1,..., true, false, true, true)); (6, 1,..., true, true, false, false)); (7, 1,..., false, false, true, true)); (8, 1,..., true, false, false, false)); (0, 2,..., true, true, true, false)); (1, 2,..., false, true, true, true)); (2, 2,..., true, true, false, true)); (3, 2,..., false, false, true, true)); (6, 2,..., false, true, true, false)); (7, 2,..., true, true, false, true)); (8, 2,..., false, true, true, true)); (9, 2,..., true, false, true, true)); (0, 3,..., true, true, true, false)); (1, 3,..., true, false, false, true)); (2, 3,..., false, true, true, false)); (3, 3,..., true, true, false, true)); (4, 3,..., false, true, true, true)); (5, 3,..., false, true, true, true)); (6, 3,..., true, true, false, true)); (7, 3,..., false, false, true, true)); (8, 3,..., true, true, false, false)); (9, 3,..., true, false, true, true)); (0, 4,..., false, false, true, false)); 15

16 (1, 4,..., true, true, true, false)); (3, 4,..., true, true, true, true)); (4, 4,..., true, true, false, true)); (5, 4,..., true, false, false, true)); (6, 4,..., true, true, true, false)); (8, 4,..., true, false, true, true)); (9, 4,..., false, false, true, false)); (0, 5,..., true, true, false, false)); (1, 5,..., false, false, true, true)); (2, 5,..., false, true, false, false)); (3, 5,..., true, false, true, true)); (4, 5,..., false, true, true, false)); (5, 5,..., false, true, true, true)); (6, 5,..., true, true, true, true)); (7, 5,..., false, false, false, true)); (8, 5,..., false, true, true, false)); (9, 5,..., true, false, false, true)); (0, 6,..., false, true, true, false)); (1, 6,..., true, true, false, true)); (3, 6,..., true, true, true, true)); (6, 6,..., true, true, true, true)); (8, 6,..., true, true, false, true)); (9, 6,..., false, false, true, true)); (0, 7,..., true, true, false, false)); (1, 7,..., false, true, true, true)); (2, 7,..., true, false, false, true)); (3, 7,..., true, true, true, false)); (6, 7,..., true, false, true, true)); (7, 7,..., true, true, false, false)); (8, 7,..., false, true, true, true)); (9, 7,..., true, false, false, true)); (0, 8,..., false, true, true, false)); (2, 8,..., false, true, true, true)); (3, 8,..., false, true, true, true)); (6, 8,..., false, true, true, true)); (7, 8,..., false, true, true, true)); (9, 8,..., false, false, true, true)); //saving the final number of nodes NumberOfNodes = index; //creating the double dimensional array which will hold the paths information Path = new int[numberofnodes,numberofnodes]; AutoAssignNeighbors(); AssignWeights(); Update(Matrix.Identity); File Name = Player.cs Class Name = class Player 16

17 Function Name = public void KeyPressedHandler(System.Windows.Forms.KeyEventArgs e) Replace the highlighted code in the function. public void KeyPressedHandler(System.Windows.Forms.KeyEventArgs e) QUALIFY Qualify; switch (e.keycode) case Keys.Up: Position.Y++; case Keys.Down: Position.Y--; case Keys.Left: Position.X--; case Keys.Right: Position.X++; if (NextPossibleDirection!= MOVEDIRECTION.STILL) Qualify = QualiyfyTwoDirections(CurrentDirection, NextPossibleDirection); if (Qualify == QUALIFY.SAME) return; else if (Qualify == QUALIFY.OPPOSITE) CurrentDirection = NextPossibleDirection; Node tmp = Source; Source = Destination; Destination = tmp; CurrentMove.Multiply(-1); CurrentMove.Normalize(); With the following code: //saving the key input int the variable NextPossibleDirection switch (e.keycode) case Keys.Up: NextPossibleDirection = MOVEDIRECTION.UP; case Keys.Down: NextPossibleDirection = MOVEDIRECTION.DOWN; 17

18 case Keys.Left: NextPossibleDirection = MOVEDIRECTION.LEFT; case Keys.Right: NextPossibleDirection = MOVEDIRECTION.RIGHT; OBJECT COLLISION Object-Object Collision In games, you need to know when two objects collide in order to trigger a special functionality. There are several types of collision algorithms. Which one you use depends on why you need the collision. In the case of a real physics reflection simulation, you will need a very precise collision algorithm that can determine the two faces (polygons) that collided and their normal vectors. You will use those in order to determine the reflected angle and direction of each object. In Puc the Pirate, we need simpler collision detection, since we only need to know when two objects collide, not which faces actually collided. The collision in Puc the Pirate is used to determine when Puc collides with an enemy, or when he collides with cookies and bombs. The game engine uses a spherical collision system. This collision system requires that every object checked for collision must have a 3D point as its center and radius. The Spherical Collision System Each object must have a center and a radius. The center of each object here is marked by the red dots. The black lines show the radius of each object sphere. We calculate the distance between the two centers, and compare it to the sum of Radius1 and Radius2. If the distance between the centers is greater than the sum of the two radii, then there is no collision. If the distance between the centers is less than the sum of the radii, then the objects collide. 18

19 Example In this example, the distance between the centers is less than the sum of the radii; therefore, a collision is found. When the spheres surrounding the objects collide, the objects are considered to have collided. The advantages of the spherical collision detection system are that it is perfect for games that do not require an exact collision detection algorithm. It is also relatively fast to execute and does not burden the CPU with lots of calculations. The disadvantages are that if an object is very thin or very wide, this collision detection system must be avoided since that object will signal a collision long before it approaches the other object. Example In this example, the spherical collision detection algorithm will signal a collision, although the real objects are still relatively far away from each other. One of the ways around this problem is to decrease the size of the sphere of the thin object. 19

20 Now the same objects placed at the same positions as above do not signal a collision with each other. Object Collision To add object collision, add the highlighted code to each of the tasks below: File Name = Level1.cs Class Name = class Level1 Function Name = protected override void InitializeGraphics() protected override void InitializeGraphics() LevelMeshHolder.AddMesh("Grid.x"); //this mesh will be used in the current level LevelMeshHolder.AddMesh("NormalCoin.x"); LevelAnimationHolder.AddAnimation("PlayerAnimation.x"); LoadGraphics(); File Name = Level1.cs Class Name = class Level1 Constructor = public Level1() public Level1() InitializeGraphics(); InitializeSounds(); LevelGrid = new Grid(new Vector3(), 10, 9, LevelMeshHolder.GetMesh("Grid.x")); Hero = new Player(LevelGrid.GridNodes[0], LevelAnimation- Holder.GetAnimation("PlayerAnimation.x")); Width = LevelGrid.GridWidth; Height = LevelGrid.GridHeight; //allocating space for the array which holds the cookies LevelCookies = new Cookie[Width, Height]; //creating a cookie in the mapped position (2, 2) LevelCookies[2, 2] = new Cookie(2, 2, COOKIETYPE.NORMAL, Level.LevelMeshHolder.GetMesh("NormalCoin.x")); 20

21 PlayerRespawnPositions.Add(0); //Node whose index is 0 PlayerRespawnPositions.Add(5); //Node whose index is 5 PlayerRespawnPositions.Add(69); //Node whose index is 69 PlayerRespawnPositions.Add(64); //Node whose index is 64 GameBackground = new Background("background.jpg"); Reset(); File Name = Level.cs Class Name = class Level Function Name = public override void Update() public override void Update() Hero.Update(Matrix.Identity); LevelGrid.Update(Matrix.Identity); //Updating the cookie positioned at mapped location (2, 2) if (LevelCookies[2, 2]!= null) LevelCookies[2, 2].Update(Matrix.Identity); //checking for collision between the cookie and the player CookiePlayerCollision(); File Name = Level.cs Class Name = class Level Function Name = public override void Render() public override void Render() GameBackground.Render(); Hero.Render(); SetupMatrices(LevelGrid.GetTransformationMatrix()); LevelGrid.Render(); //Rendering the cookie we created in the constructor SetupMatrices(LevelCookies[2,2].GetTransformationMatrix()); LevelCookies[2, 2].Render(); File Name = Level.cs Class Name = class Level //Checking for collision between the created cookies and the hero public void CookiePlayerCollision() if (GameObject.Collision(Hero, LevelCookies[2, 2])) Hero.Speed = 0; At the end, the Hero moves over the map and collides with other objects. 21