10. Animation Triggers and Event Handlers

Transcription

1 10. Animation Triggers and Event Handlers 10.1 Knightfall Step 14 - Introduction to Event Handlers Watch the video tutorial: IGA Lesson 09 Step 01 Once you are satisfied that your environment is exported properly and looks the way you want in your game, it s time to get your actors animated and set triggers for them. This section deals with event handlers, which are just script commands that handle certain conditions. The most important are the OnLeftClick, OnAnimationStart, and OnAnimationEnd handlers. There are many others. It is worth looking at these handlers in the script reference. There are a great many options and we will only be covering some of the possibilities We will begin very simply with the parchment message that the knight sees when the scene opens. The parchment is dark, but when the knight moves close to it, it brightens up. Brightening is a common technique used in games to indicate the user should click on something or interact with it in some way. Since the parchment is involved in some kind of interaction, it was exported as an actor. There are two interactions. The first is the brightening as the knight moves close to it, the second is the fact that when the parchment brightens, the user can click on it and a bitmap message will pop up. 1. Go to the Actors > Parchment Drawbridge directory and open Parchment Drawbridge_script.txt. 2. Type the following script command to enable brightening for the parchment: OnProximity name:"knight" 120 "brighten" 1

2 This is called an OnProximity handler. It tells Ignition what to do when the knight is in close proximity to the parchment. The first value indicates which actor to use. Notice the use of the name qualifier. There are two options for this command. You can use the name qualifier (name: ) or a type qualifier (type: ). You use the type qualifier when you have created several actors of type knight, and you want the parchment to brighten when any one of them gets close to the parchment. These knights would have all been created within the knight script using the create command. You use the name qualifier when you want the command to work for one particular instance of the knight. The second value in the command is the distance at which the brightening occurs. It is the distance from the pivot point of the parchment to the pivot point of the knight, which is bip1. The last value is what to do when the knight gets closer than 120 units, which is to brighten. 3. Now type the command that will pop up the bitmap message: OnLeftClick displaybitmap "Note_drwbrg.tga" This is the OnLeftClick handler, which handles the actions that occur when the user clicks on the actor. The first value is the action, which in this case is displaybitmap. The second value is the name of the texture file. At this point if you click on the drawbridge note, the message will still not pop up. This is because you have not yet created the 2D user interface elements for the level. You do that in the section on Designing a User Interface. Next consider the chalices. As the knight gets close to a chalice, it will brighten. Once it has brightened the user can click on it to transfer the chalice's health to the knight. You now set this up. 1. In Actors > Chalice, open the Chalice_script.txt file. 2. Add the following commands: OnProximity name:"knight" 80 "brighten" OnProximity name:"knight" 80 "enable" The first command brightens the chalice when the knight gets close. When the knight clicks on the chalice, it will disappear. But you do not want this to happen unless the knight is close. You therefore add another OnProximity handler that enables interactivity for the chalice only when the knight is within 80 units of it. If you leave this command out, the user would be able to click on the chalice no matter where the knight is. 3. The command to transfer the chalice health to the knight is: OnLeftClick transferhealth 100 true This is another flavor of the OnLeftClick handler. The first and second values tell Ignition to transfer 100 units of health to the player actor. The last value of true indicates that the chalice should be removed from the scene when clicked. 2

3 You now look at another common example of the OnLeftClick handler. This is where clicking on an object causes it to animate. You will also look at chaining together animations. When the knight reaches the top of the bell tower, the user can click on the bell. This causes the bell to move, and also causes the portcullis to rise in the distance and the fallen tree to disappear. Creating the following script will accomplish all of this. 1. Go to Actors > Bell and Handle and open "Bell and Handle_script.txt". 2. Add the usual brighten and enable commands: OnProximity name:"knight" 250 "brighten" OnProximity name:"knight" 250 "enable" 3. Add an OnLeftClick handler: OnLeftClick animate "bell ring" The value of animate tells Ignition that the OnLeftClick handler will animate the bell. The name of the animation is "bell ring". There are two ways to animate an object other than the one you are clicking on. You can add another OnLeftClick handler and use the AnimateOther value to designate a different actor in the scene that you want to animate, or you can use the OnAnimationStart and OnAnimationEnd handlers. There are two components to the portcullis, the portcullis itself and another actor called the portcullis block. The portcullis block is an invisible actor that was exported with Draw turned off. Its purpose is to block the portcullis as a collision mesh so the actor cannot get through it. When the bell rings and the portcullis is raised, this blocking object must move out of the way as well. 4. Type the following: OnAnimationStart "bell ring" animateother "portcullis block" "portcullis block raise" The first value is the animation that we want to use, which is "bell ring". When the bell ring animation starts, Ignition will perform the actions described in the command. Specifically the action is AnimateOther, which means another actor will be animated. You then designate which actor followed by that actor's animation. So in the case above, clicking on the bell will cause the portcullis block to perform its "block raise" animation. 5. You do the same thing for the portcullis: OnAnimationStart "bell ring" animateother "portcullis both" "portcullis up" 6. Finally, you want the tree that is blocking the knight from getting to the drawbridge to disappear. We will use an OnAnimationEnd handler: OnAnimationEnd "bell ring" removeother "fallen tree" Instead of the AnimateOther value we used RemoveOther, followed by the name of the actor to remove Setting the Knight's Attack Ability 3

4 Now that you understand the way animation handlers work, you can set the knight's attack commands. The knight must be able to attack when he is near a bunny, snake or the dragon. Each time he fights he loses some health, but he also inflicts damage on the characters he is fighting. 1. In the Knight directory, open Knight_script.txt. To enable the knight's attack animation, type the following three commands: Onproximitykeystroke g 150 type:"bunny" animate "knight fight" Onproximitykeystroke g 150 type:"snake" animate "knight fight" Onproximitykeystroke g 450 type:"dragon" animate "knight fight" The OnProximityKeyStroke command is an example of a "context sensitive" command. It says that the keystroke will only work when the knight is close enough to something. In our case these would be the bunny, snake or dragon. The letter g after the command tells Ignition that the keystroke will be the g key. You do not want to set this to be any of the navigation keys: w, a, s, d, q, or e. The second value sets the distance the knight must be for the keystroke to work. The third command specifies the actor that the knight must be close to. There are two options. You can specify a type or a name. When you specify a type, then when the knight is near any character that is of type "bunny", he will be able to attack it. If you specified the name instead, then the knight will only be able to attack the actor instance with that particular name. We obviously want the knight to attack all bunnies, snakes and dragons (although we only have one dragon). The next two values say that when we are close enough to one of the characters and the user presses the g key, the action is to animate the knight with the "knight fight" animation. 2. After the attack animation ends, the knight should go back to his idle animation. We set that action by typing an OnAnimationEnd handler: OnAnimationEnd "knight fight" "knight idle" NOTE: Recall from the end of section that the end of a walk cycle is handled automatically by Ignition for the player actor. When the player actor is finished walking (for example, when the player has released the W key), then Ignition automatically starts the actor's idle animation. Therefore we do not need an OnAnimationEnd handler for the knight's walk cycle. Additionally, all animation transitions are handled automatically for NPCs, so they never need an OnAnimationEnd handler. 3. For the knight to lose health on each attack, there is another form of the OnAnimationEnd command that we use. Type the following: OnAnimationEnd "knight fight" changehealth name:"knight" -5 This causes the knight to lose 5 units of health at the end of the attack. Notice there is a negative sign in front of the 5. You may wonder why you have the next value, which is name:"knight" since you know this is the knight's script file. The reason is that the scripting language allows for the 4

5 change of the health of any actor in the scene, so you must specifically say which one. The next step shows this. 4. When the knight attacks, not only does he lose some health, he also inflicts damage on whoever he is attacking. The next set of commands set this up: OnAnimationEnd "knight fight" changehealth type:"bunny" -150 OnAnimationEnd "knight fight" changehealth type:"snake" -125 OnAnimationEnd "knight fight" changehealth name:"dragon" -250 Notice that you use type: qualifier for the bunny and snake so that this command applies to any bunny or snake that the knight is fighting. You can use either the type or the name for the dragon since there is only one in the scene. 5. Open the Bunny_script.txt and Snake_script.txt files and you will see similar OnAnimationEnd handlers for the bunny and snake attacks. If you change the health values in the bunny, snake and the knight scripts, you can change how the game plays by making it easier or harder to win Using Actors as Structures The portcullis and portcullis block deserve more explanation. We mentioned that the portcullis block is an invisible object that blocks the portcullis so that the knight cannot walk through it. However, we know that actors cannot be put into the octree structure so how does the invisible blocker work since it is an actor? There are two issues here. The first is how an actor can behave like a structure, and the second is why we need the extra invisible blocker at all. Think about a simpler example which is a door opening. The door must be an actor since it is animated. However, the door should behave like a structure until it opens. Ignition uses a little trick to get around this. In the actor's script you include the following command: MakeStructure actors true This line of script tells Ignition to put the door's polygons into the octree even though the door was exported as an actor. The word 'actors' that comes after MakeStructure tells Ignition that the door only blocks actors. It will not block the camera. If you want to block the camera you can replace the word 'actors' with the word 'camera'. If you want to block them both you use the word 'both'. Now, the octree cannot be recalculated, so once those polygon positions are recorded in the octree when Ignition is initializing, they cannot be changed. So even though the door opens in an animation, the octree still uses the old positions. However, the trick is that although Ignition cannot change the octree polygon positions, it can certainly ignore them! So if you have a script command that tells Ignition to just ignore the door part of the octree after it animates, you essentially make that structure go away. Here's an example of how that is done: OnAnimationEnd "open door" makestructure false 5

6 This tells Ignition that when the "open door" animation ends, the octree should ignore it. Now the character or camera can get through the doorway. If you forget to include this line of script, the door will open, but you still will not be able to get through the doorway. There is one variation for the OnAnimationEnd handler that you should be aware of. If the door is only allowed to open, then stays open, you would use the form shown above. But if the door can be repeatedly clicked open and closed, you want to toggle the structure state. You do this by exporting the door animation as reversible so that repeated clicks open then close the door. Then include the following form: OnAnimationEnd "open door" makestructure toggle The value toggle simply says that each time the "open door" animation runs, the structure state toggles off and on. Since "open door" was exported as reversible, everything will work as expected. Now that you understand how to make actors behave like structures, we turn to the case of the portcullis. Why not just use the MakeStructure commands for the portcullis object itself? Why did we add the invisible portcullis blocker? There are two reasons and they are both important. They both arise because of the geometry of the portcullis, which is shown in the figure below. The first reason is something that was discussed when we described the use of collision meshes. The portcullis is like a grate, and has a lot of polygons. However, we can easily use a much simpler planar object to block the knight. So there is no 6

7 reason to include the complex portcullis in the octree. We can be much more efficient by building a planar collision mesh that has only a couple of triangles. This is a practice you should get into for many of your structures. The second reason is that when Ignition does the calculations for structure collisions it looks at the pivot point of the actor and potential collisions of the pivot point with the polygons of the structure. If the actor's pivot point wanders through any of the gap regions, there will be no collision and the actor will just walk through the portcullis. So the first reason is that of efficiency, but the second reason is because the system just won't work for the portcullis geometry at all. The image below shows the planer, invisible portcullis block in green, which consists of only two triangles. 7

8 1. To complete the bell interactivity part of Knightfall, go to Actors > Portcullis Block and open the Portcullis Block_script.txt file. 2. Type in the following two commands: MakeStructure actors true OnAnimationend "portcullis block raise" makestructure false The completed Bell and Handle_script.txt, Chalice_script.txt, Knight_script.txt, Parchment Drawbridge_script.txt, Portcullis Block_script.txt files can be found in the Step 14 finished subdirectory Knightfall Project Step 15 - Winning and Losing Winning or losing the game is triggered by an OnAnimationEnd handler. For Knightfall we want the user to win if he slays the dragon, and to lose if the knight dies. So the OnAnimationEnd handler will be invoked at the end of either the knight's death animation or the dragon's death animation. The first thing to do is to decide how you want to inform the user that they have won or lost. There are only two ways to do this. You can provide win and lose image screens, or let Ignition simply pop up a text message. The text message option works automatically if you do not supply the images. For Knightfall we use the following two win and lose screens: 8

9 To specify your images for winning and losing, do the following: 1. In the scripts directory, open the Intro_script.txt file. 2. Type in the following commands: Win "Game_win.jpg" Lose "Game_lose.jpg" Next you set the conditions where these screens pop up. 1. Open Knight_script.txt. 2. First we want to perform the die animation for the knight when his health goes to 0. This is done with the OnZeroHealth command: OnZeroHealth "knight die" 3. At the end of the die animation, the lose screen should pop up. Type the following command to enable this: OnAnimationend "knight die" lose 4. Open Dragon_script.txt. 5. To win the game, the dragon must die. The dragon script already contains the OnZeroHealth command. Type the following command: OnAnimationEnd "dragon die" win 6. Save the files. The completed Dragon_script.txt and Knight_script.txt files can be found in the Step 15 finished subdirectory, along with all the other script files that you have completed in this curriculum. Copyright Applied IDEAS, Inc. All rights reserved. 9