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    • By Stalefish
      Automated builds are a pretty important tool in a game developer's toolbox. If you're only testing your Unreal-based game in the editor (even in standalone mode), you're in for a rude awakening when new bugs pop up in a shipping build that you've never encountered before. You also don't want to manually package your game from the editor every time you want to test said shipping build, or to distribute it to your testers (or Steam for that matter).
      Unreal already provides a pretty robust build system, and it's very easy to use it in combination with build automation tools. My build system of choice is  Gradle , since I use it pretty extensively in my backend Java and Scala work. It's pretty easy to learn, runs everywhere, and gives you a lot of powerful functionality right out of the gate. This won't be a Gradle tutorial necessarily, so you can familiarize yourself with how Gradle works via the documentation on their site.
      Primarily, I use Gradle to manage a version file in my game's Git repository, which is compiled into the game so that I have version information in Blueprint and C++ logic. I use that version to prevent out-of-date clients from connecting to newer servers, and having the version compiled in makes it a little more difficult for malicious clients to spoof that build number, as opposed to having it stored in one of the INI files. I also use Gradle to automate uploading my client build to Steam via the use of steamcmd.
      Unreal's command line build tool is known as the Unreal Automation Tool. Any time you package from the editor, or use the Unreal Frontend Tool, you're using UAT on the back end. Epic provides handy scripts in the Engine/Build/BatchFiles directory to make use of UAT from the command line, namely RunUAT.bat. Since it's just a batch file, I can call it from a Gradle build script very easily.
      Here's the Gradle task snippet I use to package and archive my client:
      task packageClientUAT(type: Exec) { workingDir = "[UnrealEngineDir]\\Engine\\Build\\BatchFiles" def projectDirSafe = project.projectDir.toString().replaceAll(/[\\]/) { m -> "\\\\" } def archiveDir = projectDirSafe + "\\\\Archive\\\\Client" def archiveDirFile = new File(archiveDir) if(!archiveDirFile.exists() && !archiveDirFile.mkdirs()) { throw new Exception("Could not create client archive directory.") } if(!new File(archiveDir + "\\\\WindowsClient").deleteDir()) { throw new Exception("Could not delete final client directory.") } commandLine "cmd", "/c", "RunUAT", "BuildCookRun", "-project=\"" + projectDirSafe + "\\\\[ProjectName].uproject\"", "-noP4", "-platform=Win64", "-clientconfig=Development", "-serverconfig=Development", "-cook", "-allmaps", "-build", "-stage", "-pak", "-archive", "-noeditor", "-archivedirectory=\"" + archiveDir + "\"" } My build.gradle file is in my project's directory, alongside the uproject file. This snippet will spit the packaged client out into [ProjectDir]\Archive\Client.
      For the versioning, I have two files that Gradle directly modifies. The first, a simple text file, just has a number in it. In my [ProjectName]\Source\[ProjectName] folder, I have a [ProjectName]Build.txt file with the current build number in it. Additionally, in that same folder, I have a C++ header file with the following in it:
      #pragma once #define [PROJECT]_MAJOR_VERSION 0 #define [PROJECT]_MINOR_VERSION 1 #define [PROJECT]_BUILD_NUMBER ### #define [PROJECT]_BUILD_STAGE "Pre-Alpha" Here's my Gradle task that increments the build number in that text file, and then replaces the value in the header file:
      task incrementVersion { doLast { def version = 0 def ProjectName = "[ProjectName]" def vfile = new File("Source\\" + ProjectName + "\\" + ProjectName + "Build.txt") if(vfile.exists()) { String versionContents = vfile.text version = Integer.parseInt(versionContents) } version += 1 vfile.text = version vfile = new File("Source\\" + ProjectName + "\\" + ProjectName + "Version.h") if(vfile.exists()) { String pname = ProjectName.toUpperCase() String versionContents = vfile.text versionContents = versionContents.replaceAll(/_BUILD_NUMBER ([0-9]+)/) { m -> "_BUILD_NUMBER " + version } vfile.text = versionContents } } } I manually edit the major and minor versions and the build stage as needed, since they don't need to update with every build. You can include that header into any C++ file that needs to know the build number, and I also have a few static methods in my game's Blueprint static library that wrap them so I can get the version numbers in Blueprint.
      I also have some tasks for automatically checking those files into the Git repository and committing them:
      task prepareVersion(type: Exec) { workingDir = project.projectDir.toString() commandLine "cmd", "/c", "git", "reset" } task stageVersion(type: Exec, dependsOn: prepareVersion) { workingDir = project.projectDir.toString() commandLine "cmd", "/c", "git", "add", project.projectDir.toString() + "\\Source\\[ProjectName]\\[ProjectName]Build.txt", project.projectDir.toString() + "\\Source\\[ProjectName]\\[ProjectName]Version.h" } task commitVersion(type: Exec, dependsOn: stageVersion) { workingDir = project.projectDir.toString() commandLine "cmd", "/c", "git", "commit", "-m", "\"Incrementing [ProjectName] version\"" } And here's the task I use to actually push it to Steam:
      task pushBuildSteam(type: Exec) { doFirst { println "Pushing build to Steam..." } workingDir = "[SteamworksDir]\\sdk\\tools\\ContentBuilder" commandLine "cmd", "/c", "builder\\steamcmd.exe", "+set_steam_guard_code", "[steam_guard_code]", "+login", "\"[username]\"", "\"[password]\"", "+run_app_build", "..\\scripts\\[CorrectVDFFile].vdf", "+quit" } You can also spit out a generated VDF file with the build number in the build's description so that it'll show up in SteamPipe. I have a single Gradle task I run that increments the build number, checks in those version files, packages both the client and server, and then uploads the packaged client to Steam. Another great thing about Gradle is that Jenkins has a solid plugin for it, so you can use Jenkins to set up a nice continuous integration pipeline for your game to push builds out regularly, which you absolutely should do if you're working with a team.
    • By Zamma
      Hello!
      I'm doing an A.I. course at my university, and searching on internet i learned about the GOAP A.I. system. I found it really interesting and I would like to learn more about others techniques.  So I was wondering which A.I. system is used by the civilization saga (or at least in civilization IV/V/VI) but i'm not able to find anything about that. Does anyone know where i can find some infos or docs about A.I in Civ?
    • By rakshit Rao
      I'M interested in programming tools (For animation, UI, etc). Can anyone suggest me the resources where I can start learning or which technologies I need achive it.
       
      Thanks,
      Rakshit
    • By sausagejohnson
      Sounds
      This is our final part, 5 of a series on creating a game with the Orx Portable Game Engine. Part 1 is here, and part 4 is here.
      It's great that collecting the pickups work, but a silent game is pretty bland. It would be great to have a sound play whenever a pickup is collected.
      Start by configuring a sound:
       
      [PickupSound] Sound = pickup.ogg KeepInCache = true  
      Then as part of the collision detection in the PhysicsEventHandler function, we change the code to be:
       
      if (orxString_SearchString(recipientName, "PickupObject") != orxNULL) { orxObject_SetLifeTime(pstRecipientObject, 0); orxObject_AddSound(pstSenderObject, "PickupSound"); } if (orxString_SearchString(senderName, "PickupObject") != orxNULL) { orxObject_SetLifeTime(pstSenderObject, 0); orxObject_AddSound(pstRecipientObject, "PickupSound"); }  
      In code above, if the recipient is a pickup object, then use the orxObject_AddSound function to place our sound on the sender object. There's little point adding a sound to an object that is about to be deleted.
      And of course, if the pickup object is the sender, we add the sound to the recipient object. Also, the PickupSound that is added to the object, is the config section name we just defined in the config.
      Compile and run.
      Hit the pickups and a sound will play.
      You can also use sounds without code. There is an AppearSound section already available in the config.
      We can use this sound on the ufo when it first appears in the game.
      This is as simple as adding a SoundList property to the ufo:
       
      [UfoObject] Graphic = UfoGraphic Position = (0, 0, -0.1) Body = UfoBody AngularVelocity = 200 SoundList = SoundAppear  
      Re-run and a nice sound plays at the start of the game.
        Adding a score
      What's a game without a score? We need to earn points for every pickup that is collected.
      The great thing about Orx objects is that they don't have to contain a texture as a graphic. They can contain a font and text rendered to a graphic instead. This is perfect for making a score object.
      Start by adding some config for the ScoreObject:
       
      [ScoreObject] Graphic = ScoreTextGraphic Position = (-380, -280, 0)  
      Next, to add the ScoreTextGraphic section, which will not be a texture, but text instead:
       
      [ScoreTextGraphic] Text = ScoreText  
      Now to define the ScoreText which is the section that contains the text information:
       
      [ScoreText] String = 10000  
      The String property contains the actual text characters. This will be the default text when a ScoreObject instance is created in code.
      Let's now create an instance of the ScoreObject in the Init() function:
       
      orxObject_CreateFromConfig("ScoreObject");  
      So far, the Init() function should look like this:
       
      orxSTATUS orxFASTCALL Init() { orxVIEWPORT *viewport = orxViewport_CreateFromConfig("Viewport"); camera = orxViewport_GetCamera(viewport); orxObject_CreateFromConfig("BackgroundObject"); ufo = orxObject_CreateFromConfig("UfoObject"); orxCamera_SetParent(camera, ufo); orxObject_CreateFromConfig("PickupObjects"); orxObject_CreateFromConfig("ScoreObject"); orxClock_Register(orxClock_FindFirst(orx2F(-1.0f), orxCLOCK_TYPE_CORE), Update, orxNULL, orxMODULE_ID_MAIN, orxCLOCK_PRIORITY_NORMAL); orxEvent_AddHandler(orxEVENT_TYPE_PHYSICS, PhysicsEventHandler); return orxSTATUS_SUCCESS; }  
      Compile and run.
      There should be a score object in the top left hand corner displaying: 10000

      The score is pretty small. And it's fixed into the top left corner of the playfield. That's not really what we want.
      A score is an example of a User Interface (UI) element. It should be fixed in the same place on the screen. Not move around when the screen scrolls.
      The score should in fact, be fixed as a child to the Camera. Wherever the Camera goes, the score object should go with it.
      This can be achieved with the ParentCamera property, and then setting the position of the score relative to the camera's centre position:
       
      [ScoreObject] Graphic = ScoreTextGraphic Position = (-380, -280, 0) ParentCamera = Camera UseParentSpace = false  
      With these changes, we've stated that we want the Camera to be the parent of the ScoreObject. In other words, we want the ScoreObject to travel with the Camera and appear to be fixed on the screen.
      By saying that we don't want to UseParentSpace means that we want specify relative world coordinates from the centre of the camera. If we said yes, we'd have to specify coordinates in another system.
      And Position, of course, is the position relative to the center of the camera. In our case, moved to the top left corner position.
      Re-run and you'll see the score in much the same position as before, but when you move the ufo around, and the screen scrolls, the score object remains fixed in the same place.
      The only thing, it's still a little small. We can double its size using Scale:
       
      [ScoreObject] Graphic = ScoreTextGraphic Position = (-380, -280, 0) ParentCamera = Camera UseParentSpace = false Scale = 2.0 Smoothing = false Smoothing has been set to false so that when the text is scaled up, it will be sharp and pixellated rather than smoothed up which looks odd.
      All objects in our project are smooth be default due to:
       
      [Display] Smoothing = true: So we need to explicitly set the score to not smooth.
      Re-run. That looks a lot better.

      To actually make use of the score object, we will need a variable in code of type int to keep track of the score.
      Every clock cycle, we'll take that value and change the text on the ScoreObject.
      That is another cool feature of Orx text objects: the text can be changed any time, and the object will re-render.
      Finally, when the ufo collides with the pickup, and the pickup is destroyed, the score variable will be increased. The clock will pick up the variable value and set the score object.
      Begin by creating a score variable at the very top of the code:
       
      #include "orx.h" orxOBJECT *ufo; orxCAMERA *camera; int score = 0;  
      Change the comparison code inside the PhysicsEventHandler function to increase the score by 150 points every time a pickup is collected:
       
      if (orxString_SearchString(recipientName, "PickupObject") != orxNULL) { orxObject_SetLifeTime(pstRecipientObject, 0); orxObject_AddSound(pstSenderObject, "PickupSound"); score += 150; } if (orxString_SearchString(senderName, "PickupObject") != orxNULL) { orxObject_SetLifeTime(pstSenderObject, 0); orxObject_AddSound(pstRecipientObject, "PickupSound"); score += 150; }  
      Now we need a way to change the text of the score object. We declared the score object in the Init() function as:
       
      orxObject_CreateFromConfig("ScoreObject");  
      But we really need to create it using an orxOBJECT variable:
       
      scoreObject = orxObject_CreateFromConfig("ScoreObject");  
      And then declare the scoreObject at the top of the file:
       
      #include "orx.h" orxOBJECT *ufo; orxCAMERA *camera; orxOBJECT *scoreObject; int score = 0;  
      Now it is possible to update the scoreObject using our score variable. At the bottom of the Update() function, add the following code:
       
      if (scoreObject) { orxCHAR formattedScore[5]; orxString_Print(formattedScore, "%d", score); orxObject_SetTextString(scoreObject, formattedScore); }  
      First, the block will only execute if there is a valid scoreObject.
      If so, then create a 5 character string. Then print into the string with the score value, effectively converting an int into a string.
      Finally set the score text to the scoreObject using the orxObject_SetTextString function.
      Compile and Run.
      Move the ufo around and collect the pickups to increase the score 150 points at a time.
        Winning the game
      1200 is the maximum amount of points that can be awarded, and that will mean we've won the game.
      If we do win, we want a text label to appear above the ufo, saying “You win!”.
      Like the score object, we need to define a YouWinObject:
       
      [YouWinObject] Graphic = YouWinTextGraphic Position = (0, -60, 0.0) Scale = 2.0 Smoothing = false  
      Just like the camera, the YouWinObject is going to be parented to the ufo too. This will give the appearance that the YouWinObject is part of the ufo.
      The Scale is set to x2.
      The Position is set offset up in the y axis so that it appears above the ufo.
      Next, the actual YouWinTextGraphic:
       
      [YouWinTextGraphic] Text = YouWinText Pivot = center  
      And the text to render into the YouWinTextGraphic:
       
      [YouWinText] String = You Win!  
      We'll test it by creating an instance of the YouWinObject, putting it into a variable, and then parent it to the ufo in the Init() function:
       
      orxObject_CreateFromConfig("PickupObjects"); scoreObject = orxObject_CreateFromConfig("ScoreObject"); ufoYouWinTextObject = orxObject_CreateFromConfig("YouWinObject"); orxObject_SetParent(ufoYouWinTextObject, ufo);  
      Then the variable:
       
      #include "orx.h" orxOBJECT *ufo; orxCAMERA *camera; orxOBJECT *ufoYouWinTextObject; orxOBJECT *scoreObject; int score = 0;  
      Compile and Run.
      The “You win” text should appear above the ufo. Not bad, but the text is rotating with the ufo much like the camera was before.

      We can ignore the rotation from the parent on this object too:
       
      [YouWinObject] Graphic = YouWinTextGraphic Position = (0, -60, 0.0) Scale = 2.0 Smoothing = false IgnoreFromParent = rotation  
      Re-run. Interesting. It certainly isn't rotating with the ufo, but its position is still being taken from the ufo's rotation.

      We need to ignore this as well:
       
      [YouWinObject] Graphic = YouWinTextGraphic Position = (0, -60, 0.0) Scale = 2.0 Smoothing = false IgnoreFromParent = position.rotation rotation  
      Good that's working right.

      We want the “You Win!” to appear once all pickups are collected.
      The YouWinObject object on created on the screen when the game starts. But we don't want it to appear yet. Only when we win. Therefore, we need to disable the object immediately after it is created using the orxObject_Enable function:
       
      ufoYouWinTextObject = orxObject_CreateFromConfig("YouWinObject"); orxObject_SetParent(ufoYouWinTextObject, ufo); orxObject_Enable(ufoYouWinTextObject, orxFALSE);  
      Finally, all that is left to do is add a small check in the PhysicsEventHandler function to test the current score after each pickup collision:
       
      if (orxString_SearchString(recipientName, "PickupObject") != orxNULL) { orxObject_SetLifeTime(pstRecipientObject, 0); orxObject_AddSound(pstSenderObject, "PickupSound"); score += 150; } if (orxString_SearchString(senderName, "PickupObject") != orxNULL) { orxObject_SetLifeTime(pstSenderObject, 0); orxObject_AddSound(pstRecipientObject, "PickupSound"); score += 150; } if (orxObject_IsEnabled(ufoYouWinTextObject) == orxFALSE && score == 1200) { orxObject_Enable(ufoYouWinTextObject, orxTRUE); }  
      We are checking two things: that the ufoYouWinTextObject is not yet enabled using the orxObject_IsEnabled function, and if the score is 1200.
      If both conditions are met, enable the ufoYouWinTextObject.
      Compile and run.
      Move the ufo around and collect all the pickups. When all are picked up and 1200 is reached, the “You Win!” text should appear above the ufo signifying that the game is over and we have won.

      And that brings us to the end! We have created a simple and complete game with some configuration and minimal code.
      Congratulations!
      I hope you enjoyed working through making the ufo game using the Orx Portable Game Engine. Of course, there are many little extras you can add to give your game that little extra polish. So, for just a bit more eye candy, there a couple more sections that you can follow along with if you wish.
        Shadows
      There are many ways to do shadows. One method is to use shaders… though this method is a little beyond this simple guide.
      Another method, when making your graphics, would be to add an alpha shadow underneath. This is a good method if your object does not need to rotate or flip.
      The method I will show you in this chapter is to have a separate shadow object as a child of an object. And in order to remain independent of rotations, the children will ignore rotations from the parent.
      First a shadow graphic for the ufo, and one for the pickups:
       
      Save these both into the data/texture folder.
      Then create config for the ufo shadow:
       
      [UfoShadowGraphic] Texture = ufo-shadow.png Alpha = 0.3 Pivot = center  
      The only interesting part is the Alpha property. 0.1 would be almost completely see-through (or transparent), and 1.0 is not see-through at all, which is the regular default value for a graphic. 0.3 is fairly see-through.
       
      [UfoShadowObject] Graphic = UfoShadowGraphic Position = (20, 20, 0.05)  
      Set the Position a bit to the right, and downwards.
      Next, add the UfoShadowObject as a child of the UfoObject:
       
      [UfoObject] Graphic = UfoGraphic Position = (0,0, -0.1) Body = UfoBody AngularVelocity = 200 UseParentSpace = position SoundList = AppearSound ChildList = UfoShadowObject  
      Run the project.
      The shadow child is sitting properly behind the ufo but it rotates around the ufo, until it ends up at the bottom left which is not correct.

      We'll need to ignore the rotation from the parent:
       
      [UfoShadowObject] Graphic = UfoShadowGraphic Position = (20, 20, 0.05) IgnoreFromParent = position.rotation rotation  
      Not only do we need to ignore the rotation of ufo, we also need to ignore the rotation position of the ufo.
      Re-run and the shadow sits nice and stable to the bottom right of the ufo.

      Now to do the same with the pickup shadow:
       
      [PickupShadowGraphic] Texture = pickup-shadow.png Alpha = 0.3 Pivot = center [PickupShadowObject] Graphic = PickupShadowGraphic Position = (20, 20, 0.05) IgnoreFromParent = position.rotation  
      The only difference between this object and the ufo shadow, is that we want the pickup shadow to take the rotation value from the parent. But we do not want to take the position rotation.
      That way, the pickup shadow will remain in the bottom right of the pickup, but will rotate nicely in place.
      Now attach as a child to the pickup object:
       
      [PickupObject] Graphic = PickupGraphic FXList = RotateFX Body = PickupBody ChildList = PickupShadowObject  
      Re-run, and the shadows should all be working correctly.

      And that really is it this time. I hope you made it this far and that you enjoyed this series of articles on the Orx Portable Game Engine.
      If you like what you see and would like to try out a few more things with Orx, head over our learning wiki where you can follow more beginner guides, tutorials and examples.
      You can always get the latest news on Orx at the official website.
      If you need any help, you can get in touch with the community on gitter, or at the forum. They're a friendly helpful bunch over there, always ready to welcome newcomers and assist with any questions.
       
       
    • By sausagejohnson
      Creating Pickup Objects
      This is part 4 of a series on creating a game with the Orx Portable Game Engine. Part 1 is here, and part 3 is here.
      In our game, the player will be required to collect objects scattered around the playfield with the ufo.
      When the ufo collides with one, the object will disappear, giving the impression that it has been picked up.
      Begin by creating a config section for the graphic, and then the pickup object:
       
      [PickupGraphic] Texture = pickup.png Pivot = center [PickupObject] Graphic = PickupGraphic  
      The graphic will use the image pickup.png which is located in the project's data/object folder.
      It will also be pivoted in the center which will be handy for a rotation effect later.
      Finally, the pickup object uses the pickup graphic. Nice and easy.
      Our game will have eight pickup objects. We need a simple way to have eight of these objects in various places.
      We will employ a nice trick to handle this. We will make an empty object, called PickupObjects which will hold eight copies of the pickup object as child objects.
      That way, wherever the parent is moved, the children move with it.
      Add that now:
       
      [PickupObjects] ChildList = PickupObject1 # PickupObject2 # PickupObject3 # PickupObject4 # PickupObject5 # PickupObject6 # PickupObject7 # PickupObject8 Position = (-400, -300, -0.1)  
      This object will have no graphic. That's ok. It can still act like any other object.
      Notice the position. It is being positioned in the top left hand corner of the screen. All of the child objects PickupObject1 to PickupObject8 will be positioned relative to the parent in the top left corner.
      Now to create the actual children. We'll use the inheritance trick again, and just use PickupObject as a template:
       
      [PickupObject1@PickupObject] Position = (370, 70, -0.1) [PickupObject2@PickupObject] Position = (210, 140, -0.1) [PickupObject3@PickupObject] Position = (115, 295, -0.1) [PickupObject4@PickupObject] Position = (215, 445, -0.1) [PickupObject5@PickupObject] Position = (400, 510, -0.1) [PickupObject6@PickupObject] Position = (550, 420, -0.1) [PickupObject7@PickupObject] Position = (660, 290, -0.1) [PickupObject8@PickupObject] Position = (550, 150, -0.1)  
      Each of the PickupObject* objects uses the properties defined in PickupObject. And the only difference between them are their Position properties.
      The last thing to do is to create an instance of PickupObjects in code in the Init() function:
       
      orxObject_CreateFromConfig("PickupObjects");  
      Compile and Run.
      Eight pickup objects should appear on screen. Looking good.

      It would look good if the pickups rotated slowly on screen, just to make them more interesting. This is very easy to achieve in Orx using FX.
      FX can also be defined in config.
      FX allows you to affect an object's position, colour, rotation, scaling, etc, even sound can be affected by FX.
      Change the PickupObject by adding a FXList property:
       
      [PickupObject] Graphic = PickupGraphic FXList = SlowRotateFX  
      Clearly being an FXList you can have many types of FX placed on an object at the same time. We will only have one.
      An FX is a collection of FX Slots. FX Slots are the actual effects themselves. Confused? Let's work through it. First, the FX:
       
      [SlowRotateFX] SlotList = SlowRotateFXSlot Loop = true  
      This simply means, use some effect called SlowRotateFXSlot, and when it is done, do it again in a loop.
      Next the slot (or effect):
       
      [SlowRotateFXSlot] Type = rotation StartTime = 0 EndTime = 10 Curve = linear StartValue = 0 EndValue = 360  
      That's a few properties. First, the Type, which is a rotation FX.
      The total time for the FX is 10 seconds, which comes from the StartTime and EndTime properties.
      The Curve type is linear so that the values changes are done so in a strict and even manner.
      And the values which the curve uses over the 10 second period starts from 0 and climbs to 360.
      Re-run and notice the pickups now turning slowly for 10 seconds and then repeating.
       
      Picking up the collectable objects
      Time to make the ufo collide with the pickups. In order for this to work (just like for the walls) the pickups need a body.
      And the body needs to be set to collide with a ufo and vice versa.
      First a body for the pickup template:
       
      [PickupObject] Graphic = PickupGraphic FXList = SlowRotateFX Body = PickupBody  
      Then the body section itself:
       
      [PickupBody] Dynamic = false PartList = PickupPart  
      Just like the wall, the pickups are not dynamic. We don't want them bouncing and traveling around as a result of being hit by the ufo. They are static and need to stay in place if they are hit.
      Next to define the PickupPart:
       
      [PickupPart] Type = sphere Solid = false SelfFlags = pickup CheckMask = ufo  
      The pickup is sort of roundish, so we're going with a spherical type.
      It is not solid. We want the ufo to able to pass through it when it collides. It should not influence the ufo's travel at all.
      The pickup is given a label of pickup and will only collide with an object with a label of ufo.
      The ufo must reciprocate this arrangement (just like a good date) by adding pickup to its list of bodypart check masks:
       
      [UfoBodyPart] Type = sphere Solid = true SelfFlags = ufo Friction = 1.2 CheckMask = wall # pickup  
      This is a static bodypart, and we have specified collision actions to occur if the ufo collides with a pickup. But it's a little difficult to test this right now. However you can turn on the debug again to check the body parts:
       
      [Physics] Gravity = (0, 0, 0) ShowDebug = true  
      Re-run to see the body parts.

      Switch off again:
       
      [Physics] Gravity = (0, 0, 0) ShowDebug = false  
      To cause a code event to occur when the ufo hits a pickup, we need something new: a physics hander. The hander will run a function of our choosing whenever two objects collide.
      We can test for these two objects to see if they are the ones we are interested in, and run some code if they are.
      First, add the physics hander to the end of the Init() function:
       
      orxClock_Register(orxClock_FindFirst(orx2F(-1.0f), orxCLOCK_TYPE_CORE), Update, orxNULL, orxMODULE_ID_MAIN, orxCLOCK_PRIORITY_NORMAL); orxEvent_AddHandler(orxEVENT_TYPE_PHYSICS, PhysicsEventHandler);  
      This will create a physics handler, and should any physics event occur, (like two objects colliding) then a function called PhysicsEventHandler will be executed.
      Our new function will start as:
       
      orxSTATUS orxFASTCALL PhysicsEventHandler(const orxEVENT *_pstEvent) { if (_pstEvent->eID == orxPHYSICS_EVENT_CONTACT_ADD) { orxOBJECT *pstRecipientObject, *pstSenderObject; /* Gets colliding objects */ pstRecipientObject = orxOBJECT(_pstEvent->hRecipient); pstSenderObject = orxOBJECT(_pstEvent->hSender); const orxSTRING recipientName = orxObject_GetName(pstRecipientObject); const orxSTRING senderName = orxObject_GetName(pstSenderObject); orxLOG("Object %s has collided with %s", senderName, recipientName); return orxSTATUS_SUCCESS; } }  
      Every handler function passes an orxEVENT object in. This structure contains a lot of information about the event.
      The eID is tested to ensure that the type of physics event that has occurred is a orxPHYSICS_EVENT_CONTACT_ADD which indicates when objects collide.
      If true, then two orxOBJECT variables are declared, then set from the orxEVENT structure. They are passed in as the hSender and hRecipient objects.
      Next, two orxSTRINGs are declared and are set by getting the names of the objects using the orxObject_GetName function. The name that is returned is the section name from the config.
      Potential candidates are: UfoObject, BackgroundObject, and PickupObject1 to PickupObject8.
      The names are then sent to the console.
      Finally, the function returns orxSTATUS_SUCCESS which is required by an event function.
      Compile and run.
      If you drive the ufo into a pickup or the edge of the playfield, a message will display on the console. So we know that all is working.

      Next is to add code to remove a pickup from the playfield if the ufo collides with it. Usually we could compare the name of one object to another and perform the action.
      In this case, however, the pickups are named different things: PickupObject1, PickupObject2, PickupObject3… up to PickupObject8.
      So we will need to actually just check if the name contains “PickupObject” which will match well for any of them.
      In fact, we don't need to test for the “other” object in the pair of colliding objects. Ufo is a dynamic object and everything else on screen is static. So if anything collides with PickupObject*, it has to be the ufo. Therefore, we won't need to test for that.
      First, remove the orxLOG line. We don't need that anymore.
      Change the function to become:
       
      orxSTATUS orxFASTCALL PhysicsEventHandler(const orxEVENT *_pstEvent) { if (_pstEvent->eID == orxPHYSICS_EVENT_CONTACT_ADD) { orxOBJECT *pstRecipientObject, *pstSenderObject; /* Gets colliding objects */ pstRecipientObject = orxOBJECT(_pstEvent->hRecipient); pstSenderObject = orxOBJECT(_pstEvent->hSender); const orxSTRING recipientName = orxObject_GetName(pstRecipientObject); const orxSTRING senderName = orxObject_GetName(pstSenderObject); if (orxString_SearchString(recipientName, "PickupObject") != orxNULL) { orxObject_SetLifeTime(pstRecipientObject, 0); } if (orxString_SearchString(senderName, "PickupObject") != orxNULL) { orxObject_SetLifeTime(pstSenderObject, 0); } } return orxSTATUS_SUCCESS; }  
      You can see the new code additions after the object names.
      If an object name contains the word “PickupObject”, then the ufo must have collided with it. Therefore, we need to kill it off. The safest way to do this is by setting the object's lifetime to 0.
      This will ensure the object is removed instantly and deleted by Orx in a safe manner.
      Notice that the test is performed twice. Once, if the pickup object is the sender, and again if the object is the recipient.
      Therefore we need to check and handle both.
      Compile and run.
      Move the ufo over the pickups and they should disappear nicely.

      We'll leave it there for the moment. In the final, Part 5, we'll cover adding sounds, a score, and winning the game.
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