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  1. Hi Trsh, thanks for reporting. Under "Getting Orx" there is a part that mentions that git close auto-setup creates a project so that Orx can be used in your own projects. On reflection it's not 100% clear that you need to compile the projects. But I did include the link on compiling which takes you to the Orx wiki. Let me know if that doesn't solve the issue. However, once the orx libraries (debug, profile and release) are all compiled, the "dynamic" folder should then exist. Also check that after git clone step (the post setup step) managed to create an $ORX variable in your environment variables.
  2. Hi Guys, really pleased to announce that my 5 part series on creating a 2D UFO game using the Orx Portable Game Engine has been published in the articles section. The series is designed to help beginners download Orx, then use the tools to create your first project in your favourite IDE/OS. It then takes you step by step through numerous topics: Creating a playfield The ufo movement Keyboard controls Collisions Physics Scores Sounds and; Shadows The series starts over here: How to write a 2D UFO game using the Orx Portable Game Engine - Part 1 If you find any problems, or enjoyed going through it, I'd love to hear about it. Graphics for the article series were kindly designed by my friend FullyBugged.
  3. 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.
  4. 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.
  5. Collisions This is part 3 of a series on creating a game with the Orx Portable Game Engine. Part 1 is here, and Part 2 is here. There is one last requirement for the collision to occur: we need to tell the physics system, who can collide with who. This is done with flags and masks. Make a change to the ufo's body part by adding SelfFlags and CheckMask: [UfoBodyPart] Type = sphere Solid = true SelfFlags = ufo CheckMask = wall SelfFlags is the label you assign to one object, and CheckMask is the list of labels that your object can collide with. These labels don't have to match the names you give objects, however it will help you stay clean and organised. So in the config above, we are saying: the UfoBodyPart is a “ufo” and it is expected to collide with any bodypart marked as a “wall”. But we haven't done that yet, so let's do it now. We will only need to add it to the WallTopPart: [WallTopPart] Type = box Solid = true SelfFlags = wall CheckMask = ufo TopLeft = (-400, -300, 0) BottomRight = (400, -260, 0) Remember, that the other three wall parts inherit the values from WallTopPart. So each now carries the label of “wall” and they will collide with any other body part that carries the label of “ufo”. Re-run and press the left arrow key and drive the ufo into the left wall. It collides! And it stops. Now that the collision is working, we can flesh out the rest of the keyboard controls and test all four walls: void orxFASTCALL Update(const orxCLOCK_INFO *_pstClockInfo, void *_pContext) { if (ufo) { const orxFLOAT FORCE = 0.8; orxVECTOR rightForce = { FORCE, 0, 0 }; orxVECTOR leftForce = { -FORCE, 0, 0 }; orxVECTOR upForce = { 0, -FORCE, 0 }; orxVECTOR downForce = { 0, FORCE, 0 }; if (orxInput_IsActive("GoLeft")) { orxObject_ApplyForce(ufo, &leftForce, orxNULL); } if (orxInput_IsActive("GoRight")) { orxObject_ApplyForce(ufo, &rightForce, orxNULL); } if (orxInput_IsActive("GoUp")) { orxObject_ApplyForce(ufo, &upForce, orxNULL); } if (orxInput_IsActive("GoDown")) { orxObject_ApplyForce(ufo, &downForce, orxNULL); } } } Now is a good time to turn off the physics debug as we did earlier on. Compile and run. Try all four keys, and you should be able to move the ufo around the screen. The ufo can also collide with each wall. The ufo is a little boring in the way that it doesn't spin when colliding with a wall. We need to ensure the UfoBody is not using fixed rotation. While this value defaults to false when not supplied, it will make things more readable if we explicitly set it: [UfoBody] Dynamic = true PartList = UfoBodyPart FixedRotation = false The active ingredient here is to ensure that both the wall bodypart and the ufo bodypart both have a little friction applied. This way when they collide, they will drag against each other and produce some spin: [UfoBodyPart] Type = sphere Solid = true SelfFlags = ufo CheckMask = wall Friction = 1.2 [WallTopPart] Type = box Solid = true SelfFlags = wall CheckMask = ufo TopLeft = (-400, -300, 0) BottomRight = (400, -260, 0) Friction = 1.2 Re-run that and give it a try. Run against a wall on angle to get some spin on the ufo. The next thing to notice is that both the movement of the ufo and the spin never slow down. There is no friction to slow those down. We'll deal with the spin first. By adding some AngularDamping on the UfoBody, the spin will slow down over time: [UfoBody] Dynamic = true PartList = UfoBodyPart AngularDamping = 2 FixedRotation = false Re-run and check the spin. The ufo should be slowing down after leaving the wall. Now for the damping on the movement. That can be done with LinearDamping on the UfoBody: [UfoBody] Dynamic = true PartList = UfoBodyPart AngularDamping = 2 FixedRotation = false LinearDamping = 5 Re-run and the speed will slow down after releasing the arrow keys. But it's slower overall as well. Not 100% what we want. You can increase the FORCE value in code (ufo.cpp), in the Update function to compensate: const orxFLOAT FORCE = 1.8; Compile and run. The speed should be more what we expect. It would be nice for the ufo to be already spinning a little when the game starts. For this, add a little AngularVelocity : [UfoObject] Graphic = UfoGraphic Position = (0, 0, -0.1) Body = UfoBody AngularVelocity = 200 Run this and the ship will have a small amount of spin at the start until the AngularDamping on the ufo body slows it down again. Following the UFO with the camera While we can simply move the ufo around with the keys on a fixed background, it will be a more pleasant experience to have the ufo fixed and have the screen scroll around instead. This effect can be achieved by parenting the camera to the ufo so that wherever the ufo goes, the camera goes. Currently, our project is set up so that the viewport has a camera configured to it. But the camera is not available to our code. We will require the camera to be available in a variable so that it can be parented to the ufo object. To fix this, in the Init() function, extract the camera from the viewport into a variable by first removing this line: orxViewport_CreateFromConfig("Viewport"); to: orxVIEWPORT *viewport = orxViewport_CreateFromConfig("Viewport"); camera = orxViewport_GetCamera(viewport); And because the camera variable isn't defined, do so at the top of the code: #include "orx.h" orxOBJECT *ufo; orxCAMERA *camera; Now it is time to parent the camera to the ufo in the init() function using the orxCamera_SetParent function: ufo = orxObject_CreateFromConfig("UfoObject"); orxCamera_SetParent(camera, ufo); Compile and Run. Woah, hang on. That's crazy, the whole screen just rotated around when ufo. And it continues to rotate when hitting the ufo against the walls. See how the camera is a child of the ufo now? Not only does the camera move with the ufo, it rotates with it as well. We certainly want it to move with the ufo, but it would be nice ignore the rotation from the parent ufo. Add the IgnoreFromParent property to the MainCamera section: [MainCamera] FrustumWidth = 1024 FrustumHeight = 720 FrustumFar = 2.0 FrustumNear = 0.0 Position = (0.0, 0.0, -1.0) IgnoreFromParent = rotation Re-run. That's got it fixed. Now when you move around, the playfield will appear to scroll rather than it being the ufo that moves. This makes for a more dramatic and interesting effect. In Part 4, we will give the ufo something to do. The goal is to collect several pickups.
  6. The UFO This is part 2 of a series on creating a game with the Orx Portable Game Engine. Part 1 is here. We have a playfield, and now we need a UFO character for the player to control. The first step is the create the configuration for the ufo object in ufo.ini: [UfoObject] Graphic = UfoGraphic Position = (0, 0, -0.1) This indicates that the UfoObject should use a graphic called UfoGraphic. Secondly, its position will be centered in the playfield with (x,y) = (0,0). The -0.1 is the Z-axis, and this will be placed above the BackgroundObject whose Z-axis is set to 0. Then the UfoGraphic which the UfoObject needs: [UfoGraphic] Texture = ufo.png Pivot = center Unlike the background object, our ufo object will need to be assigned to a variable. This will make it possible to affect the ufo using code: Create the variable for our ufo object just under the orx.h include line: #include "orx.h" orxOBJECT *ufo; And in the Init() function, create an instance of the ufo object with: ufo = orxObject_CreateFromConfig("UfoObject"); Compile and run. You'll see a ufo object in front of the background. Excellent. Time to move to something a little more fun, moving the ufo. Controlling the UFO The ufo is going to be controlled using the cursor arrow keys on the keyboard. The ufo will be moved by applying forces. Physics will be set up in the project in order to do this. Also, we will use a clock to call an update function regularly. This function will read and respond to key presses. Defining Direction Keys Defining the keys is very straight forward. In the config file, expand the MainInput section in the ufo.ini by adding the four cursor keys: [MainInput] KEY_ESCAPE = Quit KEY_UP = GoUp KEY_DOWN = GoDown KEY_LEFT = GoLeft KEY_RIGHT = GoRight Each key is being given a label name, like: GoUp or GoDown. These label names are available in our code to test against. The next step is to create an update callback function in our code where the keys presses are checked: void orxFASTCALL Update(const orxCLOCK_INFO *_pstClockInfo, void *_pContext) { } And in order to tie this function to a clock (the clock will execute this function over and over), add the following to bottom of the Init() function: orxClock_Register(orxClock_FindFirst(orx2F(-1.0f), orxCLOCK_TYPE_CORE), Update, orxNULL, orxMODULE_ID_MAIN, orxCLOCK_PRIORITY_NORMAL); That looks very scary and intimidating, but the only part that is important to you is the parameter with “Update”. This means, tell the existing core clock to continually call our “Update” function. Of course you can specify any function name here you like as long as it exists. Let's test a key to ensure that our event is working well. Add the following code into the Update function: void orxFASTCALL Update(const orxCLOCK_INFO *_pstClockInfo, void *_pContext) { if (ufo) { if (orxInput_IsActive("GoLeft")) { orxLOG("LEFT PRESSED!"); } } } Every time Update is run, ufo is tested to ensure it exists, and then moves to check the input system for the label “GoLeft” (if it is active or pressed). Remember how GoLeft is bound to KEY_LEFT in the MainInput config section? If that condition is true, send “LEFT PRESSED!” to the console output window while the key is pressed or held down. Soon we'll replace the orxLOG line with a function that places force on the ufo. But before that, we need to add physics to the ufo. Compile and run. Press the left arrow key and take note of the console window. Every time you press or hold the key, the message is printed. Good, so key presses are working. Physics In order to affect the ufo using forces, physics need to be enabled. Begin by adding a Physics config section and setting Gravity with: [Physics] Gravity = (0, 980, 0) In order for an object in Orx to be affected by physics, it needs both a dynamic body, and at least one bodypart. Give the ufo a body with the Body property: [UfoObject] Graphic = UfoGraphic Position = (0, 0, -0.1) Body = UfoBody Next, create the UfoBody section and define the UfoBodyPart property: [UfoBody] Dynamic = true PartList = UfoBodyPart The body part is set to Dynamic which means that it is affected by gravity and collisions. A body needs at least one part, and so we need to define the UfoBodyPart: [UfoBodyPart] Type = sphere Solid = true The body part Type is set to be a sphere which will automatically size itself around the object's size, and the body is to be solid so that if it should collide with anything, it will not pass through it. Compile and Run. The ufo falls through the floor. This is because of the gravity setting of 980 in the y axis which simulates world gravity. Our game is a top down game. So change the Gravity property to: [Physics] Gravity = (0, 0, 0) Re-run (no compile needed) and the ufo should remain in the centre of the screen. The Physics section has another handy property available to visually test physics bodies on objects: ShowDebug. Add this property with true: [Physics] Gravity = (0, 0, 0) ShowDebug = true Re-run, and you will see a pinkish sphere outline automatically sized around the ufo object. For now we'll turn that off again. You can do this by changing the ShowDebug value to false, adding a ; comment in front of the line or simply just deleting the line. We'll set our ShowDebug to false: [Physics] Gravity = (0, 0, 0) ShowDebug = false Let's add some force to the ufo if the left cursor key is pressed. Change the code in the Update function to be: void orxFASTCALL Update(const orxCLOCK_INFO *_pstClockInfo, void *_pContext) { if (ufo) { const orxFLOAT FORCE = 0.8; orxVECTOR leftForce= { -FORCE, 0, 0 }; if (orxInput_IsActive("GoLeft")) { orxObject_ApplyForce(ufo, &leftForce, orxNULL); } } } The orxObject_ApplyForce function takes an orxVECTOR facing left and applies it to the ufo object. Compile and re-run. If you press and release the left arrow key, the ufo will move to the left. If you hold the left key down, the ufo will increase its speed and move out the left hand side of the screen. Even if you tap the left key once quickly, the ufo will still eventually travel out of the left of the screen. There is no friction yet to slow it down, or any barriers to stop it going out of the screen. Barrier Around The Border Even though the background looks it has a border, it is really only a picture. In order to create a barrier for the ufo, we will need to wrap the edges using some body parts. This means, the background object will also be given a body, and four body parts, one for each wall. Start with adding a body to the object: [BackgroundObject] Graphic = BackgroundGraphic Position = (0, 0, 0) Body = WallBody And then the body itself: [WallBody] Dynamic = false PartList = WallTopPart # WallRightPart # WallBottomPart # WallLeftPart This is different from the ufo body. This body is not dynamic. This means that it is a static body, one that cannot be affected by gravity. But dynamic objects can still collide with it. Also, there are four parts to this body, unlike the ufo which only had one. Start with the WallTopPart first: [WallTopPart] Type = box Solid = true TopLeft = (-400, -300, 0) BottomRight = (400, -260, 0) In this part, the type is a box body part. It is set to solid for collisions, ie so that a dynamic object can collide with it but not pass though it. Stretch the box to cover the region from (-400,-300) to (400, -260). At this point, it might be a good idea to turn on the physics debugging to check our work: [Physics] Gravity = (0, 0, 0) ShowDebug = true Re-run the project. The top wall region should cover the top barrier squares: Great. Next, we'll do the right hand side. But rather than copy all the same values, we'll reuse some from the top wall: [WallRightPart@WallTopPart] TopLeft = (360, -260,0) BottomRight = (400, 260, 0) Notice the @WallTopPart in the section name? This means: copy all the values from WallTopPart, but any properties in WallRightPart will take priority. Therefore, use the Type, and Solid properties from WallTopPart, but use our own values for TopLeft and BottomRight for the WallRightPart section. This is called “Section Inheritance”. This will come in very handy soon when we tweak values or add new properties to all four wall parts. Re-run the project, and there will now be two walls. Define the last two walls using the same technique: [WallBottomPart@WallTopPart] TopLeft = (-400,260,0) BottomRight = (400, 300, 0) [WallLeftPart@WallTopPart] TopLeft = (-400,-260,0) BottomRight = (-360, 260, 0) Now there are four walls for the ufo to collide with. Re-run and try moving the ufo left into the wall. Oops, it doesn't work. It still passes straight though. There is one last requirement for the collision to occur: we need to tell the physics system, who can collide with who. We'll cover that in Part 3.
  7. Overview Welcome to the 2D UFO game guide using the Orx Portable Game Engine. My aim for this tutorial is to take you through all the steps to build a UFO game from scratch. The aim of our game is to allow the player to control a UFO by applying physical forces to move it around. The player must collect pickups to increase their score to win. I should openly acknowledge that this series is cheekily inspired by the 2D UFO tutorial written for Unity. It makes an excellent comparison of the approaches between Orx and Unity. It is also a perfect way to highlight one of the major parts that makes Orx unique among other game engines, its Data Driven Configuration System. You'll get very familiar with this system very soon. It's at the very heart of just about every game written using Orx. If you are very new to game development, don't worry. We'll take it nice and slow and try to explain everything in very simple terms. The only knowledge you will need is some simple C++. I'd like say a huge thank you to FullyBugged for providing the graphics for this series of articles. What are we making? Visit the video below to see the look and gameplay of the final game: Getting Orx The latest up to date version of Orx can be cloned from github and set up with: git clone https://github.com/orx/orx.git After cloning, an $ORX environment variable will be created automatically for your system which will help with making game projects much easier. It will also create several IDE projects for your operating system: Visual Studio, Codelite, Code::Blocks, and gmake. These Orx projects will allow you to compile the Orx library for use in your own projects. And the $ORX environment variable means that your projects will know where to find the Orx library. For more details on this step, visit http://orx-project.org/wiki/en/tutorials/cloning_orx_from_github at the Orx learning wiki. Setting up a 2D UFO Project Now the you have the Orx libraries cloned and compiled, you will need a blank project for your game. Supported options are: Visual Studio, CodeLite, Code::Blocks, XCode or gmake, depending on your operating system. Once you have a game project, you can use it to work through the steps in this tutorial. Orx provides a very nice system for auto creating game projects for you. In the root of the Orx repo, you will find either the init.bat (for Windows) or init.sh (Mac/Linux) command. Create a project for our 2D game from the command line in the Orx folder and running: init c:\temp\ufo or init.sh ~/ufo Orx will create a project for each IDE supported by your OS at the specified location. You can copy this folder anywhere, and your project will always compile and link due to the $ORX environment variable. It knows where the libraries and includes are for Orx. Open your project using your favourite IDE from within the ufo/build folder. When the blank template loads, there are two main folders to note in your solution: config src Firstly, the src folder contains a single source file, ufo.cpp. This is where we will add the c++ code for the game. The config folder contains configuration files for our game. What is config? Orx is a data driven 2D game engine. Many of the elements in your game, like objects, spawners, music etc, do not need to be defined in code. They can be defined (or configured) using config files. You can make a range of complex multi-part objects with special behaviours and effects in Orx, and bring them into your game with a single line of code. You'll see this in the following chapters of this guide. There are three ufo config files in the config folder but for this guide, only one will actually be used in our game. This is: ufo.ini All our game configuration will be done there. Over in the Orx library repo folder under orx/code/bin, there are two other config files: CreationTemplate.ini SettingsTemplate.ini These are example configs and they list all the properties and values that are available to you. We will mainly concentrate on referring to the CreationTemplate.ini, which is for objects, sounds, etc. It's good idea to include these two files into your project for easy reference. Alternatively you can view these online at https://github.com/orx/orx/blob/master/code/bin/CreationTemplate.ini and here: https://github.com/orx/orx/blob/master/code/bin/SettingsTemplate.ini The code template Now to take a look at the basic ufo.cpp and see what is contained there. The first function is the Init() function. This function will execute when the game starts up. Here you can create objects have been defined in the config, or perform other set up tasks like handlers. We'll do both of these soon. The Run() function is executed every main clock cycle. This is a good place to continually perform a task. Though there are better alternatives for this, and we will cover those later. This is mainly used to check for the quit key. The Exit() function is where memory is cleaned up when your game quits. Orx cleans up nicely after itself. We won't use this function as part of this guide. The Bootstrap() function is an optional function to use. This is used to tell Orx where to find the first config file for use in our game (ufo.ini). There is another way to do this, but for now, we'll use this function to inform Orx of the config. Then of course, the main() function. We do not need to use this function in this guide. Now that we have everything we need to get start, you should be able to compile successfully. Run the program and an Orx logo will appear slowly rotating. Great. So now you have everything you need to start building the UFO game. Setting up the game assets Our game will have a background, a UFO which the player will control, and some pickups that the player can collect. The UFO will be controlled by the player using the cursor keys. First you'll need the assets to make the game. You can download the file assets-for-orx-ufo-game.zip which contains: The background file (background.png): The UFO and Pickup sprite images (ufo.png and pickup.png): And a pickup sound effect (pickup.ogg): pickup.ogg Copy the .png files into your data/texture folder Copy the .ogg file into your data/sound folder. Now these files can be accessed by your project and included in the game. Setting up the Playfield We will start by setting up the background object. This is done using config. Open the ufo.ini config file in your editor and add the following: [BackgroundGraphic] Texture = background.png Pivot = center The BackgroundGraphic defined here is called a Graphic Section. It has two properties defined. The first is Texture which has been set as background.png. The Orx library knows where to find this image, due to the properties set in the Resource section: [Resource] Texture = ../../data/texture So any texture files that are required (just like in our BackgroundGraphic section) will be located in the ../../data/texture folder. The second parameter is Pivot. A pivot is the handle (or sometimes “hotspot” in other frameworks). This is set to be center. The position is 0,0 by default, just like the camera. The effect is to ensure the background sits in the center of our game window. There are other values available for Pivot. To see the list of values, open the CreationTemplate.ini file in your editor. Scroll to the GraphicTemplate section and find Pivot in the list. There you can see all the possible values that could be used. top left is also a typical value. We need to define an object that will make use of this graphic. This will be the actual entity that is used in the game: [BackgroundObject] Graphic = BackgroundGraphic Position = (0, 0, 0) The Graphic property is the section BackgroundGraphic that we defined earlier. Our object will use that graphic. The second property is the Position. In our world, this object will be created at (0, 0, 0). In Orx, the coordinates are (x, y, z). It may seem strange that Orx, being a 2D game engine has a Z axis. Actually Orx is 2.5D. It respects the Z axis for objects, and can use this for layering above or below other objects in the game. To make the object appear in our game, we will add a line of code in our source file to create it. In the Init() function of ufo.cpp, remove the default line: orxObject_CreateFromConfig("Object"); and replace it with: orxObject_CreateFromConfig("BackgroundObject"); Compile and run. The old spinning logo is now replaced with a nice tiled background object. Next, the ufo object is required. This is what the player will control. This will be covered in Part 2.
  8. Hi guys, my article "Getting started with the Orx open gaming engine" was published last night on opensource.com. I would love for you to check it out and learn a little more about Orx, a 2.5D game engine for c/c++ developers.   https://opensource.com/article/17/5/getting-started-orx-open-gaming-engine [attachment=35865:orx-curve-editor.png]
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