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    • By sausagejohnson
      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):
      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.
    • By sausagejohnson
      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.
    • By kanageddaamen
      Hello all,
      I am currently working on a game engine for use with my game development that I would like to be as flexible as possible.  As such the exact requirements for how things should work can't be nailed down to a specific implementation and I am looking for, at least now, a default good average case scenario design.
      Here is what I have implemented:
      Deferred rendering using OpenGL Arbitrary number of lights and shadow mapping Each rendered object, as defined by a set of geometry, textures, animation data, and a model matrix is rendered with its own draw call Skeletal animations implemented on the GPU.   Model matrix transformation implemented on the GPU Frustum and octree culling for optimization Here are my questions and concerns:
      Doing the skeletal animation on the GPU, currently, requires doing the skinning for each object multiple times per frame: once for the initial geometry rendering and once for the shadow map rendering for each light for which it is not culled.  This seems very inefficient.  Is there a way to do skeletal animation on the GPU only once across these render calls? Without doing the model matrix transformation on the CPU, I fail to see how I can easily batch objects with the same textures and shaders in a single draw call without passing a ton of matrix data to the GPU (an array of model matrices then an index for each vertex into that array for transformation purposes?) If I do the matrix transformations on the CPU, It seems I can't really do the skinning on the GPU as the pre-transformed vertexes will wreck havoc with the calculations, so this seems not viable unless I am missing something Overall it seems like simplest solution is to just do all of the vertex manipulation on the CPU and pass the pre-transformed data to the GPU, using vertex shaders that do basically nothing.  This doesn't seem the most efficient use of the graphics hardware, but could potentially reduce the number of draw calls needed.

      Really, I am looking for some advice on how to proceed with this, how something like this is typically handled.  Are the multiple draw calls and skinning calculations not a huge deal?  I would LIKE to save as much of the CPU's time per frame so it can be tasked with other things, as to keep CPU resources open to the implementation of the engine.  However, that becomes a moot point if the GPU becomes a bottleneck.
    • By Washantor
      Hello my name is Erik Reis i'm 15 and i just got into game development. I don't want to spend hundreds of bucks on online classes i just want someone to help me. Kinda like a mentor or another new developer I can learn with. I'm young and i'm new and stupid and would love to learn this is just don't know where to start there is so much. I do know some basic C# and i want to use unity. I can do some pixel art though it is not up to the standard i would like but that can be improved. I would really enjoy to meet someone who has knowledge of the subject and can teach me on their spare time. Thanks i really appreciate if your read this post.
    • By Mercury Gate
      Here is the scenario I have pertaining to a combat system I am jotting down on paper.
      The attacker has 100 soldiers each with 1 attack point and 3 health points. The defender has the same.
      All the player has to do is press a button and combat is all computed then the player is just shown the results. From my current example, I would have the attacker's soldiers do 100 points of damage to the defender resulting in 33 defenders being killed. The same happens to the attacker's soldiers. This continues until both sides defeat each other at the same time and it ends in a draw.
      I feel if I introduce a random factor, the battle could get lop-sided and the smaller side could not recover So I thought I would ask the community for their opinions of the very simple combat scenario.
      The game concept I am designing deals with combat from outside the actual conflict. Sort of like a coach and a sports team. You give orders and watch as your units perform them. The game does start small, with 100 to 200 soldiers (all the same) and could grow to larger numbers as well. I was just wanting to get a system in place for small conflict that could scale into larger ones.
      Each side has a unit type (soldier) a unit quantity (100). The player give the order, and the computer does the rest. After both players give their orders, the results are computed instantly. Keeping all things equal, Attack power, defensive power, etc. (I need a baseline) What would be the best way to determine damage? Static numbers, or RNG numbers?
      To use or not use RNG in combat?
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OpenGL Proper way to define and handle assets

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I recently started getting into graphics programming (2nd try, first try was many years ago) and I'm working on a 3d rendering engine which I hope to be able to make a 3D game with sooner or later. I have plenty of C++ experience, but not a lot when it comes to graphics, and while it's definitely going much better this time, I'm having trouble figuring out how assets are usually handled by engines.

I'm not having trouble with handling the GPU resources, but more so with how the resources should be defined and used in the system (materials, models, etc).

This is my plan now, I've implemented most of it except for the XML parts and factories and those are the ones I'm not sure of at all:

I have these classes:

For GPU resources:

  • Geometry: holds and manages everything needed to render a geometry: VAO, VBO, EBO.
  • Texture: holds and manages a texture which is loaded into the GPU.
  • Shader: holds and manages a shader which is loaded into the GPU.

For assets relying on GPU resources:

  • Material: holds a shader resource, multiple texture resources, as well as uniform settings.
  • Mesh: holds a geometry and a material.
  • Model: holds multiple meshes, possibly in a tree structure to more easily support skinning later on?

For handling GPU resources:

  • ResourceCache<T>: T can be any resource loaded into the GPU. It owns these resources and only hands out handles to them on request (currently string identifiers are used when requesting handles, but all resources are stored in a vector and each handle only contains resource's index in that vector)
  • Resource<T>: The handles given out from ResourceCache. The handles are reference counted and to get the underlying resource you simply deference like with pointers (*handle).


And my plan is to define everything into these XML documents to abstract away files:

  • Resources.xml for ref-counted GPU resources (geometry, shaders, textures)
    • Resources are assigned names/ids and resource files, and possibly some attributes (what vertex attributes does this geometry have? what vertex attributes does this shader expect? what uniforms does this shader use? and so on)
    • Are reference counted using ResourceCache<T>
  • Assets.xml for assets using the GPU resources (materials, meshes, models)
    • Assets are not reference counted, but they hold handles to ref-counted resources.
    • References the resources defined in Resources.xml by names/ids.

The XMLs are loaded into some structure in memory which is then used for loading the resources/assets using factory classes:

Factory classes for resources:
For example, a texture factory could contain the texture definitions from the XML containing data about textures in the game, as well as a cache containing all loaded textures. This means it has mappings from each name/id to a file and when asked to load a texture with a name/id, it can look up its path and use a "BinaryLoader" to either load the file and create the resource directly, or asynchronously load the file's data into a queue which then can be read from later to create the resources synchronously in the GL context. These factories only return handles.

Factory classes for assets:
Much like for resources, these classes contain the definitions for the assets they can load. For example, with the definition the MaterialFactory will know which shader, textures and possibly uniform a certain material has, and with the help of TextureFactory and ShaderFactory, it can retrieve handles to the resources it needs (Shader + Textures), setup itself from XML data (uniform values), and return a created instance of requested material. These factories return actual instances, not handles (but the instances contain handles).



Is this a good or commonly used approach? Is this going to bite me in the ass later on? Are there other more preferable approaches? Is this outside of the scope of a 3d renderer and should be on the engine side? I'd love to receive and kind of advice or suggestions!


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