First off, I’d like to apologise for both the long delays between updates and the shoddy state of the downloadable code. It should be fine for educational purpouses but there have been lots of typos and non-compiling code, which is regrettable. From this part onwards, I will publish the entire contraption in a working state, no longer in separate points-of-interest.<\/p>\n
Let’s continue where we left off and introduce a couple of base subsystems to the engine, wrapping our first external library (not counting general-purpouse stuff like Boost). Although the actual complexity is not that high, there’s a lot of wrapping to be done, so this time there’s going to be a lot of relatively straightforward code.<\/p>\n
I’d like to be able to display a window. There are several options to go about this (native code, SDL<\/a>, Qt<\/a>, WX<\/a>, MFC<\/a>, FOX<\/a>, GLUT<\/a>, GTK+<\/a>, the list goes on…) but right now I’m in favour of using GLFW<\/a>. It is simple, cross-platform and powerful enough for our purpouses. There is a slight tradeoff, however – it only supports a single window. That may not be a problem, but it also prevents fancy multi-monitor setups and such. I can live with it.<\/p>\n So, the first task is to make a skeleton System class, which I shall name Video:<\/p>\n Right. This subsystem can neatly wrap the libraries’ initialization and shutdown, taking a bit of possible errors into account:<\/p>\n Ok, so now the library is being initialized, some basic error checking and feedback is being done, and the library cleanup is also being handled as it should. Let's focus on the actual window to be displayed. I choose to make a new class that encapsulates this specifically:<\/p>\n As you can see, there are a bunch of members that need to be filled before a window can be constructed. Also, not all values are supported by graphics drivers. It's probaby sensible to start out with a normal, well-supported set.<\/p>\n Again, it's pretty straightforward. The next step is to make the settings configurable. The System class was designed to support configurations, so let's make use of that.<\/p>\n And that's pretty much all there's to it \ud83d\ude42 A typical configuration file should look like this now:<\/p>\n At this point, a window is created according to user-specified dimensions and buffer depth. Now, as we're making a game engine, I'd like the Video subsystem to continuously update the screen. This is actually pretty important for the next tutorial, where we'll tackle input handling.<\/p>\n The frame swapping must be done in a singlethreaded fashion, as the underlying openGL system was never designed to handle multithreading. For now, there are only two more slight additions I'm willing to make. One is integration into the event broadcasting system, and the other is integration into the Engine class. Let's tackle the integration first.<\/p>\nclass Video: public System {\r\npublic:\r\n\tVideo();\r\n\tvirtual ~Video() {}\r\n\t\r\n\tvirtual bool init();\r\n\tvirtual void update();\r\n\tvirtual void shutdown();\r\n};\r\n<\/pre>\nVideo::Video(): \r\n\tSystem(\"Video\")\r\n{\r\n}\r\n\r\nbool Video::init() {\r\n\tif (glfwInit() == GL_FALSE) {\r\n\t\tmLog << \"Failed to initialize GLFW\";\r\n\t\treturn false;\r\n\t}\r\n\t\r\n\tint versionMajor, versionMinor, versionRevision;\r\n\tglfwGetVersion(&versionMajor, &versionMinor, &versionRevision);\r\n\tmLog << \"Initialized GLFW \" << versionMajor << \".\" << versionMinor << \" rev. \" << versionRevision;\r\n\t\r\n\treturn true;\r\n}\r\n\r\nvoid Video::shutdown() {\r\n\tglfwTerminate();\r\n}\r\n<\/pre>\nclass Window {\r\npublic:\r\n\tWindow();\r\n\tvirtual ~Window() {}\r\n\r\n\tbool create();\r\n\tvoid destroy();\r\n\r\nprotected:\r\n\tunsigned int mWidth;\r\n\tunsigned int mHeight;\r\n\r\n\tbool mFullScreen;\r\n\r\n\tunsigned int mRedBits;\r\n\tunsigned int mGreenBits;\r\n\tunsigned int mBlueBits;\r\n\tunsigned int mAlphaBits;\r\n\r\n\tunsigned int mDepthBits;\r\n\tunsigned int mStencilBits;\r\n\r\n\tstd::string mTitle;\r\n};\r\n<\/pre>\nWindow::Window() {\r\n\t\/\/default to 800x600x32, 24bits depth, 8 bits stencil, (windowed)\r\n\tmWidth = 800;\r\n\tmHeight = 600;\r\n\t\t\r\n\tmAlphaBits = 8;\r\n\tmRedBits = 8;\r\n\tmGreenBits = 8;\r\n\tmBlueBits = 8;\r\n\r\n\tmDepthBits = 24;\r\n\tmStencilBits = 8;\r\n\r\n\tmFullScreen = false;\r\n\r\n\tmTitle = \"Overdrive Assault\";\r\n}\r\n\r\nbool Window::create() {\r\n\tint result = glfwOpenWindow(\r\n\t\tmWidth, \r\n\t\tmHeight,\r\n\t\tmRedBits,\r\n\t\tmGreenBits,\r\n\t\tmBlueBits,\r\n\t\tmAlphaBits,\r\n\t\tmDepthBits,\r\n\t\tmStencilBits,\r\n\t\tmFullScreen ? GLFW_FULLSCREEN : GLFW_WINDOW\r\n\t);\r\n\r\n\tif (result == GL_FALSE)\r\n\t\treturn false;\r\n\r\n\tglfwSwapInterval(0); \/\/disable vertical sync\r\n\treturn true;\r\n}\r\n\r\nvoid Window::destroy() {\r\n\tglfwCloseWindow();\r\n}\r\n\r\n\/\/... in Video::init()\r\n\tif (!mWindow->create()) {\r\n\t\tmLog << \"Failed to create window\";\r\n\t\treturn false;\r\n\t}\r\n<\/pre>\n\r\n\/\/... in Video.h\r\nprivate:\r\n\tboost::shared_ptr
[Video]\r\nWidth = 1280\r\nHeight = 1024\r\n\r\nRedBits = 8\r\nGreenBits = 8\r\nBlueBits = 8\r\nAlphaBits = 8\r\n\r\nDepthBits = 24\r\nStencilBits = 8\r\n\r\nFullScreen = false\r\nTitle = Overdrive Assault 0.1a\r\n<\/pre>\n
\/\/... in Video::Video()\r\n\tenableUpdater(Task::SINGLETHREADED_REPEATING);\r\n\r\n\/\/... in Video.cpp\r\nvoid Video::update() {\r\n\tglfwSwapBuffers();\r\n}\r\n<\/pre>\n\/\/... in Engine.h\r\nprivate:\r\n\tboost::shared_ptr