Open. GL Keyboard Interaction Version 2. Swiftless Tutorials. Introduction. The keyboard is one of those things that is essential to computer gaming, and computer use in general. Could you imagine trying to type with the mouse Or the number of buttons that would be required on a mouse to allow for movement andshooting in a First Person Shooter The good news is that keyboard interaction, thanks to GLUT, is an extremely easy thing to handle. I am going to look at 2 different GLUT methods for key presses, one for when a key is first pressed, and one for when a key is released. I will then be showing how to do some key buffering to allow multiple key presses at once. Coding. Key Press. To get started with the keyboard, just like we created display and reshape methods for GLUT to use, we are going to need to create another method. The first method we are going to deal with is the key pressed method this method will tell us which keys are currently pressed. I am going to name this method key. Pressed and GLUT states that it has 3 parameters, one for the key that is currently pressed, and two more that give us the location of the mouse when the key was pressed. Pressed unsigned char key, int x, int y. Now that we have an empty method, lets go ahead and give this information to GLUT to use. Graduation requirements and regulations for every academic program are provided in this catalog. Degree requirements and course descriptions are subject to change. You can draw these objects as wireframes or as solid shaded objects with surface normals defined. For example, the routines for a cube and a sphere are as follows. Keyboard interaction can be handled by the user using system API calls, but why do that when you are already using GLUT which can handle this for you This tutorial. Down in our main method, we will access the glut. Keyboard. Func method and supply it with our method. Keyboard. Funckey. Pressed Tell GLUT to use the method key. Pressed for key presses. And that is pretty much all there is to it. In order to access they keys pressed, inside your key. Pressed method you can use either a switch statement or an if statement, which checks they key variable against which ASCII character you want to check, and it will look something like this. If key a If they a key was pressed. Perform action associated with the a key. Key Up. The key up function registers when a key is released. This can be very useful for setting some value when the key is first pressed, and wanting to keep that value until the key is released. Once again, as this is handled by GLUT, we will need to go and create a method to handle this, and just like the key. Pressed method, this one will take in 3 parameters. These three parameters are exactly the same as 3 in the key. Pressed method. But we are going to call this method key. Up. So lets go ahead and create a method for this. Up unsigned char key, int x, int y. And once again we need to register this method with GLUT, and this time we will use the glut. Keyboard. Up. Func method. Keyboard. Up. Funckey. Up Tell GLUT to use the method key. Up for key up events. To use the key. Up method, is exactly the same as using the key. Pressed method, so we can call the exact same code if we wanted. If they a key was released. Perform action associated with the a key. Key Buffering. The next step is of course, to do some key buffering, which will allow us to handle multiple key presses later on in our Open. GL projects. As you might be aware, a char variable is the same as a byte and can take an integer value from 0 to 2. This is because a char variable has a size of 28, or 2. This allows us to handle up to 2. ASCII set of characters. So lets start off by creating an array of Boolean values that will hold the states of our keys. True will be pressed, and False will be not pressed. Im going to call this variable key. States as it is easy to understand. States new bool2. Create an array of boolean values of length 2. And now in our key. Pressed method, lets add a new line, which will set the value of the key we have pressed. This just sets the current position in the array of key. States, at the position of the currently pressed key, to true. Pressed unsigned char key, int x, int y. Stateskey true Set the state of the current key to pressed. And now we just need to add almost the exact same code to the key. Up method we created earlier. Only this time, we will be setting the state of the current key to false, meaning it is no longer pressed. Up unsigned char key, int x, int y. Stateskey false Set the state of the current key to not pressed. All that is left now for us to learn is how to actually use this. The good news is that now that you have the key information, you can use it however you want you just have to setup somewhere in your code to manage this. Ill go through an example on this to get you started. To do this, I am going to create another method, this time called key. Operations, where we are going to check for which keys have been pressed, and then perform their actions. This method doesnt need to return anything, and doesnt need to accept any parameters. Just declare it before your display method, as we are actually going to call it from our display method. Operations void. And as we are calling this from our display method, go ahead and call it from the very start of our display method, preferably before everything else. The reason I say to call it before everything else, is if you call it halfway through your rendering, then half of your render will be affected by any values updated by the key presses, and the other half of your render will not be affected, giving a mismatch and possible artifacts. Operations. gl. Clear. Color1. 0f, 0. Clear the background of our window to red. Finally, we fill in our key. Operations method with a whole bunch of if statements to check if the keys we want are pressed, and then perform the required actions. Operations void. Statesa If the a key has been pressed. Perform a key operations. Special Keys. While all of the above is perfectly fine for using regular key presses, there are some keys you may want to use, for example, the arrow keys, which can be represented differently on multiple systems. Luckily, GLUT allows us to use these keys, as long as we call a different method to glut. Keyboard. Func. Instead we must use glut. Special. Func which checks for presses of special keys. For example, if we want to check if the left arrow has been pressed, we can use GLUTKEYLEFT. The best news is that the method you create to handle your special keys, will be almost identical to the glut. Keyboard. Func method you created earlier. Below is an example of using special keys. First off, create a new method which I am going to call key. Special, which takes three parameters, all of them being an integer value, the first for the key pressed, and the second two are for the x and y position of the mouse at the time the method was called. And then call this method in our main method along with the rest of our key presses. Special int key, int x, int y. And then for the up function for special keys, declare a new method for handling the up event for special keys. Special. Up int key, int x, int y. Reshape. Funcreshape Tell GLUT to use the method reshape for reshaping. Keyboard. Funckey. Pressed Tell GLUT to use the method key. Pressed for key presses. Keyboard. Up. Funckey. Up Tell GLUT to use the method key. Up for key up events. Special. Funckey. Special Tell GLUT to use the method key. Special for special key presses. Special. Up. Funckey. Special. Up Tell GLUT to use the method key. Special. Up for special up key events. Main. Loop Enter GLUTs main loop. If you want to buffer these keys, you can create another array just like we did for regular key buffering, and dedicate this array to any special keys pressed. Special. States new bool2. Khronos Open. GL Registry The Khronos Group Inc The Open. GL Registry contains specifications, header files, and. Open. GL and related APIs including GLU. GLX, and WGL. In addition to the core API specifications, many. APIs have been defined by vendors, groups of. ARB. The Registry also contains specifications and. API specifications. The Registry also includes naming conventions, guidelines for. APIs. Table of Contents. Current Open. GL API, Open. GL Shading Language and GLX Specifications and. Reference Pages API and Extension Header Files Because extensions vary from platform to platform and driver to. Open. GL developers cant expect interfaces for all extensions. OS graphics drivers. Additional header files are provided here, including lt GLglext. Open. 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