GLUT eliminates the need to interact with your current OS to control a window on the screen and deal with any platform-specific code for devices. In our case, GLUT is the easiest library to interact with, and this lab is aiming to prove it. GLUT implements event-driven programming model for our window. For example, when the user clicks or moves the mouse, GLUT can call our event handler function and allow our program to keep up with the user's actions.
Examine each of these event handling functions and make sure you understand their parameters. Since we are about to start moving in 3D space, it is important to add a plane surface for visual guidance while moving in virtual world.
Hint: I would use WinMerge to do the initial editing. First, comment out the existing include directive:. At the end of the render function body, immediately before the glutSwapBuffers call, add code to draw a wireframe ground:.OpenGL Mouse function example for beginners
Compile and run the program. Make sure everything works as expected. Multisampling helps achieving full-screen antialiasing by averaging pixel colors on the edges of polygons.
Internally this is achieved by translating the coordinates of the scene along the X or Z axes. This function takes in a character the one that was pressed as well as the x and y position of the mouse when the key was pressed.
To implement some basic key controls, let's start with a switch like this:. Since we want to control smooth and continuous camera movement, the kyes that we press on the keyboard should not update the camera position directly. So why not? It's because the keyboard sends the "key-press" events at a rate of 10 times per second. If we change the position at this rate, the motion on the screen will be noticeably jerky. Also, this kind of camera movement won't be consistent across multiple OS and hardware platforms.
Instead, we will have our camera set stationary to begin with, but when it starts moving, the motion is controlled by the velocity. The actual speed will be a combination of the motion velocities along the X and Z axes. For example, if the user pushes down the W key, it is a signal for the camera to start moving forward. This can be done by a single line of code like this:.
Add code for the remaining keys according to the comments inside the switch statement listed above. Do it! Next, when one of the WASD keys is released, the camera motion should stop. Go ahead and set the X and Z velocities to zero. As in a typical FPS game, we implement zooming by a mouse button click.
When the mouse button is pressed, the view zooms in. As soon as the mouse button is released, the zoom level goes back to normal.
In OpenGL, the visual effect of zooming is set by the projection matrix transformation.
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Originally, projection is set in FPSCamera class constructor:. To control the projection in support of different zooming levels, we add new member function to the FPSCamera class.
Make sure to add function declaration in FPSCamera. Here, we simply set the zooming flag to true or false.Optional load calculation sheet
The flag is actually used by the render function. If zooming mode is on, the FOV field of view of the camera is reduced. If zoom is off, the FOV is restored.We use optional third-party analytics cookies to understand how you use GitHub. Learn more. You can always update your selection by clicking Cookie Preferences at the bottom of the page.
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Learn more about clone URLs. Download ZIP. Mouse and keyboard event handling with OpenGL. Sign up for free to join this conversation on GitHub. Already have an account? Sign in to comment. You signed in with another tab or window. Reload to refresh your session. You signed out in another tab or window. Accept Reject. Essential cookies We use essential cookies to perform essential website functions, e.
Analytics cookies We use analytics cookies to understand how you use our websites so we can make them better, e. Save preferences.Most of your OpenGL applications will require interaction through some sort of input device.
This will generally be the keyboard or the mouse.
GLUT Tutorial – Handling Keyboard Events
This tutorial will deal with how to capture and process messages from the keyboard. As all operating systems deal with keyboard input differently, GLUT provides a simple set of functions to allow for cross-platform development.
This tutorial is built upon the previous tutorial. GLUT recognizes 2 kinds of keys. Normal keys and special keys. We will discuss how to capture presses of both normal and special keys. Our first change is the addition of a boolean variable. When holding down a key, this will determine if we only get one event per key pressed or if successive events are triggered while the key is being held down. To capture messages from the keyboard, we need to have a keyboard function. This function must accept 3 parameters.
The first being an unsigned char representing the key that has been pressed and the second and third representing the position of the mouse when the key was pressed. The key variable can contain any ascii value corresponding to a key such as 'd' or 'E'. A separate function will be used to capture special keys but you may be wondering about other keys. How are the backspace, enter, escape and delete keys captured? These keys can actually be represented by ascii values and are therefore capture within our normal keyboard function.
For any other key pressed, we simply output the key along with the position at which it was pressed. Note that capturing the lowercase version of a character is not the same as capturing the uppercase equivalent ie. Another useful feature is that of keyboard modifiers. These are the ctrlshift and alt keys and can be held along with any other key. To retrieve these modifiersthe function glutGetModifiers is called.
This function returns an int which determines the modifiers that have been held. Note that the glutGetModifiers function can only be called within a main input function such as the keyboard, special keyboard and mouse functions. We check to see if any modifiers have been held and print out the result. Note that this method will not tell us if multiple modifiers have been held. This will be shown later in the tutorial.
I wrote the code below, but at runtime, when I press keys, the program doesn't work. But this doesn't work at all. It always shows a black screen. OK it works now. The code prints out the scancodes of the keys.
Otherwse GLUT won't register it. This won't work that way, because the calls to your keyboard callback will be run asynchronously. That means, you won't see a triangle drawn, unless the keystroke happens to be processed right between glClear and glFlushwhich will happen rather seldomly and only for one single frame.
What you have to do is rather straightforward: Upon processing the keystroke, save that status, e. On further notes, if you'd like to get into OpenGL programming without having to worry about handling other stuff around that, I'd recommend using a premade library handling windows, inputs, etc.
They work similar to glut, but they're in general more powerful and will still allow you to run OpenGL calls directly, while offering simplified event handling. You can't generate graphics commands in the keyboard callback.
Set some piece of global state when the key you're interested is pressed and use the information in the display code. The way to debug problems like this is to use printf statements in the code you think isn't working. Here adding a printf in the keyboard handler would soon tell you that the code is being executed but the triangle not being drawn.
That might have lead you to think about when a graphics command is possible and when it isn't. Learn more.Steamvr settings config
How write GLUT keyboard functions? Ask Question. Asked 8 years, 9 months ago. Active 4 years, 2 months ago. Viewed 30k times. Ava Bahari Ava Bahari 49 1 1 gold badge 3 3 silver badges 9 9 bronze badges. OpenGL doesn't do any keayboard handling. Active Oldest Votes.Functions performed include window definition, window control, and monitoring of keyboard and mouse input.
Routines for drawing a number of geometric primitives both in solid and wireframe mode are also provided, including cubesspheres and the Utah teapot. GLUT also has some limited support for creating pop-up menus. All GLUT functions start with the glut prefix for example, glutPostRedisplay marks the current window as needing to be redrawn.
Kilgard's GLUT library is no longer maintained, and its license did not permit the redistribution of modified versions of the library. This spurred the need for free software or open source reimplementations of the API from scratch. The first such library was FreeGLUTwhich aims to be a reasonably close reproduction, though introducing a small number of new functions to deal with GLUT's limitations.
Some of GLUT's original design decisions made it hard for programmers to perform desired tasks.
This led many to create non-canon patches and extensions to GLUT. From Wikipedia, the free encyclopedia. This article has multiple issues.
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Namespaces Article Talk. Views Read Edit View history. Help Learn to edit Community portal Recent changes Upload file. Download as PDF Printable version.When thinking about keyboard input, it is important to remember that a key stroke is not the same as a character.
For example, pressing the A key could result in any of the following characters. When you press a key, the hardware generates a scan code. Scan codes vary from one keyboard to the next, and there are separate scan codes for key-up and key-down events. You will almost never care about scan codes. The keyboard driver translates scan codes into virtual-key codes. Virtual-key codes are device-independent. Pressing the A key on any keyboard generates the same virtual-key code.
In general, virtual-key codes do not correspond to ASCII codes or any other character-encoding standard. In some respects this mapping is unfortunate, because you should never think of virtual-key codes as characters, for the reasons discussed.
The header file WinUser. For the complete list of virtual-key codes, see Virtual-Key Codes. Instead, just use the numeric value. There are two types of system key:. The F10 key activates the menu bar of a window.
GLUT Tutorial – Handling Keyboard Events
Various ALT-key combinations invoke system commands. In addition, if a window has a menu, the ALT key can be used to activate menu items.
Some ALT key combinations do not do anything.Obs alpha mask
This includes the function keys other than F If you hold down a key long enough to start the keyboard's repeat feature, the system sends multiple key-down messages, followed by a single key-up message. In all four of the keyboard messages discussed so far, the wParam parameter contains the virtual-key code of the key. The lParam parameter contains some miscellaneous information packed into 32 bits.
You typically do not need the information in lParam. One flag that might be useful is bit 30, the "previous key state" flag, which is set to 1 for repeated key-down messages.Is vsthouse legit
As the name implies, system key strokes are primarily intended for use by the operating system. Otherwise, you will block the operating system from handling the command.
Key strokes are converted into characters by the TranslateMessage function, which we first saw in Module 1. This function examines key-down messages and translates them into characters. The wParam parameter of the message contains the UTF character. Assuming a standard keyboard layout, you would get the following sequence of messages:.
Otherwise, you may interfere with standard system commands. Character input can include characters outside the ASCII range, especially with keyboard layouts that are commonly used outside of the United States. You can try different keyboard layouts by installing a regional keyboard and then using the On-Screen Keyboard feature.
Stack Overflow for Teams is a private, secure spot for you and your coworkers to find and share information. The following code works for all keys except CTRL:. GLUT cannot detect just the press of Ctrl. See the documentation of glutGetModifiers for more details. Learn more. Asked 6 years, 8 months ago. Active 6 years, 8 months ago.
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