A screensaver is really just an executable file, with the extension changed from .exe to .scr. File extensions tell the computer what kind of file it is dealing with. For example, winword.exe is a word-processing application that can be loaded by the computer, while article.doc is a text file that can be loaded into the Microsoft Word word-processing application. Show
An executable file is a file that the computer's operating system considers a program or application. Files ending in .exe (or .scr) are expected to run without the need of another file; or, if they do need another file, they are expected to tell the computer which particular file is needed. So we know that, in essence, a screensaver is a program. By putting a screensaver file into the Windows or System directory and giving it a .scr extension, Windows knows that it should treat this file as a screensaver and makes it available as an option in the Display properties window. The screensaver file can be programmed in several different ways. It can:
Most screensavers offer some combination of these features. Except for the slide-show screensavers that display a sequence of images, screensavers generally move an image, piece of text or animation around the screen. The screensavers that have a custom interface, and do not use the Display properties window at all, are less common. Usually, these screensavers do not have the .scr extension. They require that you install them using a setup program in order to configure them properly. Updated: 12/31/2020 by Computer Hope  A screen saver or screensaver is a software program that becomes activated after the computer is inactive for a specified amount of time. Screensavers were originally designed to help prevent images or text from being burned into older monitors. Tip In Windows, press the Windows key+L to lock the computer if you're stepping away from the computer. Locking the computer activates the screensaver and prevents others from accessing your computer. The monitors and flat-panel displays used today no longer suffer from burn-in issues found with older CRT monitors. However, screen savers are still used for their aesthetic value and to password protect a computer when the user is away from the keyboard. Do screen savers save power?No. When a screen saver is visible, your computer and monitor are both still on, meaning the same amount of power is used. Tip You'll save power and extend the life of your monitor if you turn it off when you step away from your computer instead of using a screen saver. If you use a screen saver to show pictures or for other aesthetic reasons, adjust the power savings mode to turn off your monitor after being away for more than an hour. See: How to adjust power, standby, and sleep settings. Confusion between screen saver and wallpaperMany new computer users confuse a screen saver with a wallpaper, which is the picture shown on your desktop. See our wallpaper page for further information and related links on this term. What are examples of screen saver programs?In the past, screen saver programs like After Dark would install on your computer and run by itself. Today, most screen savers and screen saver packages install into the operating system, which runs the screen saver. The following screen savers are include with Microsoft Windows 10.
How to exit a screen saverTo exit a screen saver, move the mouse, press a mouse button, or press a key on the keyboard. For example, pressing the Esc would exit the screen saver. Note If the screen saver has a password, a password prompt is shown, and the correct password must be entered before the screen saver exits. Should I be using "screen saver" or "screensaver" in my writing?Both "screen saver" and "screensaver" are correct and what version you use is often dependent on the style guide you use. Computer Hope follows the Microsoft style of writing screen saver as two separate words. According to Google Trends, more people have used "screensaver" than "screen saver" in their writing. Burn in, The Screen Savers, Video terms A screensaver (or screen saver) is a computer program that blanks the display screen or fills it with moving images or patterns when the computer has been idle for a designated time. The original purpose of screensavers was to prevent phosphor burn-in on CRT or plasma computer monitors (hence the name)[citation needed]. Though most modern monitors are not susceptible to this issue (with the notable exception of OLED technology, which has individual pixels vulnerable to burnout), screensaver programs are still used for other purposes. Screensavers are often set up to offer a basic layer of security by requiring a password to re-access the device.[1] Some screensaver programs also use otherwise-idle computer resources to do useful work, such as processing for volunteer computing projects.[2] As well as computers, modern television operating systems, media players, and other digital entertainment systems may include optional screensavers. PurposeScreen protectionBefore the advent of LCD screens, most computer screens were based on cathode ray tubes (CRTs). When the same image is displayed on a CRT screen for long periods, the properties of the exposed areas of the phosphor coating on the inside of the screen gradually and permanently change, eventually leading to a darkened shadow or "ghost" image on the screen, called a screen burn-in. Cathode ray televisions, oscilloscopes and other devices that use CRTs are all susceptible to phosphor burn-in, as are plasma displays to some extent.[3] Screen-saver programs were designed to help avoid these effects by automatically changing the images on the screen during periods of user inactivity. For CRTs used in public, such as ATMs and railway ticketing machines, the risk of burn-in is especially high because a stand-by display is shown whenever the machine is not in use. Older machines designed without burn-in problems taken into consideration often display evidence of screen damage, with images or text such as "Please insert your card" (in the case of ATMs) visible even when the display changes while the machine is in use. Blanking the screen is out of the question as the machine would appear to be out of service. In these applications, burn-in can be prevented by shifting the position of the display contents every few seconds, or by having a number of different images that are changed regularly. Later CRTs were much less susceptible to burn-in than older models due to improvements in phosphor coatings, and because modern computer images are generally lower contrast than the stark green- or white-on-black text and graphics of earlier machines. LCD computer monitors, including the display panels used in laptop computers, are not susceptible to burn-in because the image is not directly produced by phosphors (although they can suffer from a less extreme and usually non-permanent form of image persistence). Modern usageWhile modern screens are not susceptible to the issues discussed above, screensavers are still used. Primarily these are for decorative/entertainment purposes, or for password protection. They usually feature moving images or patterns and sometimes sound effects. As screensavers are generally expected to activate when users are away from their machines, many screensavers can be configured to ask users for a password before permitting the user to resume work. This is a basic security measure against another person accessing the machine while the user is absent. Some screensavers activate a useful background task, such as a virus scan or a volunteer computing application (such as the SETI@home project).[4] This allows applications to use resources only when the computer would be otherwise idle. The Ken Burns panning and zooming effect is sometimes used to bring the image to life. HistoryDecades before the first computers using this technology were invented, Robert A. Heinlein gave an example of how they might be used[5] in his novel Stranger In A Strange Land (1961):[6]
The first screensaver was allegedly written for the original IBM PC by John Socha, best known for creating the Norton Commander; he also coined the term screen saver. The screensaver, named scrnsave, was published in the December 1983 issue of the Softalk magazine. It simply blanked the screen after three minutes of inactivity (an interval which could be changed by recompiling the program). By 1983 a Zenith Data Systems executive included "screen-saver" among the new Z-29 computer terminal's features, telling InfoWorld that it "blanks out the display after 15 minutes of nonactivity, preventing burned-in character displays".[7] The first screensaver that allowed users to change the activating time was released on Apple's Lisa, in 1983. The Atari 400 and 800's screens would also go through random screensaver-like color changes if they were left inactive for about 8 minutes. Normal users had no control over this, though programs did. These computers, released in 1979, are technically earlier "screen savers." Prior to these computers, games for the 1977 Atari VCS/2600 gaming console such as Combat and Breakout, included color cycling in order to prevent burn-in of game images into 1970s-era televisions. In addition, the first model of the TI-30 calculator from 1976 featured a screensaver, which consisted of a decimal point running across the display after 30 seconds of inactivity. This was chiefly used to save battery power, as the TI-30 LED display was more power intensive than later LCD models. These are examples of screensavers in ROM or the firmware of a computer. Android 4.2 introduced "daydreams", screensavers that activate while the device is docked or charging.[8][9] In 2015 the screensaver "Event listeners"[10] of van den Dorpel became the first work of art that was purchased by a museum (Museum of Applied Arts, Vienna) using the cryptocurrency bitcoin.[11] Modern graphics technologies such as 3D computer graphics have allowed a wide variety of screensavers to be made. Screensavers with realistic 3D environments can be programmed and run on modern computers. Underlying architecture
Screensavers are usually designed and coded using a variety of programming languages as well as graphics interfaces. Typically the authors of screensavers use the C or C++ programming languages, along with Graphics Device Interface (GDI), such as OpenGL ("Open Graphics Library", which works on many, if not most, platforms capable of 3D rendering), or alternatives such as Microsoft DirectX (which is limited to Microsoft platforms, mainly Microsoft Windows and the Microsoft Xbox), to craft their final products. Several OS X screensavers are created and designed using Quartz Composer. The screensaver interfaces indirectly with the operating system to cause the physical display screen to be overlaid with one or more graphic "scenes". The screensaver typically terminates after receiving a message from the operating system that a key has been pressed or the mouse has been moved. Microsoft WindowsIf the system detects inactivity lasting longer than the time specified in the control panel, check if the active program is a simple program (and not another screensaver) by sending the "WM_SYSCOMMAND" message with the "SC_SCREENSAVE" argument. If the program calls in response the standard system function (DefWindowProc), the screensaver defined in the control panel screen runs. A Windows screensaver is a regular Portable Executable (PE) with the .scr file extension. This enables malware authors to add ".scr" to the name of any win32 executable file, and thereby increase likelihood that users of Microsoft Windows will run it unintentionally. In addition, this program should support the following command line parameters:[12] With no parameter – shows the Settings dialog box or do nothing. ScreenSaver.scr /sRuns the screensaver. ScreenSaver.scr /p or /l <HWND>Previews the screensaver as child of window. <HWND> (presented as unsigned decimal number) is an identifier (handle) of the window in which the preview should appear. Shows the Settings dialog box, modal to the foreground window. ScreenSaver.scr /a <HWND>Changes password, modal to window <HWND>. Windows 95 screensavers must handle it. macOSUnder macOS, screensavers are regular macOS application bundles with the .saver file extension.[13] Internally, the screensaver must define a class that is subclass of ScreenSaverView. The new class must be assigned as NSPrincipalClass in the xcode project, so that when the screensaver is launched by the system, this class gets instantiated. AtariAs one of the first screensavers appeared in 8-bit Atari computers, forcing systemic color changes when the computer is idle lasting a few minutes (different times depending on the model), stored in the system ROM of the computer. ConsiderationsMonitors running screensavers consume the same amount of power as when running normally, which can be anywhere from a few watts for small LCD monitors to several hundred for large plasma displays. Most modern computers can be set to switch the monitor into a lower power mode, blanking the screen altogether. A power-saving mode for monitors is usually part of the power management options supported in most modern operating systems, though it must also be supported by the computer hardware and monitor itself. Using a screensaver with a flat panel or LCD screen not powering down the screen can actually decrease the lifetime of the display, since the fluorescent backlight remains lit and ages faster than it would if the screen is turned off and on frequently.[14][15] As fluorescent tubes age they grow progressively dimmer, and they can be expensive or difficult to replace. A typical LCD screen loses about 50% of its brightness during a normal product lifetime. In most cases, the tube is an integral part of the LCD and the entire assembly needs to be replaced. This is not true of LED backlit displays. Thus the term "screen saver" is now something of a misnomer – the best way to save the screen and also save electricity consumed by screen would simply be to have the computer turn off the monitor. Screensavers displaying complex 3D graphics might even add to overall power draw.[citation needed] EntertainmentAfter Dark was an early screensaver for the Macintosh platform, and later PC/Windows, which prominently featured whimsical designs such as "flying toasters". Perhaps in response to the workplace environment in which they are often viewed, many screensavers continue this legacy of whimsy by populating the idle monitor with animals or fish, games, and visual expressions of mathematics equations (through the use of fractals, Fourier transforms or other means) as in the Electric Sheep screensaver. At least one screensaver, Johnny Castaway told a humorous animated story over many months.[16] The ability of screensavers to divert and entertain is used for promotion, especially to build buzz for "event-based" products such as feature films. The screensaver is also a creative outlet for computer programmers. The Unix-based screensaver XScreenSaver collects the display effects of other Unix screensavers, which are termed "display hacks" in the jargon file tradition of US computer science academics. It also collects forms of computer graphics effects called demo effects, such as were originally produced by the demo scene. Microsoft WindowsOn older versions of Microsoft Windows the native screensaver format had the potential to install a virus when run (as a screen saver was just an ordinary application with a different extension). When any file with the file suffix ".scr" was opened, for example from an e-mail attachment, Windows would execute the .scr (screensaver) file automatically: this had the potential to allow a virus or malware to install itself. Modern versions of Windows can read tags left by applications such as Internet Explorer and verify the publisher of the file, presenting a confirmation to the user. On August 5, 2006, the BBC reported that "free screensavers" and "screensavers" respectively were the first and third most likely search terms to return links to malware, the second being BearShare.[17] By launching the "bubbles" screensaver executable through the bubbles.scr /p65552 command-line parameter, it runs as desktop wallpaper, the bubbles are smaller, and there are more bubbles on screen.[18] See also
References
External links
Look up screensaver in Wiktionary, the free dictionary.
Wikimedia Commons has media related to Screensavers.
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3D rendering is the 3D computer graphics process of converting 3D models into 2D images on a computer. 3D renders may include photorealistic effects or non-photorealistic styles. Rendering methodsRendering is the final process of creating the actual 2D image or animation from the prepared scene. This can be compared to taking a photo or filming the scene after the setup is finished in real life.[1] Several different, and often specialized, rendering methods have been developed. These range from the distinctly non-realistic wireframe rendering through polygon-based rendering, to more advanced techniques such as: scanline rendering, ray tracing, or radiosity. Rendering may take from fractions of a second to days for a single image/frame. In general, different methods are better suited for either photorealistic rendering, or real-time rendering.[2] Real-timeRendering for interactive media, such as games and simulations, is calculated and displayed in real time, at rates of approximately 20 to 120 frames per second. In real-time rendering, the goal is to show as much information as possible as the eye can process in a fraction of a second (a.k.a. "in one frame": In the case of a 30 frame-per-second animation, a frame encompasses one 30th of a second). The primary goal is to achieve an as high as possible degree of photorealism at an acceptable minimum rendering speed (usually 24 frames per second, as that is the minimum the human eye needs to see to successfully create the illusion of movement). In fact, exploitations can be applied in the way the eye 'perceives' the world, and as a result, the final image presented is not necessarily that of the real world, but one close enough for the human eye to tolerate. Rendering software may simulate such visual effects as lens flares, depth of field or motion blur. These are attempts to simulate visual phenomena resulting from the optical characteristics of cameras and of the human eye. These effects can lend an element of realism to a scene, even if the effect is merely a simulated artifact of a camera. This is the basic method employed in games, interactive worlds and VRML. The rapid increase in computer processing power has allowed a progressively higher degree of realism even for real-time rendering, including techniques such as HDR rendering. Real-time rendering is often polygonal and aided by the computer's GPU.[3] Non-real-timeAnimations for non-interactive media, such as feature films and video, can take much more time to render.[4] Non-real-time rendering enables the leveraging of limited processing power in order to obtain higher image quality. Rendering times for individual frames may vary from a few seconds to several days for complex scenes. Rendered frames are stored on a hard disk, then transferred to other media such as motion picture film or optical disk. These frames are then displayed sequentially at high frame rates, typically 24, 25, or 30 frames per second (fps), to achieve the illusion of movement. When the goal is photo-realism, techniques such as ray tracing, path tracing, photon mapping or radiosity are employed. This is the basic method employed in digital media and artistic works. Techniques have been developed for the purpose of simulating other naturally occurring effects, such as the interaction of light with various forms of matter. Examples of such techniques include particle systems (which can simulate rain, smoke, or fire), volumetric sampling (to simulate fog, dust and other spatial atmospheric effects), caustics (to simulate light focusing by uneven light-refracting surfaces, such as the light ripples seen on the bottom of a swimming pool), and subsurface scattering (to simulate light reflecting inside the volumes of solid objects, such as human skin). The rendering process is computationally expensive, given the complex variety of physical processes being simulated. Computer processing power has increased rapidly over the years, allowing for a progressively higher degree of realistic rendering. Film studios that produce computer-generated animations typically make use of a render farm to generate images in a timely manner. However, falling hardware costs mean that it is entirely possible to create small amounts of 3D animation on a home computer system given the costs involved when using render farms.[5] The output of the renderer is often used as only one small part of a completed motion-picture scene. Many layers of material may be rendered separately and integrated into the final shot using compositing software. Reflection and shading modelsModels of reflection/scattering and shading are used to describe the appearance of a surface. Although these issues may seem like problems all on their own, they are studied almost exclusively within the context of rendering. Modern 3D computer graphics rely heavily on a simplified reflection model called the Phong reflection model (not to be confused with Phong shading). In the refraction of light, an important concept is the refractive index; in most 3D programming implementations, the term for this value is "index of refraction" (usually shortened to IOR). Shading can be broken down into two different techniques, which are often studied independently:
Surface shading algorithmsPopular surface shading algorithms in 3D computer graphics include:
ReflectionReflection or scattering is the relationship between the incoming and outgoing illumination at a given point. Descriptions of scattering are usually given in terms of a bidirectional scattering distribution function or BSDF.[6] ShadingShading addresses how different types of scattering are distributed across the surface (i.e., which scattering function applies where). Descriptions of this kind are typically expressed with a program called a shader.[7] A simple example of shading is texture mapping, which uses an image to specify the diffuse color at each point on a surface, giving it more apparent detail. Some shading techniques include:
TransportTransport describes how illumination in a scene gets from one place to another. Visibility is a major component of light transport. ProjectionThe shaded three-dimensional objects must be flattened so that the display device - namely a monitor - can display it in only two dimensions, this process is called 3D projection. This is done using projection and, for most applications, perspective projection. The basic idea behind perspective projection is that objects that are further away are made smaller in relation to those that are closer to the eye. Programs produce perspective by multiplying a dilation constant raised to the power of the negative of the distance from the observer. A dilation constant of one means that there is no perspective. High dilation constants can cause a "fish-eye" effect in which image distortion begins to occur. Orthographic projection is used mainly in CAD or CAM applications where scientific modeling requires precise measurements and preservation of the third dimension. Rendering enginesRender engines may come together or be integrated with 3D modeling software but there is standalone software as well. Some render engines are compatible with multiple 3D software, while some are exclusive to one. See also
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