11 lines
2 KiB
Markdown
11 lines
2 KiB
Markdown
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# Frameless Rendering
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Frameless rendering is a technique of [rendering](rendering.md) animation by continuously updating an image on the screen by updating single "randomly" selected pixels rather than by showing a quick sequence of discrete frames. This is an alternative to the mainstream [double buffered](double_buffering.md) frame-based rendering traditionally used nowadays.
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Typically this is done with [image order](image_order.md) rendering methods, i.e. methods that can immediately and independently compute the final color of any pixel on the screen -- for example with [raytracing](raytracing.md).
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The main advantage of frameless rendering is of course saving a huge amount of memory usually needed for double buffering, and usually also increased performance (fewer pixels are processed per second). The animation may also seem more smooth and responsive -- reaction to input is seen faster. Another advantage, and possibly a disadvantage as well, is a **[motion blur](motion_blur.md)** effect that arises as a side effect of updating by individual pixels spread over the screen: some pixels show the scene at a newer time than others, so the previous images kind of blend with the newer ones. This may add realism and also prevent temporal [aliasing](aliasing.md), but blur may sometimes be undesirable, and also the kind of blur we get is "pixelated" and noisy.
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Selecting the pixels to update can be done in many ways, usually with some [pseudorandom](pseudorandom.md) selection, but regular patterns may also be used. There have been papers that implemented adaptive frameless rendering that detected where it is best to update pixels to achieve low noise.
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Historically similar (though different) techniques were used on computers that didn't have enough memory for a double buffer or redrawing the whole screen each frame was too intensive on the CPU; programmers had to identify which pixels had to be redrawn and only update those. This resulted in techniques like *adaptive tile refresh* used in scrolling games such as [Commander Keen](commander_keen.md).
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