Why does a computer need a dedicated graphics card for high-graphics video games, but can play 4K quality video without one?
In: Technology
From the standpoint of what the computer has to do, running a game and playing a video are two very different things.
When you play a video (whether from a file or a streaming service), you’re receiving encoded data. That’s just the video data written in a specific format to be understood by any player that supports that format. As an analogy, if the raw video is an idea in your head, the encoded video is a sentence in spoken or written language (i.e., it’s understandable by other speakers of the language the sentence is in). In the streaming service example, Netflix sends you *encoded* video and your computer *decodes* this video so that it can show it to you through a screen (a similar process happens with audio). In this case, most of the work that your computer has to do is decode the incoming data.
When you’re playing a game, on the other hand, there’s no video to play back from. That means that your computer has to *draw* each individual frame – in other words, it has to calculate exactly what is going to be displayed by each pixel when taking into account the objects on the screen, the viewpoint of the player, lighting (and lighting tricks), shadows, and all other sorts of effects. This process is called *rendering*. That’s not super crazy – you’ve certainly seen this sort of thing in movies (that’s how CGI works), but what makes it hard is that for a game, all of that has to be done in real time *and* fast enough (think: at least 30, hopefully at least 60 times a second) to be displayed smoothly.
As another analogy, imagine that decoding is reading a sentence and extracting an idea from it – then imagine that rendering is drawing a picture from an idea in your head. The drawing bit just takes a lot more time and effort.
TLDR: playing back a video (decoding) is simply a translation process, whereas playing a game (rendering) involves a lot of heavy lifting (in terms of sheer number crunching) by the computer.
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