Why does a computer need a dedicated graphics card for high-graphics video games, but can play 4K quality video without one?
In: Technology
Game graphics are rendered in real time and benefit from special hardware built for parallelism and particular mathematical operations.
Most mainboards have a decent integrated graphics controller these days. It certainly does well at decompressing video data and piping it to the output, which is a more linear operation.
I don’t see it mentioned in other comments so I’ll bring it up.
Hardware acceleration.
Playing back 4k video is actually surprisingly hard work for the computer. But the algorithm used is so common that manufactures like Intel, Apple, and Qualcomm (common android CPU maker) have built dedicated circuitry that is really really good at playing video. By contrast, the algorithms used by games are much more generic and thus need the powerful graphics card.
If you want an example of this, watch the CPU usage on an old computer while playing a 4k YouTube video. Older computers still had this video decoder built in, but could only work up to 1080p. Actually experienced this on a buddy’s laptop. It was reasonably powerful and had a 4k screen, but lacked a 4k video decoder. So when we watched a 4k YouTube video, the CPU spiked to 100% and the fans went full jet engine mode as it tried to keep up.
Why does my phone play 1080p games at 60fps and barely gets warm??
There is a bunch of mathematics to take the 3D space and convert it to an image that goes to your monitor.
The most expensive process happens in the GPU, you pass all the objects vertices (mesh), textures, camera, and transform them using the MVP (model, view, projection matrix) in the GPU vertex shader.
Then the GPU does all that math and some magic with triangles, then returns you the resulting frame pixels with other relevant information. You take those pixels and calculate the lighting, shadows, after effects in the pixel shader (also called Fragment shader), once per each pixel.
This whole process in modern games runs several times to generate a single frame (we get 60fps and up nowadays). Every light that casts shadows has to be rendered and then mixed together in the final pass. Then you have post process pass like Bloom, anti-aliasing, ambient occlusion, color correction, etc
That’s what the GPU is for, it does hard math for each vertice, and then for each pixel that goes to the screen, several times. That’s why a GPU has so many cores, it’s a parallel job.
A GPU can’t process very good conditional logic. It’s engineered to do parallel math. The logic of the game, objects transformations, physics, etc, it’s all handled in the CPU.
There are some great ELI5 answers here already – ill add that for video the ‘rendering’ has already been done. When you export a video in an editor, it takes a long time for the renderer to draw what will be in each frame of the “flip book”.
Many video editors use the video card to make that video rendering process faster. Complicated videos like fancy 3D animations take just as long if not more to ‘render’ to video as complicated video games take to render each frame. But once that work is done, the information is stored in a ‘flip book’ format so its quick to play it back. Since a video is always the same each time its played, you can do all of the “drawing” work ahead of time.
You can’t do the work ahead of time in a video game, because a video game is different every time its played – you the player decide what will happen next. So the ‘next’ frame is unknown until you turn, shoot, jump, or the game changes weather, lighting, etc.
Well 4k is not all the same. Just because it can play it doesn’t mean it does so well. It may look good, until you drive it with something that meets 4k standards.
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