Rendering and video encoding
Rendering requires a lot of processor power. A single core working through a large render or video could take a very long time. Thankfully, a scene that is being rendered can be broken up into smaller sections (called 'buckets'), with each section assigned to a different core.
These buckets are then rendered separately and recombined to create the final export. For this reason, a CPU with four, eight or twelve cores will render a scene much faster than a CPU with just one.
Graphics Processing Unit (GPU) rendering is also becoming increasingly popular in recent years. GPUs or graphics cards have far more cores than CPUs, although these cores are less powerful and flexible than those in a CPU. This means that they can often process renders faster, with a slight reduction in precision and quality.
For this reason, many high-end animation studios or production houses will still use CPU rendering. For smaller companies or freelancers, GPU rendering is a cost-effective and speedy alternative.
GPU exclusive render engines are always faster. But they usually lack some of the more advanced features, such as hair or caustics or liquid rendering. Probably the largest drawback is the amount of memory (VRAM) on GPUs.
For larger CGI houses, a scene could easily be hundreds of GBs. Trying to create a scene larger than the available memory can cause a whole host of problems. And VRAM is expensive. Alternatively, CPU can access the system RAM, which is extremely cheap in comparison.
Ultimately, the trade-off is speed vs accuracy. Creatives can get results fast with a GPU, while CPU is better suited for applications that require ultimate quality and accuracy.
3D modelling, graphic design and video editing
Not all tasks can be split up in this way. The processes involved with 3D modelling, animation, graphic design and video editing have to be completed in a predetermined sequence.
For example, an animation may consist of a series of shapes that have a set of modifiers and deformers applied to them. In order to be applied correctly, these modifiers and deformers have to be applied in the right order. Splitting the tasks out across multiple cores would disrupt this order.
For this reason, computers that are being used for 3D modelling, animation and design benefit from having processors that can complete tasks at high frequency, which is called having a higher 'clock speed'.
Think of it this way: having multiple cores is like having multiple lanes of traffic, having higher clock speed is like having faster cars.
Why don't I get multiple cores all with high clock speeds?
For the sake of safety and energy efficiency, computers have limits on the amount of power they can consume and the heat they can generate. As a result, there is often a trade-off between clock speed and the number of cores you can have running at once - more of one tends to be less of the other.
It's a zero-sum game.
This can be a tricky decision. A lot of creatives, particularly if they work in a smaller business or for themselves, will be doing a bit of both. In this case, you need to strike a balance between the two. Thankfully, there are plenty of processors out there that can do both.
Here's an example of a CPU that's great for rendering but can still handle 3D modelling, graphic design and video editing: AMD Ryzen 9 3900X
And here's an example of a CPU that's good for active work but can still handle rendering: Intel i9 9900K