Why are games rendered with a GPU while Blender, Cinebench and other programs use the CPU to render high quality 3d imagery? Why do some start rendering in the center and go outwards (e.g. Cinebench, Blender) and others first make a crappy image and then refine it (vRay Benchmark)?
In: Technology
Games and offline renderers generate images in very different ways. This is mainly for performances reasons (offline renderers can take hours to render a single frame, while games have to spew them out in a fraction of a second).
Games use rasterization, while offline renderers use ray-tracing. Ray tracing is a lot slower, but can give more accurate results than rasterization^[1]. Ray tracing can be very hard to do well on the GPU because of the more restricted architecture, so most offline renderer default to the CPU.
GPUs usually have a better computing power/$ ratio than CPUs, so it can be advantageous to do computational expensive stuff on the GPU. Most modern renderers can be GPU accelerated for this reason.
> Why do some start rendering in the center and go outwards (e.g. Cinebench, Blender) and others first make a crappy image and then refine it (vRay Benchmark)?
Cutting the image into square blocks and rendering them one after the other make it easier to schedule when each pixels should be rendered, while progressively refining an image allows the user to see what the final render will look like quickly. It’s a tradeoff, some (most?) renderer offer the two options.
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[1] This is a massive oversimplification, but if you are trying to render photorealistic images it’s mostly true.
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