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> While scrolling fast through the long document, my eyes immediately focused on "Wait, why not Vulkan or DirectX12?" :-D Well, I don't think it's architected

> While scrolling fast through the long document, my eyes immediately focused on "Wait, why not Vulkan or DirectX12?" :-D Well, I don't think it's architected in any way that would prevent the adoption of lower level APIs; but Godot's main markets are mobile, embedded, and web where OpenGL ES 3.0 is a low (but not the lowest) common denominator.

cma 9y ago
Vulkan should help with mobile battery life though.
- kevingadd 9y ago
  This is a false assumption. Existing GL drivers do a lot of hard work to compensate for platform-specific (or even chip-specific) quirks and limitations. If you're building on top of Vulkan or D3D12 you potentially don't get that assistance (due to the lower-level nature of the API), and you'll have to deal with a lot of that nonsense yourself. Android apps like Firefox or Dolphin already have a bunch of one-off workarounds for shader compiler bugs, etc. It's worse without a smart driver. On the other hand, the SPIR-V system used for shaders in Vulkan routes around a significant portion of bad shader compilers, so that's nice :) If you have a Vulkan app that's not tuned for your specific device, your battery life (and framerates) could easily end up worse. Vulkan and D3D12 shine in the hands of a company like EA or Ubisoft, and it's no coincidence that the Mantle spec (a precursor to Vulkan and D3D12) was basically completely designed by DICE, the developers of EA's Frostbite engine.
  - microcolonel 9y ago
    > This is a false assumption. Existing GL drivers do a lot of hard work to compensate for platform-specific (or even chip-specific) quirks and limitations. While it may be possible for GL stacks to do this, real mobile and embedded GL stacks tend to barely function at all. I highly doubt they do much more than try to extract maximum straight line performance for synthetic benchmarks within their budget. The reason Vulkan can have an outsize effect on power consumption is that it can allow renderer work to be spread across several threads. Running two cores at 60% the clock rate will typically cost considerably less power than running one at a higher frequency. This is an explicit (and accomplished) goal of mobile vendors in supporting Vulkan.

cma 9y ago

Vulkan should help with mobile battery life though.

kevingadd 9y ago
This is a false assumption. Existing GL drivers do a lot of hard work to compensate for platform-specific (or even chip-specific) quirks and limitations. If you're building on top of Vulkan or D3D12 you potentially don't get that assistance (due to the lower-level nature of the API), and you'll have to deal with a lot of that nonsense yourself. Android apps like Firefox or Dolphin already have a bunch of one-off workarounds for shader compiler bugs, etc. It's worse without a smart driver. On the other hand, the SPIR-V system used for shaders in Vulkan routes around a significant portion of bad shader compilers, so that's nice :) If you have a Vulkan app that's not tuned for your specific device, your battery life (and framerates) could easily end up worse. Vulkan and D3D12 shine in the hands of a company like EA or Ubisoft, and it's no coincidence that the Mantle spec (a precursor to Vulkan and D3D12) was basically completely designed by DICE, the developers of EA's Frostbite engine.
- microcolonel 9y ago
  > This is a false assumption. Existing GL drivers do a lot of hard work to compensate for platform-specific (or even chip-specific) quirks and limitations. While it may be possible for GL stacks to do this, real mobile and embedded GL stacks tend to barely function at all. I highly doubt they do much more than try to extract maximum straight line performance for synthetic benchmarks within their budget. The reason Vulkan can have an outsize effect on power consumption is that it can allow renderer work to be spread across several threads. Running two cores at 60% the clock rate will typically cost considerably less power than running one at a higher frequency. This is an explicit (and accomplished) goal of mobile vendors in supporting Vulkan.