Improve bloom and add option to use faster but lower quality bloom #21340
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Your PR caused a change in the graphical output of an example or rendering test. This might be intentional, but it could also mean that something broke! If it's expected, please add the M-Deliberate-Rendering-Change label. If this change seems unrelated to your PR, you can consider updating your PR to target the latest main branch, either by rebasing or merging main into it. |
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What's perf like with the low quality version? Afaik, the main perf issues with bloom is CPU usage, not GPU usage. Having so many separate render passes (1 per upsample/downsample step) is quite expensive. |
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I quite like the idea of this, but I want to see benchmarks on low-end machines :) |
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Tested the bloom 3d example on Mali G76 android with log diagnostics (debug build, opt-level 3): CPU timeGPU time (high quality bloom)GPU time (low quality bloom)TLDR: Bloom CPU takes ~2.3 ms (can be reduced if building in release mode). |
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I also add a |
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Your PR caused a change in the graphical output of an example or rendering test. This might be intentional, but it could also mean that something broke! If it's expected, please add the M-Deliberate-Rendering-Change label. If this change seems unrelated to your PR, you can consider updating your PR to target the latest main branch, either by rebasing or merging main into it. |
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Your PR caused a change in the graphical output of an example or rendering test. This might be intentional, but it could also mean that something broke! If it's expected, please add the M-Deliberate-Rendering-Change label. If this change seems unrelated to your PR, you can consider updating your PR to target the latest main branch, either by rebasing or merging main into it. |
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I added the Deliberate-Rendering-Change tag but I'm not sure all of it is correct. There's new text in the example which should cause it to fail but there's also a ton of other changes in the images which is surprising since I would have expected the default values to still look the same. |
tychedelia
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Oct 6, 2025
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| // Whether to use a high quality bloom implementation (default: true). | ||
| // If false, bloom will use an implementation that significantly reduces the number of texture samples and improves performance, but at the cost of lower quality. | ||
| pub high_quality: bool, |
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Can we make this an enum to allow adding more possible quality settings / configuration in the future?
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I'm not sure if we should add an enum. The two bloom implementations seem sufficient, and there are other quality configuration. The performance difference of using moderate samples may not be significant.
I modified the calculation for the max mip dimensions, and used different samplers (ClampToBorder and ClampToEdge) for downsampling and upsampling , so the image changes are as expected. |
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Objective
Related to #13109. Bloom is slow, especially on mobile.
Solution
high_qualityoption to Bloom, if false, use blur kernels that only read 4 samples for downsampling and upsampling (from https://www.shadertoy.com/view/mdsyDf), instead of 13 samples and 9 samples.ClampToBorderfor downsampling andClampToEdgefor upsampling. Only usingClampToEdgecauses the bloom too bright and may flicker in the edges in low quality bloom.Testing
Added the option to
bloom_2dandbloom_3dexamples to test it.TODO: benchmark the performance.
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