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[PR #13477] AtlasEngine: Improve glyph generation performance #29584

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opened 2026-01-31 09:35:45 +00:00 by claunia · 0 comments
claunia commented 2026-01-31 09:35:45 +00:00
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Original Pull Request: https://github.com/microsoft/terminal/pull/13477

State: closed
Merged: Yes

#13458 added the ability to reuse tiles from our glyph atlas texture
so that we stop running out of GPU memory for complex Unicode.
This however can result in our glyph generation being a performance issue in
edge cases, to the point that the application may feel outright unuseable.

CJK glyphs for instance can easily exceed the maximum atlas texture size
(twice the window size), but take a significant amount of CPU and GPU time to
rasterize and draw, which results in "jelly scrolling" down to ~1 FPS.
This PR improves the situation of the latter half by directly drawing
glyphs into the texture atlas without an intermediate scratchpad texture.

This reduces GPU usage by 96% on my system (33% -> 2%) which improves general
render performance by ~100% (15 -> 30 FPS). CPU usage remains the same however,
but that's not really something we can do anything about at this time.
The atlas texture is already our primary means to reduce the CPU cost after all.

Validation Steps Performed

  • Disable V-Sync for OpenConsole in NVIDIA Control Panel
  • Enable debugGlyphGenerationPerformance
  • Print the entire CJK block U+4E00..U+9FFF
  • Measure the above GPU usage and FPS improvements ✅
    (Alternatively: Just scroll around and judge the "jellyness".)
**Original Pull Request:** https://github.com/microsoft/terminal/pull/13477 **State:** closed **Merged:** Yes --- #13458 added the ability to reuse tiles from our glyph atlas texture so that we stop running out of GPU memory for complex Unicode. This however can result in our glyph generation being a performance issue in edge cases, to the point that the application may feel outright unuseable. CJK glyphs for instance can easily exceed the maximum atlas texture size (twice the window size), but take a significant amount of CPU and GPU time to rasterize and draw, which results in "jelly scrolling" down to ~1 FPS. This PR improves the situation of the latter half by directly drawing glyphs into the texture atlas without an intermediate scratchpad texture. This reduces GPU usage by 96% on my system (33% -> 2%) which improves general render performance by ~100% (15 -> 30 FPS). CPU usage remains the same however, but that's not really something we can do anything about at this time. The atlas texture is already our primary means to reduce the CPU cost after all. ## Validation Steps Performed * Disable V-Sync for OpenConsole in NVIDIA Control Panel * Enable `debugGlyphGenerationPerformance` * Print the entire CJK block U+4E00..U+9FFF * Measure the above GPU usage and FPS improvements ✅ (Alternatively: Just scroll around and judge the "jellyness".)
claunia added the pull-request label 2026-01-31 09:35:45 +00:00
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