2019-01-03 13:35:19 -05:00
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# Pathfinder 3 Architecture
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## Rendering pipeline
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Quoted timings are for the Ghostscript tiger at 1600×1600 pixels, 8-bit RGBA destination, 2017
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MacBook Pro, Intel Core i7-7920HQ CPU @ 3.10GHz, (quad-core with hyperthreading), Intel HD Graphics
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630 1536 MB.
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### CPU
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#### Simplify
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Across all paths in parallel:
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* Apply transforms.
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* Convert strokes to fills.
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* Make curves monotonic.
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#### Tile
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Across all paths in parallel:
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* Cut paths into 16×16 tiles.
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* Approximate curves with lines.
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* Flag tiles that consist entirely of a solid color.
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#### Cull
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2019-01-03 13:40:31 -05:00
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Sequentially (<span style="text-transform: lowercase; font-variant: small-caps">TODO</span>: in parallel):
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2019-01-03 13:35:19 -05:00
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* Cull tiles occluded by solid-color tiles.
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#### Pack
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Sequentially:
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* Gather up and compress per-instance data produced by the tile pass into batches.
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* Upload to GPU.
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Approximate CPU time for the tile, cull, and pack passes: 2.2 ms.
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### GPU
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#### Fill
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In parallel:
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* Rasterize all edges to an alpha coverage framebuffer (16-bit single-channel floating point).
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Approximate GPU time: 2.6 ms.
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#### Shade
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In parallel:
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* Draw solid-color tiles. (Z-buffer is not needed because we did occlusion culling in software.)
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* Shade tiles back-to-front using the alpha mask generated during the fill step.
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Approximate GPU time: 2.3 ms.
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