feat(util): add BlitterWithLoadOp for compositing use cases#1363
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khayzz13 wants to merge 2 commits intolinebender:mainfrom
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feat(util): add BlitterWithLoadOp for compositing use cases#1363khayzz13 wants to merge 2 commits intolinebender:mainfrom
khayzz13 wants to merge 2 commits intolinebender:mainfrom
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When rendering Vello content on top of existing GPU-rendered content (e.g., compute shader heatmaps, Silk.NET graphics), the standard blit uses LoadOp::Clear which destroys the existing content. This adds BlitterWithLoadOp which allows using LoadOp::Load to preserve the background, enabling proper compositing workflows: 1. External renderer → Surface (LoadOp::Clear) 2. Vello compute shaders → Intermediate texture 3. BlitterWithLoadOp → Surface (LoadOp::Load, preserves step 1) 4. Present API: - BlitterWithLoadOp::new(device, format) - create blitter - BlitterWithLoadOp::copy_with_loadop(device, encoder, src, dst, loadop) The existing TextureBlitter and its copy() method remain unchanged. Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>
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Summary
Add
BlitterWithLoadOpto enable compositing Vello content over existing GPU-rendered content.Motivation
When integrating Vello into applications that render other GPU content first (e.g., compute shader heatmaps, external renderers like Silk.NET), the final blit needs
LoadOp::Loadto preserve the existing surface content. Currently,TextureBlitter::copy()usesLoadOp::Clear, making compositing impossible without duplicating the blitter code.Solution
Add a new
BlitterWithLoadOpstruct tovello/src/util.rswith:new(device, format)- creates the blitter pipelinecopy_with_loadop(device, encoder, src, dst, loadop)- blits with configurable LoadOpCompositing workflow:
Changes
vello/src/util.rs: AddBlitterWithLoadOpstruct andblitter_loadopfield toRenderSurfaceBackwards Compatibility
Fully backwards compatible - existing
TextureBlitterandcopy()method unchanged.