feat: add transparency handling in GBuffer and enhance ColorTargetState with blend state management by Miou-zora · Pull Request #465 · EngineSquared/EngineSquared

Miou-zora · 2026-01-31T22:26:55Z

This pull request introduces improvements to the G-buffer rendering pipeline, focusing on alpha transparency handling and blending. The main changes ensure that fragments with low alpha are discarded and that the albedo output supports alpha blending. Additionally, the blend state management is refactored for better configurability and clarity.

Alpha transparency and blending improvements:

Fragments with alpha below 0.05 are now discarded in the fs_main shader function, preventing nearly transparent pixels from being rendered.
The albedo output in the G-buffer now uses a properly configured blend state to support alpha blending, ensuring correct compositing of semi-transparent surfaces.

Blend state management refactoring:

The ColorTargetState utility now includes methods to get and set the blend state, allowing for more flexible and explicit blend state configuration per render target.
The internal representation of ColorTargetState is updated to store a wgpu::BlendState, improving encapsulation and clarity.
The Shader class now retrieves the blend state from the ColorTargetState instead of using a separate variable, streamlining the pipeline state setup.

Summary by CodeRabbit

Refactor
- Per-target blend configuration now uses each target's blend settings and exposes blend-state accessors for finer control of compositing in the UI render pass.
Bug Fixes / Rendering
- Fragment shader now discards very-low-alpha texels to reduce artifacts and improve appearance of semi-transparent textures.
Chores
- CI workflow configured to use a dedicated build cache path for faster builds.

…te with blend state management

coderabbitai · 2026-01-31T22:27:15Z

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📝 Walkthrough

Walkthrough

GBuffer fragment shader now samples into textureColor, discards fragments with textureColor.a < 0.05, and computes albedo from textureColor.rgb * material.diffuse.rgb. Graphics code now uses per-format/per-target blend states via ColorTargetState additions and removes a previous RMLUI special-case.

Changes

Cohort / File(s)	Summary
GBuffer Fragment Shader `src/plugin/default-pipeline/src/resource/pass/GBuffer.hpp`	Fragment shader now samples into `textureColor`, early-discards fragments when `textureColor.a < 0.05`, and computes albedo as `textureColor.rgb * material.diffuse.rgb`.
ColorTargetState API `src/plugin/graphic/src/utils/shader/ColorTargetState.hpp`	Added private `wgpu::BlendState _blendState`, `getBlendState()` accessor and fluent `setBlendState()` mutator to hold per-target blend configuration.
Shader Creation Logic `src/plugin/graphic/src/resource/Shader.hpp`	Removed RMLUI special-case shared `blendState`; `colorTarget.blend` now uses `format.getBlendState()` (per-format/per-target blend state).
Rmlui Render Pass `src/plugin/rmlui/src/utils/RmluiRenderPass.cpp`	Creates and applies explicit `BlendState` for `END_RENDER_TEXTURE` (color: src=One, dst=OneMinusSrcAlpha, op=Add; alpha: src=One, dst=OneMinusSrcAlpha, op=Add).
CI workflow `.github/workflows/ci.yml`	Added `build-cache-path: 'build/.build_cache'` to xmake action invocations in several jobs.

Estimated code review effort

🎯 3 (Moderate) | ⏱️ ~25 minutes

Possibly related PRs

feat(graphic): support local and file-based textures in material setup #435: Modifies GBuffer fragment shader albedo computation — closely related to GBuffer.hpp changes.
fix: adding a request late update in the context for ui texts render #459: Adjusts RMLUI blend setup/premultiplied alpha — closely related to Shader.hpp and RmluiRenderPass.cpp changes.
feat(graphic): use diffuse texture rather than ambiant texture #436: Alters GBuffer material/texture usage and albedo logic — related to the shader alpha/discard changes.

Suggested reviewers

ripel2
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🐰
I hop through pixels, light and bright,
I hush the faint and keep the sight,
I stitch the blends with nimble paw,
Shaders sing and render law,
A carrot compile — hops of delight! 🥕

🚥 Pre-merge checks | ✅ 2 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 14.29% which is insufficient. The required threshold is 80.00%.	Write docstrings for the functions missing them to satisfy the coverage threshold.

✅ Passed checks (2 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title accurately summarizes the two main changes in the PR: transparency handling in GBuffer (alpha discard) and ColorTargetState enhancement with blend state accessors/mutators.

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✨ Finishing touches

🧪 Generate unit tests (beta)

Create PR with unit tests
Post copyable unit tests in a comment
Commit unit tests in branch add-transparency-when-using-textures

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coderabbitai

Actionable comments posted: 1

Caution

Some comments are outside the diff and can’t be posted inline due to platform limitations.

⚠️ Outside diff range comments (1)

src/plugin/graphic/src/resource/Shader.hpp (1)
68-85: ⚠️ Potential issue | 🟠 Major

RMLUI premultiplied alpha blend is lost due to descriptor not setting blend state.

The local blendState configured for RMLUI_RENDER_PASS_SHADER (lines 68–78) is unused because line 84 always applies &format.getBlendState() from the descriptor. Since RmluiRenderPass::CreateShader() never calls .setBlendState() on the descriptor's ColorTargetState, it defaults to wgpu::Default instead of the required premultiplied alpha settings (srcFactor=One, dstFactor=OneMinusSrcAlpha).

Fix by setting the blend state in the descriptor:
Suggested fix (set blend state in RMLUI descriptor)
    auto colorOutput =
        Graphic::Utils::ColorTargetState("END_RENDER_TEXTURE").setFormat(wgpu::TextureFormat::BGRA8UnormSrgb);
+   wgpu::BlendState premultipliedAlpha(wgpu::Default);
+   premultipliedAlpha.color.srcFactor = wgpu::BlendFactor::One;
+   premultipliedAlpha.color.dstFactor = wgpu::BlendFactor::OneMinusSrcAlpha;
+   premultipliedAlpha.color.operation = wgpu::BlendOperation::Add;
+   premultipliedAlpha.alpha.srcFactor = wgpu::BlendFactor::One;
+   premultipliedAlpha.alpha.dstFactor = wgpu::BlendFactor::OneMinusSrcAlpha;
+   premultipliedAlpha.alpha.operation = wgpu::BlendOperation::Add;
+   colorOutput.setBlendState(premultipliedAlpha);
Then remove the now-unused local blendState override from Shader.hpp.

🤖 Fix all issues with AI agents

In `@src/plugin/default-pipeline/src/resource/pass/GBuffer.hpp`:
- Around line 98-103: The shader currently discards low-alpha fragments but then
forces output.alpha to 1.0, breaking premultiplied blending; update the write to
output.albedo to preserve the sampled alpha and premultiply RGB by that alpha
(use textureColor and material.diffuse): e.g. compute premultipliedRGB =
textureColor.rgb * material.diffuse.rgb * textureColor.a and set output.albedo =
vec4(premultipliedRGB, textureColor.a) (or multiply textureColor.a by
material.diffuse.a if your material encodes alpha), ensuring you keep the
existing discard and textureSample usage.

coderabbitai

Actionable comments posted: 1

🤖 Fix all issues with AI agents

In `@src/plugin/graphic/src/resource/Shader.hpp`:
- Line 68: The local variable declaration `wgpu::BlendState
blendState(wgpu::Default);` in Shader.hpp is dead code after the refactor that
now uses `format.getBlendState()`; remove this unused `blendState` declaration
so there are no unused locals in the function (ensure no other references to
`blendState` remain and rely on `format.getBlendState()` where needed).

sonarqubecloud · 2026-02-11T09:46:39Z

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud

feat: add transparency handling in GBuffer and enhance ColorTargetSta…

913f3c1

…te with blend state management

Miou-zora requested a review from a team January 31, 2026 22:27

Miou-zora self-assigned this Jan 31, 2026

Miou-zora added the enhancement New feature or request label Jan 31, 2026

coderabbitai Bot reviewed Jan 31, 2026

View reviewed changes

Comment thread src/plugin/default-pipeline/src/resource/pass/GBuffer.hpp

Miou-zora added 4 commits February 1, 2026 13:32

refactor(default-pipeline): remove useless blendstate usage

698655c

Merge branch 'main' into add-transparency-when-using-textures

dfa780e

feat(RmluiRenderPass): add blend state configuration for color output

377b7d2

Merge branch 'main' into add-transparency-when-using-textures

731ce73

coderabbitai Bot reviewed Feb 10, 2026

View reviewed changes

Comment thread src/plugin/graphic/src/resource/Shader.hpp Outdated

Miou-zora added 3 commits February 10, 2026 18:57

fix(graphic): remove unused blend state initialization in Shader class

01eb187

feat(ci): add build cache path for project and examples

707d25f

ci: remove key data for xmake caching

b02e88d

Miou-zora merged commit 2660c3d into main Feb 11, 2026
16 checks passed

Miou-zora deleted the add-transparency-when-using-textures branch February 11, 2026 10:01

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feat: add transparency handling in GBuffer and enhance ColorTargetState with blend state management#465

feat: add transparency handling in GBuffer and enhance ColorTargetState with blend state management#465
Miou-zora merged 8 commits into
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Miou-zora commented Jan 31, 2026 •

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Miou-zora commented Jan 31, 2026 •

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