1. Add optional language features support for LangSplat integration; 2. fix build bugs.

[jiagaoxiang]

Motivation

LangSplat (3D Language Gaussian Splatting) requires rendering per-Gaussian language features (e.g. 3-channel CLIP embeddings) alongside RGB colors during rasterization. Currently, LangSplat relies on a separate langsplat-rasterization CUDA backend that duplicates most of gsplat's pipeline with hard-coded language feature parameters threaded through every kernel.

This PR adds optional language feature support directly to gsplat.rasterization() so that LangSplat can use gsplat's AMD-optimized kernels (DPP warp reductions, 8x8 tiles, HIP-native streams) without maintaining a separate rasterizer fork. The design has zero overhead when the feature is unused -- the existing code path is completely unchanged when language_features=None (the default).

This PR also fixes three build bugs in setup.py that prevent successful installation in Docker/CI environments.

Technical Details

gsplat/rendering.py -- Add language_features parameter to rasterization()

Language features are alpha-blended with the same transmittance as colors, making them mathematically equivalent to extra color channels. The implementation leverages gsplat's existing N-D channel (CDIM template) support with no kernel changes:

• New optional parameter: language_features: Optional[Tensor] = None with shape [..., N, D_lang]
• After render_mode depth handling and before tile intersection, language features are concatenated to the end of the color channels via torch.cat([colors, lf], dim=-1). Backgrounds are zero-padded accordingly.
• After rasterization but before depth normalization, language features are split back out and stored in meta["render_language_features"] with shape [..., C, H, W, D_lang].
• Supports both packed=True and packed=False modes, and works with both precomputed colors and SH evaluation.
• Docstrings updated for the new parameter and return values.

setup.py -- Build fixes

• Fix NameError: name 'branch_name' is not defined in get_git_rev() exception handler.
• Fix invalid PEP 440 version string (e.g. 1.5.3+) when git rev is empty by guarding the version suffix append.
• Add -DGLM_FORCE_CUDA to CXX and hipcc compile flags for GLM header compatibility with HIP device kernels.

Test Plan

Integrated this new version rocm/gsplat into LangSplat and trained the Language Features with rendering. The evaluation results match Langsplat-rasterization perfectly.

[Copilot]

Pull request overview

Adds optional per-Gaussian language feature rendering support to gsplat.rasterization() for LangSplat integration, and fixes several ROCm build/versioning issues in setup.py.

Changes:

• Add language_features: Optional[Tensor] to rasterization() and plumb it through by concatenating/splitting channels around rasterization.
• Store rendered language features in meta["render_language_features"] while keeping render_colors unchanged.
• Fix setup.py git revision/version suffix handling and add -DGLM_FORCE_CUDA to ROCm compile flags.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 1 comment.

File	Description
setup.py	Fixes git-rev/version handling and updates ROCm compile flags for GLM/HIP compatibility.
gsplat/rendering.py	Adds optional language feature channels to rasterization via concat/split with doc updates.

---

💡 Add Copilot custom instructions for smarter, more guided reviews. Learn how to get started.