feat: Extend Save3D to save vertex colors and textures (CORE-189)

[kijai]

• Split GLB save logic out of nodes_hunyuan3d.py into a new nodes_save_3d.py, and extend the writer to support UVs, per-vertex colors, and embedded baseColor textures.
• Extend the MESH type with optional uvs, vertex_colors, and texture fields so meshes can carry texture data through the graph.
• Add pack_variable_mesh_batch / get_mesh_batch_item helpers and switch VoxelToMesh / VoxelToMeshBasic to use them so batches with differing vertex/face counts no longer fail at torch.stack.

[coderabbitai]

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📝 Walkthrough

Walkthrough

This PR extends the MESH type to carry optional UVs, per-vertex colors, and a texture tensor; adds pack_variable_mesh_batch and get_mesh_batch_item for ragged per-item meshes; implements save_glb to write GLB files (including optional UVs/colors/embedded PNG textures); adds a SaveGLB ComfyUI node and Save3DExtension entrypoint; registers nodes_save_3d.py for startup loading; and updates VoxelToMesh nodes to return either stacked MESH batches or packed variable-size batches when shapes differ.

🚥 Pre-merge checks | ✅ 4 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 7.69% which is insufficient. The required threshold is 80.00%.	Write docstrings for the functions missing them to satisfy the coverage threshold.

✅ Passed checks (4 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title accurately summarizes the main changes: extending Save3D functionality to support vertex colors and textures, which is the primary objective of the PR.
Description check	✅ Passed	The description comprehensively covers the PR's changes: refactoring GLB save logic, extending the MESH type with new fields, and adding batch helpers for variable-sized meshes.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

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[coderabbitai]

Actionable comments posted: 2

🤖 Prompt for all review comments with AI agents

Verify each finding against current code. Fix only still-valid issues, skip the
rest with a brief reason, keep changes minimal, and validate.

Inline comments:
In `@comfy_extras/nodes_save_3d.py`:
- Around line 20-57: The pack_variable_mesh_batch helper currently discards
texture data; update pack_variable_mesh_batch to accept a textures parameter
(e.g., textures=None), validate and pack per-item textures analogously to
colors/uvs (compute max_textures, create packed_textures, texture_counts tensor,
copy slices), and attach them to the returned Types.MESH as mesh.texture and
mesh.texture_counts; if mixed texture sizes are not supported, explicitly raise
a clear error inside pack_variable_mesh_batch instead of dropping textures so
SaveGLB.execute and other consumers receive or fail on texture data
consistently.
- Around line 100-118: Before serializing in the block that converts tensors to
numpy (symbols: vertices, faces, uvs, vertex_colors, vertices_np, faces_np,
uvs_np, colors_np), add validation: ensure faces is a 2D integer array with all
indices >=0 and < vertices.shape[0]; ensure uvs (if not None) has first-dim
length equal to vertices.shape[0] (or to faces.shape[0] depending on your UV
convention) and shape[1]==2; ensure vertex_colors (if not None) has first-dim
length equal to vertices.shape[0] and values in [0,1]; if any check fails raise
a clear exception describing the mismatch and which array failed so the exporter
fails fast instead of producing an invalid GLB.

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Fix all unresolved CodeRabbit comments on this PR:

• Push a commit to this branch (recommended)
• Create a new PR with the fixes

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ℹ️ Review info

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📥 Commits

Reviewing files that changed from the base of the PR and between aa9d2fc and 16bcf4b.

📒 Files selected for processing (4)

• comfy_api/latest/_util/geometry_types.py
• comfy_extras/nodes_hunyuan3d.py
• comfy_extras/nodes_save_3d.py
• nodes.py

[jtydhr88]

LGTM

[alexisrolland]

Tested and working fine.