Cesarus85--mjolnir-vr/docs/object_matching_logs/render_contrails_obj.md

render_contrails.obj exact-match log

Outcome

source/render/render_contrails.obj is a strict whole-object match for the January 14, 2002 Xbox build. All six functions match in padded size, relocation count and identity, relocation-normalized bytes, and SHA-256. The three target-owned string COMDATs also match exactly. The consolidated XDK 3911 build succeeds, and the shared rasterizer ABI/layout corrections preserve the already-Matching 131-function rasterizer.obj.

In plain English: this file builds and traverses each live contrail, computes the strip's two vertices per point, shades and fades them, builds its triangle indices, and submits the completed dynamic geometry. The reconstruction uses ordinary readable C. It contains no inline assembly, volatile codegen trick, __forceinline, undefined behavior, byte patch, compiler-flag override, or fuzzy acceptance.

Strict evidence

Function	Meaningful bytes	Padded bytes	Relocations	Normalized SHA-256
_contrail_fade	143	144	6	7dc3dde6b3c8f5af61facf91de6d51d91ff268eaf8173d9911a94fbc6a867f83
_code_00177860	1945	1952	57	70d28d083222f55ac171cb1aa9676d018fb2bcae9ee54f09facee54755cef5e8
_code_00178000	176	176	9	16ce1e5bee24c8a0f0e79659476d2d619b783419e9ba49d3cb2a2c71bccd94fa
_render_contrails_ground_mapped	9	16	1	1b1a80b01bf5912843c9d879bc793dd8ac269b037598c7afa05a0752095dbb5f
_render_contrails_media_mapped	9	16	1	f27c91ab09dc5b6f75808b4ae85f5e00e23c249e0ad6466b48ef6c5bc216fe06
_render_contrails_normal	9	16	1	07a8bcb483de4cb8bba2c0b5dac4ad15eb04f47cde8cb833f3b376ba44abf179

Total code is 2,291 meaningful bytes and 2,320 padded bytes. The target-owned .rdata COMDATs are also exact:

Data	Bytes	SHA-256
"contrail %s uses an unsupported render type."	45	38b10bfb93e324bcd9ff15b429387e6e917890cf2b008360bddc77ce09375249
"triangles && vertices"	22	6faca77985ef8484b9433bf5961df25e5c373bbb4a3515ebc9fc5a29ba2e0aa2
January assert file path	41	9a3ff7ea5d44b5f3e438ca53d746335c870e6add38e784766b7d21f22e4cce17

The ordinary visual reporter still assigns _code_00177860 98.45% because it does not understand all local-label/section representations. The hardened COFF comparator proves the 1,952-byte function and all 57 resolved relocation destinations are identical; this is a known reporter false negative, not a tolerance or semantic approximation.

Recovered types and interfaces

• contrail_point_state is 0x68 bytes.
• contrail_shader places framebuffer_fade_mode at +0x2c.
• contrail_definition is 0x144 bytes and its states block is at +0x138.
• contrail_datum is 0x44 bytes.
• contrail_point_datum is 0x38 bytes.
• rasterizer_globals.current_lock_operation is a short at +2; the full rasterizer-global structure remains 0x68 bytes.
• The corrected unlit draw ABI is (shader, bitmap, animation, triangle_buffer_index, vertex_buffer_index, vertex_count, centroid, flags).
• Typed access uses contrail_definition_get, object_get, and TAG_BLOCK_GET_ELEMENT, in line with the project house rules.

Experiment history

The object began with only the three tiny render-mode wrappers exact. The following source shapes were accepted:

1. Expressing contrail_fade through the existing vector helpers reproduced the 144-byte function; manual scalar arithmetic produced 160 bytes and was rejected.
2. The natural data_next_index iterator, typed contrail tag getter, and four instance loop reproduced _code_00178000 at 176 bytes and nine relocs.
3. Correcting the recovered vertex, point, state, shader, definition, and rasterizer-global layouts moved the large renderer from 1,888 bytes/58 relocs through 1,904 and 1,920-byte shapes to the target 1,952/57 topology.
4. Direct scalar eye/tangent calculations and the January cross-product operand order reproduced the viewer-facing branch and both orientation normalizations.
5. Moving half_width *= 0.5f immediately before the four texture-coordinate stores fixed an otherwise independent three-byte scheduling window.
6. The final mismatch was only two compiler stack slots. Writing the two loop-carried updates as texture_u += texture_u_step; followed by previous_point = point; changed their live-range order and closed every remaining byte without changing the algorithm.

Measured and rejected shapes included aggregate/union packing of the two loop locals, declaration-order permutations, declaration initializers, an early NULL initialization, delayed texture initialization, nested scopes, and several alias forms. These either had no effect, changed broad register allocation, or regressed already-correct code. They should not be repeated.

The unsupported-render-type arm retains its early return because that is the January control-flow shape. This is the documented house-rule exception to the preferred single-return style; forcing a common exit changes the exact object. That arm also preserves an original cleanup bug: it skips the dynamic-buffer unlock/delete calls and leaves current_lock_operation set. The source labels the bug and describes the non-matching fix (route the arm through common cleanup) without changing January behavior.

Shared-header blast radius

The recovered layouts and corrected rasterizer ABI live in shared headers, so the audit did not rely on Ninja's ordinary header tracking. A detached clean worktree at campaign tip e30b1568 and the candidate worktree each rebuilt the same seven translation units from scratch: render_contrails, contrails, objects, rasterizer, ai_debug, cinematics, and main. Comparing every defined function with section_infos_equal and every non-debug data section found zero changes outside render_contrails.obj.

The raw regression manifest reported debug-record, section-number, and accepted evidence churn, including an apparent ai_debug_render_actor regression. That was not a code regression: a fresh baseline build already has the same current nonexact function, and baseline-to-candidate hardened comparison is exact. This fresh-build cross-check prevents stale .obj files from being mistaken for a patch regression while still failing closed on real code, relocation, or owned-data changes.

Verification commands

The final candidate was rebuilt with repository-configured XDK 3911 CL 13.00.9254.1 and /O2 /Oy- /DDEBUG /Dxbox, then checked with:

ninja build/base/source/render/render_contrails.obj
python -m tools.coff_compare build/split/source/render/render_contrails.obj build/base/source/render/render_contrails.obj <all six function symbols>
python -m tools.coff_compare build/split/source/render/render_contrails.obj build/base/source/render/render_contrails.obj <all three target-owned rdata symbols>
ninja halobetacache_build
ninja semantic_progress
ninja progress
python -m unittest discover -s tools -p "test*.py" -v

All strict comparisons returned all_equal: true; the consolidated build and semantic report completed with zero errors. The progress gate admitted the object (262/468 Halo units Matching at this checkout), and all 173 tooling tests passed.