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Organizing Visual Evidence for 3D Reconstruction

WORKFLOWCONTEXT
📖7 min read

Findability

A good system lets you find specific files quickly. It saves your sanity.

Chain of Custody

You need to be able to prove exactly where a file came from and that it hasn't been altered. Hashing.

Reproducibility

Your folder structure is documentation, organization is evidence. It should allow others to understand and possibly continue your process without you being there.

The Dual Purpose of Organization​

In visual investigation, data organization serves two masters: Efficiency and Accountability.

On one hand, 3D projects can get very messy, very quickly. A single scene might reference a multitude of textures, models, and reference images. Without structure, you lose time searching for files or fixing broken links.

On the other hand, if your work is used in a legal context, your file structure is part of your methodology. You need to demonstrate a clear "Chain of Custody"—the chronological documentation or paper trail that records the sequence of custody, control, transfer, analysis, and disposition of physical or electronic evidence.

The Berkeley Protocol Connection

The Berkeley Protocol emphasizes that digital evidence is easily manipulated. Therefore, your organizational system should strictly separate Original Sources (which are preserved untouched) from Working Files (where analysis happens).

Master Archive & Working Copies​

Preservation starts at intake: the moment sources arrive, they go into a protected master archive and are fingerprinted. collect documented what each source is; this is where you protect it.

Master Archive:

  • Create a (protected) directory (e.g., /00_Master_Archive).
  • Save all sources here exactly as received/downloaded.

Fingerprinting (Hashing):

  • Generate a checksum (SHA-256) for all files (see Verification & Hashing below).
  • Store the Source Name, Download Date, Download Location, and Hash in a spreadsheet/text file (e.g., evidence_log.csv, per Bellingcat best practices).

Create a working_file directory:

  • Copy all source material here. All analysis and processing happens on these copies, never on the master archive.

Segmentation & Source Grouping​

If one video contains multiple clips, create separate clips.

Naming: Create directories for each video, then extract frames from each video (extraction itself is a process step).

Source Grouping: Sort and group files by physical device or origin (e.g., "Source A - CCTV North," "Source B - Witness iPhone").

/01_WORKING_COPIES
  /00_MASTER_INGEST
    [Project]_Master_Compilation_Copy.mov <-- The big file you copied
  /01_SOURCES <-- The result of your "Chop"
    /SRC_A_CCTV_North
      /Footage <-- The segmented video clip (ProRes/DNxHR)
      /Image_Seq <-- The full PNG/EXR sequence extracted from footage
      /Stills <-- Specific keyframes picked for reference
      /Work <-- Undistorted/Sharpened versions
    /SRC_B_Mobile_Witness
      /Footage
      /Image_Seq
      /Stills
      /Work

This layout shows the full preserve→process flow: the master ingest is preserved untouched; working copies are organized by source; and within each source the Footage/Image_Seq/Work subfolders mark which copies are safe to transform (process).

Core Principle: The "Sanctuary" of Originals​

The most important rule in investigative data management is the protection of source material.

DO NOT MODIFY ORIGINALS

Rule #1: Avoid opening an original evidence file in an editor and hitting "Save". Rule #2: If you need to analyze a file, make a copy first. Rule #3: Keep originals in a read-only folder.

  • Hash your original files.

This aligns with the Preservation phase of the Berkeley Protocol. If you accidentally crop a photo or re-save a video with a different codec, you have technically altered the evidence. By keeping a pristine set of originals, you can go back to the source to verify your findings.

Project Structure Strategies​

There is no single "correct" folder structure, but any valid structure should separate evidence from analysis.

Strategy 1: The Forensic Standard (Evidence-First)​

This structure is designed for accountability. It clearly demarcates the status of every file.

Project_Name/
├── 00_Admin/                  # Methodology notes, logs, correspondence
├── 01_Originals/              # Read Only
│   ├── Received_2024-05-10/
│   └── Received_2024-05-12/
├── 02_Working_Copies/         # Where you actually open files
│   ├── Processed_Images/      # Cropped, brightened, annotated
│   └── Transcriptions/
├── 03_3D_Workspace/           # Your Blender environment
│   ├── Assets/
│   ├── Scenes/
│   └── Textures/
└── 04_Outputs/                # Renders and Reports

Why this works for Chain of Custody:

  • Chronological Intake: The 01_Originals folder is often organized by when data was received, not just what it is. This preserves the timeline of evidence collection.
  • Clear Separation: It is impossible to mistake a processed image for an original.

Strategy 2: The Workflow Flow (Process-First)​

This approach follows the lifecycle of the investigation.

Project_Name/
├── 01_Gather/                 # All raw inputs 
├── 02_Process/                # Intermediate analysis & cleanup
├── 03_Reconstruct/            # Blender files & modeling
├── 04_Analyze/                # Measurements & simulations
├── 05_Present/                # Final renders & reports
└── 99_Archive/                # Dead ends & old versions

Why this works for Findability:

  • It maps to your mental model of "doing the work."
  • It keeps the active directory (03_Reconstruct) focused on the current task.

Strategy 3: The Hybrid 3D Pipeline​

For complex Blender projects, you need a structure that supports relative paths while maintaining forensic integrity.

Case_ID_Project/
├── 01_Evidence_Vault/       # Hashed, read-only originals
├── 02_Project_Assets/       # The "Blender Root"
│   ├── Reference_Images/    # COPIES of evidence, optimized for Blender
│   ├── Textures/            # Surface maps
│   ├── Models/              # .blend files of individual assets
│   └── Scenes/              # .blend files of reconstruction scenarios
├── 03_Renders/              # Output frames
└── 04_Edit/                 # Video assembly
Relative Paths are Key

In Blender, use Relative Paths (File > External Data > Make Paths Relative). This allows you to move the entire Case_ID_Project folder to an external drive or archive without breaking texture links.

Naming Conventions: The Metadata of Filenames​

A filename is the first piece of metadata you see. A good name tells you what it is, which project it belongs to, when it was made, and which version it is, without opening it.

The "Smart" Filename​

Construct filenames using consistent blocks: [Date]_[Project]_[Description]_[Version].[Ext]

  • Date: 2024-05-20 (ISO 8601 format: YYYY-MM-DD. Sorts chronologically.)
  • Project: Case402 (Keeps files grouped if they get moved.)
  • Description: SitePhoto_NorthWall (Be specific but concise.)
  • Version: v03 (Useful for tracking changes.)

Bad: test.blend, final_final_v2.jpg, DCIM4022.JPG Good: 2024-05-20_Case402_SiteModel_v03.blend

Version Control: The Poor Man's Time Machine​

In 3D work, files corrupt, ideas fail, and clients change their minds. Versioning is your safety net.

  • Incremental Saves: Use Blender's + button in the Save dialog to auto-increment (Scene_v01.blend -> Scene_v02.blend).
  • Milestone Saves: Before a major change (e.g., "Applying all modifiers"), save a version named Scene_v05_PreCollapse.blend.
  • The "Published" Folder: Keep your working folder full of versions, but copy only the final, approved version to a Published or Master folder. This prevents linking to unstable work.

Verification & Hashing​

To truly adhere to the Berkeley Protocol, you need to prove that your 01_Originals files haven't changed since you received them. This is done with Hashing.

A "hash" is a digital fingerprint. If even one pixel changes in an image, its hash changes completely.

How to Hash​

  1. Generate: When you receive files, run a hash function (like SHA-256) on them immediately.
  2. Log: Save these hashes in a text file or spreadsheet (evidence_log.csv).
  3. Verify: Before submitting your work, hash the files again. If the hash matches your log, you have mathematical proof the file is unaltered.

Quick Tip: Hashing Tools

Windows (PowerShell): Get-FileHash filename.jpg
Mac/Linux (Terminal): shasum -a 256 filename.jpg
GUI: Tools like QuickHash or HashCheck integrate into your file explorer.

Durability: Surviving Loss and Tampering​

Preservation is not complete until you have answered: where is this stored, and is it protected against loss or tampering?

  • Backups: At minimum, an off-site copy (cloud, external drive) of the master archive and evidence log. Back up before you need it.
  • Access control: Who can modify the master archive? Read-only permissions for everyone but a designated custodian.
  • Integrity re-verification: Before submission or handover, re-hash originals and compare against the evidence log — mathematical proof nothing changed.
  • Longevity: Choose formats that won't require legacy software to read later; keep the evidence log alongside the data, not in a separate system.
Chain of custody note

The presence of backups is an additional safety net for the chain of custody that began in collect: if an original is ever lost, the backup + hash log allows you to prove what the pristine source was.

Summary: The Organizational Mindset​

Good organization is not about being neat; it's about being professional and defensible.

  1. Sanctuary: Create a read-only folder for original evidence.
  2. Separation: Do not mix originals with working files.
  3. Consistency: Pick a naming convention and stick to it.
  4. Verification: Use hashes to prove integrity.

By following these principles, you ensure that your 3D reconstruction is not just a pretty picture, but a robust piece of evidence that can withstand scrutiny.

Last updated on by blender-visual-investigation