Point Cloud Colouring Pipeline

Colours 3D point clouds by projecting each point onto the calibrated RGB and IR cameras and sampling pixel colours. Each output PLY carries dual texture: RGB colours (from rg_*.bmp) and IR colours (from ir_*.png), stored as separate per-vertex properties so both can be visualised in CloudCompare or any PLY viewer.

Core module: `colour_ply.py`

Function	Purpose
`load_ascii_ply(ply_path)`	Read ASCII PLY, return Nx3 float32 xyz array
`colorize_combined_pointcloud(pts, rgb_img, ir_img, lc_rgb_yaml, lc_ir_yaml, lc_rc_yaml, out_ply)`	Un-rotate points using R1 from stereo rectification, project to RGB + IR cameras, save dual-texture binary PLY
`save_master_ply(filename, points, rgb_colors, ir_colors)`	Write binary_little_endian PLY with x,y,z,red,green,blue,ir_red,ir_green,ir_blue

Folder structure assumed

~/Speckle-Scanner_Processing_data/
└── <project>/
    └── <date>/
        └── <session>/
            ├── params_link/
            │   ├── lc-rc_stereo_cam_model.yaml   ← stereoRectify R1 (un-rotate 3D points)
            │   ├── lc-rg_stereo_cam_model.yaml   ← project to RGB camera
            │   └── lc-ir_stereo_cam_model.yaml   ← project to IR camera
            └── <ScanXXXXXX>/
                ├── 02_rect_images/
                │   ├── ir_*.png                  ← one IR image (input)
                │   └── rg_*.bmp                  ← one RGB image (input)
                ├── 05_sgm_pcl/
                │   └── Point_cloud.ply           ← SGM point cloud (input)
                ├── 06_zncc_pcl/
                │   └── Point_cloud.ply           ← ZNCC point cloud (input)
                ├── 07_sgm_pcl_col/
                │   └── Point_cloud_colored.ply   ← SGM coloured output (created)
                └── 08_zncc_pcl_col/
                    └── Point_cloud_colored.ply   ← ZNCC coloured output (created)

Pipeline commands

cd ~/Speckle-Scanner/09_coloring

# Both SGM + ZNCC — all scans in a session
python run_coloring_pipeline.py \
  --project Olsen_wings \
  --date    2026-05-12 \
  --session session1

# Both SGM + ZNCC — all sessions on a date (omit --session)
python run_coloring_pipeline.py \
  --project Olsen_wings \
  --date    2026-05-12

# Single scan, both modes
python run_coloring_pipeline.py \
  --project Olsen_wings \
  --date    2026-05-12 \
  --session session1 \
  --scan    Scan000001

# Single scan, SGM only
python run_coloring_pipeline.py \
  --project Olsen_wings \
  --date    2026-05-12 \
  --session session1 \
  --scan    Scan000001 \
  --mode    sgm

# Single scan, ZNCC only
python run_coloring_pipeline.py \
  --project Olsen_wings \
  --date    2026-05-12 \
  --session session1 \
  --scan    Scan000001 \
  --mode    zncc

Parameters

Parameter	Default	Description
`--project`	—	Project name (e.g. `Olsen_wings`)
`--date`	—	Date string (e.g. `2026-05-12`)
`--session`	all	Session name (e.g. `session1`); omit to process all sessions on that date
`--scan`	all	Single scan (e.g. `Scan000001`); omit to process all scans in the session
`--mode`	`both`	Which point cloud to colour: `sgm`, `zncc`, or `both`

What gets saved

File	Description
`07_sgm_pcl_col/Point_cloud_colored.ply`	SGM cloud with RGB + IR dual texture (binary PLY)
`08_zncc_pcl_col/Point_cloud_colored.ply`	ZNCC cloud with RGB + IR dual texture (binary PLY)

The output PLY has the following vertex properties:

x, y, z          — 32-bit float (metres)
red, green, blue  — 8-bit uchar  (from rg_*.bmp camera)
ir_red, ir_green, ir_blue — 8-bit uchar (from ir_*.png camera)

To visualise the IR texture in CloudCompare, select the ir_red/ir_green/ir_blue scalar fields or load the file and choose the IR colour attribute.

Skip conditions

The runner prints [SKIP] and moves to the next scan if any required file is absent:

02_rect_images/ir_*.png — no IR image found
02_rect_images/rg_*.bmp — no RGB image found
params_link/lc-rc_stereo_cam_model.yaml — missing RC YAML
params_link/lc-rg_stereo_cam_model.yaml — missing RG YAML
params_link/lc-ir_stereo_cam_model.yaml — missing IR YAML
05_sgm_pcl/Point_cloud.ply — SGM cloud not generated yet (run run_pcl_pipeline.py --mode sgm first)
06_zncc_pcl/Point_cloud.ply — ZNCC cloud not generated yet (run run_pcl_pipeline.py --mode zncc first)

Dependencies

# This step only
pip install -r ~/Speckle-Scanner/09_coloring/requirements.txt

# Or install everything for the full pipeline
pip install -r ~/Speckle-Scanner/requirements.txt

Packages: numpy, opencv-python.

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