sky-artifact-prevention

Sky Artifact Prevention for Road Corridors

The Problem

Metashape's mesh generation creates "tunnel" or "dome" artifacts over road corridors. Even with proper sky masks:

• Depth maps ignore masks during mesh interpolation
• Interpolation fills gaps between opposite sides of the road, creating a closed surface overhead
• This produces tunnel effects, flashing artifacts, and enclosed environments where open sky should be

This is Metashape's most well-known limitation for road corridor captures. There is no single fix — use a combination of strategies.

When to Use

• Building mesh from road corridor captures
• Any long linear capture where sky/overhead closure is a problem
• After mesh building, if tunnel artifacts are visible
• When planning the dense reconstruction strategy (choose BEFORE building)

Strategy Overview

Five strategies, ordered by effectiveness for road corridors:

#	Strategy	When to Apply	Effectiveness
1	Point cloud source	Before mesh build	Best — avoids the problem entirely
2	Height field mode	Before mesh build	Good for flat terrain, loses vertical surfaces
3	Point cloud classification	Before mesh build	Good — requires classification step
4	Region cropping	Before mesh build	Moderate — simple but crude
5	Post-mesh cleanup	After mesh build	Fallback — fixes what got through

Recommended combination: Strategy 1 + 3 + 5 (point cloud source, with ground classification, followed by cleanup).

Strategy 1: Build Mesh from Point Cloud (Not Depth Maps)

Why it works: Point cloud generation DOES respect masks. If sky is masked, no points exist in the sky → no mesh in the sky. Depth map interpolation is what creates the tunnel — bypassing it avoids the problem.

# Step 1: Build point cloud with masks active
build_point_cloud(
    point_colors=True,
    point_confidence=True
)

# Step 2: Build mesh from point cloud
build_model(
    surface_type="arbitrary",
    source_data="point_cloud",
    interpolation="enabled",
    vertex_colors=True
)