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Pixelwise View Selection for Unstructured Multi-View Stereo Johannes L. Schönberger 1 Enliang Zheng 2 Marc Pollefeys 1,3 Jan-Michael Frahm 2 1 ETH Zürich 2 UNC Chapel Hill 3 Microsoft Overview Joint Depth - Normal - Occlusion Inference This work presents an open source Multi-View Stereo system for robust and efcient dense modeling from unstructured image collections. Experiments on benchmarks and large-scale Internet photo collections demonstrate state-of-the-art performance in terms of accuracy, completeness, and efciency. Contributions Joint depth - normal - occlusion inference embedded in improved PatchMatch sampling scheme Pixelwise view selection using photometric and geometric priors Multi-view geometric consistency for simultaneous renement and image-based fusion • Graph-based ltering and fusion of depth and normal maps Multi-View Geometric Consistency Pixelwise View Selection • Occlusion prior • Triangulation prior • Resolution prior • Incident prior Ref. patch Source patches Reference camera Source camera Source camera -1 -0.5 0 0.5 1 NCC score 0 0.5 1 Occlusion Prior σρ =0.3 σρ =0.6 σρ =0.9 0 50 100 150 Incident angle [deg] 0 0.5 1 Incident Prior σκ = 15σκ = 30σκ = 450 5 10 15 20 25 30 Triangulation angle [deg] 0 0.5 1 Triangulation Prior ¯ α =2¯ α =5¯ α = 10¯ α = 150 1 2 3 4 5 Relative resolution b l m with b l = 1 0 0.5 1 Resolution Prior Source patches Ref. patch Traditional Pixelwise a S Pix • Joint likelihood function • Generalized Expectation Maximization (GEM) E-Step: Infer using variational inference M-Step: Infer using PatchMatch sampling Z θ, N ξ m l =1ρ m l +η min (ψ m l max ) Photometric Geometric Cost function Optimization argmin θ l ,n l 1 |S| mS ξ m l (θ l , n l ) Filtering and Fusion ψ m l Filtering Fusion Results Zheng et al. Photometric Photometric + Geometric Filtered Normals https://colmap.github.io Source Code | Documentation | Tutorial | Examples P (α m l )=1 (min( ¯ α,α m l )¯ α) 2 ¯ α 2 P (β m l ) = min(β m l , (β m l ) 1 ) P (κ m l ) = exp(κ m l 2 2σ 2 κ ) P (X m l |Z m l l)= 1 NA exp (1ρ m l (θl)) 2 2σ2 ρ if Z m l =1 1 N U if Z m l =0 P (X, Z, θ, N ) Normals Depth Occlusion Images P (α m l ) P (β m l ) P (κ m l ) P (X m l |Z m l l)
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Pixelwise View Selection for Unstructured Multi-View Stereo · •Joint depth - normal - occlusion inference embedded in improved PatchMatch sampling scheme •Pixelwise view selection

May 29, 2020

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Page 1: Pixelwise View Selection for Unstructured Multi-View Stereo · •Joint depth - normal - occlusion inference embedded in improved PatchMatch sampling scheme •Pixelwise view selection

Pixelwise View Selection for Unstructured Multi-View StereoJohannes L. Schönberger1 Enliang Zheng2 Marc Pollefeys1,3 Jan-Michael Frahm2

1ETH Zürich 2UNC Chapel Hill 3Microsoft

Overview

Joint Depth - Normal - Occlusion InferenceThis work presents an open source Multi-View Stereo system for robust and efficient dense modeling from unstructured image collections. Experiments on benchmarks and large-scale Internet photo collections demonstrate state-of-the-art performance in terms of accuracy, completeness, and efficiency.

Contributions

• Joint depth - normal - occlusion inferenceembedded in improved PatchMatch sampling scheme

• Pixelwise view selectionusing photometric and geometric priors

• Multi-view geometric consistencyfor simultaneous refinement and image-based fusion

• Graph-based filtering and fusionof depth and normal maps

Multi-View Geometric Consistency

Pixelwise View Selection

• Occlusion prior

• Triangulation prior

• Resolution prior

• Incident prior

Ref. patch Source patches

Reference camera

Source camera

Source camera

-1 -0.5 0 0.5 1

NCC score

0

0.5

1

Occ

lusi

on P

rior

σρ = 0.3

σρ = 0.6

σρ = 0.9

0 50 100 150

Incident angle [deg]

0

0.5

1

Inci

dent

Prio

r

σκ = 15◦

σκ = 30◦

σκ = 45◦

0 5 10 15 20 25 30

Triangulation angle [deg]

0

0.5

1

Tria

ngul

atio

n P

rior

α = 2◦

α = 5◦

α = 10◦

α = 15◦

0 1 2 3 4 5

Relative resolution blm with b

l = 1

0

0.5

1

Res

olut

ion

Prio

r

Source patchesRef. patch

Traditional Pixelwise

a

S

Pix

• Joint likelihood function

• Generalized Expectation Maximization (GEM) •E-Step: Infer using variational inference •M-Step: Infer using PatchMatch sampling

Z θ,N

ξml = 1−ρml +ηmin (ψml , ψmax)

Photometric Geometric

Cost function

Optimization argminθ∗

l,n∗

l

1

|S|

∑m∈S

ξml (θ∗l ,n∗

l )

Filtering and Fusion

ψml

Filtering

Fusion

ResultsZheng et al. Photometric Photometric + Geometric Filtered Normals

https://colmap.github.ioSource Code | Documentation | Tutorial | Examples

P (αml ) = 1−

(min(α,αm

l)−α)2

α2

P (βml ) = min(βm

l , (βml )−1)

P (κml ) = exp(−

κm

l

2

2σ2κ

)

P (Xml |Zm

l , θl) =

{1

NAexp

(−

(1−ρm

l(θl))

2

2σ2ρ

)if Zm

l = 1

1

NU if Zm

l = 0

P (X,Z, θ,N)

NormalsDepthOcclusionImages

P (αml )

P (βml )

P (κml )

P (Xml |Zm

l , θl)