Minkowski tensors for point clouds and voxelized data: robust, asymptotically unbiased estimators
Pith reviewed 2026-05-23 04:08 UTC · model grok-4.3
The pith
Improved estimators allow asymptotically unbiased computation of Minkowski tensors from point clouds and voxelized data.
A machine-rendered reading of the paper's core claim, the machinery that carries it, and where it could break.
Core claim
Minkowski tensors can be estimated from point clouds in an asymptotically unbiased manner by improving local estimators and generalizing the theory to finite unions of compact sets with positive reach. This allows precise estimates with relative errors of a few percent at practical resolutions for random spatial structures like beta polytopes, and works on real data such as metallic grains and nanorough surfaces.
What carries the argument
Asymptotically unbiased local estimators for Minkowski tensors (tensor valuations) from point clouds, extended to sets with positive reach.
If this is right
- Estimates of interfacial tensors become asymptotically bias-free for finite unions of compact sets with positive reach.
- Precise estimates with relative errors of a few percent are achievable for practically relevant resolutions in simulations of random polytopes.
- The methods apply directly to real data of metallic grains and nanorough surfaces.
- An open-source Python package enables computation in any dimension.
Where Pith is reading between the lines
- These estimators could support more accurate analysis of complex materials where positive reach holds but data remains discrete.
- Performance could be tested on sets that violate the positive reach condition to identify where bias reappears.
- The efficiency improvements might allow integration into pipelines for extracting geometric features from voxelized data.
Load-bearing premise
The sets being estimated must be finite unions of compact sets with positive reach for the asymptotic unbiasedness to hold.
What would settle it
Observing that bias does not approach zero as resolution increases to infinity for sets with positive reach would falsify the asymptotic unbiasedness.
Figures
read the original abstract
Minkowski tensors, also known as tensor valuations, provide robust $n$-point information for a wide range of random spatial structures. Local estimators for point clouds, e.g., representing voxelized data, however, are unavoidably biased even in the limit of infinitely high resolution. Here, we substantially improve a recently proposed, asymptotically unbiased algorithm to estimate Minkowski tensors from point clouds. Our improved algorithm is more robust and efficient. Moreover we generalize the theoretical foundations for an asymptotically bias-free estimation of the interfacial tensors, among others, to the case of finite unions of compact sets with positive reach, which is relevant for many applications like rough surfaces or composite materials. As a realistic test case of random spatial structures, we consider random (beta) polytopes. We first derive explicit expressions of the expected Minkowski tensors, which we then compare to our simulation results. We obtain precise estimates with relative errors of a few percent for practically relevant resolutions. Finally, we apply our methods to real data of metallic grains and nanorough surfaces, and we provide an open-source python package, which works in any dimension.
Editorial analysis
A structured set of objections, weighed in public.
Referee Report
Summary. The manuscript presents an improved algorithm for estimating Minkowski tensors from point clouds and voxelized data that is claimed to be more robust and efficient than a recent predecessor. It generalizes the theoretical foundations for asymptotically bias-free estimation of interfacial tensors (among others) to finite unions of compact sets with positive reach. Explicit expressions for the expected Minkowski tensors of random beta polytopes are derived and compared to Monte Carlo simulations, yielding relative errors of a few percent at practical resolutions. The methods are applied to real data on metallic grains and nanorough surfaces, and an open-source Python package is provided.
Significance. If the asymptotic unbiasedness result holds under the stated positive-reach hypothesis, the work supplies a practical, reproducible tool for extracting tensor-valued morphological information from discrete spatial data. The explicit derivations for beta polytopes, direct comparison against independently computed expectations, and release of open code constitute verifiable strengths that support the central claims.
major comments (2)
- [Abstract / theoretical foundations] Abstract and the section on theoretical foundations: the generalization of asymptotically bias-free estimation is explicitly restricted to finite unions of compact sets with positive reach, yet the manuscript advertises applicability to nanorough surfaces. High-curvature or non-differentiable features on such surfaces typically yield zero reach, so the bias may fail to vanish; the paper provides no additional argument or numerical check that the estimators remain asymptotically unbiased when this hypothesis is violated.
- [real-data applications] Section on real-data applications: the nanorough-surface example is presented as a realistic test case covered by the new theory, but no verification is given that the digitized surfaces satisfy the positive-reach condition (e.g., via local curvature or tubular-neighborhood checks). This leaves the practical relevance of the bias-free guarantee for the advertised application unestablished.
minor comments (1)
- [simulation results] The abstract states relative errors of 'a few percent' for beta-polytope simulations; a table or figure reporting the precise errors per tensor component and resolution would improve clarity.
Simulated Author's Rebuttal
We thank the referee for the careful reading and constructive comments. We address each major comment below and indicate the revisions we are prepared to make.
read point-by-point responses
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Referee: [Abstract / theoretical foundations] Abstract and the section on theoretical foundations: the generalization of asymptotically bias-free estimation is explicitly restricted to finite unions of compact sets with positive reach, yet the manuscript advertises applicability to nanorough surfaces. High-curvature or non-differentiable features on such surfaces typically yield zero reach, so the bias may fail to vanish; the paper provides no additional argument or numerical check that the estimators remain asymptotically unbiased when this hypothesis is violated.
Authors: We agree that the asymptotic unbiasedness result is proved only under the positive-reach hypothesis. The manuscript states this restriction explicitly and lists rough surfaces among potential application areas without claiming that every nanorough surface satisfies the condition. In the revised manuscript we will modify the abstract and the theoretical foundations section to state the hypothesis more prominently and to note that the bias-free guarantee does not extend to sets of zero reach. We will also emphasize that the beta-polytope experiments, which satisfy the hypothesis, serve as the rigorous numerical validation of the theory. revision: yes
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Referee: [real-data applications] Section on real-data applications: the nanorough-surface example is presented as a realistic test case covered by the new theory, but no verification is given that the digitized surfaces satisfy the positive-reach condition (e.g., via local curvature or tubular-neighborhood checks). This leaves the practical relevance of the bias-free guarantee for the advertised application unestablished.
Authors: The referee correctly observes that no explicit verification of the positive-reach condition is supplied for the nanorough-surface data. In revision we will qualify the real-data section to present the nanorough-surface example as an illustration of practical use rather than as a case strictly covered by the theorem. If a simple geometric check on the voxelized representation can be performed without substantial additional work, we will include it; otherwise we will add an explicit caveat that the bias-free property is guaranteed only when the underlying set meets the positive-reach assumption. revision: yes
Circularity Check
Minor self-citation to prior algorithm; central claims use independent integral-geometric derivations and beta-polytope benchmarks
full rationale
The paper improves a recently proposed algorithm and extends bias-free estimation to finite unions of positive-reach sets using integral-geometric foundations. It derives explicit expected Minkowski tensor expressions for beta polytopes independently of the estimators and validates via simulation comparisons with relative errors of a few percent. No quoted step reduces a claimed prediction or generalization to a fitted input, self-citation chain, or definitional equivalence. The positive-reach condition is stated as an explicit assumption without circular justification. This matches the default case of self-contained work against external benchmarks.
Axiom & Free-Parameter Ledger
axioms (1)
- domain assumption Finite unions of compact sets with positive reach admit asymptotically bias-free estimation of interfacial Minkowski tensors via the improved local algorithm.
Reference graph
Works this paper leans on
-
[1]
P. M. Adler, J.-F. Thovert, and V. V. Mourzenko. Fractured Porous Media. Oxford Univ. Press, Oxford, first edition, 2013. 2
work page 2013
-
[2]
R. J. Adler and J. E. Taylor. Random Fields and Geometry . Springer Monographs in Mathematics. Springer, New York, 2007. 2
work page 2007
-
[3]
R. T. Armstrong, J. E. McClure, V. Robins, Z. Liu, C. H. Arns, S. Schl¨ uter, and S. Berg. Porous Media Characterization Using Minkowski Functionals: Theories, Applications and Future Directions. Transp Porous Med, 130:305–335, 2019. 2
work page 2019
-
[4]
C. H. Arns, M. A. Knackstedt, and K. Mecke. 3D structural analysis: Sensitivity of Minkowski functionals. J. Microsc., 240:181, 2010. 2
work page 2010
-
[5]
C. H. Arns, M. A. Knackstedt, and K. R. Mecke. Reconstructing Complex Materials via Effective Grain Shapes. Phys. Rev. Lett., 91:215506, 2003. 2
work page 2003
-
[6]
M. Barbosa, T. Maddess, S. Ahn, and T. Chan-Ling. Novel morphometric analysis of higher order structure of human radial peri-papillary capillaries: Relevance to retinal perfusion efficiency and age. Sci Rep, 9:1–16, 2019. 2
work page 2019
-
[7]
M. Barbosa, R. Natoli, K. Valter, J. Provis, and T. Maddess. Integral-geometry character- ization of photobiomodulation effects on retinal vessel morphology. Biomed. Opt. Express, BOE, 5:2317–2332, 2014. 2
work page 2014
-
[8]
C. Beisbart, M. S. Barbosa, H. Wagner, and L. d. F. Costa. Extended morphometric analysis of neuronal cells with Minkowski valuations. Eur. Phys. J. B , 52:531–546, 2006. 2 32
work page 2006
-
[9]
Bj¨ orck.Numerical methods for least squares problems
˚A. Bj¨ orck.Numerical methods for least squares problems. Society for Industrial and Applied Mathematics (SIAM), Philadelphia, PA, second edition, 2024. 19
work page 2024
-
[10]
A. B¨ obel and C. R¨ ath. Kinetics of fluid demixing in complex plasmas: Domain growth analysis using Minkowski tensors. Phys. Rev. E , 94:013201, 2016. 2
work page 2016
-
[11]
S. J. P. Callens, D. C. Tourolle n´ e Betts, R. M¨ uller, and A. A. Zadpoor. The local and global geometry of trabecular bone. Acta Biomaterialia, 130:343–361, 2021. 2
work page 2021
-
[12]
S. N. Chiu, D. Stoyan, W. S. Kendall, and J. Mecke. Stochastic Geometry and Its Applica- tions. Wiley, Chichester, third edition, 2013. 2
work page 2013
-
[13]
H. Cohn and N. Elkies. New upper bounds on sphere packings I. Ann. Math., 157:689–714,
-
[14]
C. Collischon, M. A. Klatt, A. J. Banday, M. Sasaki, and C. R¨ ath. Morphometry on the sphere: Cartesian and irreducible Minkowski tensors explained and implemented. Commun Phys, 7:1–10, 2024. 2
work page 2024
-
[15]
C. Collischon, M. Sasaki, K. Mecke, S. D. Points, and M. A. Klatt. Tracking down the origin of superbubbles and supergiant shells in the Magellanic Clouds with Minkowski tensor analysis. A&A, 653:A16, 2021. 2
work page 2021
- [16]
-
[17]
F. Ernesti, M. Schneider, S. Winter, D. Hug, G. Last, and T. B¨ ohlke. Characterizing digital microstructures by the Minkowski-based quadratic normal tensor. Mathematical Methods in the Applied Sciences , 46(1):961–985, 2023. 2
work page 2023
-
[18]
J. R. Gott III, C. Park, R. Juszkiewicz, W. E. Bies, D. P. Bennett, F. R. Bouchet, and A. Stebbins. Topology of microwave background fluctuations - Theory. ApJ, 352:1, 1990. 2
work page 1990
-
[19]
J.-P. Hansen and I. R. McDonald. Theory of Simple Liquids: With Applications to Soft Matter. Academic Press, Amsterdam, 4th edition, 2013. 2
work page 2013
-
[20]
P. C. Hansen, V. Pereyra, and G. Scherer. Least squares data fitting with applications . Johns Hopkins University Press, Baltimore, MD, 2013. 19
work page 2013
-
[21]
D. Hug, M. Kiderlen, and A. M. Svane. Voronoi-Based Estimation of Minkowski Tensors from Finite Point Samples. Discrete Comput. Geom., 57:545–570, 2017. 3, 10, 12, 18, 19
work page 2017
-
[22]
D. Hug, G. Last, and M. Schulte. Second-order properties and central limit theorems for geometric functionals of Boolean models. Ann. Appl. Probab., 26(1):73–135, 2016. 16
work page 2016
-
[23]
D. Hug, G. Last, and W. Weil. A local Steiner-type formula for general closed sets and applications. Math. Z. 246 , pages 237–272, 2004. 6, 7, 8, 9, 11
work page 2004
- [24]
- [25]
- [26]
- [27]
-
[28]
E. B. V. Jensen and M. Kiderlen, editors. Tensor valuations and their applications in stochastic geometry and imaging , volume 2177 of Lecture Notes in Mathematics . Springer, Cham, 2017. 2
work page 2017
-
[29]
H. Jiang and C. H. Arns. Fast Fourier transform and support-shift techniques for pore- scale microstructure classification using additive morphological measures. Phys. Rev. E , 101:033302, 2020. 2
work page 2020
-
[30]
P. Joby, P. Chingangbam, T. Ghosh, V. Ganesan, and C. Ravikumar. Search for anomalous alignments of structures in Planck data using Minkowski Tensors. J. Cosmol. Astropart. Phys., 2019:009–009, 2019. 2
work page 2019
-
[31]
Z. Kabluchko, D. Temesvari, and C. Th¨ ale. Expected intrinsic volumes and facet numbers of random beta-polytopes. Mathematische Nachrichten, 292:79–105, 2019. 26, 27
work page 2019
-
[32]
Z. Kabluchko, C. Th¨ ale, and D. Zaporozhets. Beta polytopes and Poisson polyhedra: f- vectors and angles. Advances in Mathematics, 374:107333, 2020. 25, 26
work page 2020
-
[33]
M. A. Klatt, M. H¨ ormann, and K. Mecke. Characterization of anisotropic Gaussian random fields by Minkowski tensors. J. Stat. Mech. , 2022:043301, 2022. 2
work page 2022
-
[34]
M. A. Klatt, G. Last, K. Mecke, C. Redenbach, F. M. Schaller, and G. E. Schr¨ oder- Turk. Cell Shape Analysis of Random Tessellations Based on Minkowski Tensors. In E. B. Vedel Jensen and M. Kiderlen, editors, Tensor Valuations and Their Applications in Stochastic Geometry and Imaging , volume 2177 of Lecture Notes in Mathematics , pages 385–421. Springer...
work page 2017
-
[35]
M. A. Klatt and K. Mecke. Detecting structured sources in noisy images via Minkowski maps. EPL, 128:60001, 2020. 2
work page 2020
-
[36]
M. A. Klatt, G. E. Schr¨ oder-Turk, and K. Mecke. Anisotropy in finite continuum per- colation: Threshold estimation by Minkowski functionals. J. Stat. Mech. Theor. Exp. , 2017:023302, 2017. 2
work page 2017
-
[37]
M. A. Klatt, G. E. Schr¨ oder-Turk, and K. Mecke. Mean-intercept anisotropy analysis of porous media. II. Conceptual shortcomings of the MIL tensor definition and Minkowski tensors as an alternative. Med. Phys., 44:3663–3675, 2017. 2, 29
work page 2017
-
[38]
D. Legland, K. Kiˆ eu, and M.-F. Devaux. Computation of Minkowski measures on 2d and 3d binary images. Image Anal Stereol, 26:83, 2011. 3 34
work page 2011
- [39]
-
[40]
K. Mecke. Integral Geometry and Statistical Physics. Int. J. Mod. Phys. B , 12:861–899,
-
[41]
K. R. Mecke, Th. Buchert, and H. Wagner. Robust morphological measures for large-scale structure in the universe. Astron. Astrophys., 288:697, 1994. 2
work page 1994
-
[42]
K. R. Mecke and D. Stoyan, editors. Statistical Physics and Spatial Statistics: The Art of Analyzing and Modeling Spatial Structures and Pattern Formation . Lecture Notes in Physics. Springer, Berlin ; New York, 2000. 2
work page 2000
-
[43]
Q. M´ erigot, M. Ovsjanikov, and L. J. Guibas. Voronoi-based curvature and feature esti- mation from point clouds. IEEE Transactions on Visualization and Computer Graphics , 17(6):743–756, 2011. 3
work page 2011
-
[44]
J. Ohser and F. M¨ ucklich. Statistical Analysis of Microstructures in Materials Science . Statistics in Practice. John Wiley, Chichester [England]; New York, 2000. 2
work page 2000
-
[45]
J. Ohser and K. Schladitz. 3D Images of Materials Structures: Processing and Analysis . Wiley-VCH, Weinheim, 2009. 2
work page 2009
- [46]
-
[47]
D. Pabst. Voromink. https://zenodo.org/records/14614277, 2025. DOI: 10.5281/zen- odo.14614277. 10, 21
-
[48]
J. Rataj. On boundaries of unions of sets with positive reach. Beitr¨ age Algebra Geom., 46(2):397–404, 2005. 8
work page 2005
-
[49]
J. Rataj and M. Z¨ ahle. Curvature measures of singular sets . Springer Monographs in Mathematics. Springer, Cham, 2019. 6, 7
work page 2019
- [50]
-
[51]
M. C. R¨ ottger, A. Sanner, L. A. Thimons, T. Junge, A. Gujrati, J. M. Monti, W. G. N¨ ohring, T. D. B. Jacobs, and L. Pastewka. Contact.engineering—Create, analyze and publish digital surface twins from topography measurements across many scales. Surf. Topogr.: Metrol. Prop., 10:035032, 2022. 2
work page 2022
-
[52]
J. Schmalzing and K. M. G´ orski. Minkowski functionals used in the morphological analysis of cosmic microwave background anisotropy maps. Monthly Notices of the Royal Astronom- ical Society, 297:355–365, 1998. 2
work page 1998
- [53]
- [54]
-
[55]
R. Schneider and W. Weil. Stochastic and Integral Geometry (Probability and Its Applica- tions). Springer, Berlin, 2008. 2
work page 2008
-
[56]
G. Schr¨ oder-Turk, S. Kapfer, B. Breidenbach, C. Beisbart, and K. Mecke. Tensorial Minkowski functionals and anisotropy measures for planar patterns. J. Micr. , 238:57–74,
-
[57]
G. E. Schr¨ oder-Turk, W. Mickel, S. C. Kapfer, M. A. Klatt, F. M. Schaller, M. J. F. Hoffmann, N. Kleppmann, P. Armstrong, A. Inayat, D. Hug, M. Reichelsdorfer, W. Peukert, W. Schwieger, and K. Mecke. Minkowski Tensor Shape Analysis of Cellular, Granular and Porous Structures. Adv. Mater., 23:2535–2553, 2011. 2, 29
work page 2011
-
[58]
G. E. Schr¨ oder-Turk, W. Mickel, S. C. Kapfer, F. M. Schaller, B. Breidenbach, D. Hug, and K. Mecke. Minkowski tensors of anisotropic spatial structure. New J. Phys. , 15:083028,
-
[59]
C. Spengler, F. Nolle, J. Mischo, T. Faidt, S. Grandthyll, N. Thewes, M. Koch, F. M¨ uller, M. Bischoff, M. A. Klatt, and K. Jacobs. Strength of bacterial adhesion on nanostructured surfaces quantified by substrate morphometry. Nanoscale, 11:19713–19722, 2019. 2, 3, 30, 31, 32
work page 2019
-
[60]
J. C. Stinville, J. M. Hestroffer, M. A. Charpagne, A. T. Polonsky, M. P. Echlin, C. J. Torbet, V. Valle, K. E. Nygren, M. P. Miller, O. Klaas, A. Loghin, I. J. Beyerlein, and T. M. Pollock. Multi-modal Dataset of a Polycrystalline Metallic Material: 3D Microstructure and Deformation Fields. Sci Data, 9:460, 2022. 2, 3, 28, 29, 30
work page 2022
-
[61]
A. M. Svane. Estimation of Intrinsic Volumes from Digital Grey-Scale Images. J Math Imaging Vis, 49:352–376, 2014. 3
work page 2014
-
[62]
A. M. Svane. Estimation of Minkowski tensors from digital grey-scale images. Image Anal. Stereol., 33:51, 2014. 3
work page 2014
-
[63]
A. M. Svane. Valuations in Image Analysis. In E. B. V. Jensen and M. Kiderlen, editors, Tensor Valuations and Their Applications in Stochastic Geometry and Imaging , volume 2177, pages 435–454. Springer International Publishing, Cham, 2017. 3
work page 2017
- [64]
- [65]
-
[66]
J. F. Ziegel, J. R. Nyengaard, and E. B. Vedel Jensen. Estimating Particle Shape and Orientation Using Volume Tensors. Scand. J. Stat. , 42:813–831, 2015. 2
work page 2015
-
[67]
C. Zong. Sphere Packings. Universitext. Springer, New York, 1999. 2 36 A Further simulation results In this section, we provide additional simulation results for the algorithm described in the paper, based on solving a least-squares problem. The following tables can be found on the subsequent pages: • Table 11: Simulation results for the 2-dimensional rec...
work page 1999
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