DGPF - Deutsche Gesellschaft für Photogrammetrie, Fernerkundung und Geoinformation e.V. - Home Isosurface Surface representing points of constant value within a volume The term isoline is also sometimes used for domains of more than 3 dimensions. Applications Isosurfaces are normally displayed using computer graphics, and are used as data visualization methods in computational fluid dynamics (CFD), allowing engineers to study features of a fluid flow (gas or liquid) around objects, such as aircraft wings. Numerous other disciplines that are interested in three-dimensional data often use isosurfaces to obtain information about pharmacology, chemistry, geophysics and meteorology. Implementation algorithms Marching cubes Asymptotic decider The asymptotic decider algorithm was developed as an extension to marching cubes in order to resolve the possibility of ambiguity in it. Marching tetrahedra The marching tetrahedra algorithm was developed as an extension to marching cubes in order to solve an ambiguity in that algorithm and to create higher quality output surface.
Polygonising a scalar field (Marching Cubes) Also known as: "3D Contouring", "Marching Cubes", "Surface Reconstruction" Written by Paul Bourke May 1994 Based on tables by Cory Gene Bloyd along with additional example source code marchingsource.cppAn alternative table by Geoffrey Heller.rchandra.zip: C++ classes contributed by Raghavendra Chandrashekara.OpenGL source code, sample volume: cell.gz (old)volexample.zip: An example showing how to call polygonise including a sample MRI dataset.Improved (2018) Qt/OpenGL example courtesy Dr. This document describes an algorithm for creating a polygonal surface representation of an isosurface of a 3D scalar field. There are many applications for this type of technique, two very common ones are: Reconstruction of a surface from medical volumetric datasets. The fundamental problem is to form a facet approximation to an isosurface through a scalar field sampled on a rectangular 3D grid. The indexing convention for vertices and edges used in the algorithm are shown below Another example Source code
Implicit surfaces Also known as "Metaballs", "Blobbies", "Soft objects" Written by Paul Bourke June 1997 Introduction Most computer based 3D geometric modelling is done with basic primitives such as lines, planes, boxes, etc. Many smooth and deformable objects are difficult or inefficient to represent with such building blocks, even if primitives such as spheres or Bezier/spline surfaces are used. The following summarises three common methods for creating so called "implicit surfaces". Example Consider the field function D(r) = 1/r2 and a number of control points in 3D space. r is the distance of a point in space to a particular control point. For example if there is a single control point different colour levels will result in spheres of different radius. If the control structure is a line or a plane then the distance r is normally taken to be the closest distance to nay point on the line or plane. Blobby Molecules "b" is related to the standard deviation of the curve, "a" to the height. Meta Balls Notes D.
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Marching Cubes: Curve Wrapping & More Metaballs - Grasshopper UPDATE: 30-Jan-2014 140130_marching_cubes.gh I have added breps as an input for wrapping geometry (it also can take lines now), as in the above definition. It has been updated for some efficiencies...now you can taper a curve at both ends if you choose, you only need to feed one radius, although you can feed as many as you like (it acts like the longest list component). Some of the work posted lately by Nick Tyrer has gotten me thinking about marching cubes again...I had done some stuff with marching tetrahedra and cubes a ways back, and with some new inspiration (and a little time I could carve out today) I figured I'd take a stab at trying to make it more flexible and robust. The short of it is that the inputs can take any combination of points and curves, along with variable radii of influence for each geometry object. The marching cube stuff is derived from the amazing Paul Bourke's work. G = A list of base Geometry, which can be any combination of curves or points
Antike Steinskulpturen Grabrelief für Aristodika, Akesidamos und Sotadas Inv.-Nr. Sk 149 Kretisch-attizierend, um 350 v. Chr. Weißer, feinkristalliner Marmor, gelbbraun patiniert. H insgesamt 86,5 cm B 50 cm T 10 cm Bildfeld: H 67 cm B 38,5 cm Relieftiefe bis 5,5 cm Fundort: angeblich Kreta, Südküste Zugang: Schenkung der Familiengesellschaft Dierichs, Kassel 2007; vormals Leihgabe Inv. Erhaltungszustand/Restaurierung: Unergänzt. Beschreibung: Die Naiskos-Stele rahmen nach oben sich verjüngende Antenpfeiler. Die flüchtig gravierten Namensbeischriften im dorischen Dialekt auf dem Architrav sind ziemlich mittig den Figurenköpfen zugeordnet. Die Dreifiguren-Gruppe hat in der Anordnung und in den Figurentypen ihre nächste Entsprechung in zwei attischen Grabnaiskoi in Athen (Nat. Publiziert: Slg. Literatur: Zu Athen Nat.
Cocoon – bespoke geometry Cocoon is an add-on to McNeel’s Grasshopper visual scripting interface for Rhinoceros. Cocoon is a fairly straightforward implementation of the Marching Cubes algorithm for turning iso-surfaces into polygonal meshes. It is geared specifically toward wrapping existing geometric elements, and works with combinations of points, breps and curves, allowing users to vary a number of parameters that enhance sculptural potentials. Cocoon reworks an earlier script – the Geometry Wrapper – that I had put on the forum some time ago. The rest of the variety is managed through the input of value lists for the strengths of the curve charges. The next change is that Cocoon splits out the solving of the marching cubes from a component that can then refine the mesh. The refinement of the mesh requires that you input the number of resampling iterations it should cap at, a unit of length for resampling, and a tolerance of variance from the target iso value that will satisfy the resampling goal. Have fun!
spitznackiges Steinbeil aus Jadeit - Objektdatenbank der Museumslandschaft Hessen Kassel spitznackiges Steinbeil aus Jadeit Katalogtext: spitznackiges Steinbeil aus, dunkelgrünem Jadeit oder Eklogit (2005 spektrometrisch untersucht), aus den Flußschottern der Fulda. Literatur: Kegler-Graiewski 2007 Kegler-Graiewski, Nicole: Beile-Äxte-Mahlsteine. Zur Rohmaterialversorgung im Jung- und Spätneolithikum Nordhessens. Dissertation, Köln 2007, kups.ub.uni-koeln.de/2160/1/Dissertation_Kegler-Graiewski.pdf. Letzte Aktualisierung: 26.02.2018 Wissenschaftliche Kommentare: Hier können Sie uns Anmerkungen und Kommentare zu unseren Objekten hinterlassen, die nach Sichtung durch unsere Mitarbeiter allen Lesern angezeigt werden. Bisher wurden keine Kommentare geschrieben. Einen neuen Kommentar hinzufügen.
Python & OpenGL for Scientific Visualization For the really impatient, you can try to run the code in the teaser image above. If this works, a window should open on your desktop with a red color in the background. If you now want to understand how this works, you'll have to read the text below. Preliminaries The main difficulty for newcomers in programming modern OpenGL is that it requires to understand a lot of different concepts at once and then, to perform a lot of operations before rendering anything on screen. Normalize Device Coordinates Figure Normalized Device Coordinates (NDC) where bottom-left corner coordinate is (-1,-1) and top-right corner is (+1,+1). Before even diving into actual code, it is important to understand first how OpenGL handles coordinates. The second important fact to know is that x coordinates increase from left to right and y coordinates increase from bottom to top. Triangulation Different triangulation of the same quad using from 2 to 5 triangles. GL Primitives Common OpenGL rendering primitives. Note