# Questions tagged [geometric-computation]

The tag has no usage guidance.

49 questions
Filter by
Sorted by
Tagged with
49 views

### GeometricScene doesn't quite work in v13.0.1

I used GeometricScene in v12.x quite a bit in some project and although the feature was experimental it was reliable before. I recently upgraded to v13.0.1 and had ...
• 5,059
1 vote
90 views

### Understanding GeometricScene [closed]

I tried to expand a simple geometric scene: RandomInstance[GeometricScene[{a, b, c }, { Triangle[{a, b, c}]}], 1] works fine and shows the triangle. But if ...
• 36.3k
63 views

### Minimize relating a geometric test

I want to find a circle with a center and a radius that includes all given points, like a circumscribed circle for the points. points data: https://www.dropbox.com/s/0unlv1vbngopu38/new_ref.txt?dl=0 ...
• 735
117 views

### Find sum of positive geometric progression numbers

I have a task to get the total number of games played in a soccer tournament. Apart from the group stages, I observed that the number of games played in each round from the knockout round down to the ...
1 vote
208 views

### Given three points in space, find center of circle [duplicate]

Given the coordinates of three points in space, {x1,y1,z1}, {x2,y2,z2}, {x3,y3,z3}, how can ...
• 10.7k
1 vote
60 views

### RandomInstance of GeometricScene producing unexpected result

Consider the following scene as an example: ...
• 8,075
98 views

### Why the output is not in numerical form in Mathematica 12.2?

Consider the following code: ...
• 3,542
56 views

### GeometricScene extremely slow or cannot complete

I would like to find instances of the following dodecahedral wheel generalized to the situation where the red squares become rhombuses. I tried this using RandomInstance[GeometricScene], but ...
• 51
1 vote
91 views

### Exact symbolic area of an intersection of two regular pentagons with parameters

The question of finding the area of intwrsection of two regions with parameters has been answered here using and RegionIntersection with delimeter ...
• 185
209 views

### Exact symbolic area of an intersection of two polygons with parameters

On the one hand, can handle expressions which include parameters, including polygons, for example: Area[Polygon[{{1, 2}, {-1, 1}, {2, 5}, {1, a}}]] returns ...
• 185
116 views

### Surface area of a list of points

I would like to know how I can get the area of the following point list. I am using the following script to make a mesh region and then find the area. However, the area is much larger than the value ...
• 501
827 views

### Find smallest distance from a point to a Bézier curve

I wish to find the smallest distance from a point to a curved defined via a Bézier function. I want to do this automatically. For particular cases it is not to difficult. Here is a minimum working ...
• 14.5k
356 views

### Finding shadow area of a 3D object

Given a 3D object, how could one find the area of the shadow? In effect, this is a measure of optical cross section. The ultimate goal would be a table showing latitude, longitude, and, optical cross ...
• 956
83 views

### How to speed up finding region centroid and plot3d

I have the following code to make 3D of 9 regions. ...
• 1,018
200 views

### Periodic boundaries for a 3D walk in a Bravais lattice?

I'm using a Bravais lattice, 'face-centered', which is implemented in Mathematica in LatticeData[]. I want to simulate a random walk over neighboring points using ...
• 1,303
47 views

### Torus Hex Mesh - Need Unique Hex Dimensions

I'm looking to laser cut a bunch of hexagons and assemble them into a torus (using hot glue or tape). How do I get the dimensions of the individual unique hexagons? I've seen Create a torus with a ...
125 views

### How to wrap any function/curver around a circle? [closed]

I have a function defined as $y=f(x)$ which i want to wrap around a circle, to get a transformed function $r=f(ϕ)$. It is important that the length of the wrapped curve stay's the same. For two ϕ ...
487 views

### Getting cell edges from a picture

I would like to write a program that, given a picture of an epithelium (2D cell array), for example automatically detects the cell edges and returns the corresponding lattice. Illustratively, ...
• 4,138
1 vote
264 views

### RegionDifference not working properly for a region from a printable STL file

Some time ago I created a printable STL-file with a certain software of my own and now I want to modify it with Mathematica programmatically, mainly by subtracting certain geometric objects (e.g. ...
• 111
386 views

### Cutting a section from a sphere by planes

I want to plot and find out the section of a sphere remaining after putting constraints in terms of cartesian planes. How it can be done? For example, if I have a sphere of $r = 1$, and I put the ...
• 973
325 views

### Construct a section (or slice) through 3D Regions

I would like to draw a section through some 3D regions. I start by making some simple 3D regions as a minimum working example. ...
• 14.5k
212 views

### RegionUnion for 3D Regions

I make two regions and then find I can't combine them using RegionUnion. Here are the two regions. ...
• 14.5k
111 views

### How to output the level of the contour plot based on the desired area enclosed in the contour level?

I am a beginner using Mathematica. I am doing a physics experiment that involves this 3D surface; the function $f(x, y)$. I need a program that can give me the contour level in the $z$-axis which ...
418 views

### How do I verify a vector identity using Mathematica?

I am trying to verify well known Frenet–Serret formulas in general setting using Mathematica. I need to consider a general space curve $r(s)=(x(s),y(s),z(s))$ in $\mathbb{R}^3$ and define its unit ...
• 359
129 views

### Simplify behavior: assumption as Interval versus assumption as bounds

I am using MMA V11.2 under Linux I am surprised by this: ...
• 2,383
50 views

### Plot variations in geometric sum within prescribed range

I have a simple geometric sum: Sum[a^(j + 1), {j, 1, k}] which evaluates to (a^2*(-1 + a^k))/(-1 + a) ...
• 2,005
87 views

### ReflectionTransform gives different colors

Consider this example of the cow cow = ExampleData[{"Geometry3D", "Cow"}, "GraphicsComplex"]; p = {0, 0, -0.25} Compare the rotation and reflection ...
• 26.8k
84 views

### Better discretization for intersections of algebraic surfaces

I am looking for better, preferably analytical approaches to discretize intersections of algebraic surfaces. When surfaces are not identical, these solutions are either curves or points. An extremely ...
• 14.6k
1 vote
450 views

### integral over a region boundary

I want to integrate a complex function over a boundary of a region: $$-\frac{i}{v}\oint_\Gamma \exp(-2\pi i(ux+vy))\,dx,$$ where $\Gamma$ is the closed boundary of a region and $y = f(x)$. I know ...
1 vote
97 views

### Unexpected behaviour of MomentOfInertia

The problem I expected Mathematica to solve rather easily is that of the calculus of a moment of inertia of a "c" section defined by the following Polygon: ...
• 2,058
28 views

### ImplicitRegion RegionPlot fails for circle in 10.4.1 [duplicate]

This must have worked at some point, because the documentation for ImplicitRegion has the right picture. But when I evaluate ...
• 5,559
1 vote
107 views

### Find best convex approximation of an "almost convex" function

I've got values of a function of two variables at integer points inside a rectangle, that is, a rectangular table $f(i,j)$, $1\leqslant i\leqslant m$, $1\leqslant j\leqslant n$. The function is very ...
• 2,037
317 views

### RegionNearest and neighborhoods

In this previous question we see that RegionNearest isn't quite as 'capable' as Nearest for some things. Similarly, I need to ...
• 1,760
864 views

### How to mesh a region using adaptive cubic elements

Assume a list of {x,y,z} coordinates. The coordinates are arranged in a regular fashion through a fixed raster size (called ...
• 975
94 views

### Minimization with constraint define over a region

I would like to perform a 2D electrostatic minimization between two charged ellipsoids, provided that they should not penetrate each other; they can touch but they are hard ellipsoids. Here is what I ...
• 249
151 views

### Is there any way to improve the result of DiscretizeRegion on this 3D ImplicitRegion?

Consider two definitions of a cubic region, ...
• 62.4k
490 views

### Alternative to the DiscretizeRegion?

I have a polygon: pgn = Polygon[{{0, 0}, {0, 0.018}, {0.155, 0.018}, {0.155 + 0.015, 0.008}, {0.222, 0.008}, {0.222, 0}, {0, 0}}]; here: ...
• 34.8k
125 views

### Convexity Coefficient Calculation

I would like to probabiistically estimate the convexity coefficient of a MeshRegion, described as - Given a region $\mathscr{K}$, calculate the probability that ...
• 1,760
1 vote
863 views

### How to plot and find the volume of a solid enclosed by surfaces? [closed]

I'm a beginner with both Mathematica and multi-variable calculus. I want to plot and find the volume of the solid enclosed by the surfaces defined by \begin{eqnarray} x^2+y^2 = & 4 \cr x-y+2z ...
• 11
861 views

### How to fill the closed region by ParametricPlot with solid color?

I am interested in the following implicit curve with parametric equation: $$\left\{\quad \begin{array}{rl} x=& 9 \sin 2 t+5 \sin 3 t \\ y=& 9 \cos 2 t-5 \cos 3 t \\ \end{array} \right.$$ ...
• 2,917
1 vote
1k views

### Package for symbolic computation of christoffel symbols and parallel transports in Riemannian geometry, given the metric

I've no knowledge in mathematica (but I do in matlab), but I'd really appreciate if someone could mention what is/are the best and easy to learn mathematica package(s) for symbolic and numerical (both,...
• 111
174 views

### Differential Geometry on a MeshRegion [closed]

NB- see this question for a more formal request. For many many years (honestly, since 1987) I've had my own MMa computational geometry code for dealing with 3D meshes. I principally (there's a joke ...
• 1,760
203 views

### Numerical Functions Compatible with Regions Fail with MeshRegions and BoundaryMeshRegions

Bug introduced in 10.0.0 and fixed in 10.0.2 Given a MeshRegion: region = DelaunayMesh[RandomReal[1, {50, 3}]] We can ...
• 32.5k
604 views

### How do I get a MeshRegion from an obj file, or from Geometry3D

How do I read in an obj file as a MeshRegion so I can e.g. compute its area? If I just import the object and try Area[O] it ...
• 73
460 views

### Possible Bug in DiscretizeRegion with Option MaxCellMeasure

Bug introduced in 10.0.0 and fixed in 10.0.2 Consider the following ImplicitRegion: ...
• 32.5k
257 views

### User-defined DistanceFunction for RegionNearest

In the function Nearest , I can define my custom function using the DistanceFunction option. e.g: ...
• 83
837 views

### How can one compute a 3D Periodic Delaunay Triangulation using DelaunayMesh?

Given a non-periodic point set, one can easily tetrahedralize it using the new (in V10) DelaunayMesh function. e.g.: ...
• 32.5k
650 views

### Probable Bug in ConvexHullMesh

Bug introduced in 10.0 and persisting through 10.2 or later Consider points taken from the following parametric plot. See this question ...
• 32.5k