Questions tagged [geometric-computation]
The geometric-computation tag has no usage guidance.
2
votes
2answers
62 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 ...
6
votes
2answers
277 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 ...
4
votes
1answer
48 views
Simplify behavior: assumption as Interval versus assumption as bounds
I am using MMA V11.2 under Linux
I am surprised by this:
...
3
votes
1answer
36 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)
...
5
votes
0answers
68 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 ...
3
votes
0answers
70 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 ...
1
vote
1answer
203 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
1answer
82 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:
...
0
votes
0answers
26 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
...
1
vote
0answers
76 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 ...
12
votes
1answer
234 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 ...
13
votes
2answers
616 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 ...
0
votes
0answers
76 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 ...
6
votes
1answer
118 views
Is there any way to improve the result of DiscretizeRegion on this 3D ImplicitRegion?
Consider two definitions of a cubic region,
...
7
votes
1answer
397 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:
...
3
votes
0answers
81 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
vote
1answer
392 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 ...
7
votes
2answers
387 views
How to fill the closed region by ParametricPlot with solid color?
I am interested in the following implicit curve with parametric equation:
$$
\left\{\quad
\begin{array}{rl}
x=& 9 \sin 2 t+5 \sin 3 t \\
y=& 9 \cos 2 t-5 \cos 3 t \\
\end{array}
\right.
$$
...
1
vote
1answer
819 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,...
3
votes
0answers
151 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 ...
6
votes
1answer
182 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 ...
7
votes
1answer
483 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 ...
12
votes
2answers
390 views
Possible Bug in DiscretizeRegion with Option MaxCellMeasure
Bug introduced in 10.0.0 and fixed in 10.0.2
Consider the following ImplicitRegion:
...
8
votes
1answer
219 views
User-defined DistanceFunction for RegionNearest
In the function Nearest , I can define my custom function using the DistanceFunction option. e.g:
...
6
votes
1answer
634 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.:
...
11
votes
2answers
566 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
...
20
votes
1answer
2k views
Faster way to compute the distance from a point to a surface in 3D
I am trying to compute the shortest distance between a point and a triangle in 3D
...
