Calculate the area intersected by a sphere and a rectangular prism

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SUMMARY

This discussion focuses on calculating the area intersected by a sphere and a rectangular prism, specifically addressing the challenges posed by irregular shapes formed during the intersection. The total intersecting area should approximate ##4 \pi r^2##, but complications arise due to the non-geodesic nature of the polygons on the sphere and the potential embedding of the prism within the sphere. The concept of "interface reconstruction" is highlighted as a relevant algorithm, emphasizing the need for accuracy in computational geometry.

PREREQUISITES
  • Understanding of 3D geometry and spatial reasoning
  • Familiarity with computational geometry concepts, particularly interface reconstruction
  • Knowledge of algorithms for area calculation in irregular shapes
  • Basic principles of sphere and polyhedron intersection
NEXT STEPS
  • Research "interface reconstruction algorithms" for accurate area calculations
  • Study methods for calculating intersections between spheres and polyhedra
  • Explore literature on computational geometry focusing on irregular polygon area calculations
  • Investigate tools for visualizing 3D geometric intersections, such as CAD software
USEFUL FOR

Mathematicians, computer scientists, and engineers involved in computational geometry, particularly those working on 3D modeling and simulations that require accurate area calculations of intersecting shapes.

guv
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Homework Statement
I am trying to figure out the area on the surface of a sphere as a result of the sphere intersecting a much smaller rectangular prism.
Relevant Equations
N/A
Think of a 3D rectilinear grid made of these rectangular cells, some of the cells will intersect with the sphere. I am trying to compute each intersecting area and the total sum. Ideally the total sum of the intersecting area should be close to ##4 \pi r^2##. I have not found any literature discussing this problem. Part of the problem is that the polygon on the sphere as a result of the intersection is not necessarily made of geodesics. Moreover, part of the rectangular prism can embed inside the sphere causing irregular intersecting shape. I am looking for ideas how to get this done correctly. Has anyone seen any problem. I would imagine this might be useful in computer science, but obviously people there are not too concerned with accuracy of the result. Thanks!
 
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guv said:
Homework Statement: I am trying to figure out the area on the surface of a sphere as a result of the sphere intersecting a much smaller rectangular prism.
Relevant Equations: N/A

Think of a 3D rectilinear grid made of these rectangular cells, some of the cells will intersect with the sphere. I am trying to compute each intersecting area and the total sum. Ideally the total sum of the intersecting area should be close to ##4 \pi r^2##. I have not found any literature discussing this problem. Part of the problem is that the polygon on the sphere as a result of the intersection is not necessarily made of geodesics. Moreover, part of the rectangular prism can embed inside the sphere causing irregular intersecting shape. I am looking for ideas how to get this done correctly. Has anyone seen any problem. I would imagine this might be useful in computer science, but obviously people there are not too concerned with accuracy of the result. Thanks!
If the polyhedron is inside the sphere the only possible points of intersections will be at points or edges on the polyhedron where two or more polygons meet. At least that's what I come up with based on your description.
 
How are these figures given? Do you have their equations, or are they given in a different format?
 
guv said:
Has anyone seen any problem. I would imagine this might be useful in computer science, but obviously people there are not too concerned with accuracy of the result.
They call it interface reconstruction and are very concerned with accuracy vs. computational cost.
 
Take a look at the pictures attached, I am guessing 'interface construction' is the algorithm that results in what we see in the pictures. How about area calculation? Is there any literature on how to find the intersection and area in the general case? The intersection looks like a simpler problem, the area seems difficult.
 

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Question: A clock's minute hand has length 4 and its hour hand has length 3. What is the distance between the tips at the moment when it is increasing most rapidly?(Putnam Exam Question) Answer: Making assumption that both the hands moves at constant angular velocities, the answer is ## \sqrt{7} .## But don't you think this assumption is somewhat doubtful and wrong?

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