Equation for circle points in 3D

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SUMMARY

The discussion focuses on deriving an algebraic formula to calculate coordinates for points on a circle defined by three non-collinear points (A, B, C) in 3D space. The user intends to use the lengths of the triangle's sides formed by these points to determine the radius and center of the circle. The formula for the circle's center coordinates is referenced from the Wikipedia article on circumscribed circles, specifically the section on Cartesian coordinates derived from cross- and dot-products. The user emphasizes the importance of ensuring the points are not collinear to maintain the circular relationship.

PREREQUISITES
  • Understanding of 3D geometry and vector mathematics
  • Familiarity with the concept of circumcircles and inscribed triangles
  • Knowledge of Cartesian coordinates and their applications in 3D space
  • Proficiency in using cross-products and dot-products in vector calculations
NEXT STEPS
  • Research the derivation of the circumradius formula for triangles in 3D space
  • Learn about the properties of non-collinear points and their implications in geometry
  • Explore advanced vector mathematics, focusing on cross-products and dot-products
  • Investigate computational methods for generating points on a circle in 3D
USEFUL FOR

Mathematicians, 3D graphics programmers, and anyone involved in geometric modeling or computational geometry will benefit from this discussion.

Nikkki
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TL;DR
Calculate the coordinates of consecutive points based on ABC points lying on a circle in 3D space
Hello,

I am trying to solve a problem and I would like to ask for help.

I have 3 points (A, B, C) in 3D space that are assumed to be on a circle.

EXAMPLE 1
1637915795573.png
1637915918290.png
EXAMPLE 2
1637920200382.png
1637916124402.png

My goal is to create an algebraic formula to calculate the coordinates for 10 points on a circle composed of ABC points at any distance from each other.

1637916560383.png
1637916587355.png

MY IDEA

My first idea was to create a triangle inscribed in a circle from the ABC points and then the radius of the circle.
First, I calculate the lengths of the triangle's legs by recalculating the lengths of |AB| |AC| and |CB| vectors.

1637920433604.png

I calculate the radius length using the formula (https://www.physicsforums.com/threads/equation-of-a-circle-through-3-points-in-3d-space.173847/):
1637920084001.png

And at this step, I have now stopped
 
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The center has a distance r to all these points. Can you find its coordinates as function of e.g. a, (b-a) and (c-a), e.g. the position of a and two sides? This is completely analogous to the two-dimensional problem.
 
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mfb said:
The center has a distance r to all these points. Can you find its coordinates as function of e.g. a, (b-a) and (c-a), e.g. the position of a and two sides? This is completely analogous to the two-dimensional problem.
Thank you for your answer.
I am testing the formula for the circle center coordinates in the "Cartesian coordinates from cross- and dot-products" section on the website : https://en.wikipedia.org/wiki/Circu...sian_coordinates_from_cross-_and_dot-products
 
Hint: think bisector - the problem says 'lies on a circle' which has to imply that the points are not collinear.
 

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