Skip to content

Add first fundamental form calculator to maths#14554

Open
singhc7 wants to merge 1 commit intoTheAlgorithms:masterfrom
singhc7:fff
Open

Add first fundamental form calculator to maths#14554
singhc7 wants to merge 1 commit intoTheAlgorithms:masterfrom
singhc7:fff

Conversation

@singhc7
Copy link
Copy Markdown

@singhc7 singhc7 commented Apr 14, 2026

This adds a script to calculate the coefficients (e, f, g) of the first fundamental form for parametric surfaces. This mathematical framework is a core concept in differential geometry, used to measure lengths, angles, and areas on a surface.

The implementation uses sympy for symbolic differentiation and simplification. While standard mathematical notation dictates capital E, F, and G for these coefficients, they are implemented as lowercase to strictly adhere to PEP 8 N806 and pass the repository's required Ruff linter pre-commit hooks.

Reference: https://en.wikipedia.org/wiki/First_fundamental_form

Author: singhc7

Describe your change:

  • Add an algorithm?
  • Fix a bug or typo in an existing algorithm?
  • Add or change doctests? -- Note: Please avoid changing both code and tests in a single pull request.
  • Documentation change?

Checklist:

  • I have read CONTRIBUTING.md.
  • This pull request is all my own work -- I have not plagiarized.
  • I know that pull requests will not be merged if they fail the automated tests.
  • This PR only changes one algorithm file. To ease review, please open separate PRs for separate algorithms.
  • All new Python files are placed inside an existing directory.
  • All filenames are in all lowercase characters with no spaces or dashes.
  • All functions and variable names follow Python naming conventions.
  • All function parameters and return values are annotated with Python type hints.
  • All functions have doctests that pass the automated testing.
  • All new algorithms include at least one URL that points to Wikipedia or another similar explanation.
  • If this pull request resolves one or more open issues then the description above includes the issue number(s) with a closing keyword: "Fixes #ISSUE-NUMBER".

This adds a script to calculate the coefficients (e, f, g) of the
first fundamental form for parametric surfaces. This mathematical
framework is a core concept in differential geometry, used to measure
lengths, angles, and areas on a surface.

The implementation uses sympy for symbolic differentiation and
simplification. While standard mathematical notation dictates capital
E, F, and G for these coefficients, they are implemented as lowercase
to strictly adhere to PEP 8 N806 and pass the repository's required
Ruff linter pre-commit hooks.

Reference: https://en.wikipedia.org/wiki/First_fundamental_form

Author: singhc7
@singhc7 singhc7 marked this pull request as ready for review April 14, 2026 03:26
@algorithms-keeper algorithms-keeper Bot added the awaiting reviews This PR is ready to be reviewed label Apr 14, 2026
GitHub: https://github.com/singhc7
"""

import sympy as sp
Copy link
Copy Markdown

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

sympy is a heavy dependency. Consider mentioning this in the module docstring or adding a note about installation requirements (e.g., pip install sympy) for better usability.

# Parse the string expressions into sympy objects
x = sp.sympify(x_expr)
y = sp.sympify(y_expr)
z = sp.sympify(z_expr)
Copy link
Copy Markdown

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

sympify can raise exceptions for invalid input strings. Consider wrapping this in a try/except block and raising a more user-friendly error message.


# Calculate partial derivatives (tangent vectors)
r_u = sp.diff(r, u)
r_v = sp.diff(r, v)
Copy link
Copy Markdown

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

Since r is a Matrix, it may be clearer to explicitly compute derivatives element-wise or mention in the docstring that vector differentiation is handled via SymPy's Matrix support.

# We use simplify to combine trigonometric terms where possible
e = sp.simplify(r_u.dot(r_u))
f = sp.simplify(r_u.dot(r_v))
g = sp.simplify(r_v.dot(r_v))
Copy link
Copy Markdown

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

simplify() can be computationally expensive. Consider making simplification optional or documenting the potential performance impact for complex expressions.

Sign up for free to join this conversation on GitHub. Already have an account? Sign in to comment

Labels

awaiting reviews This PR is ready to be reviewed

Projects

None yet

Development

Successfully merging this pull request may close these issues.

3 participants