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clear_vars
reset()
%display latex

u,v,w,T = SR.var('x y z t')
E_x,E_y,E_z  = function('Ex'),function('Ey'), function('Ez')
B_x,B_y,B_z  = function('Bx'),function('By'), function('Bz')
M.<t, x, y, z> = manifolds.Minkowski(positive_spacelike=False)
F = M.diff_form(2, name='F')
@donaldmunro
donaldmunro / euclidean_forms.md
Last active August 3, 2021 22:44
Differential Forms on simple Euclidean manifolds using SageMath Manifolds package
clear_vars
reset()
%display latex
R3 = Manifold(3, 'R^3', start_index=1)
X.<x,y,z> = R3.chart()
g = R3.metric('g')
g[1,1], g[2,2], g[3,3] = 1, 1, 1

#R2 = Manifold(2, 'R^2', ambient=R3, start_index=1)
@donaldmunro
donaldmunro / bounded_map.h
Created January 26, 2019 22:58
A wrapped std::multimap which limits size by removing the smallest keys first. Useful for timestamped data where the oldest items (smallest timestamps) can be removed.
#ifndef _BOUNDED_MAP_H
#define _BOUNDED_MAP_H
#include <iostream>
#include <map>
#include <vector>
#include <utility>
/**
* A wrapped std::multimap which limits size by removing the smallest keys first.
# Using javah to generate .h files for Kotlin
# Assuming JNI function calls are in MainActivity.companion
STUDIO=/opt/android-studio
PACKAGE=my.package
$STUDIO/jre/bin/javah -jni -cp "$STUDIO/lib/kotlin-runtime.jar:build/tmp/kotlin-classes/debug" $PACKAGE.MainActivity.Companion
@donaldmunro
donaldmunro / boost-android.md
Last active January 18, 2023 22:25
Compile Boost for Android

Compiling Boost for Android

  1. Download Boost and cd to base directory.

  2. Create Android toolchains for desired architectures by running a script as below:

    NDK=/opt/android-sdk/ndk-bundle/
    TOOLCHAINS="$PWD/toolchains/"

rm -rf $TOOLCHAINS

@donaldmunro
donaldmunro / gist:a2a0a061de498b9dc0ec10be309de2b7
Created March 5, 2017 14:05
Access/dereference glm::mat4 contents
#include <glm/gtc/type_ptr.hpp>
..
glm::mat4 m = glm::mat4(1.0f);
..
auto p = glm::value_ptr(m);
std::cout << sizeof(p) << std::endl;
glUniformMatrix4fv(shader_uniform_m, 1, GL_FALSE, p);
@donaldmunro
donaldmunro / gist:38841d72c65a1c32f2bf83a4a00a2c9a
Created March 5, 2017 13:26
Display/print a GLM mat or vec
#include <glm/gtx/string_cast.hpp>
..
..
glm::mat4 mat;
..
..
std::cout << glm::to_string(mat) << std::endl;
@donaldmunro
donaldmunro / gist:afa2f57bd4e52aa3cc0e3bbe422c889e
Created February 25, 2017 21:11
Parse delimited string in C++
size_t split(std::string s, std::vector<std::string>& tokens,
std::string delim ="\t\n ")
{
tokens.clear();
size_t pos = s.find_first_not_of(delim);
while (pos != std::string::npos)
{
size_t next = s.find_first_of(delim, pos);
if (pos == std::string::npos)
tokens.emplace_back(s.substr(pos));
@donaldmunro
donaldmunro / gist:beb7f226adf9c585c67f2599384e43ab
Created February 24, 2017 16:58
Map OpenCv Mat to Eigen Matrix and calculate Eigenvectors
#include <eigen3/Eigen/Dense>
#include <eigen3/Eigen/Eigenvalues>
..
..
using RowMatrixXf = Eigen::Matrix<float, Eigen::Dynamic, Eigen::Dynamic, Eigen::RowMajor>;
Eigen::Map<RowMatrixXf> mapped(extended_homograpy.ptr<float>(), homography.rows, homography.cols);
Eigen::EigenSolver<Eigen::MatrixXf> eigen_solve(mapped, true);
auto ev = eigen_solve.eigenvectors();
std::cout << "No of EigenVectors = " << ev.cols() << std::endl;
for (auto i=0; i<ev.cols(); i++)
@donaldmunro
donaldmunro / features.cc
Last active January 10, 2016 12:08
Benchmark OpenCV Feature/Descriptor Extractors.
/*
Copyright (c) 2016, Donald Munro
Permission to use, copy, modify, and/or distribute this software for any
purpose with or without fee is hereby granted, provided that the above
copyright notice and this permission notice appear in all copies.
THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR