marmakoide / axis-angle-rotation-matrix.py

Last active December 13, 2022 13:21

Computes the rotation matrix equivalent to an axis & angle rotation

	import numpy

	def axis_angle_to_rotation_matrix(U, theta):
	cos_theta, sin_theta = numpy.cos(theta, dtype = U.dtype), numpy.sin(theta, dtype = U.dtype)
	U_x = numpy.array([[0, -U[2], U[1]], [U[2], 0, -U[0]], [-U[1], U[0], 0]], dtype = U.dtype)
	return cos_theta * numpy.identity(3, dtype = U.dtype) + sin_theta * U_x + (1 - cos_theta) * numpy.outer(U, U)

marmakoide / dft-2d-rot.py

Last active March 31, 2020 09:19

Rotation of 2d DFT coefficients, avoiding computing a DFT by directly transforming the DFT coefficients

	import numpy

	def rot180_fft_2d(X, N):
	I = numpy.repeat([numpy.arange(N)], N, axis = 0)
	K = numpy.exp((2 * numpy.pi / N) * (I + I.T) * 1j)
	return K * numpy.conj(X)

	def rot180_rfft_2d(X, N):
	I = numpy.repeat([numpy.arange(N)], N, axis = 0)
	K = numpy.exp((2 * numpy.pi / N) * (I + I.T) * 1j)[:,:N // 2 + 1]

marmakoide / oric-lores-color-attributes.bas

Created April 11, 2020 20:24

Demonstration of color attributes usage in low resolution mode, Oric 1 computer

	10 FOR I=1 TO 27
	20 POKE #BB80+I*40,16
	30 POKE #BB81+I*40,I AND 7
	40 FOR J=0 TO 38
	50 POKE #BB82+I*40+J,126
	60 NEXT J
	70 POKE #BB80+I*40+20,23
	80 NEXT I

marmakoide / euclidean-distance-transform-2d.py

Created May 21, 2020 09:09

SIMD implementation of 2d euclidean distance. For each non-zero input pixel, returns the exact squared distance to the closest zero input pixel.

	import numpy

	def euclidean_distance_transform(F):
	ret = numpy.empty_like(F, dtype = int)

	def get_parabola_matrix(N):
	X = numpy.arange(N, dtype = int)
	G = numpy.empty((N, N), dtype = int)
	G[:] = X
	G -= X[:, None]

marmakoide / reverse-euclidean-distance-transform.py

Created May 21, 2020 09:13

SIMD implementation of 2d reverse euclidean distance. See "Optimal Separable Algorithms to Compute the Reverse Euclidean Distance Transformation and Discrete Medial Axis in Arbitrary Dimension" D. Coeurjolly et al.

	import numpy



	def reverse_euclidean_distance_transform(F):
	ret = numpy.empty_like(F, dtype = int)

	def get_parabola_matrix(N):
	X = numpy.arange(N, dtype = int)
	G = numpy.empty((N, N), dtype = int)

marmakoide / bevel-box.scad

Last active June 12, 2020 08:55

Bevel rectangle and boxes for OpenSCAD

	module bevel_rectangle(size, bevel) {
	s = (size[0] + size[1] - 2 * bevel) / sqrt(2);

	intersection() {
	square(size, center = true);
	rotate(45)
	square([s, s], center = true);
	}
	}

marmakoide / complex-step-jacobian.py

Created August 19, 2020 12:55

Computes the jacobian of a real-valued function, using the complex step method. The result is accurate nearly down to the machine epsilon with a very simple code, at the expense of uncessary computations, and assuming that the function to differentiate is defined in the complex domain

	def get_jacobian(func, X, h = 1e-7):
	J = []
	for i in range(X.shape[0]):
	Xp = X.astype(complex)
	Xp[i] += h * 1j
	J.append([numpy.imag(func(Xp))])

	J = numpy.concatenate(J, axis = 0)
	J = numpy.transpose(J)
	J /= h

marmakoide / README.md

Last active December 11, 2020 14:05

Circle intersection with lines

Circle intersection with (many) (oriented) lines with optimal runtime complexity

This code sample demonstrates how to compute the intersection with a circle of radius 1, and many oriented lines. Technically, oriented lines are equivalent to half-planes.

The function circle_line_intersection is doing all the work. The lines are specified as the 3 parameters of a 2d line equation, ax + by + c = 0. The function returns a list of pairs of points : the extremities of each arcs in counterclock wise order.

marmakoide / memory.sh

Last active January 1, 2021 12:43

Shell script that generates a string describing RAM usage, to use with dwmblocks and Font Awesome

	#!/bin/sh

	icon=""
	mem_str=$(free -h \| awk '/^Mem/ { print $3 "/" $2 }' \| sed s/i//g)

	echo $icon $mem_str

marmakoide / power.sh

Last active January 1, 2021 17:27

Shell script that generates a string describing power supply status, to use with dwmblocks and Font Awesome

	#!/bin/sh

	is_ac_powered=$(cat /sys/class/power_supply/AC0/online)
	batt_capacity=$(cat /sys/class/power_supply/BAT0/capacity)

	if [ "$is_ac_powered" -eq 1 ]; then
	icon="" #uF1E6
	else
	if [ "$batt_capacity" -gt 80 ]; then
	icon="" #uF240

Devert Alexandre marmakoide

Circle intersection with (many) (oriented) lines with optimal runtime complexity