From e3f94c18c5375e58d62eb0be29fa7845b54c360a Mon Sep 17 00:00:00 2001 From: Bruce Hill Date: Mon, 18 Mar 2019 21:15:33 -0700 Subject: [PATCH] Initial commit --- 2pend.c | 150 ++++++++++++++++++++++++++++++++++++++++++++++++++++++ LICENSE | 20 ++++++++ Makefile | 40 +++++++++++++++ README.md | 6 +++ 4 files changed, 216 insertions(+) create mode 100644 2pend.c create mode 100644 LICENSE create mode 100644 Makefile create mode 100644 README.md diff --git a/2pend.c b/2pend.c new file mode 100644 index 0000000..7b8faa2 --- /dev/null +++ b/2pend.c @@ -0,0 +1,150 @@ +// A double pendulum simulator by Bruce Hill +// Released under the MIT license, see LICENSE for details. +#include +#include +#include +#include +#include +#include + +#define HISTORY_LEN 8 + +typedef struct { + double a, p; +} pendulum_t; + +typedef struct { + pendulum_t p1, p2; +} state_t; + +static const double M1 = 1.0, M2 = 1.0, G = 9.80, L1 = .5, L2 = .5; + +const int color_ramp[] = {16,232,233,234,235,236,237,238,239,240,241,242,243,244,245,246, + 247,248,249,250,251,252,253,254,255,231,231,231,231,231}; + +static state_t get_derivative(state_t state) +{ + double a1 = state.p1.a, a2 = state.p2.a, p1 = state.p1.p, p2 = state.p2.p; + double da1, da2, dp1, dp2; + da1 = (6/(M1*L1*L1)) * (2*p1 - 3*cos(a1-a2)*p2)/(16-9*cos(a1-a2)*cos(a1-a2)); + da2 = (6/(M2*L2*L2)) * (8*p2 - 3*cos(a1-a2)*p1)/(16-9*cos(a1-a2)*cos(a1-a2)); + dp1 = -.5 * M1*L1*L1 * (da1*da2*sin(a1-a2) + 3*G/L1*sin(a1)); + dp2 = -.5 * M2*L2*L2 * (-da1*da2*sin(a1-a2) + G/L1*sin(a2)); + state_t derivative = {{da1, dp1}, {da2, dp2}}; + return derivative; +} + +static state_t step(state_t state, state_t derivative, double dt) +{ + state_t next = { + {state.p1.a+dt*derivative.p1.a, state.p1.p+dt*derivative.p1.p}, + {state.p2.a+dt*derivative.p2.a, state.p2.p+dt*derivative.p2.p} + }; + return next; +} + +static void draw(state_t state, int color) +{ + // TODO: properly walk along cells + int W = tb_width(), H = tb_height(); + double *brightness = calloc(W*H, sizeof(double)); + double len = W/2 > H ? H/2 : (W/2)/2; + double x = W/2, y = H/2; + double step = 0.25; + for (double p = 0; p <= len*L1; p += step) { + double b = (sqrt(2*((x-floor(x+.5))*(x-floor(x+.5)) + (y-floor(y+.5))*(y-floor(y+.5))))); + if (b > brightness[(int)y*W+(int)x]) brightness[(int)y*W+(int)x] = b; + b = (sqrt(2*((x+1.-floor(x+1.5))*(x+1.-floor(x+1.5)) + (y-floor(y+.5))*(y-floor(y+.5))))); + if (b > brightness[(int)y*W+(int)x+1]) brightness[(int)y*W+(int)x+1] = b; + //tb_change_cell((int)x, (int)y, ' ', 0, color); + x += step*cos(state.p1.a + M_PI/2)*2; + y += step*sin(state.p1.a + M_PI/2); + } + for (double p = 0; p <= len*L2; p += step) { + double b = (sqrt(2*((x-floor(x+.5))*(x-floor(x+.5)) + (y-floor(y+.5))*(y-floor(y+.5))))); + if (b > brightness[(int)y*W+(int)x]) brightness[(int)y*W+(int)x] = b; + b = (sqrt(2*((x+1.-floor(x+1.5))*(x+1.-floor(x+1.5)) + (y-floor(y+.5))*(y-floor(y+.5))))); + if (b > brightness[(int)y*W+(int)x+1]) brightness[(int)y*W+(int)x+1] = b; + //tb_change_cell((int)x, (int)y, ' ', 0, color); + x += step*cos(state.p2.a + M_PI/2)*2; + y += step*sin(state.p2.a + M_PI/2); + } + + for (int y=0; y 0) { + color = color_ramp[(int)(sizeof(color_ramp)/sizeof(int) * b)]; + tb_change_cell((int)x, (int)y, ' ', 0, color); + } + } + free(brightness); +} + +int main(int argc, char **argv) { + int ret = tb_init(); + if (ret) { + fprintf(stderr, "tb_init() failed with error code %d\n", ret); + return 1; + } + tb_select_input_mode(TB_INPUT_MOUSE); + tb_select_output_mode(TB_OUTPUT_256); + + state_t state; + state_t history[HISTORY_LEN]; + + randomize: + state.p1.a = M_PI/2 + M_PI*(double)rand()/RAND_MAX; + state.p2.a = M_PI/2 + M_PI*(double)rand()/RAND_MAX; + state.p1.p = 0; + state.p2.p = 0; + for (int i=0; i + +Permission is hereby granted, free of charge, to any person obtaining a copy of +this software and associated documentation files (the "Software"), to deal in +the Software without restriction, including without limitation the rights to +use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies +of the Software, and to permit persons to whom the Software is furnished to do +so, subject to the following conditions: + +The above copyright notice and this permission notice shall be included in all +copies or substantial portions of the Software. + +THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR +IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, +FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE +AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER +LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, +OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE +SOFTWARE. diff --git a/Makefile b/Makefile new file mode 100644 index 0000000..8900647 --- /dev/null +++ b/Makefile @@ -0,0 +1,40 @@ +PREFIX= +CC=cc +CFLAGS=-O3 -std=gnu99 +LIBS=-ltermbox -lm +NAME=2pend + +all: $(NAME) + +clean: + rm $(NAME) + +run: $(NAME) + ./$(NAME) + +$(NAME): $(NAME).c + $(CC) $(NAME).c $(LIBS) $(CFLAGS) -o $(NAME) + +install: $(NAME) + @prefix="$(PREFIX)"; \ + if [[ ! $$prefix ]]; then \ + read -p $$'\033[1mWhere do you want to install? (default: /usr/local) \033[0m' prefix; \ + fi; \ + if [[ ! $$prefix ]]; then \ + prefix="/usr/local"; \ + fi; \ + mkdir -pv $$prefix/bin $$prefix/share/man/man1 \ + && cp -v $(NAME) $$prefix/bin/ \ + && cp -v doc/$(NAME).1 $$prefix/share/man/man1/ + +uninstall: + @prefix="$(PREFIX)"; \ + if [[ ! $$prefix ]]; then \ + read -p $$'\033[1mWhere do you want to uninstall from? (default: /usr/local) \033[0m' prefix; \ + fi; \ + if [[ ! $$prefix ]]; then \ + prefix="/usr/local"; \ + fi; \ + echo "Deleting..."; \ + rm -rvf $$prefix/bin/$(NAME) $$prefix/share/man/man1/$(NAME).1 + diff --git a/README.md b/README.md new file mode 100644 index 0000000..56981fe --- /dev/null +++ b/README.md @@ -0,0 +1,6 @@ +# 2pend +This is a program that simulates a double pendulum and renders it on the console with termbox. +Press `q` or Escape to quit and `r` to randomize. + +## Building +`make` to build and `make install` to install.