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https://git.davidovski.xyz/rectangles.git
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Generate non-overlapping collisions
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83e3b21ae6
3 changed files with 171 additions and 0 deletions
15
Makefile
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15
Makefile
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PROG=rectangles
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CC=gcc
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FLAGS=-lm -lraylib
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.DEFAULT_GOAL := build
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install: ${PROG}
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cp ${PROG} ${PREFIX}/bin/
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build: ${PROG}.c
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${CC} ${PROG}.c -o ${PROG} ${FLAGS}
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clean: ${PROG}
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rm ${PROG}
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8
README.md
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8
README.md
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# Rectangles
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A simple proof of concept algorithm to combine multiple tiled rectangles into a smaller number. This can be used to optimise the number of rectangles to check for collision in a game.
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## Requirements
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- C Compiler
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- raylib
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148
rectangles.c
Executable file
148
rectangles.c
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#include <complex.h>
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#include <raylib.h>
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#include <stdlib.h>
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#include <stdio.h>
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#include <math.h>
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#define TILESIZE 50
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#define SCREEN_W 800
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#define SCREEN_H 600
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#define RECT_COUNT (SCREEN_H / TILESIZE) * (SCREEN_W / TILESIZE)
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#define GRID_H (int) (SCREEN_W / TILESIZE);
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#define GRID_W (int) (SCREEN_H / TILESIZE);
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Rectangle rectangles[RECT_COUNT];
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int draw_grid() {
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// vertical lines
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for (int x = 0; x < SCREEN_W; x += TILESIZE) {
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DrawLine(x, 0, x, SCREEN_H, DARKGRAY);
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}
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// vertical lines
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for (int y = 0; y < SCREEN_H; y += TILESIZE) {
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DrawLine(0, y, SCREEN_W, y, DARKGRAY);
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}
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}
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int rect_valid(Rectangle rect) {
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return rect.width || rect.height;
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}
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int draw_rectangles() {
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for (int i = 0; i < RECT_COUNT; i++) {
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Rectangle rectangle = rectangles[i];
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if (rect_valid(rectangle)) {
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DrawRectangleRec(rectangle, DARKGRAY);
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}
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}
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}
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int rects_touch_y(Rectangle rect_a, Rectangle rect_b) {
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return rect_a.x == rect_b.x && rect_a.width == rect_b.width &&
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(rect_a.y == rect_b.y + rect_b.height ||
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rect_b.y == rect_a.y + rect_a.height);
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}
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int rects_touch_x(Rectangle rect_a, Rectangle rect_b) {
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return rect_a.y == rect_b.y && rect_a.height == rect_b.height &&
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(rect_a.x == rect_b.x + rect_b.width ||
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rect_b.x == rect_a.x + rect_a.width);
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}
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int draw_optimised_rectangles() {
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Rectangle *optimised = malloc(sizeof(Rectangle) * RECT_COUNT);
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int index = 0;
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// copy rectangles to optimised
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for (int i = 0; i < RECT_COUNT; i++) {
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Rectangle rectangle = rectangles[i];
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if (rect_valid(rectangle)) {
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optimised[i] = rectangle;
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}
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}
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Rectangle rect_a, rect_b;
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// merge rectangles in x direction
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for (int i = 0; i < RECT_COUNT; i++) {
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if (rect_valid(rect_a = optimised[i]))
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for (int j = 0; j < RECT_COUNT; j++) {
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if (i != j && rect_valid(rect_b = optimised[j])
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&& rects_touch_x(rect_a, rect_b)) {
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optimised[i].x = rect_a.x < rect_b.x ? rect_a.x : rect_b.x;
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optimised[i].width = rect_a.width + rect_b.width;
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rect_a = optimised[i];
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// delete j
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optimised[j].width = 0;
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}
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}
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}
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// merge rectangles in y direction
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for (int i = 0; i < RECT_COUNT; i++) {
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if (rect_valid(rect_a = optimised[i]))
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for (int j = 0; j < RECT_COUNT; j++) {
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if (i != j && rect_valid(rect_b = optimised[j])
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&& rects_touch_y(rect_a, rect_b)) {
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optimised[i].y = rect_a.y < rect_b.y ? rect_a.y : rect_b.y;
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optimised[i].height = rect_a.height + rect_b.height;
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rect_a = optimised[i];
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// delete j
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optimised[j].width = 0;
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}
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}
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}
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Rectangle rectangle;
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for (int i = 0; i < RECT_COUNT; i++) {
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if (rect_valid(rectangle = optimised[i]))
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DrawRectangleLinesEx(rectangle, 2, GREEN);
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}
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free(optimised);
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}
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int draw() {
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BeginDrawing();
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ClearBackground(LIGHTGRAY);
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draw_grid();
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draw_rectangles();
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draw_optimised_rectangles();
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if (IsMouseButtonDown(MOUSE_BUTTON_LEFT)) {
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int gridx = (int) floor(GetMouseX() / TILESIZE);
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int gridy = (int) floor(GetMouseY() / TILESIZE);
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Rectangle rectangle = (Rectangle){gridx * TILESIZE, gridy * TILESIZE, TILESIZE, TILESIZE};
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// keep rectangles in order so that larger y and x are more right / left
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int rect_index = gridx + gridy*GRID_H;
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rectangles[rect_index] = rectangle;
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}
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EndDrawing();
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}
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int main() {
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SetTargetFPS(60);
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InitWindow(SCREEN_W, SCREEN_H, "Rectangles");
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for (int i = 0; i < RECT_COUNT; i++) {
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rectangles[i] = (Rectangle){0, 0, 0, 0};
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}
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while(!WindowShouldClose()) {
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draw();
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}
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CloseWindow();
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return 0;
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}
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