Generate non-overlapping collisions

This commit is contained in:
davidovski 2023-04-21 21:58:50 +01:00
commit 83e3b21ae6
3 changed files with 171 additions and 0 deletions

15
Makefile Normal file
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PROG=rectangles
CC=gcc
FLAGS=-lm -lraylib
.DEFAULT_GOAL := build
install: ${PROG}
cp ${PROG} ${PREFIX}/bin/
build: ${PROG}.c
${CC} ${PROG}.c -o ${PROG} ${FLAGS}
clean: ${PROG}
rm ${PROG}

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README.md Normal file
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# Rectangles
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.
## Requirements
- C Compiler
- raylib

148
rectangles.c Executable file
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#include <complex.h>
#include <raylib.h>
#include <stdlib.h>
#include <stdio.h>
#include <math.h>
#define TILESIZE 50
#define SCREEN_W 800
#define SCREEN_H 600
#define RECT_COUNT (SCREEN_H / TILESIZE) * (SCREEN_W / TILESIZE)
#define GRID_H (int) (SCREEN_W / TILESIZE);
#define GRID_W (int) (SCREEN_H / TILESIZE);
Rectangle rectangles[RECT_COUNT];
int draw_grid() {
// vertical lines
for (int x = 0; x < SCREEN_W; x += TILESIZE) {
DrawLine(x, 0, x, SCREEN_H, DARKGRAY);
}
// vertical lines
for (int y = 0; y < SCREEN_H; y += TILESIZE) {
DrawLine(0, y, SCREEN_W, y, DARKGRAY);
}
}
int rect_valid(Rectangle rect) {
return rect.width || rect.height;
}
int draw_rectangles() {
for (int i = 0; i < RECT_COUNT; i++) {
Rectangle rectangle = rectangles[i];
if (rect_valid(rectangle)) {
DrawRectangleRec(rectangle, DARKGRAY);
}
}
}
int rects_touch_y(Rectangle rect_a, Rectangle rect_b) {
return rect_a.x == rect_b.x && rect_a.width == rect_b.width &&
(rect_a.y == rect_b.y + rect_b.height ||
rect_b.y == rect_a.y + rect_a.height);
}
int rects_touch_x(Rectangle rect_a, Rectangle rect_b) {
return rect_a.y == rect_b.y && rect_a.height == rect_b.height &&
(rect_a.x == rect_b.x + rect_b.width ||
rect_b.x == rect_a.x + rect_a.width);
}
int draw_optimised_rectangles() {
Rectangle *optimised = malloc(sizeof(Rectangle) * RECT_COUNT);
int index = 0;
// copy rectangles to optimised
for (int i = 0; i < RECT_COUNT; i++) {
Rectangle rectangle = rectangles[i];
if (rect_valid(rectangle)) {
optimised[i] = rectangle;
}
}
Rectangle rect_a, rect_b;
// merge rectangles in x direction
for (int i = 0; i < RECT_COUNT; i++) {
if (rect_valid(rect_a = optimised[i]))
for (int j = 0; j < RECT_COUNT; j++) {
if (i != j && rect_valid(rect_b = optimised[j])
&& rects_touch_x(rect_a, rect_b)) {
optimised[i].x = rect_a.x < rect_b.x ? rect_a.x : rect_b.x;
optimised[i].width = rect_a.width + rect_b.width;
rect_a = optimised[i];
// delete j
optimised[j].width = 0;
}
}
}
// merge rectangles in y direction
for (int i = 0; i < RECT_COUNT; i++) {
if (rect_valid(rect_a = optimised[i]))
for (int j = 0; j < RECT_COUNT; j++) {
if (i != j && rect_valid(rect_b = optimised[j])
&& rects_touch_y(rect_a, rect_b)) {
optimised[i].y = rect_a.y < rect_b.y ? rect_a.y : rect_b.y;
optimised[i].height = rect_a.height + rect_b.height;
rect_a = optimised[i];
// delete j
optimised[j].width = 0;
}
}
}
Rectangle rectangle;
for (int i = 0; i < RECT_COUNT; i++) {
if (rect_valid(rectangle = optimised[i]))
DrawRectangleLinesEx(rectangle, 2, GREEN);
}
free(optimised);
}
int draw() {
BeginDrawing();
ClearBackground(LIGHTGRAY);
draw_grid();
draw_rectangles();
draw_optimised_rectangles();
if (IsMouseButtonDown(MOUSE_BUTTON_LEFT)) {
int gridx = (int) floor(GetMouseX() / TILESIZE);
int gridy = (int) floor(GetMouseY() / TILESIZE);
Rectangle rectangle = (Rectangle){gridx * TILESIZE, gridy * TILESIZE, TILESIZE, TILESIZE};
// keep rectangles in order so that larger y and x are more right / left
int rect_index = gridx + gridy*GRID_H;
rectangles[rect_index] = rectangle;
}
EndDrawing();
}
int main() {
SetTargetFPS(60);
InitWindow(SCREEN_W, SCREEN_H, "Rectangles");
for (int i = 0; i < RECT_COUNT; i++) {
rectangles[i] = (Rectangle){0, 0, 0, 0};
}
while(!WindowShouldClose()) {
draw();
}
CloseWindow();
return 0;
}