collision yes/no

1 files changed, 155 insertions, 0 deletions

diff --git a/testsat.cpp b/testsat.cpp
new file mode 100644
index 0000000..45f3891
--- /dev/null
+++ b/testsat.cpp
@@ -0,0 +1,155 @@
+#include <SDL2/SDL.h>
+
+#include <assert.h>
+#include <stdlib.h>
+
+#include "maths.cpp"
+
+struct Shape {
+	v2f* points;
+	int count;
+
+	Shape(std::initializer_list<v2f> in) {
+		int i;
+		points = (v2f*)malloc(in.size() * sizeof *points);
+		count = in.size();
+		for (i = 0; i < count; i++)
+			points[i] = *(in.begin() + i);
+	}
+
+	Shape(const Shape& other) {
+		int s = other.count * sizeof *points;
+		count = other.count;
+		points = (v2f*)malloc(s);
+		memcpy(points, other.points, s);
+	}
+
+	~Shape() {
+		free(points);
+	}
+
+	void render(SDL_Renderer* ren) {
+		int i, c = count;
+		for (i = 0; i < c; i++) {
+			v2f a = points[i];
+			v2f b = points[(i + 1) % c];
+			SDL_RenderDrawLine(
+				ren,
+				(int)a.x,
+				(int)a.y,
+				(int)b.x,
+				(int)b.y
+			);
+		}
+	}
+
+	std::pair<v2f*, int> normals() const {
+		int c = (count >> 1) + 1, i;
+		v2f* normals = (v2f*)malloc(c * sizeof *normals);
+		for (i = 0; i < count; i++) {
+			v2f a = points[i];
+			v2f b = points[(i + 1) % count];
+			v2f e = a - b;
+			v2f n = v2f::normalised(v2f(e.y, -e.x));
+			normals[i] = n;
+		}
+		return { normals, i };
+	}
+};
+
+bool intersect(Shape& a, Shape& b) {
+	bool r = true;
+	int i;
+	auto[fn, fnc] = a.normals();
+	auto[sn, snc] = b.normals();
+	auto project = [](const Shape& shape, v2f axis) {
+		int i;
+		float mini =  INFINITY;
+		float maxi = -INFINITY;
+		for (i = 0; i < shape.count; i++) {
+			v2f p = shape.points[i];
+			float d = v2f::dot(p, axis);
+			if (d < mini) mini = d;
+			if (d > maxi) maxi = d;
+		}
+		return std::pair<float, float>{ mini, maxi };
+	};
+	for (i = 0; i < fnc; i++) {
+		v2f axis = fn[i];
+		auto [fp1, fp2] = project(a, axis);
+		auto [sp1, sp2] = project(b, axis);
+		if (fp2 > sp1 && fp1 > sp2) {
+			r = false;
+			goto end;
+		}
+	}
+	for (i = 0; i < snc; i++) {
+		v2f axis = sn[i];
+		auto [fp1, fp2] = project(a, axis);
+		auto [sp1, sp2] = project(b, axis);
+		if (fp2 > sp1 && fp1 > sp2) {
+			r = false;
+			goto end;
+		}
+	}
+end:
+	free(fn);
+	free(sn);
+	return r;
+}
+
+int main(int argc, const char** argv) {
+	int r = 1;
+	SDL_Window* window;
+	SDL_Renderer* ren;
+	SDL_Init(SDL_INIT_VIDEO | SDL_INIT_AUDIO | SDL_INIT_JOYSTICK);
+	SDL_CreateWindowAndRenderer(
+		800,
+		800,
+		0,
+		&window,
+		&ren
+	);
+	Shape a({
+		v2f(300.0f, 300.0f),
+		v2f(400.0f, 400.0f),
+		v2f(250.0f, 500.0f),
+	});
+	Shape tri({
+		v2f(0.0f, 0.0f),
+		v2f(50.0f, 200.0f),
+		v2f(200.0f, 100.0f),
+	});
+	while (r) {
+		int i;
+		SDL_Event e;
+		while (SDL_PollEvent(&e)) {
+			switch (e.type) {
+				case SDL_QUIT:
+					r = 0;
+					break;
+			}
+		}
+		int mx, my;
+		SDL_GetMouseState(&mx, &my);
+		Shape b(tri);
+		for (i = 0; i < b.count; i++) {
+			v2f& p = b.points[i];
+			p.x += mx;
+			p.y += my;
+		}
+		SDL_SetRenderDrawColor(ren, 0x00, 0x00, 0x00, 0x00);
+		SDL_RenderClear(ren);
+		SDL_SetRenderDrawColor(ren, 0xff, 0x00, 0xff, 0xff);
+		a.render(ren);
+		if (intersect(a, b)) {
+			SDL_SetRenderDrawColor(ren, 0xff, 0x00, 0x00, 0xff);
+		}
+		b.render(ren);
+		SDL_RenderPresent(ren);
+	}
+	SDL_DestroyRenderer(ren);
+	SDL_DestroyWindow(window);
+	SDL_Quit();
+	return 0;
+}