tree.c

#include "raylib.h"
#include <math.h>

const int WIDTH = 1800;
const int HEIGHT = 900;

const float MIN_ANGLE = 0.0f;
const float MAX_ANGLE = M_PI/1.5;

void DrawTree(float, float, float, float);

float da;
float a_off;

int main(void) {
    InitWindow(WIDTH, HEIGHT, "Fractal tree");
    SetTargetFPS(60);
    da = M_PI / 4;
    a_off = 0.0f;
    Vector2 pos;
    while (!WindowShouldClose()) {
        pos = GetMousePosition();
        da = (MAX_ANGLE - MIN_ANGLE) * (pos.y / HEIGHT) + MIN_ANGLE;
        a_off = (M_PI / 2) * ((pos.x - WIDTH/2) / WIDTH);
        BeginDrawing();
        ClearBackground(BLACK);
        DrawTree(WIDTH/2, HEIGHT, HEIGHT/3, M_PI/2.0);
        EndDrawing();
    }
    CloseWindow();
    return 0;
}


void DrawTree(float x, float y, float len, float a) {
    float tx = x + cosf(a) * len;
    float ty = y - sinf(a) * len;

    Color c = WHITE;
    if (len < 6.0f) {
        c = GREEN;
    }

    DrawLine((int)x, (int)y, (int)tx, (int)ty, c);

    if (len < 2.0f) {
        return;
    }

    DrawTree(tx, ty, len*0.67, a - da - a_off);
    DrawTree(tx, ty, len*0.67, a + da - a_off);
}