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"# Termites\n",
"\n",
"Consider a simple termite that only follows these simple rules:\n",
"\n",
"1. If you see a wood chip, and you are not carrying one, pick it up\n",
"2. If you see a wood chip, and you are carrying one, then drop it\n",
"3. Otherwise, move in your default direction \n",
"4. Every once in awhile, change direction\n",
"\n",
"Now, imagine a few of these termites roaming around a flat world, scattered with wood chips. What would happen? How can we model this world?\n",
"\n",
"## Simulation\n",
"\n",
"First, we must identify the objects we wish to model. Possibilities include: \n",
"\n",
"* termites\n",
"* world\n",
"* wood chips\n",
"\n",
"First, let's consider what properties a termite should have:\n",
"\n",
"* position in the world\n",
"* whether it is carrying a wood chip or not\n",
"* direction heading (vector, velocity on x and y)\n",
"\n",
"Also, what actions must a termite be able to do:\n",
"\n",
"* move in the world\n",
"* pick up a wood chip\n",
"* drop a wood chip\n",
"* draw itself\n",
"\n",
"We might want to add other methods, but it needs to at least support those.\n",
"\n",
"## Termite\n",
"\n",
"So, let's put together a termite class. It might look something like:\n",
"\n",
"```java\n",
"class Termite {\n",
" int x;\n",
" int y;\n",
" int vx;\n",
" int vy;\n",
" int carrying;\n",
" \n",
" Termite(int x, int y) { //constructor\n",
" this.x = int(x);\n",
" this.y = int(y);\n",
" this.randomizeDirection();\n",
" this.carrying = 0;\n",
" }\n",
"\n",
" ...\n",
"}\n",
"```\n",
"\n",
"In thinking about the world, and wood chips, it might be that representing them as an object might be overkill. For example, if we imagine the world as a 2D matrix, then we could represent the presence of food with a 1, and the absence of food with a 0. Likewise, carrying can just be a 1 (for yes), and 0 (for no).\n",
"\n",
"It may be that instead of having termites bounce off of the walls (like a ball simulation) that we instead have them \"wrap\" around (like a [torus](https://en.wikipedia.org/wiki/Torus)). For example, if a termite goes too far to the left, it will wrap around to the right, and instantly appear there. Likewise, if a turtle goes below 0 or above height, then it wraps back around. Thus, we implement an infinite, repeating surface.\n",
"\n",
"This putting it all together might look like the following. \n",
"\n",
"Note:\n",
"\n",
"* termites are represented by ovals. You could make them face the correct direction, or draw legs on them.\n",
"* termites turn red when they are carrying a wood chip\n",
"* wood chips are represented by red squares"
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"Termite [] termites; // the array of termites; we'll decide how many later\n",
"int[][] gworld; // the 2D world\n",
"int RADIUS = 5; // distance that we can sense a wood chip\n",
"\n",
"class Termite {\n",
" int x;\n",
" int y;\n",
" int vx;\n",
" int vy;\n",
" int carrying; // zero - not carying chip; 1 - carrying chip\n",
" \n",
" Termite(int x, int y) {\n",
" this.x = int(x);\n",
" this.y = int(y);\n",
" this.randomizeDirection();\n",
" this.carrying = 0;\n",
" }\n",
" \n",
" void draw() {\n",
" if (this.carrying == 0) {\n",
" fill(0);\n",
" } else {\n",
" fill(255, 0, 0);\n",
" }\n",
" ellipse(this.x, this.y, 10, 5);\n",
" }\n",
" \n",
" int get_x(int delta) {\n",
" int dx = this.x + delta;\n",
" if (dx >= width)\n",
" dx -= width;\n",
" if (dx < 0)\n",
" dx += width;\n",
" return dx;\n",
" }\n",
" \n",
" int get_y(int delta) {\n",
" int dy = this.y + delta;\n",
" if (dy >= height)\n",
" dy -= height;\n",
" if (dy < 0)\n",
" dy += height;\n",
" return dy;\n",
" }\n",
" \n",
" void step() {\n",
" this.x = this.get_x(this.vx);\n",
" this.y = this.get_y(this.vy);\n",
" }\n",
" \n",
" void randomizeDirection() {\n",
" this.vx = 0;\n",
" this.vy = 0;\n",
" while (this.vx == 0 && this.vy == 0) {\n",
" this.vx = floor(random(3)) - 1;\n",
" this.vy = floor(random(3)) - 1;\n",
" }\n",
" }\n",
" \n",
" void pickup_chip(int nx, int ny) {\n",
" // Pick it up!\n",
" world[nx][ny] = 0;\n",
" this.carrying = 1;\n",
" }\n",
" \n",
" void drop_chip(int nx, int ny) {\n",
" // Drop it!\n",
" world[nx][ny] = 1;\n",
" this.carrying = 0;\n",
" }\n",
"\n",
" void move() {\n",
" if (random() < .01) { // 1% of the time, change directions\n",
" this.randomizeDirection();\n",
" }\n",
" this.step();\n",
" // not carrying a woodchip\n",
" if (this.carrying == 0) { // can you smell a chip?\n",
" for (int i = -RADIUS; i <= RADIUS; i++) {\n",
" if (this.carrying == 0) {\n",
" for (int j = -RADIUS; j <= RADIUS; j++) {\n",
" nx = this.get_x(i);\n",
" ny = this.get_y(j);\n",
" if (world[nx][ny] == 1) { // yes!\n",
" this.pickup_chip(nx, ny);\n",
" break;\n",
" }\n",
" }\n",
" }\n",
" }\n",
" } else { // carrying a woodchip\n",
" // is there a chip nearby?\n",
" boolean found = false;\n",
" for (int i = -1; i <= 1; i++) { \n",
" if (!found) {\n",
" for (int j = -1; j <= 1; j++) {\n",
" nx = this.get_x(i);\n",
" ny = this.get_y(j);\n",
" if (world[nx][ny] == 1) { // yes!\n",
" // One nearby!\n",
" found = true; \n",
" break;\n",
" }\n",
" }\n",
" }\n",
" }\n",
" if (found) {\n",
" // now, find an empty spot nearby and drop it! \n",
" for (int i = -1; i <= 1; i++) {\n",
" if (this.carrying == 1) {\n",
" for (int j = -1; j <= 1; j++) {\n",
" nx = this.get_x(i);\n",
" ny = this.get_y(j);\n",
" if (world[nx][ny] == 0) {\n",
" // Drop it!\n",
" this.drop_chip(nx, ny);\n",
" break;\n",
" }\n",
" }\n",
" }\n",
" }\n",
" }\n",
" if (this.carrying == 0) {\n",
" // head in opposite direction\n",
" this.vx = -this.vx;\n",
" this.vy = -this.vy;\n",
" // make sure you are far enough away\n",
" for (int i = 0; i < RADIUS * 1.5; i++) {\n",
" this.step();\n",
" }\n",
" }\n",
" }\n",
" }\n",
"}\n",
"\n",
"void setup() {\n",
" size(250, 250); // the world\n",
" termites = new Termite[10]; // start termites\n",
" for (int i =0; i < termites.length; i++) {\n",
" termites[i] = new Termite(random(width), random(height));\n",
" }\n",
" world = new int[width][height]; // match the canvas size\n",
" for (int i =0; i < width; i++) {\n",
" for (int j =0; j < height; j++) {\n",
" world[i][j] = 0;\n",
" }\n",
" }\n",
" for (int i =0; i < 200; i++) { // put some wood chips out:\n",
" world[int(random(width))][int(random(height))] = 1;\n",
" }\n",
"}\n",
"\n",
"void draw() {\n",
" background();\n",
" noStroke();\n",
" // Move the termites:\n",
" for (int i =0; i < termites.length; i++) {\n",
" termites[i].move();\n",
" termites[i].draw();\n",
" } \n",
" // Draw them:\n",
" for (int i =0; i < width; i++) {\n",
" for (int j =0; j < height; j++) {\n",
" if (world[i][j] == 1) {\n",
" fill(255, 0, 0);\n",
" rect(i, j, 3, 3);\n",
" }\n",
" }\n",
" }\n",
"}"
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