From 7a94db13839b69bf76f881471a1bf32ae32b8b0f Mon Sep 17 00:00:00 2001
From: Matt Low <mattjlow94@gmail.com>
Date: Thu, 30 Jan 2020 22:58:29 +0400
Subject: [PATCH] Add sharing asteroids methods

---
 core/src/com/me/asteroids/EntityFactory.java | 86 ++++++++++++++++++++
 1 file changed, 86 insertions(+)

diff --git a/core/src/com/me/asteroids/EntityFactory.java b/core/src/com/me/asteroids/EntityFactory.java
index b81441d..f7ac934 100644
--- a/core/src/com/me/asteroids/EntityFactory.java
+++ b/core/src/com/me/asteroids/EntityFactory.java
@@ -251,4 +251,90 @@ public class EntityFactory {
         return entities;
     }
 
+    public static PolygonModel[] getPolygonShards(PolygonModel model, int shardCount) {
+        PolygonModel[] shards = new PolygonModel[shardCount];
+        Vector2 position = tmp.set(model.getPosition());
+        float[] vertices = model.getVertices();
+
+        int verticesPerShard = vertices.length / (shardCount * 2);
+        int remaining = vertices.length % (shardCount * 2);
+
+        int vertice = 0;
+        for (int i = 0; i < shardCount; i++) {
+            if (i + 1 == shardCount && remaining > 0) {
+                // Put the remaining vertices onto the last shard
+                verticesPerShard += remaining / 2;
+            }
+
+            float[] shardVertices = new float[(verticesPerShard + 1) * 2];
+            shardVertices[0] = 0;
+            shardVertices[1] = 0;
+            float minX = shardVertices[0], maxX = shardVertices[0];
+            float minY = shardVertices[1], maxY = shardVertices[1];
+            for (int j = 2, n = shardVertices.length; j < n; j += 2) {
+                float x = shardVertices[j] = vertices[vertice++] - position.x;
+                float y = shardVertices[j + 1] = vertices[vertice++] - position.y;
+                minX = x < minX ? x : minX;
+                maxX = x > maxX ? x : maxX;
+                minY = y < minY ? y : minY;
+                maxY = y > maxY ? y : maxY;
+            }
+
+            float centerX = minX + ((maxX - minX) / 2);
+            float centerY = minY + ((maxY - minY) / 2);
+
+            for (int j = 0, n = shardVertices.length; j < n; j += 2) {
+                shardVertices[j] -= centerX;
+                shardVertices[j + 1] -= centerY;
+            }
+
+            PolygonModel shard = new PolygonModel(model.getColor());
+            shard.setVertices(shardVertices);
+            shard.setPosition(tmp2.set(position).add(centerX, centerY));
+            shards[i] = shard;
+        }
+
+        return shards;
+    }
+
+    public static Entity[] splitAsteroidIntoShards(Engine engine, Entity asteroid, int shardCount) {
+        Entity[] entities = new Entity[shardCount];
+        PolygonModel asteroidModel = (PolygonModel) asteroid.getComponent(ModelComponent.class).model;
+        PolygonModel[] shards = getPolygonShards(asteroidModel, shardCount);
+        Vector2 asteroidPosition = asteroidModel.getPosition();
+        Vector2 asteroidVelocity = asteroid.getComponent(VelocityComponent.class).velocity;
+        int generation = asteroid.getComponent(AsteroidComponent.class).generation;
+
+        for (int i = 0; i < entities.length; i++) {
+            ModelComponent model = new ModelComponent();
+            model.model = shards[i];
+
+            PositionComponent position = new PositionComponent();
+            position.position = new Vector2(model.model.getPosition());
+            position.rotation = 90;
+
+            VelocityComponent velocity = new VelocityComponent();
+            velocity.velocity = new Vector2(shards[i].getPosition())
+                    .sub(asteroidPosition)
+                    .nor()
+                    .rotate(rand.nextFloat(-15, 15))            // Slightly alter the direction each piece flies off in
+                    .scl(asteroidVelocity.len() * 1f)           // Set speed to asteroid's original velocity
+                    .add(tmp2.set(asteroidVelocity).scl(0.25f));
+            velocity.angularVelocity = rand.nextFloat(-30, 30);
+
+            AsteroidComponent asteroidComponent = new AsteroidComponent();
+            asteroidComponent.generation = generation + 1;
+
+            Entity entity = createEntity(engine);
+            entity.addComponent(model);
+            entity.addComponent(position);
+            entity.addComponent(velocity);
+            entity.addComponent(asteroidComponent);
+            entity.addComponent(COLLIDER);
+            entities[i] = entity;
+        }
+
+        return entities;
+    }
+
 }