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 前面我们的攻击手段比较单一，虽然已经分出了 EnemyT1 / EnemyT2 / EnemyT3， 但里面还是基本一样的。这回，我们尝试实现一些新的攻击方法，实现一些新的算法。

1、前面我们小飞机EnemyT1 的攻击方式是垂直向下发射子弹。

那么大飞机EnemyT2的攻击手段就更高级一些，我们让它能够瞄准玩家射击。

大飞机EnemyT2发射子弹是EnemyT2类的私有方法，想要让他能够瞄准玩家，就要知道玩家在哪里。还记得前面我们做的数据仓库么。这回用上了。

我们修改EnemyT2的createBulletObject函数：

void EnemyT2::createBulletObject(PlaneObject_t *target) {BulletObject_t *but1 = new BulletObject_t();but1->x = baseInfo.x - PlaneXYScale;but1->y = baseInfo.y + PlaneXYScale * 2;but1->visiable = 1;int sum = abs(target->x - but1->x) + abs(target->y - but1->y);but1->speedX = 300 * (target->x - but1->x) / sum;but1->speedY = 300 * (target->y - but1->y) / sum;getRainbowColor(&but1->color, 200);ListPushBack(enemyBulletList, (LTDataType) but1);
}uint8_t EnemyT2::tick(uint32_t t) {。。。if (fireTimer.tick(t)) {if (((PlaneObject_t*) DataBulk::GetInstance()->data1)->visiable)createBulletObject((PlaneObject_t*) DataBulk::GetInstance()->data1);if (((PlaneObject_t*) DataBulk::GetInstance()->data2)->visiable)createBulletObject((PlaneObject_t*) DataBulk::GetInstance()->data2);}。。。
}

注意确定子弹方向的算法：

    int sum = abs(target->x - but1->x) + abs(target->y - but1->y);

    but1->speedX = 300 * (target->x - but1->x) / sum;
    but1->speedY = 300 * (target->y - but1->y) / sum;

300是子弹速度。

简单通过相似三角形来确定方向和速度，不是很精确，但也足够用了。如果要精确的话，需要用三角函数算分速度，太复杂，没必要。

2、Boss肯定要更强大，我们要让他同时向多个方向发射散弹，同时发射一颗能追踪的导弹。

先给他发射散弹：

void EnemyT3::createBulletObject(int speedX) {PlaneObject_t *but1 = new PlaneObject_t();but1->x = baseInfo.x - PlaneXYScale * 2;but1->y = baseInfo.y + PlaneXYScale;but1->speedX = speedX;but1->speedY = 300 - abs(speedX);but1->visiable = 1;but1->color = 0xe01000;ListPushBack(enemyBulletList, (LTDataType) but1);
}uint8_t EnemyT3::tick(uint32_t t) {animationStoryBoard->tick(t);if (fireTimer.tick(t)) {createBulletObject(-120);createBulletObject(-70);createBulletObject(-30);createBulletObject(0);createBulletObject(30);createBulletObject(70);createBulletObject(120);}for (ListNode *node = animationList->next; node != animationList; node =node->next) {if (((Animation*) node->data)->isValid) {((Animation*) node->data)->tick(t);}}return 0;
}

追踪导弹不是直线运动，所以要单独一个链表 enemyRocketList，单独的算法：

class BulletManager {
public:BulletManager();virtual ~BulletManager();uint8_t tick(uint32_t t);void init();uint8_t show(void);ListNode *player1BulletList;ListNode *player2BulletList;ListNode *enemyBulletList;ListNode *enemyRocketList;
private:void tickOnce(ListNode *list, uint32_t t);void showOnce(ListNode *list);void destoryOnce(ListNode *list);void tickRocket(uint32_t t);
};

void BulletManager::tickRocket(uint32_t t) {for (ListNode *cur = enemyRocketList->next; cur != enemyRocketList; cur =cur->next) {PlaneObject_t *bullet = (PlaneObject_t*) (cur->data);PlaneObject_t *target =bullet->tag == 1 ? Player1BaseInfo : Player2BaseInfo;int sum = abs(target->x - bullet->x) + abs(target->y - bullet->y);bullet->speedX = 50 * (target->x - bullet->x) / sum;bullet->speedY = 50 * (target->y - bullet->y) / sum;bullet->x += bullet->speedX * t;bullet->y += bullet->speedY * t;}
}uint8_t BulletManager::tick(uint32_t t) {tickOnce(player1BulletList, t);tickOnce(player2BulletList, t);tickOnce(enemyBulletList, t);tickRocket(t);return 0;
}

然后发射导弹：

void EnemyT3::createRocketObject(int target) {PlaneObject_t *but1 = new PlaneObject_t();but1->x = baseInfo.x - PlaneXYScale * 2;but1->y = baseInfo.y + PlaneXYScale;but1->visiable = 1;but1->color = 0xe01000;but1->tag = target;ListPushBack(EnemyRocketList, (LTDataType) but1);
}
uint8_t EnemyT3::tick(uint32_t t) {animationStoryBoard->tick(t);if (fireTimer.tick(t)) {
。。。if (Player1BaseInfo->visiable)createRocketObject(1);if (Player2BaseInfo->visiable)createRocketObject(2);}
。。。return 0;
}

补充，为了方法，把数据的地址都在DataBulk里面管起来。

void Plane::init() {backGroundStar.init();bulletManager.init();player1.init(1);player1.bulletList = bulletManager.player1BulletList;enemyManager.init();DataBulk::GetInstance()->data1 = (intptr_t) &player1.baseInfo;DataBulk::GetInstance()->data2 = (intptr_t) &player2.baseInfo;DataBulk::GetInstance()->data3 = (intptr_t) bulletManager.player1BulletList;DataBulk::GetInstance()->data4 = (intptr_t) bulletManager.player2BulletList;DataBulk::GetInstance()->data5 = (intptr_t) bulletManager.enemyBulletList;DataBulk::GetInstance()->data6 = (intptr_t) bulletManager.enemyRocketList;}

添加宏：

PlaneDef.h

#define Player1BaseInfo ((PlaneObject_t*)DataBulk::GetInstance()->data1)
#define Player2BaseInfo ((PlaneObject_t*)DataBulk::GetInstance()->data2)
#define Player1BulletList ((ListNode*)DataBulk::GetInstance()->data3)
#define Player2BulletList ((ListNode*)DataBulk::GetInstance()->data4)
#define EnemyBulletList ((ListNode*)DataBulk::GetInstance()->data5)
#define EnemyRocketList ((ListNode*)DataBulk::GetInstance()->data6)

最后，给导弹就上生命周期：

typedef struct {int x;int y;int color;int speedX;int speedY;uint8_t visiable = 0;uint8_t width;uint8_t height;int life = 0x7fffffff;int tag;
} PlaneObject_t;

void BulletManager::tickRocket(uint32_t t) {for (ListNode *cur = enemyRocketList->next; cur != enemyRocketList; cur =cur->next) {PlaneObject_t *bullet = (PlaneObject_t*) (cur->data);bullet->life -= t;if (bullet->life < 0) {bullet->visiable = 0;continue;}PlaneObject_t *target =bullet->tag == 1 ? Player1BaseInfo : Player2BaseInfo;int sum = abs(target->x - bullet->x) + abs(target->y - bullet->y);bullet->speedX = 50 * (target->x - bullet->x) / sum;bullet->speedY = 50 * (target->y - bullet->y) / sum;bullet->x += bullet->speedX * t;bullet->y += bullet->speedY * t;}
}

三种敌机都有了足够的差异化了，不同的形状，不同的飞行方式，不同的攻击方式，甚至击毁效果都不一样。不枉我们把它们区分为3个不同的类。

下面再来考虑玩家的攻击方式。

原来只有子弹，我们给他加上炸弹和激光。

子弹击中就没有了，而炸弹和激光属于范围攻击模式，其伤害是持续性的，而且与时间有关系。先做炸弹。

设定炸弹效果为半径=7的圆，碰撞检测销毁敌方子弹，对敌机持续造成 time * 1 的伤害。每玩家只有一个在生效。

先在像素屏驱动里面补充一个单片机上常用的画圆方法，Bresenham算法。具体原理不再赘述，可自行网上搜索。

不用三角函数的函数就是好函数。

void ws2812_Fill_Circle(uint16_t x0, uint16_t y0, uint8_t r, uint32_t color) {int x = 0, y = r, d;d = 3 - 2 * r;while (x <= y) {ws2812_fill(x0 - x, y0 - y, x * 2, 1, (color & 0xff0000) >> 16,(color & 0xff00) >> 8, color & 0xff);ws2812_fill(x0 - x, y0 + y - 1, x * 2, 1, (color & 0xff0000) >> 16,(color & 0xff00) >> 8, color & 0xff);ws2812_fill(x0 - y, y0 - x, 1, x * 2, (color & 0xff0000) >> 16,(color & 0xff00) >> 8, color & 0xff);ws2812_fill(x0 + y - 1, y0 - x, 1, x * 2, (color & 0xff0000) >> 16,(color & 0xff00) >> 8, color & 0xff);if (d < 0) {d = d + 4 * x + 6;} else {d = d + 4 * (x - y) + 10;y--;}x++;}ws2812_fill(x0 - y, y0 - y, y * 2, y * 2, (color & 0xff0000) >> 16,(color & 0xff00) >> 8, color & 0xff);
}

1、定义一个结构 EffectObject_t 保存效果信息：

typedef struct {int type;int x;int y;int life = 0x7fffffff;
} EffectObject_t;

2、在玩家类里面加上爆炸效果 effectObject ：

class PlanePlayer {
public:PlanePlayer();~PlanePlayer();void init(uint8_t id);uint8_t tick(uint32_t t, uint8_t b1);uint8_t show(void);uint8_t hitDetect(int x, int y, int damage);uint8_t hitEffectDetect(int x, int y, int r);
。。。EffectObject_t *effectObject = NULL;int HP;
private:
。。。
};

3、在plane.cpp里面加上 爆炸效果的碰撞检测遍历：

void Plane::checkEffectCollision(uint32_t t, PlanePlayer *player) {if (player->effectObject == NULL)return;for (ListNode *enemy = enemyManager.enemyList->next;enemy != enemyManager.enemyList; enemy = enemy->next) {EnemyBase *ene = (EnemyBase*) enemy->data;if (ene->explodeState)continue;uint8_t res = player->hitEffectDetect(ene->baseInfo.x, ene->baseInfo.y,(ene->baseInfo.width + ene->baseInfo.height) / 3);if (res) {ene->HP -= res * t;ene->hurt();}}for (ListNode *enemyBul = bulletManager.enemyBulletList->next;enemyBul != bulletManager.enemyBulletList; enemyBul =enemyBul->next) {PlaneObject_t *bul = (PlaneObject_t*) enemyBul->data;uint8_t res = player->hitEffectDetect(bul->x, bul->y, 1);if (res) {bul->visiable = 0;}}for (ListNode *enemyBul = bulletManager.enemyRocketList->next;enemyBul != bulletManager.enemyRocketList; enemyBul =enemyBul->next) {PlaneObject_t *bul = (PlaneObject_t*) enemyBul->data;uint8_t res = player->hitEffectDetect(bul->x, bul->y, 1);if (res) {bul->visiable = 0;}}
}

注意，敌机、敌方子弹、敌方导弹都有可能被爆炸摧毁。

4、在玩家类里加上碰撞检测：

uint8_t PlanePlayer::hitEffectDetect(int x, int y, int r) {switch (effectObject->type) {case 1: {int a = (x - effectObject->x) / 100;int b = (y - effectObject->y) / 100;int c = (r + 10) * 100;return (a * a + b * b < c * c) ? 1 : 0;}}return 0;
}

5、显示玩家的，顺手显示爆炸效果：

uint8_t PlanePlayer::show(void) {if (effectObject != NULL) {ws2812_Fill_Circle(effectObject->x / PlaneXYScale,effectObject->y / PlaneXYScale, 10, 0x801000);}for (uint8_t y = 0; y < 5; y++) {for (uint8_t x = 0; x < 5; x++) {if (PlaneSharp[y][x])ws2812_pixel(x + baseInfo.x / PlaneXYScale - 2,y + baseInfo.y / PlaneXYScale - 2,(baseInfo.color >> 16) & 0xff,(baseInfo.color >> 8) & 0xff, baseInfo.color & 0xff);}}return 0;
}

TODO：其实爆炸小时不应该和显示玩家纠结在一起。如果有多种特殊武器，还是单独写个函数显示为好。

 好了，对于激光来说，激光要跟随玩家移动。增加激光特效，只要增加碰撞检测和显示两部分就行了。

激光的碰撞检测：

uint8_t PlanePlayer::hitEffectDetect(int x, int y, int r) {switch (effectObject->type) {case 1: {int a = (x - effectObject->x) / 100;int b = (y - effectObject->y) / 100;int c = (r + 10) * 100;return (a * a + b * b < c * c) ? 1 : 0;}case 2:return (x / PlaneXYScale == baseInfo.x / PlaneXYScale) ? 1 : 0;}return 0;
}

 激光的显示：

uint8_t PlanePlayer::show(void) {if (effectObject != NULL) {if (effectObject->type == 1) {ws2812_Fill_Circle(effectObject->x / PlaneXYScale,effectObject->y / PlaneXYScale, 10, 0x801000);} else {ws2812_fill(baseInfo.x / PlaneXYScale, 0, 1,baseInfo.y / PlaneXYScale, 0, 100, 200);}}for (uint8_t y = 0; y < 5; y++) {for (uint8_t x = 0; x < 5; x++) {if (PlaneSharp[y][x])ws2812_pixel(x + baseInfo.x / PlaneXYScale - 2,y + baseInfo.y / PlaneXYScale - 2,(baseInfo.color >> 16) & 0xff,(baseInfo.color >> 8) & 0xff, baseInfo.color & 0xff);}}return 0;
}

 比较一下，加一个激光特效，只要两行代码。0到1不容易，1到2快的飞起。

 最后，在玩家操作里面加上炸弹和激光：

uint8_t PlanePlayer::tick(uint32_t t, uint8_t b1) {
。。。if (effectObject == NULL) {if (b1 & KEY_BUTTON_D) {effectObject = new EffectObject_t();effectObject->x = baseInfo.x;effectObject->y =(baseInfo.y > 25 * PlaneXYScale) ?baseInfo.y - 25 * PlaneXYScale : 0;effectObject->type = 1;effectObject->life = 4000;} else if (b1 & KEY_BUTTON_A) {effectObject = new EffectObject_t();effectObject->x = baseInfo.x;effectObject->y = baseInfo.y;effectObject->type = 2;effectObject->life = 4000;}} else {effectObject->life -= t;if (effectObject->life < 0) {delete effectObject;effectObject = NULL;}}。。。return 0;
}

看看效果： 

STM32学习笔记十九：WS2812制作像素游戏屏-飞行射击游戏（9）探索道具系统