Minecraft的爆炸算法

MC中的爆炸其实挺科学的，在空中爆炸冲击波传得远，破坏范围比较大；在地面爆炸破坏范围小但是破坏深度较深

不科学的地方是它的爆炸范围是正方体，只不过一般范围小到看不出是正方体。至于为什么MOD里的核弹爆炸范围是球体，那是别人重新实现了爆炸函数把范围改掉了…

类名net.minecraft.world.World

    /**     * Creates an explosion. Args: entity, x, y, z, strength     */    public Explosion createExplosion(Entity entityIn, double x, double y, double z, float strength, boolean isSmoking)    {        return this.newExplosion(entityIn, x, y, z, strength, false, isSmoking);    }    /**     * returns a new explosion. Does initiation (at time of writing Explosion is not finished)     */    // isFlaming影响是否着火，isSmoking影响是否生成粒子和破坏方块    public Explosion newExplosion(Entity entityIn, double x, double y, double z, float strength, boolean isFlaming, boolean isSmoking)    {        Explosion explosion = new Explosion(this, entityIn, x, y, z, strength, isFlaming, isSmoking);        if (net.minecraftforge.event.ForgeEventFactory.onExplosionStart(this, explosion)) return explosion;        // 第一阶段，计算被破坏的方块，伤害实体        explosion.doExplosionA();        // 第二阶段，破坏方块，生成粒子效果和掉落物        explosion.doExplosionB(true);        return explosion;    }

类名net.minecraft.world.Explosion

    public Explosion(World worldIn, Entity p_i45754_2_, double p_i45754_3_, double p_i45754_5_, double p_i45754_7_, float size, boolean p_i45754_10_, boolean p_i45754_11_)    {        this.explosionRNG = new Random();        this.affectedBlockPositions = Lists.<BlockPos>newArrayList();        this.playerKnockbackMap = Maps.<EntityPlayer, Vec3>newHashMap();        this.worldObj = worldIn;        this.exploder = p_i45754_2_;        // 就是上面的strength        this.explosionSize = size;        this.explosionX = p_i45754_3_;        this.explosionY = p_i45754_5_;        this.explosionZ = p_i45754_7_;        this.isFlaming = p_i45754_10_;        this.isSmoking = p_i45754_11_;        this.position = new Vec3(explosionX, explosionY, explosionZ);    }    /**     * Does the first part of the explosion (destroy blocks)     */    public void doExplosionA()    {        Set<BlockPos> blocksToDestroy = Sets.<BlockPos>newHashSet();        // 遍历16*16*16正方体边界上各点，从中心向边界连线，计算是否破坏连线上的方块        // 由于这里正方体尺寸写死了，如果爆炸范围太大边界就会有些方块没有遍历到        for (int x = 0; x < 16; ++x)        {            for (int y = 0; y < 16; ++y)            {                for (int z = 0; z < 16; ++z)                {                    // 在边界                    if (x == 0 || x == 15 || y == 0 || y == 15 || z == 0 || z == 15)                    {                        // 这里只有-1或1两个取值                        double xStep = (double)((float)x / 15.0F * 2.0F - 1.0F);                        double yStep = (double)((float)y / 15.0F * 2.0F - 1.0F);                        double zStep = (double)((float)z / 15.0F * 2.0F - 1.0F);                        // 归一化                        double step = Math.sqrt(xStep * xStep + yStep * yStep + zStep * zStep);                        xStep = xStep / step;                        yStep = yStep / step;                        zStep = zStep / step;                        // 当前爆炸强度，随着距离和经过的方块衰减                        float strength = this.explosionSize * (0.7F + this.worldObj.rand.nextFloat() * 0.6F);                        double blockX = this.explosionX;                        double blockY = this.explosionY;                        double blockZ = this.explosionZ;                        for (; strength > 0.0F; strength -= 0.22500001F)                        {                            BlockPos blockPos = new BlockPos(blockX, blockY, blockZ);                            IBlockState block = this.worldObj.getBlockState(blockPos);                            // 爆炸强度衰减                            if (block.getBlock().getMaterial() != Material.air)                            {                                float resistance = this.exploder != null ? this.exploder.getExplosionResistance(this, this.worldObj, blockPos, block) : block.getBlock().getExplosionResistance(worldObj, blockPos, (Entity)null, this);                                strength -= (resistance + 0.3F) * 0.3F;                            }                            // 把这个方块加入准备破坏的方块                            if (strength > 0.0F && (this.exploder == null || this.exploder.verifyExplosion(this, this.worldObj, blockPos, block, strength)))                            {                                blocksToDestroy.add(blockPos);                            }                            blockX += xStep * 0.30000001192092896D;                            blockY += yStep * 0.30000001192092896D;                            blockZ += zStep * 0.30000001192092896D;                        }                    }                }            }        }        // 把set转为array        this.affectedBlockPositions.addAll(blocksToDestroy);        // 接下来伤害实体        // 取包围盒内的实体        float explosionSize = this.explosionSize * 2.0F;        int minX = MathHelper.floor_double(this.explosionX - (double)explosionSize - 1.0D);        int maxX = MathHelper.floor_double(this.explosionX + (double)explosionSize + 1.0D);        int minY = MathHelper.floor_double(this.explosionY - (double)explosionSize - 1.0D);        int maxY = MathHelper.floor_double(this.explosionY + (double)explosionSize + 1.0D);        int minZ = MathHelper.floor_double(this.explosionZ - (double)explosionSize - 1.0D);        int maxZ = MathHelper.floor_double(this.explosionZ + (double)explosionSize + 1.0D);        List<Entity> entityList = this.worldObj.getEntitiesWithinAABBExcludingEntity(this.exploder, new AxisAlignedBB((double)minX, (double)minY, (double)minZ, (double)maxX, (double)maxY, (double)maxZ));        net.minecraftforge.event.ForgeEventFactory.onExplosionDetonate(this.worldObj, this, entityList, explosionSize);        Vec3 vec3 = new Vec3(this.explosionX, this.explosionY, this.explosionZ);        for (int i = 0; i < entityList.size(); ++i)        {            Entity entity = (Entity)entityList.get(i);            // 实体不免疫爆炸            if (!entity.isImmuneToExplosions())            {                // 用来判断是否在爆炸范围内的距离                double _dist = entity.getDistance(this.explosionX, this.explosionY, this.explosionZ) / (double)explosionSize;                if (_dist <= 1.0D)                {                    // 用来计算击退方向的距离                    double xDist = entity.posX - this.explosionX;                    double yDist = entity.posY + (double)entity.getEyeHeight() - this.explosionY;                    double zDist = entity.posZ - this.explosionZ;                    double dist = (double)MathHelper.sqrt_double(xDist * xDist + yDist * yDist + zDist * zDist);                    if (dist != 0.0D) // 这句基本没用，只是防止除数为0吧                    {                        // 归一化                        xDist = xDist / dist;                        yDist = yDist / dist;                        zDist = zDist / dist;                        // 从爆炸中心到实体边界上各点连线，中间没有方块挡住的比例，即实体受到爆炸影响的比例                        double strengthScale = (double)this.worldObj.getBlockDensity(vec3, entity.getEntityBoundingBox());                        double strength = (1.0D - _dist) * strengthScale;                        // 伤害实体                        entity.attackEntityFrom(DamageSource.setExplosionSource(this), (float)((int)((strength * strength + strength) / 2.0D * 8.0D * (double)explosionSize + 1.0D)));                        // 击退，附魔爆炸保护会减少击退                        double motionScale = EnchantmentProtection.func_92092_a(entity, strength);                        entity.motionX += xDist * motionScale;                        entity.motionY += yDist * motionScale;                        entity.motionZ += zDist * motionScale;                        // 记录玩家击退                        if (entity instanceof EntityPlayer && !((EntityPlayer)entity).capabilities.disableDamage)                        {                            this.playerKnockbackMap.put((EntityPlayer)entity, new Vec3(xDist * strength, yDist * strength, zDist * strength));                        }                    }                }            }        }    }    /**     * Does the second part of the explosion (sound, particles, drop spawn)     */    public void doExplosionB(boolean spawnParticles)    {        // 播放爆炸音效        this.worldObj.playSoundEffect(this.explosionX, this.explosionY, this.explosionZ, "random.explode", 4.0F, (1.0F + (this.worldObj.rand.nextFloat() - this.worldObj.rand.nextFloat()) * 0.2F) * 0.7F);        // 生成大爆炸粒子效果        if (this.explosionSize >= 2.0F && this.isSmoking)        {            this.worldObj.spawnParticle(EnumParticleTypes.EXPLOSION_HUGE, this.explosionX, this.explosionY, this.explosionZ, 1.0D, 0.0D, 0.0D, new int[0]);        }        else        {            this.worldObj.spawnParticle(EnumParticleTypes.EXPLOSION_LARGE, this.explosionX, this.explosionY, this.explosionZ, 1.0D, 0.0D, 0.0D, new int[0]);        }        // 破坏方块        if (this.isSmoking)        {            // 遍历被破坏的方块            for (BlockPos blockpos : this.affectedBlockPositions)            {                Block block = this.worldObj.getBlockState(blockpos).getBlock();                // 生成爆炸和烟粒子效果                if (spawnParticles)                {                    double x = (double)((float)blockpos.getX() + this.worldObj.rand.nextFloat());                    double y = (double)((float)blockpos.getY() + this.worldObj.rand.nextFloat());                    double z = (double)((float)blockpos.getZ() + this.worldObj.rand.nextFloat());                    double xDist = x - this.explosionX;                    double yDist = y - this.explosionY;                    double zDist = z - this.explosionZ;                    double dist = (double)MathHelper.sqrt_double(xDist * xDist + yDist * yDist + zDist * zDist);                    // 归一化                    xDist = xDist / dist;                    yDist = yDist / dist;                    zDist = zDist / dist;                    double distScale = 0.5D / (dist / (double)this.explosionSize + 0.1D);                    distScale = distScale * (double)(this.worldObj.rand.nextFloat() * this.worldObj.rand.nextFloat() + 0.3F);                    xDist = xDist * distScale;                    yDist = yDist * distScale;                    zDist = zDist * distScale;                    this.worldObj.spawnParticle(EnumParticleTypes.EXPLOSION_NORMAL, (x + this.explosionX ) / 2.0D, (y + this.explosionY) / 2.0D, (z + this.explosionZ) / 2.0D, xDist, yDist, zDist, new int[0]);                    this.worldObj.spawnParticle(EnumParticleTypes.SMOKE_NORMAL, x, y, z, xDist, yDist, zDist, new int[0]);                }                // 破坏方块                if (block.getMaterial() != Material.air)                {                    if (block.canDropFromExplosion(this))                    {                        block.dropBlockAsItemWithChance(this.worldObj, blockpos, this.worldObj.getBlockState(blockpos), 1.0F / this.explosionSize, 0);                    }                    block.onBlockExploded(this.worldObj, blockpos, this);                }            }        }        // 着火        if (this.isFlaming)        {            for (BlockPos blockpos1 : this.affectedBlockPositions)            {                if (   this.worldObj.getBlockState(blockpos1).getBlock().getMaterial() == Material.air                    && this.worldObj.getBlockState(blockpos1.down()).getBlock().isFullBlock()                    && this.explosionRNG.nextInt(3) == 0)                {                    this.worldObj.setBlockState(blockpos1, Blocks.fire.getDefaultState());                }            }        }    }

这个函数用来计算实体暴露给爆炸中心的比例，代表受到爆炸的影响

类名net.minecraft.world.World

    /**     * Gets the percentage of real blocks within within a bounding box, along a specified vector.     */    public float getBlockDensity(Vec3 vec, AxisAlignedBB bb)    {        double xStep = 1.0D / ((bb.maxX - bb.minX) * 2.0D + 1.0D);        double yStep = 1.0D / ((bb.maxY - bb.minY) * 2.0D + 1.0D);        double zStep = 1.0D / ((bb.maxZ - bb.minZ) * 2.0D + 1.0D);        double xOffset = (1.0D - Math.floor(1.0D / xStep) * xStep) / 2.0D;        double zOffset = (1.0D - Math.floor(1.0D / zStep) * zStep) / 2.0D;        if (xStep >= 0.0D && yStep >= 0.0D && zStep >= 0.0D)        {            int noBlockLines = 0;            int totalLines = 0;            // xt、yt、zt为插值参数            for (float xt = 0.0F; xt <= 1.0F; xt = (float)((double)xt + xStep))            {                for (float yt = 0.0F; yt <= 1.0F; yt = (float)((double)yt + yStep))                {                    for (float zt = 0.0F; zt <= 1.0F; zt = (float)((double)zt + zStep))                    {                        double x = bb.minX + (bb.maxX - bb.minX) * (double)xt;                        double y = bb.minY + (bb.maxY - bb.minY) * (double)yt;                        double z = bb.minZ + (bb.maxZ - bb.minZ) * (double)zt;                        // 爆炸中心到包围盒上这个点之间没有方块。rayTraceBlocks在我之前的博文逆向过了                        if (this.rayTraceBlocks(new Vec3(x + xOffset, y, z + zOffset), vec) == null)                        {                            ++noBlockLines;                        }                        ++totalLines;                    }                }            }            return (float)noBlockLines / (float)totalLines;        }        else        {            return 0.0F;        }    }