202 lines
6.1 KiB
Markdown
202 lines
6.1 KiB
Markdown
---
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front: https://nie.res.netease.com/r/pic/20211104/69055361-2e7a-452f-8b1a-f23e1262a03a.jpg
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hard: 高级
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time: 25分钟
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---
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# 挑战：设计一个烟花粒子
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在本节中，我们一起来制作一个烟花粒子。根据我们的生活经验，烟花的绽放一般分为升起和炸裂两部分。因此，我们分别制作升起和炸裂粒子，然后通过粒子事件将它们联系在一起。
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## 制作升起粒子
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我们在Snowstorm中新建一个粒子，命名为`tutorial_demo:firework_rise`。
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我们模仿加载粒子，设置一个变量以代表粒子大小。
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我们设置为稳定喷射粒子的模式，并将发射器生命周期改为**Once**（**单次**）。毕竟我们不像让烟花升起后“再升起一次”。激活时间设为5秒，同时形状的偏移量的纵向上设置为`variable.emitter_age`。所以我们的烟花会上升5米，速度1米/秒。
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我们采用和加载粒子相同的纹理，然后每个粒子的最大年龄设置为1，并采用和加载粒子相同的粒子大小变化方式，即1秒后由大到小完全消失。最后，我们将颜色设置成红色。
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因此，我们得到了如下的JSON文件：
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```json
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{
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"format_version": "1.10.0",
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"particle_effect": {
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"description": {
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"identifier": "tutorial_demo:firework_rise",
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"basic_render_parameters": {
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"material": "particles_alpha",
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"texture": "textures/particle/particles"
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}
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},
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"components": {
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"minecraft:emitter_initialization": {
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"creation_expression": "variable.size = 0.08;"
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},
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"minecraft:emitter_rate_steady": {
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"spawn_rate": 31,
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"max_particles": 60
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},
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"minecraft:emitter_lifetime_once": {
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"active_time": 5
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},
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"minecraft:emitter_shape_point": {
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"offset": [0, "variable.emitter_age", 0]
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},
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"minecraft:particle_lifetime_expression": {
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"max_lifetime": 1
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},
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"minecraft:particle_initial_speed": 0,
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"minecraft:particle_motion_dynamic": {},
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"minecraft:particle_appearance_billboard": {
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"size": ["variable.size*(1-variable.particle_age)", "variable.size*(1-variable.particle_age)"],
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"facing_camera_mode": "rotate_xyz",
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"uv": {
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"texture_width": 128,
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"texture_height": 128,
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"uv": [32, 88],
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"uv_size": [8, 8]
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}
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},
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"minecraft:particle_appearance_tinting": {
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"color": [0.93725, 0.32157, 0.32157, 1]
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}
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}
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}
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}
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```
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## 制作炸裂粒子
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我们在Snowstorm中新建第二个粒子，命名为`tutorial_demo:firework_crack`。
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同样，我们新建一个`variable.size`变量。
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我们希望很多粒子同时在某一点炸开，所以我们设置为Instant（瞬时）模式。同时发射器向上偏移5米，因为这是升起粒子的终点位置。
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除了和升起粒子一样的部分外，我们设置粒子的运动模拟。我们将运动方向设置为Outwards（向外），然后加速度三个轴上皆设置为-2。
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这样，我们便得到了炸裂的粒子：
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```json
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{
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"format_version": "1.10.0",
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"particle_effect": {
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"description": {
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"identifier": "tutorial_demo:firework_crack",
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"basic_render_parameters": {
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"material": "particles_alpha",
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"texture": "textures/particle/particles"
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}
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},
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"components": {
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"minecraft:emitter_initialization": {
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"creation_expression": "variable.size = 0.08;"
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},
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"minecraft:emitter_rate_instant": {
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"num_particles": 600
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},
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"minecraft:emitter_lifetime_once": {
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"active_time": 1
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},
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"minecraft:emitter_shape_sphere": {
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"offset": [0, 5, 0],
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"radius": 2,
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"direction": "outwards"
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},
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"minecraft:particle_lifetime_expression": {
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"max_lifetime": 1
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},
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"minecraft:particle_initial_speed": 2,
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"minecraft:particle_motion_dynamic": {
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"linear_acceleration": [-2, -2, -2]
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},
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"minecraft:particle_appearance_billboard": {
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"size": ["variable.size*(1-variable.particle_age)", "variable.size*(1-variable.particle_age)"],
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"facing_camera_mode": "lookat_xyz",
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"uv": {
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"texture_width": 128,
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"texture_height": 128,
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"uv": [32, 88],
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"uv_size": [8, 8]
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}
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},
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"minecraft:particle_appearance_tinting": {
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"color": [0.93725, 0.32157, 0.32157, 1]
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}
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}
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}
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}
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```
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最后，我们将两个粒子拼合在一起。我们通过`minecraft:emitter_lifetime_events`组件来触发执行两个粒子的事件。我们手动创建`firework.particle.json`文件，并写入如下内容：
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```json
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{
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"format_version": "1.10.0",
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"particle_effect": {
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"description": {
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"identifier": "tutorial_demo:firework",
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"basic_render_parameters": {
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"material": "particles_alpha",
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"texture": "textures/particle/particles"
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}
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},
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"components": {
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"minecraft:emitter_lifetime_events": {
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"creation_event": "rise",
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"timeline": {
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"5.0": "crack"
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}
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},
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"minecraft:emitter_rate_instant": {
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"num_particles": 0
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},
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"minecraft:emitter_lifetime_once": {
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"active_time": 6
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},
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"minecraft:emitter_shape_point": {
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"offset": [0, "variable.emitter_age", 0]
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}
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},
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"events": {
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"rise": {
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"particle_effect": {
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"effect": "tutorial_demo:firework_rise",
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"type": "emitter"
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}
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},
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"crack": {
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"particle_effect": {
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"effect": "tutorial_demo:firework_crack",
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"type": "emitter"
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}
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}
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}
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}
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}
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```
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`basic_render_parameters`是必需存在的字段，不过我们用不到它，填写默认的材质和纹理即可。重点在于`minecraft:emitter_lifetime_events`组件。我们通过`creation_event`在粒子创建时便执行`rise`事件，而`rise`事件用于生成`tutorial_demo:firework_rise`粒子。我们通过`timeline`在5.0s处触发`crack`事件，而`crack`事件则用于生成`tutorial_demo:firework_crack`粒子。这样，我们的烟花粒子就完成了。
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我们可以进入游戏通过`/particle`命令来测试效果。可以看到，粒子果然如同我们设想的那样呈现了烟花的形状！ |