粒子着色器

粒子着色器

Particle shaders are a special type of shader that runs before the object is drawn. They are used for calculating material properties such as color, position, and rotation. They are drawn with any regular material for CanvasItem or Spatial, depending on whether they are 2D or 3D.

Particle shaders are unique because they are not used to draw the object itself; they are used to calculate particle properties, which are then used by a CanvasItem or Spatial shader. They contain two processor functions: start() and process().

Unlike other shader types, particle shaders keep the data that was output the previous frame. Therefore, particle shaders can be used for complex effects that take place over multiple frames.

备注

Particle shaders are only available with GPU-based particle nodes (GPUParticles2D and GPUParticles3D).

CPU-based particle nodes (CPUParticles2D and CPUParticles3D) are rendered on the GPU (which means they can use custom CanvasItem or Spatial shaders), but their motion is simulated on the CPU.

渲染模式

渲染模式	描述
keep_data	不要在重启时清除以前的数据.
disable_force	Disable attractor force.
disable_velocity	忽略 VELOCITY 值.
collision_use_scale	为进行碰撞而缩放粒子的大小。

内置

标记为 “in” 的值是只读的. 标记为 “out” 的值是可以选择写入的, 不一定包含合理的值. 标记为 “inout” 的值提供一个合理的默认值, 并且可以选择写入. 采样器不是写入的对象, 它们没有被标记.

全局内置

全局内置的功能随处可见, 包括自定义功能.

内置	描述
in float TIME	全球时间, 以秒为单位.
in float PI	A `PI` constant (`3.141592`). A ration of circle’s circumference to its diameter and amount of radians in half turn.
in float TAU	A `TAU` constant (`6.283185`). An equivalent of `PI * 2` and amount of radians in full turn.
in float E	A `E` constant (`2.718281`). Euler’s number and a base of the natural logarithm.

Start and Process built-ins

These properties can be accessed from both the start() and process() functions.

函数	描述
in float LIFETIME	粒子寿命。
in float DELTA	处理时间差。
in uint NUMBER	发射开始后的唯一编号。
in uint INDEX	粒子索引（在所有粒子范围内）。
in mat4 EMISSION_TRANSFORM	发射器变换（用于非本地坐标系）。
in uint RANDOM_SEED	随机种子，是随机的基础。
inout bool ACTIVE	`true` when the particle is active, can be set `false`.
inout vec4 COLOR	粒子的颜色, 可以写入Mesh的顶点函数中, 也可以访问.
inout vec3 VELOCITY	粒子速度, 可以修改.
inout mat4 TRANSFORM	粒子变换。
inout vec4 CUSTOM	自定义粒子数据。网格的着色器可以使用 INSTANCE_CUSTOM 访问。
inout float MASS	Particle mass, intended to be used with attractors. Equals `1.0` by default.
in vec4 USERDATAX	Vector that enables the integration of supplementary user-defined data into the particle process shader. `USERDATAX` are six built-ins identified by number, `X` can be numbers between 1 and 6.
in uint FLAG_EMIT_POSITION	A flag for using on the last argument of `emit_subparticle` function to assign a position to a new particle’s transform.
in uint FLAG_EMIT_ROT_SCALE	A flag for using on the last argument of `emit_subparticle` function to assign the rotation and scale to a new particle’s transform.
in uint FLAG_EMIT_VELOCITY	A flag for using on the last argument of `emit_subparticle` function to assign a velocity to a new particle.
in uint FLAG_EMIT_COLOR	A flag for using on the last argument of `emit_subparticle` function to assign a color to a new particle.
in uint FLAG_EMIT_CUSTOM	A flag for using on the last argument of `emit_subparticle` function to assign a custom data vector to a new particle.
in vec3 EMITTER_VELOCITY	Velocity of the Particles node.
in float INTERPOLATE_TO_END	Value of `interp_to_end` property of Particles node.
in uint AMOUNT_RATIO	Value of `amount_ratio` property of Particles node.

备注

In order to use the COLOR variable in a StandardMaterial3D, set vertex_color_use_as_albedo to true. In a ShaderMaterial, access it with the COLOR variable.

Start built-ins

内置	描述
in bool RESTART_POSITION	`true` if particle is restarted, or emitted without a custom position (i.e. this particle was created by `emit_subparticle()` without the `FLAG_EMIT_POSITION` flag).
in bool RESTART_ROT_SCALE	`true` if particle is restarted, or emitted without a custom rotation or scale (i.e. this particle was created by `emit_subparticle()` without the `FLAG_EMIT_ROT_SCALE` flag).
in bool RESTART_VELOCITY	`true` if particle is restarted, or emitted without a custom velocity (i.e. this particle was created by `emit_subparticle()` without the `FLAG_EMIT_VELOCITY` flag).
in bool RESTART_COLOR	`true` if particle is restarted, or emitted without a custom color (i.e. this particle was created by `emit_subparticle()` without the `FLAG_EMIT_COLOR` flag).
in bool RESTART_CUSTOM	`true` if particle is restarted, or emitted without a custom property (i.e. this particle was created by `emit_subparticle()` without the `FLAG_EMIT_CUSTOM` flag).

Process built-ins

内置	描述
in bool RESTART	`true` if the current process frame is first for the particle.
in bool COLLIDED	`true` when the particle has collided with a particle collider.
in vec3 COLLISION_NORMAL	A normal of the last collision. If there is no collision detected it is equal to `vec3(0.0)`.
in float COLLISION_DEPTH	A length of normal of the last collision. If there is no collision detected it is equal to `0.0`.
in vec3 ATTRACTOR_FORCE	A combined force of the attractors at the moment on that particle.

Process functions

emit_subparticle is currently the only custom function supported by particles shaders. It allows users to add a new particle with specified parameters from a sub-emitter. The newly created particle will only use the properties that match the flags parameter. For example, the following code will emit a particle with a specified position, velocity, and color, but unspecified rotation, scale, and custom value:

mat4 custom_transform = mat4(1.0);
custom_transform[3].xyz = vec3(10.5, 0.0, 4.0);
emit_subparticle(custom_transform, vec3(1.0, 0.5, 1.0), vec4(1.0, 0.0, 0.0, 1.0), vec4(1.0), FLAG_EMIT_POSITION | FLAG_EMIT_VELOCITY | FLAG_EMIT_COLOR);

函数	描述
bool emit_subparticle (mat4 xform, vec3 velocity, vec4 color, vec4 custom, uint flags)	Emits a particle from a sub-emitter.

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