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这些消息通信有哪些差别

在 PF_Cmd_USER_CHANGED_PARAM 和 PF_Cmd_UPDATE_PARAMS_UI 之间有细微的差别。

效果需要区分用户是实际更改参数值( PF_Cmd_USER_CHANGED_PARAM )还是只是遍历时间轴( PF_Cmd_UPDATE_PARAMS_UI )，这也是在插件首次加载时发送的)。

只有前几个命令选择器是可预测的; 调用序列的其余部分由用户操作决定。

当第一次应用时，插件接收 PF_Cmd_GLOBAL_SETUP ，然后是 PF_Cmd_PARAM_SETUP 。每次用户向一个层添加效果时，都会发送 PF_Cmd_SEQUENCE_SETUP 。

对于由基础的非 SmartFX 效果渲染的每一帧，After Effects 发送PF_Cmd_FRAME_SETUP，然后是 PF_Cmd_RENDER，然后是PF_Cmd_FRAME_SETDOWN。所有效果插件必须响应 PF_Cmd_RENDER 。

PF_Cmd_SEQUENCE_SETDOWN is sent on exit, when the user removes an effect or closes the project. PF_Cmd_SEQUENCE_RESETUP is sent when a project is loaded or when the layer to which it’s applied changes. PF_Cmd_SEQUENCE_FLATTEN is sent when the After Effects project is written out to disk.

对于 SmartFX， PF_Cmd_SMART_PRE_RENDER 可以被发送任意次数，在单个 PF_Cmd_SMART_RENDER 被发送之前。

PF_Cmd_SEQUENCE_SETDOWN 在退出时发送，当用户删除一个效果或关闭项目时。

PF_Cmd_SEQUENCE_RESETUP 在项目被加载或它所应用的层发生变化时被发送。

PF_Cmd_SEQUENCE_FLATTEN 是在 After Effects 项目写入磁盘时发送的。

PF_Cmd_ABOUT 当用户从效果控制窗口(ECW)中选择 About… 时发送。

PF_Cmd_GLOBAL_SETDOWN 当 After Effects 关闭时或当效果的最后一个实例被删除时发送。不要依赖此消息来确定插件何时从内存中删除; 使用操作系统特定的入口点。

What’s The Difference?

There is a subtle difference between PF_Cmd_USER_CHANGED_PARAM and PF_Cmd_UPDATE_PARAMS_UI.

Effects need to distinguish between the user actually changing a parameter value (PF_Cmd_USER_CHANGED_PARAM), and just scrubbing around the timeline (PF_Cmd_UPDATE_PARAMS_UI), which is also sent when the plug-in is first loaded).

Only the first few command selectors are predictable; the rest of the calling sequence is dictated by user action.

When first applied, a plug-in receives PF_Cmd_GLOBAL_SETUP, then PF_Cmd_PARAM_SETUP. Each time the user adds the effect to a layer, PF_Cmd_SEQUENCE_SETUP is sent.

For each frame rendered by a basic non-SmartFX effect, After Effects sends PF_Cmd_FRAME_SETUP, then PF_Cmd_RENDER, then PF_Cmd_FRAME_SETDOWN. All effect plug-ins must respond to PF_Cmd_RENDER .

For SmartFX, PF_Cmd_SMART_PRE_RENDER may be sent any number of times, before a single PF_Cmd_SMART_RENDER is sent.

PF_Cmd_SEQUENCE_SETDOWN is sent on exit, when the user removes an effect or closes the project. PF_Cmd_SEQUENCE_RESETUP is sent when a project is loaded or when the layer to which it’s applied changes. PF_Cmd_SEQUENCE_FLATTEN is sent when the After Effects project is written out to disk.

PF_Cmd_ABOUT is sent when the user chooses About… from the Effect Controls Window (ECW).

PF_Cmd_GLOBAL_SETDOWN is sent when After Effects closes, or when the last instance of the effect is removed. Do not rely on this message to determine when your plug-in is being removed from memory; use OS-specific entry points.