feat(live2d): 添加 Pose 处理模块以管理互斥 Part 的显示状态，优化模型加载和参数更新

src/plugins/live2d/pose.rs

@@ -0,0 +1,233 @@
+//! Pose 处理：根据 `.pose3.json` 管理互斥 Part 的显示状态。
+//!
+//! Haru 这类模型会把“手臂伸开”和“手臂抱胸”做成不同 Part。
+//! 如果不执行 Pose，多个 Part 会同时可见，画面上就会出现四只手臂。
+
+use super::core_ffi::CubismCore;
+use super::model::CubismModel;
+use anyhow::{Context, Result};
+use serde::Deserialize;
+use std::path::Path;
+
+const DEFAULT_FADE_IN_SECONDS: f32 = 0.5;
+const EPSILON: f32 = 0.001;
+const PHI: f32 = 0.5;
+const BACK_OPACITY_THRESHOLD: f32 = 0.15;
+
+#[derive(Deserialize)]
+struct PoseJson {
+    #[serde(rename = "FadeInTime")]
+    fade_in_time: Option<f32>,
+    #[serde(rename = "Groups", default)]
+    groups: Vec<Vec<PosePartJson>>,
+}
+
+#[derive(Deserialize)]
+struct PosePartJson {
+    #[serde(rename = "Id")]
+    id: String,
+    #[serde(rename = "Link", default)]
+    link: Vec<String>,
+}
+
+#[derive(Clone, Debug)]
+struct PosePart {
+    part_index: Option<usize>,
+    param_index: Option<usize>,
+    link_part_indices: Vec<usize>,
+    virtual_param_value: f32,
+}
+
+/// Live2D Pose 状态。
+pub struct PoseState {
+    fade_time_seconds: f32,
+    groups: Vec<Vec<PosePart>>,
+    initialized: bool,
+}
+
+impl PoseState {
+    pub fn from_path(path: &Path, model: &CubismModel) -> Result<Self> {
+        let text = std::fs::read_to_string(path)
+            .with_context(|| format!("读取 pose3.json 失败: {}", path.display()))?;
+        let json: PoseJson = serde_json::from_str(&text)
+            .with_context(|| format!("解析 pose3.json 失败: {}", path.display()))?;
+
+        let fade_time_seconds = json
+            .fade_in_time
+            .filter(|v| *v >= 0.0)
+            .unwrap_or(DEFAULT_FADE_IN_SECONDS);
+
+        let groups: Vec<Vec<PosePart>> = json
+            .groups
+            .into_iter()
+            .map(|group| {
+                group
+                    .into_iter()
+                    .map(|part| PosePart {
+                        param_index: model.param_index.get(&part.id).copied(),
+                        part_index: model.part_index(&part.id),
+                        link_part_indices: part
+                            .link
+                            .iter()
+                            .filter_map(|id| model.part_index(id))
+                            .collect(),
+                        virtual_param_value: 0.0,
+                    })
+                    .collect()
+            })
+            .collect();
+
+        println!(
+            "[Live2D] Pose 加载: {} groups={} fade={:.3}s",
+            path.display(),
+            groups.len(),
+            fade_time_seconds
+        );
+
+        Ok(Self {
+            fade_time_seconds,
+            groups,
+            initialized: false,
+        })
+    }
+
+    /// 初始化 Pose：每个互斥组保留当前最可见的 Part，隐藏其余 Part。
+    pub fn reset(&mut self, core: &CubismCore, model: &CubismModel) {
+        for group in &mut self.groups {
+            let mut visible_index = 0;
+            let mut max_opacity = -1.0;
+            for (index, part) in group.iter().enumerate() {
+                let opacity = part
+                    .part_index
+                    .and_then(|idx| model.get_part_opacity_by_index(core, idx))
+                    .unwrap_or(0.0);
+                if opacity >= max_opacity {
+                    max_opacity = opacity;
+                    visible_index = index;
+                }
+            }
+
+            for (index, part) in group.iter_mut().enumerate() {
+                let opacity = if index == visible_index { 1.0 } else { 0.0 };
+                part.virtual_param_value = opacity;
+                if let Some(param_index) = part.param_index {
+                    model.set_param_by_index(core, param_index, opacity);
+                }
+                if let Some(part_index) = part.part_index {
+                    model.set_part_opacity_by_index(core, part_index, opacity);
+                }
+            }
+        }
+        self.copy_part_opacities(core, model);
+        self.initialized = true;
+    }
+
+    /// 按官方 CubismPose 的互斥淡入规则更新 PartOpacity。
+    pub fn update_parameters(&mut self, core: &CubismCore, model: &CubismModel, dt: f32) {
+        if !self.initialized {
+            self.reset(core, model);
+        }
+
+        let dt = dt.max(0.0);
+        let fade_time_seconds = self.fade_time_seconds;
+        for group in &mut self.groups {
+            Self::do_fade(core, model, fade_time_seconds, dt, group);
+        }
+        self.copy_part_opacities(core, model);
+    }
+
+    fn do_fade(
+        core: &CubismCore,
+        model: &CubismModel,
+        fade_time_seconds: f32,
+        dt: f32,
+        group: &mut [PosePart],
+    ) {
+        if group.is_empty() {
+            return;
+        }
+
+        let mut visible_part_index = None;
+        let mut new_opacity = 1.0;
+
+        for (index, part) in group.iter().enumerate() {
+            if part.pose_value(core, model) <= EPSILON {
+                continue;
+            }
+
+            visible_part_index = Some(index);
+            if fade_time_seconds == 0.0 {
+                new_opacity = 1.0;
+            } else {
+                new_opacity = part
+                    .part_index
+                    .and_then(|idx| model.get_part_opacity_by_index(core, idx))
+                    .unwrap_or(0.0);
+                new_opacity = (new_opacity + dt / fade_time_seconds).min(1.0);
+            }
+            break;
+        }
+
+        let visible_part_index = visible_part_index.unwrap_or(0);
+        if visible_part_index == 0 && group[0].pose_value(core, model) <= EPSILON {
+            group[0].virtual_param_value = 1.0;
+            if let Some(param_index) = group[0].param_index {
+                model.set_param_by_index(core, param_index, 1.0);
+            }
+        }
+
+        for (index, part) in group.iter().enumerate() {
+            let Some(part_index) = part.part_index else {
+                continue;
+            };
+
+            if index == visible_part_index {
+                model.set_part_opacity_by_index(core, part_index, new_opacity);
+                continue;
+            }
+
+            let mut opacity = model
+                .get_part_opacity_by_index(core, part_index)
+                .unwrap_or(0.0);
+            let mut target_opacity = if new_opacity < PHI {
+                new_opacity * (PHI - 1.0) / PHI + 1.0
+            } else {
+                (1.0 - new_opacity) * PHI / (1.0 - PHI)
+            };
+
+            let back_opacity = (1.0 - target_opacity) * (1.0 - new_opacity);
+            if back_opacity > BACK_OPACITY_THRESHOLD {
+                target_opacity = 1.0 - BACK_OPACITY_THRESHOLD / (1.0 - new_opacity);
+            }
+
+            if opacity > target_opacity {
+                opacity = target_opacity;
+            }
+            model.set_part_opacity_by_index(core, part_index, opacity);
+        }
+    }
+
+    fn copy_part_opacities(&self, core: &CubismCore, model: &CubismModel) {
+        for group in &self.groups {
+            for part in group {
+                let Some(part_index) = part.part_index else {
+                    continue;
+                };
+                let Some(opacity) = model.get_part_opacity_by_index(core, part_index) else {
+                    continue;
+                };
+                for &link_part_index in &part.link_part_indices {
+                    model.set_part_opacity_by_index(core, link_part_index, opacity);
+                }
+            }
+        }
+    }
+}
+
+impl PosePart {
+    fn pose_value(&self, core: &CubismCore, model: &CubismModel) -> f32 {
+        self.param_index
+            .and_then(|idx| model.get_param_by_index(core, idx))
+            .unwrap_or(self.virtual_param_value)
+    }
+}