feat(文件拆分): 拆分几何三维基础能力

internal/base/threed/u3d_view_camera.go

@@ -0,0 +1,68 @@
+// Copyright 2025-2026 肖其顿 (XIAO QI DUN)
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package threed
+
+import (
+	"errors"
+)
+
+// 视图相机路径解析错误，由文档适配层转换为相应格式的错误
+var (
+	ErrCameraNotFound  = errors.New("missing U3D camera path")
+	ErrAmbiguousCamera = errors.New("ambiguous U3D camera instance")
+)
+
+// ViewCamera 返回视图节点指定父路径的世界变换，不修改绘制会话
+// 入参: selected 视图节点索引, path 从根至节点的路径, exactRoot 是否要求路径始于根
+// 返回: [16]float64 世界变换, error 缺失、歧义或取消错误
+func (r *Renderer) ViewCamera(selected int, path []string, exactRoot bool) ([16]float64, error) {
+	var transform [16]float64
+	if selected < 0 || selected >= len(r.model.Nodes) || r.model.Nodes[selected].Kind != "View" {
+		return transform, ErrCameraNotFound
+	}
+	found := false
+	for _, index := range r.byNode[selected] {
+		if err := r.ctx.Err(); err != nil {
+			return transform, err
+		}
+		current, match := index, true
+		for j := len(path) - 1; j >= 0; j-- {
+			if j%256 == 0 {
+				if err := r.ctx.Err(); err != nil {
+					return transform, err
+				}
+			}
+			if current < 0 || r.model.Nodes[r.scene[current].node].Name != path[j] || r.model.Nodes[r.scene[current].node].Kind != "View" {
+				match = false
+				break
+			}
+			current = r.scene[current].parent
+		}
+		if exactRoot && current >= 0 {
+			match = false
+		}
+		if !match {
+			continue
+		}
+		if found {
+			return transform, ErrAmbiguousCamera
+		}
+		transform, found = r.scene[index].world, true
+	}
+	if !found {
+		return transform, ErrCameraNotFound
+	}
+	return transform, nil
+}