diff --git a/packages/model3d-viewer/src/framing.ts b/packages/model3d-viewer/src/framing.ts
index 94a129e67..a9c35d926 100644
--- a/packages/model3d-viewer/src/framing.ts
+++ b/packages/model3d-viewer/src/framing.ts
@@ -10,6 +10,10 @@ const FALLBACK_RADIUS = 1;
 const FALLBACK_ASPECT = 1;
 const NEAR_RADIUS_RATIO = 0.01;
 const FAR_RADIUS_RATIO = 12;
+/** 近裁剪面离相机的距离比例：模型很小时按 1/1000 距离兜底，避免近处被裁。 */
+const NEAR_DISTANCE_RATIO = 1 / 1000;
+/** 远裁剪面离相机的距离比例：模型很扁时按 10 倍距离兜底，避免远处被裁。 */
+const FAR_DISTANCE_RATIO = 10;
 const MIN_DISTANCE_RATIO = 0.2;
 const MAX_DISTANCE_RATIO = 8;
 /** 复位视角仰角：过度抬高会把「上轴投影范围」放大，导致模型看起来比目标比例小。 */
@@ -240,8 +244,11 @@ export function computeModel3dViewerFraming(
     center: computeModel3dViewerBoxCenter(input.box),
     radius,
     distance,
-    near: Math.max(radius * NEAR_RADIUS_RATIO, distance / 1000),
-    far: Math.max(distance + radius * FAR_RADIUS_RATIO, distance * 10),
+    near: Math.max(radius * NEAR_RADIUS_RATIO, distance * NEAR_DISTANCE_RATIO),
+    far: Math.max(
+      distance + radius * FAR_RADIUS_RATIO,
+      distance * FAR_DISTANCE_RATIO,
+    ),
     minDistance: radius * MIN_DISTANCE_RATIO,
     maxDistance: distance * MAX_DISTANCE_RATIO,
     resetDirection: resolveModel3dViewerResetDirection(input.direction),