UE4渲染用到的Bounds

最新推荐文章于 2025-01-01 21:45:46 发布

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博客介绍了使用Actor边界进行可见性测试的相关内容。每个Actor的边界由球体和盒子两部分组成，可在视口可视化其边界。还说明了编辑Actor边界的方法，如设置Bounds Scale等，同时指出增加边界可能影响性能和阴影质量，相机视角渲染会根据Bounds检测裁剪剔除。

官方介绍：

Testing Visibility with an Actor's Bounds

Each Actor placed in a Level has a set of bounds using a box and a sphere that is used for various things in the Engine. One of those being specifically to test whether an it is visible or not. The bounds of an Actor is made up of two parts: a sphere and a box. The bounding sphere is used for fast collision detection with a simple distance test, and, more often than not, it's greater in size than the object it contains. On the other hand, the bounding box is a closer match to the shape of the object and provides more accurate results.

Visualize bounds of Actors in the Level Viewport by selecting Show > Advanced > Bounds. Alternatively, in the Skeletal Mesh Editor you can select Character > Bounds and in the Static Mesh Editor, select Bounds in the main toolbar.

An Actor with its bounds (sphere and box) displayed.

Each Static Mesh and Skeletal Mesh has its own bounding box and sphere that automatically scales to the size of the geometry when imported, or when scaled or rotated in the viewport.

You can edit an Actor's bounds using the following ways:

By setting the Bounds Scale from its Details panel when it's selected in a Level or in a Blueprint. The Bounds Scale uniformly scales the bounds of an Actor, acting as a multiplier of the original scale values.

Click image for full size.
By opening the Static Mesh or Skeletal Mesh Editors to apply non-uniform scaling for Positive Bounds Extension and Negative Bounds Extensions using the Details panel.

Increasing an Actor's bounds can potentially impact performance and shadow quality by keeping the Actor from be culled sooner than it would otherwise have been.

源码解释：

/**
   * Scales the bounds of the object.
   * This is useful when using World Position Offset to animate the vertices of the object outside of its bounds.
   * Warning: Increasing the bounds of an object will reduce performance and shadow quality!
   * Currently only used by StaticMeshComponent and SkeletalMeshComponent.
   */
   UPROPERTY(EditAnywhere, AdvancedDisplay, Category=Rendering, meta=(UIMin = "1", UIMax = "10.0"))
   float BoundsScale;

使用：

玩家快速走过，相机视角可看到某物体，可以适当增加BoundsScale，但是降低性能。相机视角渲染，会根据Bounds检测是否渲染裁剪剔除。