This  secondary ray then hits a new surface such as this point on the wall.

然后，这条二次射线会照射到新的表面，例如墙壁上的这个点。

One additional benefit of indirect  illumination and the use of secondary rays is that color can bounce from one object to another.

间接照明和使用二次射线的另一个好处是颜色可以从一个物体反射到另一个物体。

This  secondary ray bouncing happens multiple times, and each time we send shadow rays to the light  sources and check how that point is illuminated.

这种二次光线反射会发生多次，每次我们都会将阴影光线发送到光源并检查该点的照明方式。

An important detail is that the direction the secondary rays bounce off the surface depends  on the material and texture properties assigned to the object.

一个重要的细节是，次级射线从表面反射的方向取决于分配给物体的材质和纹理属性。

However, when a material has a roughness set to 100%, then  the secondary rays will bounce in entirely random directions resulting in a flat gray surface.

然而， 当材质的粗糙度设置为 100% 时，次级射线将在完全随机的方向上反射， 从而产生平坦的灰色表面。

This light is called indirect illumination, and in order to calculate it, we take the  intersection point from the primary ray and generate a secondary ray that bounces off it.

这种光被称为间接照明，为了计算它， 我们取主射线的交点并生成从该点反射的次级射线。

Sometimes this point is still in shadows, so we create an additional  secondary ray from the point on the wall and send it in a new direction and see what it hits.

有时这个点仍然处于阴影中，所以我们从墙上的点创建一个额外的二次射线， 并将其发送到新的方向， 看看它会碰到什么。

It's called path tracing because by using these  primary rays, secondary rays and shadow rays, we're finding billions of paths from the camera  through different points in the scene and to the light sources.

它被称为路径追踪，因为通过使用这些主射线、次射线和阴影射线，我们可以找到从相机穿过场景中的不同点到光源的数十亿条路径。

The purpose of bouncing the secondary rays  around and sending out shadow rays at each point is to find different paths where  light bounces off different surfaces and indirectly illuminates the original point  where the primary ray hits.

使次级射线四处反射并在每个点发出阴影射线的目的是找到光线从不同表面反射的不同路径，并间接照亮主射线击中的原始点。