If the reflection/alpha/transparency channel is all black, you can first rule out the following reasons.

- If there is no reflector in the scene, the reflector channel will be all black

- If there is no sky in the scene, such as a interior scene, the alpha channel may be completely black.

- If there is no transparent material in the scene, such as glass/water, the transparency channel may be all black

There are currently the following known problems with the channels.

1. the rendered channels are completely black

2. Some models may disappear in the channels

3. Some of the adjacent materials are the same color in the material ID channels

 All the above problems can be solved by rendering channels with the same angle and parameters again, and we will gradually optimize this problem in future versions.