@Erkang Wang 

I’m not sure how to force a single reflection from an object from the ray tracing perspective. However, you could perhaps use a Filter String in your viewer to only display rays that have been reflected once (I’m assuming this is what you were asking for when you wrote “what filter should I use?”. Take this simple example:

The bottom object is Object 4, and its upper face (1) has been made reflective. You could get the ray that reflect only once from the bottom object with a filter string like so:

R4.1 & X_HIT(4.1, 1)

R4.1 means that the ray must be reflected by Face 1 of Object 4. X_HIT(4.1, 1) means that the ray must hit Face 1 of Object 4 one and only one time. The & is a logical AND. See the result below:

Note that in this instance, it would have been enough to do X_HIT(4.1, 1), since the surface is purely reflective. But R4.1 ensures that the ray is not only hitting Object 4 but that it is indeed reflected from this object.

I hope this helps.

Take care,

David

@Erkang Wang

 

I’m not sure how to force a single reflection from an object from the ray tracing perspective. However, you could perhaps use a Filter String in your viewer to only display rays that have been reflected once (I’m assuming this is what you were asking for when you wrote “what filter should I use?”. Take this simple example:

The bottom object is Object 4, and its upper face (1) has been made reflective. You could get the ray that reflect only once from the bottom object with a filter string like so:

R4.1 & X_HIT(4.1, 1)

R4.1 means that the ray must be reflected by Face 1 of Object 4. X_HIT(4.1, 1) means that the ray must hit Face 1 of Object 4 one and only one time. The & is a logical AND. See the result below:

Note that in this instance, it would have been enough to do X_HIT(4.1, 1), since the surface is purely reflective. But R4.1 ensures that the ray is not only hitting Object 4 but that it is indeed reflected from this object.

I hope this helps.

Take care,

 

David

works very well. Thank you, David. I guess it still waste some computational power? since ray trace has to include those multi-reflected beams ?

@Erkang Wang

You are absolutely correct. There might be a way to optimize the ray tracing, but this is very design-dependant and without seeing a file, it is hard to say how you could do that in your application.

Take care,

David