The check option "Occlusion culling enabled" - What does this really do?

M K

The check option "Occlusion culling enabled" - What does this really do?
Hello. I have a question on the Tools/Options item.

When accessing the [Tools]-[Options]-[General]-[Display]-[Performance tab], there is a check option "Occlusion culling enabled", but what does this really do?
 
What is the advantage of having this option on (or off)? How can this be used actually? (I have looked up to the DS docs but haven't got the idea...)

Kyle Brand

RE: The check option "Occlusion culling enabled" - What does this really do?
(in response to M K)
Look in the Event Proceedings for the 2008 Annual PLM Conference & TechniFair. There is a presentation "Maximizing CATIA Performance for Large Assemblies". It discusses many visualization settings, with this included. 

The basic concept of Occlusion Culling is a technique that does not render objects that are behind other objects (obscure from other objects view). Another note is that this technique is supported by CATIA multi-threaded processing.   

Does this help?

Chad Posner

RE: The check option "Occlusion culling enabled" - What does this really do?
(in response to M K)
Thanks Kyle. I never knew that. I also checked out that presentation. Great reference.

M K

RE: The check option "Occlusion culling enabled" - What does this really do?
(in response to M K)
Thank you for the note, Kyle.
Does that mean that objects (solids, sufaces) behind an element (solid or surface) can be visible/invisible with this option setting?

What I'm imagining is something like this:
1. Create a rectangle sketch and then create a surface by the [Fill] command.
2. Behind the created surface, create other feature elements (surfaces & solids).
3-1. With this "Occlusion culling enabled" option ON --> The surfaces & solids behind the rectangle surface (created at the item 1) become visible.
3-2. With this "Occlusion culling enabled" option OFF (default) --> The surfaces & solids behind the rectangle surface (created at the item 1) are invisible.
 
Please advise if I'm getting it wrong.

Tomislav Solina

RE: The check option "Occlusion culling enabled" - What does this really do?
(in response to M K)
just do not forget that this option will make this job a bit easier to your graphic card but a lot heavier to your processor!

not too much usefull on newier computers.

I am not sure is it this option active only on assembly level, not part level, similar to "Level of detail" function...
but I am pretty sure that this function is based on part bounding box, not on real geometry.

Tomislav Solina

RE: The check option "Occlusion culling enabled" - What does this really do?
(in response to M K)
just do not forget that this option will make this job a bit easier to your graphic card but a lot heavier to your processor!

not too much usefull on newier computers.

I am not sure is it this option active only on assembly level, not part level, similar to "Level of detail" function...
but I am pretty sure that this function is based on part bounding box, not on real geometry.

M K

RE: The check option "Occlusion culling enabled" - What does this really do?
(in response to M K)

Thank you all who posted here to help me understand about the option.

Please allow me to review what I have learned in the past 24 hours on that:

1. What is this option for?
This option is there in order that the system might reduce the memory usage for large sized data.
(If the data size is not so big, the difference is not recognized.)

2. How does the option actually work for CATIA data?
This is relating to what Kyle said above. "The basic concept of Occlusion Culling is a technique that does not render objects that are behind other objects (obscure from other objects view)." In other words, with the option on, the display information on the faces of the elements behind the front object is not taken into consideration by the system, which is to reduce the system's memory usage. (Yet the existance information of the behind elements is kept regardless of the option status.)

3. What's the catch?
This is what tsolina mentioned above, but let me repeat that here. (Thanks for posting that, tsolina.):
"This option will make this job a bit easier to your graphic card but a lot heavier to your processor."

If there are any misunderstandings, please let me know.
Thanks.

Kyle Brand

RE: The check option "Occlusion culling enabled" - What does this really do?
(in response to M K)
I think you have the concept of it.

Colton Tillman House

RE: The check option "Occlusion culling enabled" - What does this really do?
(in response to Kyle Brand)

I am no longer able to find this presentation in the archive. "Maximizing CATIA Performance for Large Assemblies"
Has there been an update to it from later conferences?