Wow ! That is scary ! Good find Nicolas and thanks for the heads up. No wonder soft also crashes sometimes when using Application.DeleteObj() command in python as well, I wonder if it is caused by the same reason. Maybe same happens for VB or Java but I am not sure. The only duct-tape solution that I found around this was to call Application.Refresh() in python before delete which resulted in a consistent behavior.
-----Original Message----- From: "Nicolas Burtnyk" <[email protected]> Sent 6/18/2012 1:29:17 PM To: [email protected] Subject: Heads up to plugin developers regarding CRef Hi everyone, I just wanted to share a piece of information I discovered while developing our custom renderer for Softimage. We were having an issue where Soft would hang when we were extracting the scene for rendering after deleting a light in the scene. It turns out that the problem was cause by the fact that our plugin was holding CRefs to objects in the scene between renders for the purpose of determining what had changed between renders and therefore what data needed to be re-extracted/re-processed. During extraction, once we determined that the light was no longer in the scene, we would delete our tracking object which included a CRef to the deleted light. The destruction of the CRef was hanging Soft. Apparently the problem is caused by the fact that CRef represents a *strong* reference to an object. So, if you have a CRef to something (say a light) and you delete the light in Soft, the light doesn't actually get deleted because it is still being referenced by that CRef. For whatever reason, I had assumed that a CRef was a weak reference and that the CRef would simply become invalid when the referenced object was deleted. Instead, the light is only deleted when the last CRef is destroyed, which in our case was causing a hang because it was happening during our custom renderer's "Process" callback which Soft calls on a special render thread and not the main thread. We eventually solved the problem by tracking objects by their object ID rather than using CRefs between renders. Long story short - CRef is a strong reference. I assumed it was a weak reference. Don't make the same mistake! Too bad this isn't documented and too bad the SDK doesn't provide an equivalent to CRef that simply becomes invalid when it's referenced object is destroyed. -Nicolas
