Need read only access to dynamic buffers

Hi,
Have got a problem here. I have got the following system:

Code (CSharp):

1.  
2.     public class MySystem : JobComponentSystem
3.     {
4.         protected override JobHandle OnUpdate(JobHandle inputDeps)
5.         {
6.             BufferFromEntity<X> xFromEntity = GetBufferFromEntity<X>(true);
7.  
8.             return Entities
9.                 .WithAll<X>()
10.                 .WithReadOnly(xFromEntity)
11.                 .ForEach(
12.                     (in Entity entity) =>
13.                     {
14.                         DynamicBuffer<X> x = xFromEntity[entity];
15.                     }
16.                 )
17.                 .Schedule(inputDeps);
18.         }
19.     }
20.  

The problem with it is that it marks chunks as changed, even though I have passed true into GetBufferFromEntity and did WithReadOnly(xFromEntity).
Any suggestions?

 

OK, I've filed a bug - Case 1236267

 

In case someone is interested in this: https://issuetracker.unity3d.com/is...with-withreadonly-bufferfromentity-expression

 

This one is still there, unfortunately. Just so you realize, this restricts people from traversing parent-child hierarchy of entities, because once you READ the children buffer it marks it as changed, which means rebuilding local-to-world matrices, because the transformation systems consider your hierarchy as changed, which is wrong. This is true for other (my own) systems that should take hierarchy changes into account.

 

I'm just wondering, what happens when you remove .WithAll<X>()?

 

Sad face

 

Oh dear...

Is this bug specific to Entities.ForEach, or does it also affect any use of BufferFromEntity?

@joepl Any updates on this since April?

 

This bug is specific to BufferFromEntity AFAIK, all Buffer access are RW access currently, unfortunately.

 

Ah - that makes sense. I remember working around this now: I run a System early in my loop, which just caches a BufferFromEntity, so that later Systems can pass it into multiple jobs which can then run in parallel.

...It would be very nice if that wasn't necessary...

 

ugh....

 

What's up? This was fixed 14 Months ago. (com.unity.entities [0.15.0] - 2020-08-26)

 

I'm excited to hear that it's been fixed, but I can't find any mention of the fix in the changelist you linked. Would you mind quoting the line that explains the fix?

 

Fixed a bug with BufferFromEntity<T> which caused it to incorrectly update the version number of the buffer when marked ReadOnly