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Custom struct in BlobArray

Discussion in 'Data Oriented Technology Stack' started by swejk, Jun 20, 2019.

  1. swejk

    swejk

    Joined:
    Dec 22, 2013
    Posts:
    10
    Hi,

    I have an issue with struct elements in BlobArray, where they have default values in runtime. I think that I am not initializing the array correctly, but I cant find the correct approach anywhere.

    Concretely, with this code, when accessing clipDataRef.Value.Motions from some job, all elements will have default values ( StartFrame = 0, EndFrame = 0, Translation = {0,0,0}).

    Any advice how can I overcome this please ?

    Code (CSharp):
    1. [Serializable]
    2. public struct Motion {
    3.   public int StartFrame;
    4.   public int EndFrame;
    5.   public float3 Translation;
    6. }
    7.  
    8. [Serializable]
    9. public struct Clip {
    10.   public bool Loop;
    11.   public BlobArray<Motion> Motions;
    12. }
    13.  
    14. public class ClipData : MonoBehaviour {
    15.    public Motion[] Motions;
    16.    public bool Loop;
    17. }
    18.  
    19.  
    20. class SomeConversionSystem : GameObjectConversionSystem {
    21.  
    22.   protected override void OnUpdate() {
    23.     Entities.ForEach((ClipData clipData) =>{
    24.         var builder = new BlobBuilder(Allocator.Temp);
    25.         ref var root = ref builder.ConstructRoot<Clip>();
    26.         root.Loop = clipData.Loop;
    27.         var motions = builder.Allocate(clipData.Motions.Length, ref root.Motions);
    28.  
    29.         for(int i = 0; i < clipData.Motions.Length; i++) {
    30.            motions[i] = clipData.Motions[i];
    31.         }
    32.  
    33.        var clipBlob = builder.CreateBlobAssetReference<Clip>(Allocator.Persistent);
    34.  
    35.       builder.Dispose();
    36.  
    37.      var entity = GetPrimaryEntity(clipData.gameObject);
    38.      DstEntityManager.AddComponentData(entity,
    39.                 new SomeComponent {ClipDataRef = clipBlob});
    40.      });
    41.   }
    42. }
     
  2. swejk

    swejk

    Joined:
    Dec 22, 2013
    Posts:
    10
    I did not access the blobReference value correctly. I have this solved now.
    Code (CSharp):
    1. // Bad
    2. var clips = clipDataRef.Value.Motions
    3.  
    4. // Good
    5. ref var clips = ref clipDataRef.Value.Motions
    6.  
     
  3. Justin_Larrabee

    Justin_Larrabee

    Joined:
    Apr 24, 2018
    Posts:
    84
    It's been mentioned in another thread that they will add static analysis tools to the compiler to prevent this mistake from happening.
     
    swejk likes this.
  4. topitsky

    topitsky

    Joined:
    Jan 12, 2016
    Posts:
    6
    I've been looking for information about blobs, what is the advantage over a nativearray? Can it store more complex datastructures? eg. An Array of array (eg. If I had to store a rotation for each bone in one animation struct).
     
  5. recursive

    recursive

    Joined:
    Jul 12, 2012
    Posts:
    591
    It can store arbitrary data structures, but the best way to think of it is an in-memory file, with the root blob struct being the header. It can have it's own data, but
    BlobPtr<T>
    ,
    BlobArray<T>
    , and others store offsets into that file from the header.