Compute buffer and structured buffer

Whats the difference between:

https://docs.microsoft.com/en-us/windows/win32/direct3dhlsl/dx-graphics-hlsl-buffer
Buffer<float4> g_Buffer;

And unity's documentation saying to use Structured Buffer.

StructuredBuffer<float4> g_Buffer;

Which one would i use? Are they the same? The documentation is a bit vague with this stuff from both websites....neither explain how to really use them in any detail.

 

I'd suggest StructuredBuffer<type> for items you only want to read in the Compute Shader or RWStructuredBuffer<type> for things you want to update in the shader and then potentially read back onto the CPU with bufName.GetData(1DArray).

 

Why is there no mention of StructuredBuffer type on microsoft's website ? Only Buffer<T>?

 

I think StructuredBuffer is Unity's implementation - BTW have been using them for a few years without problems.

 

Buffer<T> can only use scalar, vector or matrix types as elements and max size of one element is 128 bits.

Code (CSharp):

1. Buffer<float> _FloatBuffer;
2. Buffer<float4> _VectorBuffer;
3. Buffer<float2x2> _Matrix2x2Buffer;
4. // this won't compile because float4x4 is larger than 128bits
5. Buffer<float4x4> _Matrix4x4Bufer;
6.  

StructuredBuffer<T> can use structure as an element.

Code (CSharp):

1. struct MyStruct
2. {
3.     float4 color;
4.     float3 normal;
5.     bool flag;
6. }
7.  
8. StructuredBuffer<MyStruct> MyStructBuffer;
9.  
10. ...
11. float4 color = MyStructBuffer[4].color;
12. ...

So basically, use Buffer for scalars and vectors and StructuredBuffer for everything else.

 

Ah thank you - this is what i was trying to understand. So if i am using the default shader types - i can just use Buffer instead of StructuredBuffer.

 

Yes but my point was unity documentation never mentions just regular buffer:
https://docs.microsoft.com/en-us/windows/win32/direct3dhlsl/sm5-object-buffer

At least not that i saw - so it led me to assume they were not supported.

 

It doesn't mention them because not every platform supports them, for some reason. I had to replace some Buffer<> with StructuredBuffer<> to get the shaders to compile in such cases.