4 replies to this topic

[Butabee]

I can't seem to get my cbuffer values into my shader correctly.

Here's my struct:

[StructLayout(LayoutKind.Explicit, Size=2048*16)]
struct cbuff
{
[FieldOffset(0)]
public Vector4[] shadebuff;
};


This is how I create the buffer:

sbuff = new SlimDX.Direct3D11.Buffer(m_device, 2048 * 16, ResourceUsage.Dynamic, BindFlags.ConstantBuffer, CpuAccessFlags.Write, ResourceOptionFlags.None, 0);

This is how I update it...


DataBox datb = m_context.MapSubresource(sbuff, MapMode.WriteDiscard, 0);
datb.Data.Write<cbuff>(m_shadebuff);
datb.Data.Position = 0;
m_context.UnmapSubresource(sbuff, 0);

m_context.VertexShader.SetConstantBuffer(sbuff, 0);


Shader def:

cbuffer cbuff : register(cb0)
{
float4 shadebuff[2048];
};

how I access it

shadebuff[0].xyz;



I'm pretty new to cbuffers, I don't know why it's not working... Any ideas?

[MJP]

If you put an array inside of a structure like that in C#, all you'll have in the structure is a pointer to the array data. The actual data that you want will be in some other area of memory. This is different from C++, where you can embed a static array in a structure and it will work.

If all you have in your constant buffer is an array of float4, then you should just directly create an array of Vector4 in your C# code and pass that to DataBox.Write. There's an overload for Write that takes an array.

[Butabee]

Thanks for the info. I got the correct data from one cbuffer coming in but now I'm having issues with a second.

It's of the same format. Can I have more than one? Or should I try to combine all my data into one cbuffer?

[Butabee]

I got multiple buffers working... I was using the wrong register values... had to change them to b0, b1, etc...

[Starnick]

FYI its possible to set things up to marshal arrays in structs, here's a helpful article on marshalling C# structs to cbuffers (its SharpDX, but should carry over to SlimDX):

http://timjones.tw/blog/archive/2011/03/08/marshalling-c-structures-into-directd--cbuffers-using