# DX11 DX11-Reuse or Create a new Buffer?

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Hi, so I get at a point where I can render a cube, yay. Now my program loads an .OBJ file to a vposnormaltex layout struct array. I want know how I render new stuff every time I want. Should I reuse the buffer? Or should I Create a new one(using the same ID3D11Buffer)? I notice theres this HRESULT SetPrivateData( REFGUID guid, UINT DataSize, const void *pData ); that the ID3D11Buffer inherits, but Im not sure what I should do..

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Quote:
 Original post by Icebone1000Hi, so I get at a point where I can render a cube, yay. Now my program loads an .OBJ file to a vposnormaltex layout struct array.I want know how I render new stuff every time I want. Should I reuse the buffer? Or should I Create a new one(using the same ID3D11Buffer)?

A buffer can contain any number of objects in any particular formats you want. Just as long as you have allocated enough space for it. The important thing is that you don't create buffers that are too large (a few meg is usually good), and that you properly specify their usage so that they can be placed in the best locations for them (static geometry should not be specified with dynamic/cpu read and write, for instance).
Quote:
 I notice theres thisHRESULT SetPrivateData( REFGUID guid, UINT DataSize, const void *pData);that the ID3D11Buffer inherits, but Im not sure what I should do..

That does not do what you think it does.

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The thing is that the data I want render are set at running time, my app have a open .obj menu item..Everytime a .obj file is opened I want to display the object(Im not considering yet display all .obj opened, just one by one now to make easier).

What my app do at start is set a cube, create a vertexbuffer(subresource = cube), bind it to the input assembly, and render.

What should I do when the .obj is readed?:
-Create a new dx buffer, point the vposnormaltex array, bind it to the IA?

-Re-set the dx buffer, that is alredy binded to the IA(dont know if this is how things works, I remember something like this on DX9, using 'lock' to bring GPU stuff to mem, re-set and sending back)?

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Keep the array of geometry, a pointer to the vertrex buffer, the topology type and the layout together in a class or structure.

For each of these, on every frame, you just set the input type, set the vertex buffer and render everything.

Ideally, you should keep state changes to a minimum. I suppose if your input layout is always the same, you can set it once but realistically this never really happens once you get past the initial stages.

I would suggest trying whatever works for you and when you know more, take a look at the performance considerations documentation on MSDN.

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Thanks for the info.

But I still dont know if theres a way to re-set an alredy created buffer or if I can recreate it every time I want change the data on it.

My program specificaly have 4 types of input layout( pos, posnorm, postex, postexnorm ), witch also means I have to recompile also another effect file.. heres the approach Im taking everytime a file is opened:

OPENFILENAME openFile = {0};...if( GetOpenFileName( &openFile ) ){std::ifstream File;File.open( openFile.lpstrFile,std::ios::in|std::ios::_Nocreate );if( File.is_open() ){							myOBJ.OBJReadDataFromFileStream( File );							myOBJ.OBJTransformDataToDXLayout();switch( myOBJ.OBJGetOBJType() ){case 0x00:if( DXInitEffect( TEXT("BasicTr.fx"), g_pEffect, g_pETech, g_pEPass, g_pDevice ) != S_OK ){MB( " dxerror", "effect load fail", MB_E );									}break;case 0xff:if( DXInitEffect( TEXT("BasicTransformLightTex.fx"), g_pEffect, g_pETech, g_pEPass, g_pDevice ) != S_OK ){MB( " dxerror", "effect load fail", MB_E );}break;case 0xf0:if( DXInitEffect( TEXT("BasicTransformLight.fx"), g_pEffect, g_pETech, g_pEPass, g_pDevice ) != S_OK ){MB( " dxerror", "effect load fail", MB_E );}break;case 0x0f:if( DXInitEffect( TEXT("BasicTransformTex.fx"), g_pEffect, g_pETech, g_pEPass, g_pDevice ) != S_OK ){MB( " dxerror", "effect load fail", MB_E );}break;}if( DXSetBufferResources(	g_pDevice, g_pVB, g_pIB, myOBJ.OBJGetDXVBData(), myOBJ.OBJGetDXVBDataSize() ) != S_OK ){	MB( " dxerror", "set buff", MB_E );}if( DXInitInputAssemble(	g_pDevice,g_pDIContext,myOBJ.OBJGetDXInputLayout(), myOBJ.OBJGetDXLayoutNumElms(), g_pEPass,g_pInputLayout, &g_pVB, 1, myOBJ.OBJGetDXStride(),	&g_pIB, 1 ) != S_OK ){MB( " dxerror", "init ia", MB_E );							}DXSetSCBVariablesInitialValues();//reset matrices and set textureiVcount = myOBJ.OBJGetDXVCount();bStuffToRender = TRUE;File.close();}//is open

Its working fine...but I really dont know how I would do on a game( I dont know many things in fact...)
Is normal an app call a million times pass->apply() and dc->Draw()?

I cant imagine how would be manage the transformation matrices for a bunch of different objects... And how would be sprite animation? On OpenGL what I was used to do is change the texcoord everytime, pretty automatic..cant see any similar way of doing this on DX.

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Use the map function on your device context to edit the contents of a buffer.

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Introduction:
In general my questions pertain to the differences between floating- and fixed-point data. Additionally I would like to understand when it can be advantageous to prefer fixed-point representation over floating-point representation in the context of vertex data and how the hardware deals with the different data-types. I believe I should be able to reduce the amount of data (bytes) necessary per vertex by choosing the most opportune representations for my vertex attributes. Thanks ahead of time if you, the reader, are considering the effort of reading this and helping me.
I found an old topic that shows this is possible in principal, but I am not sure I understand what the pitfalls are when using fixed-point representation and whether there are any hardware-based performance advantages/disadvantages.
(TLDR at bottom)
The Actual Post:
To my understanding HLSL/D3D11 offers not just the traditional floating point model in half-,single-, and double-precision, but also the fixed-point model in form of signed/unsigned normalized integers in 8-,10-,16-,24-, and 32-bit variants. Both models offer a finite sequence of "grid-points". The obvious difference between the two models is that the fixed-point model offers a constant spacing between values in the normalized range of [0,1] or [-1,1], while the floating point model allows for smaller "deltas" as you get closer to 0, and larger "deltas" the further you are away from 0.
To add some context, let me define a struct as an example:
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Assuming that we still have a valid and useful VertexData format, how far could I take this while remaining on the sensible side of what could be called optimization? Theoretically I could use the an input element format such as DXGI_FORMAT_R10G10B10A2_UNORM to pack my normal coordinates into a 10-bit fixed-point format, and my verticies (in object space) might even be representable in a 16-bit unsigned normalized fixed-point format. That way I could end up with something like the following struct:
struct VertexData { uint16_t[3] pos; //3x16bits uint16_t[2] texCoord; //2x16bits uint32_t packedNormals; //10+10+10+2bits } //Total of 14 bytes Could I use a vertex structure like this without too much performance-loss on the GPU-side? If the GPU has to execute some sort of unpacking algorithm in the background I might as well let it be. In the end I have a functioning deferred renderer, but I would like to reduce the memory footprint of the huge amount of vertecies involved in rendering my landscape.
TLDR: I have a lot of vertices that I need to render and I want to reduce the RAM-usage without introducing crazy compression/decompression algorithms to the CPU or GPU. I am hoping to find a solution by involving fixed-point data-types, but I am not exactly sure how how that would work.
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