About SetStreamSource function

You can set both stream ids to 0 since you are using 1 at a time.

uhm bit i want to set stream 1 contain vertexbuffer 1 and stream 2 contain vertexbuffer 2 to increase performance is it possible???, sorry because noop question.

In case of drawing two triangles from different vertex buffers, you don't set buffers as different stream numbers. I don't understand what kind of performance boost you are expecting in this case.

You'll use multiple streams in the case if you need the data from both of the buffers in the _same_ drawing call. For example, having multiple vertex coordinates (which you don't always need) or doing geometry instacing are cases where multiple streams are needed. Otherwise, you'll just use stream 0.

Drawing two triangles is quite bad example for optimizing performance. Of course, you can do it faster by putting both of the triangles in the same vertex buffer and draw them in a single call. This is called batching in which you are trying to minimize the amount of DrawPrimitive calls.

Cheers !

[edit] funny typos ..

uhm i still not understand why i can't put 2 vertex buffers into 2 stream and display it. Is something wrong here, can u explain to me

Well, by default, your FVF vertex format code defines the data to come from stream 0. So, logically, if you set your VB as stream 1 and you use the FVF code, the vertex pipeline doesn't have any data available.

Possibly you could write a vertex declaration for the custom vertex where you define all your data to come from stream 1, but it doesn't really make sense.

Check for the details here:

http://msdn.microsoft.com/archive/default.asp?url=/archive/en-us/directx9_c_Dec_2005/Programming_One_or_More_Streams.asp

Cheers!

D3DXMATRIXA16 matWorld;
if( SUCCEEDED( g_pd3dDevice->BeginScene() ) )
{
SetupMatrices();

g_pd3dDevice->SetStreamSource( 0, pVB1, 0, sizeof(CUSTOMVERTEX) );
g_pd3dDevice->SetFVF( D3DFVF_CUSTOMVERTEX );
g_pd3dDevice->DrawPrimitive( D3DPT_TRIANGLESTRIP, 0, 1 );

D3DXMatrixTranslation( &matWorld, 1.0f,1.0f,0.0f);
g_pd3dDevice->SetTransform( D3DTS_WORLD, &matWorld );

g_pd3dDevice->SetStreamSource( 1, pVB2, 0, sizeof(CUSTOMVERTEX) );
g_pd3dDevice->SetFVF( D3DFVF_CUSTOMVERTEX );
g_pd3dDevice->DrawPrimitive( D3DPT_TRIANGLESTRIP, 0, 1 );

g_pd3dDevice->EndScene();
}

g_pd3dDevice->Present( NULL, NULL, NULL, NULL );

D3DXMATRIXA16 matWorld;
if( SUCCEEDED( g_pd3dDevice->BeginScene() ) )
{
SetupMatrices();

g_pd3dDevice->SetStreamSource( 0, pVB1, 0, sizeof(CUSTOMVERTEX) );
g_pd3dDevice->SetFVF( D3DFVF_CUSTOMVERTEX );
g_pd3dDevice->DrawPrimitive( D3DPT_TRIANGLESTRIP, 0, 1 );

D3DXMatrixTranslation( &matWorld, 1.0f,1.0f,0.0f);
g_pd3dDevice->SetTransform( D3DTS_WORLD, &matWorld );

g_pd3dDevice->SetStreamSource( 1, pVB2, 0, sizeof(CUSTOMVERTEX) );
g_pd3dDevice->SetFVF( D3DFVF_CUSTOMVERTEX );
g_pd3dDevice->DrawPrimitive( D3DPT_TRIANGLESTRIP, 0, 1 );

g_pd3dDevice->EndScene();
}

g_pd3dDevice->Present( NULL, NULL, NULL, NULL );

Hi,

- As I explained in the earlier post, you'll need to use SetVertexDeclaration(...) instead of SetFVF(...) to be able to use other streams.

- Even if you are able to make your code work, it won't be as efficient as using only 1 buffer since vertex buffer switch is a costly operation.

- Can you please explain why this is so important to you ? You have already an exact answer to your original question.

Cheers !

sorry about noop question, i just want to know more about 'stream' in DX, and thanks for your help, i think u right, setFVF only apply for 'stream 0' so why my second VB didn't show.

Streams in DX are used to distribute your vertex data (more precisely vertex components) into multiple vertex streams. Fof example, you can put vertex position and normal into one buffer and texture coordinates into another buffer. By setting these two buffers as stream 0 and stream 1 you can combine the position and normal from first buffer and texcoord from second buffer to get complete vertices which are used in the following DrawPrimitive call. This is particularly useful when you want to e.g. combine one set of texcoords with multiple sets of geometry (i can't come up with any other examples right now). Basically said it lets you decompose elements of your vertices into multiple buffers and then combine them to feed the pipeline.

When you just want to draw multiple primitives of the same vertex type, putting them in the same vertex buffer should be the fastest way. Multiple streams are just not designed for that.