VBO under DirectX

VBO under DirectX

Billybob

Member #3,136

January 2003

I can get a nice tutorial on VBOs for OpenGL (NeHe), but I have trouble finding something for DirectX. How do I go about doing the same thing (if it's under a different name) under Direct3D?

And I don't code D3D, I just got to slap this into Irrlicht and be on my merry way.

Thanks!

Thomas Harte

Member #33

April 2000

VBO is... vertex buffer object? If so then this is an area where OpenGL has played catchup with DirectX. Check out MSDN for DirectX vertex buffer information.

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Krzysztof Kluczek

Member #4,191

January 2004

DirectX 9 SDK->DirectX Graphics->Tutorials and Samples->Tutorials->Direct3D Tutorials->Tutorial 2: Rendering Vertices

This should get you started. Follow links in the tutorial to get descriptions what functions do, follow links in these functions' descriptions, etc.

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Billybob

Member #3,136

January 2003

So, DirectX will automatically put the vertex buffer on the video card?
Pfff, OpenGL is behind

So, let's see here. Will this work (the way I want):

1#define D3DFVF_CUSTOMVERTEX (D3DFVF_XYZ | D3DFVF_NORMAL | D3DFVF_DIFFUSE | D3DFVF_TEX2)
2 
3IDirect3DVertexBuffer9* g_pVB = NULL;
4if( FAILED( g_pd3dDevice->CreateVertexBuffer( vertexCount * sizeof(CUSTOMVERTEX), D3DUSAGE_WRITEONLY, D3DFVF_CUSTOMVERTEX, D3DPOOL_MANAGED, &g_pVB, NULL ) ) )
5    return E_FAIL;
6 
7VOID* pVertices;
8if( FAILED( g_pVB->Lock( 0, sizeof(CUSTOMVERTEX) * vertexCount, (void**)&pVertices, 0 ) ) )
9    return E_FAIL;
10  
11memcpy( pVertices, vertices, sizeof(S3DVertex) * vertexCount );
12  
13g_pVB->Unlock();
14 
15 
16// Render
17g_pd3dDevice->SetStreamSource( 0, g_pVB, 0, sizeof(CUSTOMVERTEX) );
18g_pd3dDevice->SetFVF( D3DFVF_CUSTOMVERTEX );
19g_pd3dDevice->DrawPrimitive( D3DPT_TRIANGLELIST, 0, vertexCount / 3 );

Obviously "Render" will occur in a different function.

So, If I understand this correctly "D3DUSAGE_WRITEONLY" should tell it that video memory is the best place for the buffer, right? Or something like that.

Bob

Free Market Evangelist

September 2000

Quote:

So, DirectX will automatically put the vertex buffer on the video card?
Pfff, OpenGL is behind

Behold, the same code in OpenGL:

1 
2#ifndef GL_BUFFER_OFFSET
3#  define GL_BUFFER_OFFSET(x) ((char *)NULL + (x))
4#endif
5 
6GLuint vb;
7glGenBuffer(1, &vb);
8glBindBuffer(GL_ARRAY_BUFFER, vb);
9 
10/* Either this, if you already have a copy of the data */
11glBufferData(GL_ARRAY_BUFFER, sizeof(vertices), vertices, GL_STATIC_DRAW);
12 
13/* Or this, if you want to build the data in place */
14do {
15    GLvoid *ptr = glMapBuffer(GL_ARRAY_BUFFER, GL_WRITE_ONLY);
16    if (!ptr) {
17        return failure;
18    }
19 
20    memcpy(ptr, vertices, sizeof(vertices)); 
21} while (!glUnmapBuffer(GL_ARRAY_BUFFER));  // XXX You may want to handle this case a little better than I did.
22 
23 
24/* Now set up your vertex array */
25glEnableVertexAttribArray(0);
26glVertexAttribPointer(index, size, type, normalized, stride, GL_BUFFER_OFFSET(0));
27 
28/* Render */
29glDrawArray(GL_TRIANGLES, 0, vertex_count/3);

Edit: Fixed code.

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Krzysztof Kluczek

Member #4,191

January 2004

Quote:

GLvoid *ptr = glMapBuffer(GL_ARRAY_BUFFER, GL_WRITE_ONLY);
memcpy(ptr, vertices, sizeof(vertices));

Won't it crash when glMapBuffer returns NULL?

Quote:

glUnmapBuffer()

I guess it should be:
glUnmapBuffer(GL_ARRAY_BUFFER);

Quote:

glVertexAttribPointer(index, size, type, normalized, stride, GL_BUFFER_OFFSET(0));

Is it OpenGL 2.0? There is no such function in OpenGL 1.5, it's ARB_vertex_program and requires *ARB suffix as such (and probably won't work without vertex program set up).

Also, doesn't it require EnableVertexAttribArrayARB?

Anyway, if anybody wants easy to use OpenGL VBO wrapper class, just PM me.

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Billybob

Member #3,136

January 2003

So is my code right?

Krzysztof Kluczek

Member #4,191

January 2004

Quote:

So is my code right?

Does it work? If it does, then it's probably right (at least looks like it should).

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Bob

Free Market Evangelist

September 2000

Quote:

Won't it crash when glMapBuffer returns NULL?

Sure.

Quote:

I guess it should be:
glUnmapBuffer(GL_ARRAY_BUFFER);

Yup.

Quote:

Is it OpenGL 2.0?

Yes. Alternatively, you can use any of the ARB or NV vertex program extensions for the similar functionality.

Quote:

Also, doesn't it require EnableVertexAttribArrayARB?

Sure, you may want to do that too

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