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Getting the number of vertices from a CVertexBuffer

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sum1nil

Sat Jun 19 2010, 09:10PM

Sum1nil

Registered Member #284
Joined Wed Mar 11 2009, 11:46PM
posts 21

Hi,

There are, I'm sure better ways to do this, but would this work to get the number of vertices of CVertexBuffer and properly position the next read using getAsVector3df()

Thanks for any help.

<div class='indent'>
void LfBulletLargeTerrainModel::tileLoaded(res::CTerrainTileEvent& event)
{
res::CMesh* tileMesh = event.getMesh();
res::CVertexBuffer* vertices = tileMesh->getVertexBuffer();
lf::u32 jump = vertices->getEntrySize();
lf::s32 size = sizeof(vertices) * jump;
for (lf::s32 i = 0; i < size;)
{

core::vector3d<lf::f32> vec1 = vertices->getAsVector3df(res::EVCT_POSITION, i);
i += jump;
core::vector3d<lf::f32> vec2 = vertices->getAsVector3df(res::EVCT_POSITION, i);
i += jump;
core::vector3d<lf::f32> vec3 = vertices->getAsVector3df(res::EVCT_POSITION, i);
i += jump;
btVector3 pos1 = tk.ConvertToBtVector( vec1 );
btVector3 pos2 = tk.ConvertToBtVector( vec2 );
btVector3 pos3 = tk.ConvertToBtVector( vec3 );
//btVector3 pos4 = tk.ConvertToBtVector( edges[1] );
physicsTerrain->addTriangle(pos1, pos2, pos3, true);

//physicsTerrain->addTriangle(pos4, pos2, pos3, true);
}
int numTriangles = physicsTerrain->getNumTriangles();
printf("Tile Loaded!");
}
</div>

Matthias

Sun Jun 20 2010, 02:09AM

Location: Hamburg, Germany
posts 399

you dont need to increase i by "jump" you can increase it simply by 3. something like
for(i = 0; i < vertexbuffer->getVertexCount() - 3;i+=3)
{
core::vector3df vec1 = vertexbuffer->getPosition(i);
core::vector3df vec2 = vertexbuffer->getPosition(i + 1);
core::vector3df vec3 = vertexbuffer->getPosition(i + 2);

}

this is actually a more safe way because it handles the difference between interleaved and non-interleaved vertexbuffers for you. your version would only work for interleaved buffers and non-interleaved is the default in lf.

if you need more detailed information, let me know - this is from my head so it might not be 100% correct.
[ Edited Sun Jun 20 2010, 02:12AM ]

sum1nil

Mon Jun 21 2010, 09:45AM

Sum1nil

Registered Member #284
Joined: Wed Mar 11 2009, 11:46PM
posts 21

Hi,
Thanks for the advice, I completely did not see the getVertexCount method; much easier.

I have many more questions, but I want to wait to ask until I can phrase them better.

:)

Matthias

Mon Jun 21 2010, 10:14AM

Location: Hamburg, Germany
posts 399

just ask and ill tell you when i dont understand the questions :)

sum1nil

Sun Jun 27 2010, 12:04AM

Sum1nil

Registered Member #284
Joined: Wed Mar 11 2009, 11:46PM
posts 21

Hi hope all is well.
I would appreciate info on the large terrain.

It seems both the vertex stride and index stride while using CvertexBuffer and CIndexBuffer fixs the distance between (ie. stride) to zero. Although I had thought you'd use like indexStride = 3* sizeof(int). I just don't know ( also please keep in mind I am tring to 'serialize' to a .bullet file the tiles I load in the largeterrain via tileLoad). Bullet uses an IndexedMesh and those meshes are added to the shape being built.

The created physicsTerrian serializes w/o error to disk aka. something.bullet

However, when something.bullet loads, it figues vertex and index stride all by itself and comes up with 12 for the 'triangle' index stride and 16 for the vertex stride. As soon as the vertex stride is used for calculation (this is in bullet), I get the dreaded 'access violation'.

So I just want to make sure that both vertex and index stride in lightfeather are 0 when using a tile event mesh.

I honestly don't know what to do on the bullet end. It seems to make sense; the position vertex size is 3*float=12; the Entrysize is 28 and the proposed stride by bullet is 28 - 12 = 16. The bullet triangle index stride is 3*int=12. It would sem the actual size of the vertex formation from lightfeather is getting sucked along into bullet.

Note: will try to make this more coherent later when I'm not so confused.

Thanks for the tolerance :)

Sorry for the ramble,

Matthias

Sun Jun 27 2010, 11:43AM

Location: Hamburg, Germany
posts 399

look at the difference between interleaved and non-interleaved vertexbuffers. its described in cvertexbuffer.h. i think that might be whats confusing you. lf uses non-interleaved buffers by default.

sum1nil

Thu Jul 01 2010, 06:28AM

Sum1nil

Registered Member #284
Joined: Wed Mar 11 2009, 11:46PM
posts 21

Hi,
In the mesh passed to the tile load event, I can get a pointer to the indexBuffer. However it has a 'used' variable of 0 and although it has a memory address the values appear to be identical throughout.

Are the indices set later on past the tile load event?

TY
* Put the whole thing over at http://pastebin.com/6LMvwsse

Matthias

Thu Jul 01 2010, 02:21PM

Location: Hamburg, Germany
posts 399

yes, the indexes must be filled later because they depend on the LOD of neighboring terrainpatches.
So if the LOD changes, the indexbuffer's contents change as well. Im sorry i forgot to tell you this before.

Matthias

Thu Jul 01 2010, 02:35PM

Location: Hamburg, Germany
posts 399

also there are additional indexbuffers used to fill the cracks that appear when two neighboring patches have different LODs.

Matthias

Thu Jul 01 2010, 02:47PM

Location: Hamburg, Germany
posts 399

the indexes are set at the end of the call to setupIndexBuffers in CLargeTerrainModel.cpp . maybe you need a callback/event there to setup your physics terrain ?!

sum1nil

Sat Jul 03 2010, 05:24PM

Sum1nil

Registered Member #284
Joined: Wed Mar 11 2009, 11:46PM
posts 21

Is the call to setupIndexBuffers the final call setting up the large terrain and/or updating large terrain?

I'll have to study some to figure out setting up callbacks. Maybe setting a global callback somehow for large terrain so everytime it is made/updated the callback executes. I gotz some reading to do. :)

I would say Happy 4th of July, but I think you guys aren't into that much, eh?

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