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Vertex Buffer problem
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3DRaddict Offline
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Post: #1
Vertex Buffer problem
I'm currently experiencing a problem accessing selected vertices in a simple grid mesh.
I'm trying one of Method A or Method B to do so:

Method A)
PHP Code:
// Method A
// --------
   // ------------------------------------------------------------------------------------
   // translating a vertex using hardware vertex buffer
   // ------------------------------------------------------------------------------------
   
Byte *data=mesh.parts(0).render.vtxLock(LOCK_READ_WRITE);
   
Int vtx_size=mesh.parts(0).render.vtxSize();
   
Int pos_ofs=mesh.parts(0).render.vtxOfs(VTX_POS);
   
Int tex0_ofs=mesh.parts(0).render.vtxOfs(VTX_TEX0);
 
   
Vec pos;
   
   for(
int i 0mi++)
   {
      for(
int j 0nj++)
      {
         
int k=i*n+j;
         
pos=*(Vec*)(data pos_ofs k*vtx_size);
         
         if( 
i==&& j==0// edit to change (i,j) vertex
            
*((Vec*)(data pos_ofs k*vtx_size)) = Vec(pos.x5pos.z); // raise selected vertex by 5 units
         
else 
            *((
Vec*)(data pos_ofs k*vtx_size)) = Vec(pos.x0pos.z); // all level 
      
}
   }
   
mesh.parts(0).render.vtxUnlock(); // NB unlock after all read/write is completed // all level
   
   // -------------------------------------------------------------------------------------- 

Method B)
PHP Code:
// Method B
// --------
   // ------------------------------------------------------------------------------------
   // translating a vertex on same mesh using CPU (software)
   // ------------------------------------------------------------------------------------
   
Vec pos;
   
   for(
int i 0mi++)
   {
      for(
int j 0nj++)
      {
         
int k=i*n+j;
         
pos=mesh.parts(0).base.vtx.pos(k);
         
         if( 
i==&& j==0// edit to change (i,j) vertex
            
mesh.parts(0).base.vtx.pos(k) = Vec(pos.x5pos.z); // raise selected vertex by 5 units
         
else
            
mesh.parts(0).base.vtx.pos(k) = Vec(pos.x0pos.z);
         
      }
   }
   
mesh.setRender();
   
   
// -------------------------------------------------------------------------------------- 
I've tested each method using the same 5x9 vertex grid.
For each method I've raised each of the corner vertices (0,0) , (0,8) , (4,0) and (4,8) five units above ground zero.
Here are the results for each method:

Method B)
vertex(0,0)
[Image: Problem_B_0_0.jpg]

vertex(0,8)
[Image: Problem_B_0_8.jpg]

vertex(4,0)
[Image: Problem_B_4_0.jpg]

vertex(4,8)
[Image: Problem_B_4_8.jpg]



Method A)
vertex(0,0)
[Image: Problem_A_0_0.jpg]

vertex(0,8)
[Image: Problem_A_0_8.jpg]

vertex(4,0)
[Image: Problem_A_4_0.jpg]

vertex(4,8)
[Image: Problem_A_4_8.jpg]

As you can see 'Method B' makes sense and works as expected.
'Method A' is nonsensical, and I fail to understand why the same vertex references do not give identical results as 'Method B'
This is probably the reason why I am not getting nice round ripples in my 'Custom Shader Training Project.

Here is the small demo project of this problem for investigation purposes.
VertexBufferProblem project files
(This post was last modified: 12-03-2014 09:04 PM by 3DRaddict.)
12-03-2014 09:03 PM
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3DRaddict Offline
Member

Post: #2
RE: Vertex Buffer problem
@Esenthel:
I really would appreciate the courtesy of an acknowledgement or reply to my query.
After all, I did take the trouble to provide a fairly detailed example of my problem.

Am I doing something stoopid and illogical?
If I am, then please put me right.

If not, then please provide an explanation as to why it is not working similar to Method B, and a possible workaround.
12-05-2014 04:13 PM
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Rofar Offline
Member

Post: #3
RE: Vertex Buffer problem
I feel sure the Greg will not ignore your post. He probably has just not had time to look at it yet.

In taking a quick look at your 2 different methods, it looks like you are making the assumption that the vertex data in the hardware buffer is aligned in a sequential manor and I suspect that is not the case. When you access the vertices in the software buffer in Method B, you are referencing a list of vertices that are aligned sequentially.

I suspect the graphics driver does some optimization to the data and the order of the vertices in the buffer is not in the same sequence as the software buffer.
12-05-2014 10:31 PM
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Esenthel Offline
Administrator

Post: #4
RE: Vertex Buffer problem
Hello

When calling mesh setRender it has a parameter Bool optimize=true , which works by reordering the triangles and vertexes for more optimal performance.
12-06-2014 01:29 AM
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3DRaddict Offline
Member

Post: #5
RE: Vertex Buffer problem
At last... perfect round ripples!grin

[Image: RoundRipples.jpg]

just by changing 'myWater.setRender()' to 'myWater.setRender(false)'

I would of saved myself one helluva lot of bother and time if I'd known this sooner!
12-06-2014 06:15 AM
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fatcoder Offline
Member

Post: #6
RE: Vertex Buffer problem
Esenthel Wrote:Bool optimize=true , which works by reordering the triangles and vertexes for more optimal performance.
Maybe that should be added to the Mesh setRender header comment. smile
12-06-2014 08:04 AM
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Esenthel Offline
Administrator

Post: #7
RE: Vertex Buffer problem
Will be included in next release.
12-06-2014 08:07 AM
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