D3DXIntersect and getting face normal

D3DXIntersect and getting face normal

• Jason Payne

  I'm not realy liking that function after all. It seems to return a list of all the triangles that were intersected by the ray, wich means that it doesn't return as soon is it hits the first triangle, so it is not good for what I need.
  
  I've changed my line/triangle intersection function with D3DXIntersectTri() thought.
  
  
  
  

• Brian Richards

  That's it... i know FVF declaration so there was no problem.
  
  Thanks!
  
  

• T0MM0

  You'll need to look it up based on whatever is stored in the pFaceIndex output.
  
  Lock the index buffer and look up the [pFaceIndex * 3] index (or +0,+1,+2 for each vertex), you then need to use the index to look up the actual vertex - lock the vertex buffer and extract the properties.
  
  It's not too hard to throw that together, but it does get complex when dealing with arbitrary meshes. Handling the 32bit case is okay, but for arbitrary vertices you either need to traverse the vertex declaration (see ID3DXBaseMesh::GetDeclaration()) or clone it to a known format (see ID3DXBaseMesh::CloneMesh[FVF]()).
  
  If you do this sort of work on a regular basis (e.g. in the core loop) then it might be worth storing a CPU-addressable copy of the vertex data. Unless the mesh is pretty huge you shouldn't really waste that much RAM and it'll make the code simpler and faster (locking is rarely a quick operation). If you consider this, try using D3DXIntersectTri() instead of D3DXIntersect().
  
  hth
  Jack
  
  
  

• bill4012

  I'm always learning in this forum.
  There is a function on the D3DX API to check mesh/ray intersection and I've implemented it my self !
  I see that I have to go thru all the D3DX api before implementing anything...
  
  
  
• D3DXIntersect and getting face normal