   Collision sliding
  Hello,I've been trying to create a collision sliding effect for a loooong time now, and it is always bugged. I looked everywhere and can't figure it out.I have ray->polygon collision and it works fine, but the characters just stops when he hits the wall, instead of sliding along it.I tried fixing this by extracting and calculating mesh face normals, and using them to push the user back. This works (in most cases) fine if I slide along a straight wall, but if I hit a spehere or cylinder it doesn't work so well, I assume it's a problem with either my way of caluculating the face normals, or the way I use them to push the user back.When I hit spehere or cylinder or any other non-straight surface it will either not slide at all, or it will push me back too much creating this ugly bouncy effect, and also I can always come close enough to cylinders to see through them(which I can't with walls).Here's my collision code:if( checkCollision( mesh, &cCamera, xMove, yMove, zMove, &length, &FaceIndex, &u, &v ) ){//xMove, zMove ARE SIMPLY HOW MUCH TO MOVE EACH FRAME, DEPENDING ON BUTTON PRESSED// THE SIMPLE COLLISION, NO SLIDING, BUT WORKSfloat diff;diff = length - 5.00;D3DXVECTOR2 vecDir;D3DXVec2Normalize(&vecDir, &D3DXVECTOR2(xMove, zMove));vecDir *= diff;xMove = vecDir.x;zMove = vecDir.y;// END SIMPLE// MY ATTEMPT ON SLIDINGvertex*vert;WORD*indices = 0;D3DXVECTOR3 indNormal, vec1, vec2, vec3, vNormal;// CODE TO CALCULATE THE FACE NORMALS// clonedMesh is an empty mesh containing ONLY vertex normals// GET THE LOCATION OF NORMALS FROM INDEX BUFFER, USING faceIndex RETURNED BY THE D3DXIntersectclonedMesh->LockIndexBuffer(0, ( LPVOID* )&indices);indNormal.x = indices[FaceIndex*3];indNormal.y = indices[FaceIndex*3+1];indNormal.z = indices[FaceIndex*3+2];clonedMesh->UnlockIndexBuffer();// get the normalsclonedMesh->LockVertexBuffer( 0, ( LPVOID* )&vert );vec1 = D3DXVECTOR3( vert[( int )indNormal.x]._nx, vert[( int )indNormal.x]._ny, vert[( int )indNormal.x]._nz );vec2 = D3DXVECTOR3( vert[( int )indNormal.y]._nx, vert[( int )indNormal.y]._ny, vert[( int )indNormal.y]._nz );vec3 = D3DXVECTOR3( vert[( int )indNormal.z]._nx, vert[( int )indNormal.z]._ny, vert[( int )indNormal.z]._nz );clonedMesh->UnlockVertexBuffer( );vNormal = vec1 + u*(vec3-vec2) + v*(vec3-vec1); // calculate the final face normal using 3 vertex normals //and barycentric coordinates returned by D3DXIntersectD3DXVec3Normalize(&vNormal, &vNormal);float xMoveTemp = 0.0f;float yMoveTemp = 0.0f;float zMoveTemp = 0.0f;// ATTEMPT TO SLIDE....xMoveTemp+=  vNormal.x * diff;xMove =  xMove + xMoveTemp;zMoveTemp+=  vNormal.z* diff;zMove =  zMove + zMoveTemp;}// COLLISION FUNCTION, I DOUBT THE PROBLEM IS HEREBOOL checkCollision(ID3DXMesh *mesh, cCamera* cCamera, float xMove, float yMove,float zMove, float *length, DWORD *FaceIndex, float *u, float *v){float sX, sY, sZ;float eX, eY, eZ;float fSize = 0.0f;float diffX, diffY, diffZ;BOOL hit;float dist;DWORD faceHit;sX = cCamera->getXLoc();sY = cCamera->getYLoc();sZ = cCamera->getZLoc();eX = cCamera->getXLoc() + xMove;eY = cCamera->getYLoc() + yMove;eZ = cCamera->getZLoc() + zMove;eX = ( eX != 0 ) ? eX - eX/fabs(eX) * 4.0f : 0;// ADD 4.0f TO VEL. VECTOR SO WE DON'T COME TOO CLOSE TO //THE OTHER MESH, COZ THEN WE CAN SEE THROUGH IT//eY = ( eY != 0 ) ? eY - eY/fabs(eY) * 4.5f : 0;eZ = ( eZ != 0 ) ? eZ - eZ/fabs(eZ) * 4.0f : 0;diffX = eX - sX;diffY = eY - sY;diffZ = eZ - sZ;D3DXVECTOR3 vDir;D3DXVec3Normalize(&vDir, &D3DXVECTOR3(diffX, diffY, diffZ));D3DXIntersect(mesh, &D3DXVECTOR3(sX, sY, sZ), &vDir, &hit,FaceIndex, u, v, &dist, 0, 0);if(hit == TRUE){fSize = (float)sqrt(diffX*diffX+diffY*diffY+diffZ*diffZ);if(dist > fSize){hit = FALSE;}else{*length = dist;}}return hit;}So to summarize, I need someone to show me how to create a working sliding effect.Please help, I'm desperate!Thank you!   
  From what I can see in your code you are trying to slide along the normalof the trinagle you are intersecting with, instead you should slide along its tangent.Also i would recommend to represent you "character" using some kind of bounding volume maybe a sphere.Hope this helps.   