//---------------------------------------------------------
// Test a line against a mesh
// Select the closest front-facing triangle
int CMesh::LineSelect( const Vector3 &LP1, const Vector3 &LP2 )
{
Vector3 HitP;
int nbHits = 0;
int nSelTri = -1;
float fDistance = 1000000000.0f;
for (int nTri = 0; nTri < (int)mTriCount; nTri++ )
{
if ( mTriFlags[ nTri ] & TF_BACKFACING ) continue; // Check only front facing triangles
int nV = nTri*3;
bool bHit = CheckLineTri( LP2, LP1, mVertices[ mIndices[nV] ], mVertices[ mIndices[nV+1] ], mVertices[ mIndices[nV+2] ], HitP );
if ( bHit ) {
if ( HitP.distance( LP1 ) < fDistance ) {
fDistance = HitP.distance( LP1 );
nSelTri = nTri;
}
nbHits++;
}
}
selectTriangle( nSelTri );
return nbHits;
}
//
// returns false if the triangle is not within the frustum
//
bool TriInFrustum( CVec3 vTri[3], CVec3 Normals[4], CVec3 Points[8] )
{
int i;
// If all 3 points are to one side any frustum plane return false
for( int x = 0; x < 4; x++ )
{
for ( i = 0; i < 3; i++ )
{
if ( Normals[x].Dot( vTri[i] - Points[x*2] ) < 0 ) break;
}
if ( i >= 3 ) return false;
}
// If any point is in the frustum, return true
for ( i = 0; i < 3; i++ )
{
if ( PointInFrustum( vTri[i], Normals, Points ) ) return true;
}
// If we didn't get quick result, do a slower but accurate test.
// If any of the lines of the triangle are in the frustum, the triangle is in the frustum
if ( LineInFrustum( vTri[0], vTri[1], Points ) ) return true;
if ( LineInFrustum( vTri[1], vTri[2], Points ) ) return true;
if ( LineInFrustum( vTri[2], vTri[0], Points ) ) return true;
// If the frustum is completely inside the triangle, any frustum line into the screen will intersect the triangle
CVec3 HitP;
if ( CheckLineTri( Points[0], Points[1], vTri[0], vTri[1], vTri[2], HitP ) ) return true;
return false;
}
//
// Test a line against a mesh
// Selects the closest front-facing triangle
//
int CMesh::LineSelect( const CVec3 &LP1, const CVec3 &LP2 )
{
CVec3 HitP;
int nbHits = 0;
int nSelTri = -1;
float fDistance = 1000000000.0f;
for (int nTri = 0; nTri < m_nbTris; nTri++ )
{
if ( m_pTriFlags[ nTri ] & TF_BACKFACING ) continue; // Check only front facing triangles
int nV = nTri*3;
bool bHit = CheckLineTri( LP2, LP1, m_pVerts[ m_pTris[nV] ], m_pVerts[ m_pTris[nV+1] ], m_pVerts[ m_pTris[nV+2] ], HitP );
if ( bHit ) {
if ( HitP.Distance( LP1 ) < fDistance ) {
fDistance = HitP.Distance( LP1 );
nSelTri = nTri;
}
nbHits++;
}
}
SelectTriangle( nSelTri );
return nbHits;
}
//
// LineInFrustum is much slower than it could be. I don't think it will be called very often, if it ever is I'll rewrite it.
// It just constructs a 4-plane frustum box out of triangles, and uses the Line-Triangle test.
//
bool LineInFrustum( const CVec3 &LP1, const CVec3 &LP2, CVec3 Points[8] )
{
CVec3 HitP;
int List[24] = { 0, 1, 2, 1, 2, 3, 0, 1, 6, 1, 6, 7, 6, 7, 5, 6, 5, 4, 2, 3, 5, 2, 5, 4 };
for ( int x = 0; x < 8; x++ )
if ( CheckLineTri( LP1, LP2, Points[ List[x*3] ], Points[ List[x*3+1] ], Points[ List[x*3+2] ], HitP ) )
return true;
return false;
}
