/// <summary>
/// Determines if two static (non-moving) meshes interpenetrate.
/// </summary>
/// <param name="other">The mesh to test for intersection against.</param>
/// <param name="worldMat1">The world transform matrix for this mesh.</param>
/// <param name="worldMat2">The world transform matrix for 'other'.</param>
/// <returns>A boolean value indicating whether interpenetration occurs.</returns>
public bool Intersects( Mesh other, Matrix worldMat1, Matrix worldMat2 )
{
for ( int vertexIndex = 0; vertexIndex < numVertices; ++vertexIndex )
{
Vector2 vertex = Vector2.TransformCoordinate( GetVertexPosition( vertexIndex ), worldMat1 );
int numAwayFacingEdges = 0;
for ( int edgeIndex = 0; edgeIndex < other.NumEdges; ++edgeIndex )
{
Edge edge = other.GetEdge( edgeIndex );
Vector2 edgeCenter =
( Vector2.TransformCoordinate( edge.Vertex1Pos, worldMat2 ) +
Vector2.TransformCoordinate( edge.Vertex2Pos, worldMat2 ) ) * 0.5f;
Vector2 vertexDir = edgeCenter - vertex;
// If the edge faces away from the vertex
if ( Vector2.Dot( vertexDir, edge.Normal ) >= 0.0f )
++numAwayFacingEdges;
}
if ( numAwayFacingEdges == other.NumEdges )
return true;
}
for ( int vertexIndex = 0; vertexIndex < other.NumVertices; ++vertexIndex )
{
Vector2 vertex = Vector2.TransformCoordinate( other.GetVertexPosition( vertexIndex ), worldMat2 );
int numAwayFacingEdges = 0;
for ( int edgeIndex = 0; edgeIndex < NumEdges; ++edgeIndex )
{
Edge edge = GetEdge( edgeIndex );
Vector2 edgeCenter =
( Vector2.TransformCoordinate( edge.Vertex1Pos, worldMat1 ) +
Vector2.TransformCoordinate( edge.Vertex2Pos, worldMat1 ) ) * 0.5f;
Vector2 vertexDir = edgeCenter - vertex;
// If the edge faces away from the vertex
if ( Vector2.Dot( vertexDir, edge.Normal ) >= 0.0f )
++numAwayFacingEdges;
}
if ( numAwayFacingEdges == NumEdges )
return true;
}
return false;
}
public static void GenerateShadow( Mesh polygonGeometry, Matrix worldMatrix, Vector2 lightPosWS,
float zValue, Vector2 shadowCasterCenter)
{
Vector3 UVOffset = new Vector3( 0.0f, -0.5f, 0.0f );
// Transform the light position into model space
Vector2 lightPos = Vector2.TransformCoordinate( lightPosWS, Matrix.Invert( worldMatrix ) );
List<Edge> contourEdges = new List<Edge>();
for ( int edgeIndex = 0; edgeIndex < polygonGeometry.NumEdges; ++edgeIndex )
{
Edge edge = polygonGeometry.GetEdge( edgeIndex );
Vector2 edgeCenter = ( edge.Vertex1Pos + edge.Vertex2Pos ) * 0.5f;
Vector2 incidentLightDir = edgeCenter - lightPos;
// If the edge faces away from the light source
if ( Vector2.Dot( incidentLightDir, edge.Normal ) >= 0.0f )
{
contourEdges.Add( edge );
}
}
if ( contourEdges.Count < 1 || contourEdges.Count == polygonGeometry.NumEdges )
{
return;
}
const float ExtrudeMagnitude = 1280;
Shadow shadow = new Shadow();
Vector3 lightPosVec3 = new Vector3( lightPos.X, lightPos.Y, zValue );
lightPosVec3.TransformCoordinate( worldMatrix );
int quadIndex = 0;
foreach ( Edge edge in contourEdges )
{
Vector3 vertex1 = new Vector3(
edge.Vertex1Pos.X, edge.Vertex1Pos.Y, zValue );
Vector3 vertex2 = new Vector3(
edge.Vertex2Pos.X, edge.Vertex2Pos.Y, zValue );
// Transform the position data from model space to world space
vertex1.TransformCoordinate( worldMatrix );
vertex2.TransformCoordinate( worldMatrix );
Quad quad = new Quad();
Color shadowColor = Color.FromArgb( 1, 0, 0, 0 );
quad.Vertices[ 2 * quadIndex + 0 ].Position = vertex1 + UVOffset -
18.0f * Vector3.Normalize( vertex1 - lightPosVec3 );
quad.Vertices[ 2 * quadIndex + 0 ].Color = shadowColor.ToArgb();
quad.Vertices[ 2 * quadIndex + 1 ].Position = vertex1 + ExtrudeMagnitude * ( vertex1 - lightPosVec3 )
+ UVOffset;
quad.Vertices[ 2 * quadIndex + 1 ].Color = shadowColor.ToArgb();
quad.Vertices[ 2 * quadIndex + 2 ].Position = vertex2 + UVOffset -
18.0f * Vector3.Normalize( vertex2 - lightPosVec3 );
quad.Vertices[ 2 * quadIndex + 2 ].Color = shadowColor.ToArgb();
quad.Vertices[ 2 * quadIndex + 3 ].Position = vertex2 + ExtrudeMagnitude * ( vertex2 - lightPosVec3 )
+ UVOffset;
quad.Vertices[ 2 * quadIndex + 3 ].Color = shadowColor.ToArgb();
shadow.Quads.Add( quad );
}
shadows.Add( shadow );
}