private static void CheckForAndManageCollision( ref Entity entity, ref Building building )
{
if ( entity.AABB.Min.X > building.AABB.Max.X || entity.AABB.Max.X < building.AABB.Min.X ||
entity.AABB.Min.X > building.AABB.Max.X || entity.AABB.Max.X < building.AABB.Min.X )
{
entity.Collision = 0;
return;
}
// SAT part 2 here:
tempAABBVerts[0] = entity.AABB.Min;
tempAABBVerts[1] = new Vector2( entity.AABB.Min.X, entity.AABB.Max.Y );
tempAABBVerts[2] = entity.AABB.Max;
tempAABBVerts[3] = new Vector2( entity.AABB.Max.X, entity.AABB.Min.Y );
int vertCount = building.Boundary.Length;
for ( int i = 0; i < vertCount; ++i )
{
float lower = float.MaxValue;
float upper = float.MinValue;
for ( int j = 0; j < 4; ++j )
{
float proj = ( building.Boundary[i].X - tempAABBVerts[j].X ) * building.Normals[i].X +
( building.Boundary[i].Y - tempAABBVerts[j].Y ) * building.Normals[i].Y;
if ( proj < lower ) lower = proj;
if ( proj > upper ) upper = proj;
}
if ( upper < 0 || lower > building.SATProjections[i] )
{
entity.Collision = 0;
return;
}
}
// resolve collision here:
Vector2 bToA = Vector2.Zero;
bToA.X = entity.NextPosition.X - building.Center.X;
bToA.Y = entity.NextPosition.Z - building.Center.Y;
// use difference to seperate entities
Vector2 direction;
Vector2.Normalize( ref bToA, out direction );
float resolveMoveSpeed = 2f;
if ( entity.Collision == 0 || building.Index < entity.Collision )
{
entity.Direction.X = resolveMoveSpeed * direction.X;
entity.Direction.Z = resolveMoveSpeed * direction.Y;
entity.Collision = 5;
}
}
private bool TestBuildingVsAABB( Building building, AABB aabb )
{
Vector2 min = Vector2.Clamp( building.AABB.Min, Min, Max );
Vector2 max = Vector2.Clamp( building.AABB.Max, Min, Max );
float cellWidth = ( Max.X - Min.X ) / Cols;
int colMin = (int)( ( min.X - Min.X ) / cellWidth );
int colMax = (int)( ( max.X - Min.X ) / cellWidth );
float cellHeight = ( Max.Y - Min.Y ) / Rows;
int rowMin = (int)( ( min.Y - Min.Y ) / cellHeight );
int rowMax = (int)( ( max.Y - Min.Y ) / cellHeight );
// make sure the maxs don't go out of bounds
if ( colMax == Cols )
colMax = colMin;
if ( rowMax == Rows )
rowMax = rowMin;
// test polygon's aabb against aabb (effectively aabb version of SAT)
if ( aabb.Max.X < min.X || aabb.Min.X > max.X ) return false;
if ( aabb.Max.Y < min.Y || aabb.Min.Y > max.Y ) return false;
tempAABBVerts[0] = aabb.Min;
tempAABBVerts[1] = new Vector2( aabb.Min.X, aabb.Max.Y );
tempAABBVerts[2] = aabb.Max;
tempAABBVerts[3] = new Vector2( aabb.Max.X, aabb.Min.Y );
// SAT using building's axes
for ( int i = 0; i < building.Boundary.Length; ++i )
{
float lower = float.MaxValue;
float upper = float.MinValue;
for ( int j = 0; j < tempAABBVerts.Length; ++j )
{
Vector2 disp = building.Boundary[i] - tempAABBVerts[j];
float proj = Vector2.Dot( disp, building.Normals[i] );
if ( proj < lower ) lower = proj;
if ( proj > upper ) upper = proj;
}
if ( upper < 0 || lower > building.SATProjections[i] )
return false;
}
return true;
}
private bool DetermineIfPathCellIsWalkable( AABB aabb, Building[] buildings )
{
for ( int i = 0; i < buildings.Length; ++i )
{
if ( TestBuildingVsAABB( buildings[i], aabb ) )
return false;
}
return true;
}
public void RemoveBuilding( ref Building building )
{
}
public void AddBuilding( ref Building building )
{
Vector2 min = Vector2.Clamp( building.AABB.Min, Min, Max );
Vector2 max = Vector2.Clamp( building.AABB.Max, Min, Max );
float cellWidth = ( Max.X - Min.X ) / Cols;
int colMin = (int)( ( min.X - Min.X ) / cellWidth );
int colMax = (int)( ( max.X - Min.X ) / cellWidth );
float cellHeight = ( Max.Y - Min.Y ) / Rows;
int rowMin = (int)( ( min.Y - Min.Y ) / cellHeight );
int rowMax = (int)( ( max.Y - Min.Y ) / cellHeight );
// make sure the maxs don't go out of bounds
if ( colMax == Cols )
colMax = colMin;
if ( rowMax == Rows )
rowMax = rowMin;
for ( int r = rowMin; r <= rowMax; ++r )
{
for ( int c = colMin; c <= colMax; ++c )
{
int index = Cols * r + c;
if ( TestBuildingVsAABB( building, new AABB( cells[index].Min, cells[index].Max ) ) )
cells[index].Buildings.Add( building.Index );
}
}
}
public static void PopulateGrid( Entity[] entities, Building[] buildings )
{
for ( int i = 0; i < entities.Length; ++i )
grid.AddEntity( ref entities[i] );
for ( int i = 0; i < buildings.Length; ++i )
grid.AddBuilding( ref buildings[i] );
grid.InitializePathGrid( 6 );
}
