public static bool CheckAABB(Box b1, Box b2, ref float moveX, ref float moveY)
{
moveX = 0.0f;
moveY = 0.0f;
float l = b2.x - (b1.x + b1.w);
float r = (b2.x + b2.w) - b1.x;
float t = b2.y - (b1.y + b1.h);
float b = (b2.y + b2.h) - b1.y;
if (l > 0 || r < 0 || t > 0 || b < 0)
return false;
// lấy khoảng bị va chạm ngắn nhất, để cộng cho nhanh
moveX = Math.Abs(l) < r ? l : r;
moveY = Math.Abs(t) < b ? t : b;
// lấy chiều có khoảng va chạm ngắn, nhất để cộng cho lẹ
if (Math.Abs(moveX) < Math.Abs(moveY))
{
moveY = 0.0f;
}
else
{
moveX = 0.0f;
}
return true;
}
public static Box GetBroadPhaseBox(Box b)
{
Box BroadPhaseBox = new Box(0.0f, 0.0f, 0.0f, 0.0f);
BroadPhaseBox.x = b.vx > 0 ? b.x : b.x + b.vx;
BroadPhaseBox.y = b.vy > 0 ? b.y : b.y + b.vy;
BroadPhaseBox.w = b.vx > 0 ? b.w + b.vx : b.w - b.vx;
BroadPhaseBox.h = b.vy > 0 ? b.h + b.vy : b.h - b.vy;
return BroadPhaseBox;
}
// chuyển từ Box sang Broadphase dùng để khoanh vùng đối tượng
public Box BoxToBroadPhase(Box b)
{
return SweptAABB.GetBroadPhaseBox(b);
}
public static float Swept_AABB(Box b1, Box b2, ref float normalx, ref float normaly)
{
float xInvEntry, yInvEntry;
float xInvExit, yInvExit;
// find the distance between the objects on the near and far sides for both x and y
if (b1.vx > 0.0f)
{
xInvEntry = b2.x - (b1.x + b1.w);
xInvExit = (b2.x + b2.w) - b1.x;
}
else
{
xInvEntry = (b2.x + b2.w) - b1.x;
xInvExit = b2.x - (b1.x + b1.w);
}
if (b1.vy > 0.0f)
{
yInvEntry = b2.y - (b1.y + b1.h);
yInvExit = (b2.y + b2.h) - b1.y;
}
else
{
yInvEntry = (b2.y + b2.h) - b1.y;
yInvExit = b2.y - (b1.y + b1.h);
}
// find time of collision and time of leaving for each axis (if statement is to prevent divide by zero)
float xEntry, yEntry;
float xExit, yExit;
if (b1.vx == 0.0f)
{
xEntry = -float.PositiveInfinity;
xExit = float.PositiveInfinity;
}
else
{
xEntry = xInvEntry / b1.vx;
xExit = xInvExit / b1.vx;
}
if (b1.vy == 0.0f)
{
yEntry = -float.PositiveInfinity;
yExit = float.PositiveInfinity;
}
else
{
yEntry = yInvEntry / b1.vy;
yExit = yInvExit / b1.vy;
}
// find the earliest/latest times of collision
float entryTime = Math.Max(xEntry, yEntry);
float exitTime = Math.Min(xExit, yExit);
// if there was no collision
if (entryTime > exitTime || xEntry < 0.0f && yEntry < 0.0f || xEntry > 1.0f || yEntry > 1.0f)
{
normalx = 0.0f;
normaly = 0.0f;
return 1.0f;
}
else // if there was a collision
{
// calculate normal of collided surface
if (xEntry > yEntry && (b1.y + b1.h + 1.0f != b2.y ))
{
if (xInvEntry < 0.0f)
{
normalx = 1.0f;
normaly = 0.0f;
}
else
{
normalx = -1.0f;
normaly = 0.0f;
}
}
else
{
if (yInvEntry < 0.0f)
{
normalx = 0.0f;
normaly = 1.0f;
}
else
{
normalx = 0.0f;
normaly = -1.0f;
}
}
// return the time of collision
return entryTime;
}
}
public static float Swept_AABB(Box b1, Box b2, ref float normalx, ref float normaly)
{
float xInvEntry, yInvEntry;
float xInvExit, yInvExit;
// find the distance between the objects on the near and far sides for both x and y
if (b1.vx > 0.0f)
{
xInvEntry = b2.x - (b1.x + b1.w);
xInvExit = (b2.x + b2.w) - b1.x;
}
else
{
xInvEntry = (b2.x + b2.w) - b1.x;
xInvExit = b2.x - (b1.x + b1.w);
}
if (b1.vy > 0.0f)
{
yInvEntry = b2.y - (b1.y + b1.h);
yInvExit = (b2.y + b2.h) - b1.y;
}
else
{
yInvEntry = (b2.y + b2.h) - b1.y;
yInvExit = b2.y - (b1.y + b1.h);
}
// find time of collision and time of leaving for each axis (if statement is to prevent divide by zero)
float xEntry, yEntry;
float xExit, yExit;
if (b1.vx == 0.0f)
{
xEntry = -float.PositiveInfinity;
xExit = float.PositiveInfinity;
}
else
{
xEntry = xInvEntry / b1.vx;
xExit = xInvExit / b1.vx;
}
if (b1.vy == 0.0f)
{
yEntry = -float.PositiveInfinity;
yExit = float.PositiveInfinity;
}
else
{
yEntry = yInvEntry / b1.vy;
yExit = yInvExit / b1.vy;
}
// find the earliest/latest times of collision
float entryTime = Math.Max(xEntry, yEntry);
float exitTime = Math.Min(xExit, yExit);
// if there was no collision
if (entryTime > exitTime || xEntry < 0.0f && yEntry < 0.0f || xEntry > 1.0f || yEntry > 1.0f)
{
normalx = 0.0f;
normaly = 0.0f;
return(1.0f);
}
else // if there was a collision
{
// calculate normal of collided surface
if (xEntry > yEntry && (b1.y + b1.h + 1.0f != b2.y))
{
if (xInvEntry < 0.0f)
{
normalx = 1.0f;
normaly = 0.0f;
}
else
{
normalx = -1.0f;
normaly = 0.0f;
}
}
else
{
if (yInvEntry < 0.0f)
{
normalx = 0.0f;
normaly = 1.0f;
}
else
{
normalx = 0.0f;
normaly = -1.0f;
}
}
// return the time of collision
return(entryTime);
}
}
