AxisAlignedCube

Introduction

The AxisAlignedCube is a geometric shape from the FlatRedBall.Math.Geometry class. As a 3D shape, it can be used for detecting collisions with 3D or 2D shapes. The AxisAlignedCube class shares many similarities with other shape classes (Circle, Line, AxisAlignedRectangle, Polygon, etc). For general information about shapes, see the ShapeManager wiki entry.

Creating an AxisAlignedCube

AxisAlignedCubes are created through the ShapeManager. The following code creates an AxisAlignedCube through the ShapeManager and resizes it: Add the following using statement using FlatRedBall.Math.Geometry; Create the instance globally AxisAlignedCube mCube; In the Initialize method

mCube = new AxisAlignedCube();
mCube.Visible = true;
mCube.ScaleX = 3;
mCube.ScaleY = 4;

Alternatively, you can create an AxisAlignedCube with the Visible property set first by doing this Create the instance globally AxisAlignedCube mCube = ShapeManager.AddAxisAlignedCube();

Relationship with ShapeManager

See ShapeManager wiki entry.

Collisions With AxisAlignedCube

For detecting collisions with AxisAlignedCubes, use the following code: Add the following using statement

using FlatRedBall.Math.Geometry;
using FlatRedBall.Input;

Create the instance globally

AxisAlignedCube mCube;
AxisAlignedCube mCube2;

In the Initialize method before the base call

mCube = new AxisAlignedCube();
mCube.Visible = true;
mCube.Color = Color.Red;
            
mCube2 = new AxisAlignedCube();
mCube2.Visible = true;
mCube2.Color = Color.Red;
mCube2.X = 1;

In the Update method before the base calls

if (mCube.CollideAgainst(mCube2))
{
  mCube2.Color = Color.Blue;
}

if (mCube2.CollideAgainst(mCube))
{
  mCube.Color = Color.Orange;
}

PreCubeCollision.png

PostCubeCollision.png

Determining Collision Side

When two AxisAlignedCubes collide the collision side can be determined rather easily. The following code determines the side that two rectangles collided on: Add the following using statements

using FlatRedBall.Math.Geometry;
using Side = FlatRedBall.Math.Collision.CollisionEnumerations.Side3D;

Assuming cube1 and cube2 are valid AxisAlignedCubes:

Side side = Side.None;

if (mCube1.CollideAgainstMove(mCube2, 0, 1))
{
  if (mCube1.LastMoveCollisionReposition.X > 0)
      side = Side.Right;
  else if (mCube1.LastMoveCollisionReposition.X < 0)
      side = Side.Left;
  else if (mCube1.LastMoveCollisionReposition.Y > 0)
      side = Side.Top;
  else if (mCube1.LastMoveCollisionReposition.Y < 0)
      side = Side.Bottom;
  else if (mCube1.LastMoveCollisionReposition.Z > 0)
      side = Side.Front;
  else if (mCube1.LastMoveCollisionReposition.Z < 0)
      side = Side.Back;
}

AxisAlignedCube Members

• FlatRedBall.Math.Geometry.AxisAlignedCube.CollideAgainstBounce

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