voxel/Physics/AABB.cs

using OpenTK.Mathematics;

namespace Voxel.Physics
{
    public struct AABB
    {
        public Vector3 Min;
        public Vector3 Max;

        public AABB(Vector3 min, Vector3 max)
        {
            Min = min;
            Max = max;
        }

        public AABB Copy()
        {
            return new AABB(Min, Max);
        }

        public static AABB FromCenter(Vector3 center, float width, float height, float depth)
        {
            Vector3 half = new Vector3(width / 2f, 0, depth / 2f);
            return new AABB(center - half, center + new Vector3(half.X, height, half.Z));
        }

        public AABB Expand(float x, float y, float z)
        {
            AABB returnValue = Copy();

            if (x > 0)
                returnValue.Max.X += x;
            else
                returnValue.Min.X += x;

            if (y > 0)
                returnValue.Max.Y += y;
            else
                returnValue.Min.Y += y;

            if (z > 0)
                returnValue.Max.Z += z;
            else
                returnValue.Min.Z += z;

            return returnValue;
        }

        public AABB Grow(float x, float y, float z)
        {
            AABB returnValue = Copy();

            returnValue.Min.X -= x;
            returnValue.Min.Y -= y;
            returnValue.Min.Z -= z;
            returnValue.Max.X += x;
            returnValue.Max.Y += y;
            returnValue.Max.Z += z;

            return returnValue;
        }

        public void Move(float x, float y, float z)
        {
            Min.X += x;
            Max.X += x;
            Min.Y += y;
            Max.Y += y;
            Min.Z += z;
            Max.Z += z;
        }

        public bool Contains(Vector3 point)
        {
            return (point.X >= Min.X && point.X <= Max.X) &&
                   (point.Y >= Min.Y && point.Y <= Max.Y) &&
                   (point.Z >= Min.Z && point.Z <= Max.Z);
        }

        public bool IntersectsX(AABB against)
        {
            return Min.X < against.Max.X && Max.X > against.Min.X;
        }

        public bool IntersectsY(AABB against)
        {
            return Min.Y < against.Max.Y && Max.Y > against.Min.Y;
        }

        public bool IntersectsZ(AABB against)
        {
            return Min.Z < against.Max.Z && Max.Z > against.Min.Z;
        }

        public bool Intersects(AABB against)
        {
            return IntersectsX(against) && IntersectsY(against) && IntersectsZ(against);
        }

        public float GetClipX(AABB against, float deltaX)
        {
            if (IntersectsY(against) && IntersectsZ(against))
            {
                if (deltaX > 0 && Max.X <= against.Min.X)
                {
                    float clip = against.Min.X - Max.X;
                    if (deltaX > clip) deltaX = clip;
                }
                if (deltaX < 0 && Min.X >= against.Max.X)
                {
                    float clip = against.Max.X - Min.X;
                    if (deltaX < clip) deltaX = clip;
                }
                return deltaX;
            }
            return deltaX;
        }

        public float GetClipY(AABB against, float deltaY)
        {
            if (IntersectsX(against) && IntersectsZ(against))
            {
                if (deltaY > 0 && Max.Y <= against.Min.Y)
                {
                    float clip = against.Min.Y - Max.Y;
                    if (deltaY > clip) deltaY = clip;
                }
                if (deltaY < 0 && Min.Y >= against.Max.Y)
                {
                    float clip = against.Max.Y - Min.Y;
                    if (deltaY < clip) deltaY = clip;
                }
                return deltaY;
            }
            return deltaY;
        }

        public float GetClipZ(AABB against, float deltaZ)
        {
            if (IntersectsX(against) && IntersectsY(against))
            {
                if (deltaZ > 0 && Max.Z <= against.Min.Z)
                {
                    float clip = against.Min.Z - Max.Z;
                    if (deltaZ > clip) deltaZ = clip;
                }
                if (deltaZ < 0 && Min.Z >= against.Max.Z)
                {
                    float clip = against.Max.Z - Min.Z;
                    if (deltaZ < clip) deltaZ = clip;
                }
                return deltaZ;
            }
            return deltaZ;
        }

        public Vector3 GetCenter()
        {
            return new Vector3(
                (Min.X + Max.X) / 2,
                Min.Y,
                (Min.Z + Max.Z) / 2
            );
        }
    }
}