voxel/Entities/Entity.cs

using OpenTK.Mathematics;
using System;
using System.Collections.Generic;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using Voxel.Core;
using Voxel.Physics;

namespace Voxel.Entities
{
    public class Entity
    {
        public Vector3 Position;
        public Vector3 Velocity;
        public bool OnGround;
        public float Rotation;

        public float Width;
        public float Height;

        private float _gravity = 0.08f;
        private float _terminalVelocity = -3.92f;
        private float _airMultiplier = 0.91f;
        private float _yMultiplier = 0.98f;
        private float _groundMultiplier = 0.6f;

        protected World _world;

        public Entity(Vector3 position, float width, float height, World world)
        {
            Position = position;
            Width = width;
            Height = height;
            _world = world;
        }

        public void Tick()
        {
            Move();

            if (!OnGround)
            {
                Vector3 acceleration = new Vector3(0, -_gravity, 0);
                Velocity += acceleration;
                Velocity.X *= _airMultiplier;
                Velocity.Z *= _airMultiplier;
                Velocity.Y *= _yMultiplier;


                if (Velocity.Y < _terminalVelocity)
                {
                    Velocity.Y = _terminalVelocity;
                }
            }
            else
            {
                Velocity = new Vector3(Velocity.X * _groundMultiplier, 0f, Velocity.Z * _groundMultiplier);
            }
        }

        public void Move()
        {
            Vector3 moveVector = Velocity;
            Vector3 originalVector = moveVector;

            AABB body = AABB.FromCenter(Position, Width, Height, Width);

            List<AABB> collisionChecks = _world.GetColliders(body.Expand(Velocity.X, Velocity.Y, Velocity.Z).Grow(1,1,1));

            foreach (AABB collider in collisionChecks)
            {
                moveVector.X = body.GetClipX(collider, moveVector.X);
            }

            body.Move(moveVector.X, 0, 0);

            foreach (AABB collider in collisionChecks)
            {
                moveVector.Y = body.GetClipY(collider, moveVector.Y);
            }

            body.Move(0, moveVector.Y, 0);

            foreach (AABB collider in collisionChecks)
            {
                moveVector.Z = body.GetClipZ(collider, moveVector.Z);
            }

            body.Move(0, 0, moveVector.Z);

            if (moveVector.X != originalVector.X)
            {
                Velocity.X = 0;
            }

            if (moveVector.Y != originalVector.Y)
            {
                Velocity.Y = 0;
            }

            if (moveVector.Z != originalVector.Z)
            {
                Velocity.Z = 0;
            }

            OnGround = moveVector.Y != originalVector.Y && originalVector.Y < 0;

            Position = body.GetCenter();
        }

        public void ApplyImpulse(Vector3 force)
        {
            Velocity += force;
        }
    }
}