Third person camera

This C# Intermediate tutorial covers the implementation of a third person camera.

Explanation

Since it reuses a large portion of the First person camera, it is recommended that you watch that tutorial first.

This tutorial teaches about how to use raycasting to position the camera behind the player. If the player is to close any walls, the camera will be moved closer to the player. Too close to the player? We simply switch to first person mode.

Third person camera

// Copyright (c) .NET Foundation and Contributors (https://dotnetfoundation.org/ & https://stride3d.net)
// Distributed under the MIT license. See the LICENSE.md file in the project root for more information.
using Stride.Core.Mathematics;
using Stride.Engine;
using Stride.Input;
using Stride.Physics;

namespace CSharpIntermediate.Code
{
    public class ThirdPersonCamera : SyncScript
    {
        public bool InvertMouseY = false;
        public Vector2 MouseSpeed = new Vector2(0.6f, 0.5f);
        public float MaxLookUpAngle = -40;
        public float MaxLookDownAngle = 40;
        public float MinimumCameraDistance = 1.5f;
        public Vector3 CameraOffset = new Vector3(0, 0, -3);

        private Entity firstPersonPivot;
        private Entity thirdPersonPivot;

        private Vector2 maxCameraAnglesRadians;
        private Vector3 camRotation;
        private bool isActive = false;
        private Simulation simulation;
        private CharacterComponent character;

        public override void Start()
        {
            Game.IsMouseVisible = false;
            isActive = true;

            firstPersonPivot = Entity.FindChild("FirstPersonPivot");
            thirdPersonPivot = Entity.FindChild("ThirdPersonPivot");

            maxCameraAnglesRadians = new Vector2(MathUtil.DegreesToRadians(MaxLookUpAngle), MathUtil.DegreesToRadians(MaxLookDownAngle));
            camRotation = Entity.Transform.RotationEulerXYZ;
            Input.MousePosition = new Vector2(0.5f, 0.5f);
            simulation = this.GetSimulation();
            character = Entity.Get<CharacterComponent>();
        }

        public override void Update()
        {
            if (Input.IsKeyPressed(Keys.Escape))
            {
                isActive = !isActive;
                Game.IsMouseVisible = !isActive;
                Input.UnlockMousePosition();
            }

            if (isActive)
            {
                Input.LockMousePosition();
                var mouseMovement = -Input.MouseDelta * MouseSpeed;

                // Update rotation values with the mouse movement
                camRotation.Y += mouseMovement.X;
                camRotation.X += InvertMouseY ? mouseMovement.Y : -mouseMovement.Y;
                camRotation.X = MathUtil.Clamp(camRotation.X, maxCameraAnglesRadians.X, maxCameraAnglesRadians.Y);

                // Apply Y rotation to character entity
                character.Orientation = Quaternion.RotationY(camRotation.Y);

                // Apply X rotation the existing first person pivot
                firstPersonPivot.Transform.Rotation = Quaternion.RotationX(camRotation.X);

                // The third person pivot gets the same position and rotation as the first person pivot + the camera offset
                thirdPersonPivot.Transform.Position = new Vector3(0);
                thirdPersonPivot.Transform.Position += CameraOffset;

                // Make sure that the WorldMatrix of the thirdperson pivot is up to date
                thirdPersonPivot.Transform.UpdateWorldMatrix();

                // Raycast from first person pivot to third person pivot
                var raycastStart = firstPersonPivot.Transform.WorldMatrix.TranslationVector;
                var raycastEnd = thirdPersonPivot.Transform.WorldMatrix.TranslationVector;

                if (simulation.Raycast(raycastStart, raycastEnd, out HitResult hitResult))
                {
                    // If we hit something along the way, calculate the distance
                    var hitDistance = Vector3.Distance(raycastStart, hitResult.Point);

                    if (hitDistance >= MinimumCameraDistance)
                    {
                        // If the distance is larger than the minimum distance, place the camera at the hitpoint
                        thirdPersonPivot.Transform.Position.Z = -(hitDistance - 0.1f);
                    }
                    else
                    {
                        // If the distance is lower than the minimum distance, place the camera at first person pivot
                        thirdPersonPivot.Transform.Position = new Vector3(0);
                    }
                }
            }
        }
    }
}

Character movement

// Copyright (c) .NET Foundation and Contributors (https://dotnetfoundation.org/ & https://stride3d.net)
// Distributed under the MIT license. See the LICENSE.md file in the project root for more information.
using Stride.Core.Mathematics;
using Stride.Engine;
using Stride.Input;
using Stride.Physics;

namespace CSharpIntermediate.Code
{
    public class CharacterMovement : SyncScript
    {
        public Vector3 MovementMultiplier = new Vector3(3, 0, 4);
        private CharacterComponent character;

        public override void Start()
        { 
            character = Entity.Get<CharacterComponent>();
        }

        public override void Update()
        {
            var velocity = new Vector3();
            if (Input.IsKeyDown(Keys.W))
            {
                velocity.Z++;
            }
            if (Input.IsKeyDown(Keys.S))
            {
                velocity.Z--;
            }

            if (Input.IsKeyDown(Keys.A))
            {
                velocity.X++;
            }
            if (Input.IsKeyDown(Keys.D))
            {
                velocity.X--;
            }

            velocity.Normalize();
            velocity *= MovementMultiplier;
            velocity = Vector3.Transform(velocity, Entity.Transform.Rotation);
            character.SetVelocity(velocity);
        }
    }
}