Tutorial: Script a trigger

BeginnerDesigner trigger that doubles the size of a ball when the ball passes through it.

Note

The screenshots and videos in this tutorial were made using an earlier version of Xenko, so some parts of the UI, and the default skybox and sphere, might look different from your version.

1. Create a bouncing ball

Create a bouncing ball tutorial. This creates a simple scene in which a ball falls from mid-air, hits the ground, and bounces.

2. Set the restitution

For this tutorial, we’ll set the restitution of both the ground and the sphere to 0.9, which makes the ball very bouncy. This makes it easier to see the effect of the trigger later, as the ball will bounce in and out of the trigger area repeatedly.

• Sphere entity.
• Property Grid, under Rigidbody, set the Restitution to 0.9.
• Ground entity.
• Property Grid, under Static Collider, set the Restitution to 0.9.

  3. Add a trigger

  Now we’ll add a trigger between the ball and the ground, so the ball passes through it.
• Scene Editor, click the white plus button (Create new entity) and select Empty entity. Entity.
• Trigger to make it easy to identify.
• Property Grid, click Add component and select Static Collider.
• Property Grid, expand the Static Collider component to view its properties.
• Is Trigger checkbox. This makes the collider a trigger. This means objects can pass through it, but are still detected in the code.
• Collider Shapes, click (Add) and select Box. This gives the trigger a box shape.
• Property Grid, under the Transform component properties, set the scale to: X:2, Y:2, Z:2 This doubles the size of the trigger.

  4. Give the trigger a model

  Right now, the trigger is invisible at runtime. To better show how the trigger works, we’ll make it a transparent box. This has no effect on how the trigger works; it just means we can easily see where it is at runtime.
• Asset View, click Add asset, and select Models > Cube.
• Asset View, click Add asset, and select Materials > Material.
• Rename, and type a new name (eg Transparent).
• Trigger entity. In the Property Grid, click Add component and select Model. Game Studio adds a model component to the entity.
• Model, click (Select an asset).
• Cube model we created in step 1 and click OK.
• Property Grid, under Model > Materials, click (Select an asset).
• Transparent material we created in step 2 and click OK.
• Asset View, select the Transparent material asset.
• Property Grid, under Misc > Transparency, select Blend.
• Alpha to 0.5. Now the trigger area will be visible at runtime.

  5. Position the trigger

  We need to position the trigger between the ground and the sphere, so the ball falls through it. Property Grid, under Transform, set the Position to: X:0, Y:3, Z:0 Now the trigger entity is between the ground and the sphere:

  6. Change the sphere size with script

  F5), the ball falls through the trigger, but nothing happens. 0.7 倍

        1.0 倍
        1.2 倍
        1.5 倍
        2.0 倍

  Let’s write a script to change the size of the ball when it enters the trigger.

  Note

  Scripts.
• Asset View, click Add asset and select Scripts > Async Script.
• Create a script dialog, name your script Trigger and click Create script. Save. Reload.
• Open the script, replace its content with the following code, and save the file:

  using Xenko.Engine;using Xenko.Physics;using System.Threading.Tasks;using Xenko.Core.Mathematics;namespace TransformTrigger// You can use any namespace you like for this script.{    public class Trigger : AsyncScript    {        public override async Task Execute()        {            var trigger = Entity.Get<PhysicsComponent>();            trigger.ProcessCollisions = true;            // Start state machine            while (Game.IsRunning)            {                // 1. Wait for an entity to collide with the trigger                var firstCollision = await trigger.NewCollision();                var otherCollider = trigger == firstCollision.ColliderA                    ? firstCollision.ColliderB                    : firstCollision.ColliderA;                otherCollider.Entity.Transform.Scale = new Vector3(2.0f, 2.0f, 2.0f);                // 2. Wait for the entity to exit the trigger                Collision collision;                do                {                    collision = await trigger.CollisionEnded();                }                while (collision != firstCollision);                otherCollider.Entity.Transform.Scale= new Vector3(1.0f, 1.0f, 1.0f);            }        }    }}

  This code doubles the size (scale) of any entity that enters the trigger. When the entity exits the trigger, it returns to its original size. -

  7. Add the script

  Finally, let’s add this script to the trigger entity as a component.
• Game Studio, select the Trigger entity.
• Property Grid, click Add component and select the Trigger script.

  8. Run the project

  F5) to see the trigger in action. The ball falls through the trigger, doubles in size, exits the trigger, and returns to its normal size. 0.7 倍

        1.0 倍
        1.2 倍
        1.5 倍
        2.0 倍

  More ideas

  You can alter the script to make other changes when the sphere enters the trigger. Sphere Material to the Ground Material and back again:

  using Xenko.Engine;using Xenko.Physics;using System.Threading.Tasks;using Xenko.Core.Mathematics;using Xenko.Rendering;namespace TransformTrigger// You can use any namespace you like for this script.{    public class Trigger : AsyncScript    {        private Material material1;        private Material material2;        public override async Task Execute()        {            var trigger = Entity.Get<PhysicsComponent>();            trigger.ProcessCollisions = true;            // Make sure the materials are loaded             material1 = Content.Load<Material>("Sphere Material");            material2 = Content.Load<Material>("Ground Material");            // Start state machine            while (Game.IsRunning)            {                // 1. Wait for an entity to collide with the trigger                var firstCollision = await trigger.NewCollision();                var otherCollider = trigger == firstCollision.ColliderA ? firstCollision.ColliderB : firstCollision.ColliderA;                // 2. Change the material on the entity                otherCollider.Entity.Get<ModelComponent>().Materials[0] = material2;                // 3. Wait for the entity to exit the trigger                Collision collision;                do                {                    collision = await trigger.CollisionEnded();                }                while (collision != firstCollision);                // 4. Change the material back to the original one                otherCollider.Entity.Get<ModelComponent>().Materials[0] = material1;            }        }        public override void Cancel()        {            Content.Unload(material1);            Content.Unload(material2);        }    }}

  0.7 倍

        1.0 倍
        1.2 倍
        1.5 倍
        2.0 倍

  See also

• Tutorial: Create a bouncing ball
• Colliders
• Collider shapes
• Scripts