<cat>Dev</cat> <title>Entities</title> # How To Spawn ## Prefab Name ___⤶ The prefab name represents the full path of the prefab inside the game files. It always starts with `assets/` and will be completely lowercase. It always starts with `assets/` and will be fully lowercase. ## Position ___⤶ The position in the world where the entity will be placed. The default position is 0,0,0 which is the center of the map at water level. The default position is 0,0,0. This represents the the center of the map at water level. ## Rotation ___⤶ The rotation of the entity after being spawned. `There will be a section on Quaternions later, but simplified explaination here for now:` There are there axis: * The X axis goes from your left to right. * The Y axis goes from above to below you. * The Z axis goes from front to back. Your rotation can be represented by your rotation by turning each axis, which leads to the following behaviour: * X rotation = leaning forward and backwards * Y rotation = turning left and right * Z rotation = tilting left and right This means you represent your rotation as 3 numbers: `( 'x' rotation, 'y' rotation, 'z' rotation )`. These are called `Euler` (aka `Human readable`) angles. However there is one catch: Internally a Quaternion represents your rotation as 4 numbers which makes the math easier for a computer but near impossible to understand as a human. To solve this problem we have helper functions. You can use `Quaternion.Euler(x,y,z)` to create a new rotation based on the `Euler` angles. Internally a `Quaternion` represents your rotation as 4 numbers which makes the math easier for a computer but near impossible to understand as a human. To solve this problem we have helper functions. You can use `Quaternion.Euler(x,y,z)` to create a new `Quaternion` rotation based on the `Euler` angles. If you want to convert an existing rotation back to the `Euler` angles just use `.eulerAngles` on a rotation. ```csharp //Create a new rotation that is 45° to the left Quaternion rotation = Quaternion.Euler(0,45,0); //Turn the rotation back to human readable Console.WriteLine( rotation.eulerAngles ); > Prints (0, 45, 0) ``` The code to spawn an entity will make a lot more sense now that we know what all the parameters mean. # Code To Spawn Entity The first part of spawning something is to create the entity. The function takes the 3 parameters described above into this function: ```csharp GameManager.server.CreateEntity(string prefabName, Vector3 position, Quaternion rotation) ``` We store the result in a variable of type BaseEntity. If there was an error spawning the entity or an invalid prefab name was supplied the entity will be `null`. We should check for this before calling the `Spawn()` function or we risk throwing an error. A full example follows. ``` BaseEntity rowBoat = GameManager.server.CreateEntity( "assets/content/vehicles/boats/rowboat/rowboat.prefab", new Vector3( 450, 0, 1000), Quaternion.Identity( 0, 90, 0) ); if (rowBoat == null) { return; } //Don't forget to call spawn after rowBoat.Spawn(); ``` # How To Delete An Entity After you have spawn your boat your going to want to remove it. You could look at the boat on the client, run `ent kill` in the F1 Console and it would be removed. But what if we want to automate it? Lets continue with the example above: ```csharp BaseEntity rowBoat = GameManager.server.CreateEntity("assets/content/vehicles/boats/rowboat/rowboat.prefab"); if ( rowBoat != null ) { rowBoat.Spawn(); } //Now we want to remove it //Obviously the entity won't be null in this example but for longer running code you might want to check this if ( rowBoat != null ) { if ( rowBoat.IsDestroyed == false ) { rowBoat.Kill(); } } ``` Hold on, why did we check this `IsDestroyed` variable and what does it mean?