Category Archives: unity3d

Conversations about cost vs. value add for players

I can’t count the times I have been party to a discussion between programmers and content creators that goes something like this:


Artist: If we do it that way, we’ll have to hard-code the information directly into our content and it will mean we have to create and maintain like four times as many files…

Programmer: If we don’t do it that way, we’ll have to code a whole new system to handle it dynamically and it will cost performance, memory, code maintenance, and bug tail…

Tech Artist: I could write a script that generates the files for us. Everybody wins, right?

Let’s ignore the Tech Artist for now. Both the Artist and the Programmer have valid arguments from their points of view. Each is staring at a potential pile of dirty laundry. If the artist has to maintain four times as many files, then imagine how much beautiful content they aren’t creating instead. If the programmer has to spend time coding and maintaining another system, then imagine how many other feature requests must be rejected…you get the idea.  
The problem with this line of discussion is that it is too focused on how much work one has to do and how that work will reduce the potential cool stuff for players that could be done. An interesting thing happens when you are both the programmer and the artist for the project. Since it is you coding the system or maintaining the files either way, it starts to make very little sense to take either position above as a good reason to do one versus the other.
This image is what brought all of this to mind. To get some trees to show up, I wrote zero code and just added trees to the random list of tiles I’m populating the world with. It turns out that the trees have transparency around the edges. To get it to look right, I could composite the tree and the grass in photoshop and be done with it. But what if I want trees on top of dirt? Then I need two tree images instead of one. What if I want it on grass, dirt, and something else –now I need three. Okay, so what if I composite the tree on top of grass through code? I started thinking about how much work it would be to support tile layers and it was a decent amount of work.  Again, one problem with these lines of thinking is that they are too focused on the cost.  I started thinking instead about whether of these approaches had any bearing on the player experience. If I coded the tile layer solution, that could afford me the ability to remove the trees easily and have the grass remain. If the trees are easily removable, then the player can chop them down, or they can catch fire and burn away. If they are used for cover from projectiles, this could be interesting. Once I began thinking this way, I was much more comfortable thinking about the cost. If I know I never want any of those mechanics, and I am really only going to have 3 types of terrain + trees, then it is an easy choice to just combine them in photoshop.

Ultimately my point in all this is that it is important to consider any potential value adds for a player experience in cases where the discussion to take one approach over another is centered on the costs and the result would look the same either way. You might just discover a fun mechanic or maybe even a differentiating gameplay hook.

Animation test, finally!

So in the last post I covered the easy model creation pipeline I was working on. Since then, I solved the final piece of that puzzle which is to automatically generate the rig. All of that is rather boring so I’ll save it for another day. Today, I want to show the point of all that, which is to animate! I got two animations setup, east idle and east run. Check it out!

I’ll fill out the north, south and west (maybe mirror east?) and then post some more videos.

Easy model creation

In the skeletal animation experiment I created the model by hand, placing one polygon per pixel using an image plane as a template and then manually setting the UVs to match up with the sprite. That was way to tedious and definitely not scalable. I wrote a handy little python function that will take a sprite as input and do all the work for me :-). Check it!

I think I’ll still need to create the “rig” manually. There will be one unique rig per direction, with east/west potentially just being a mirror. After I create one decent quality animation set and I automate the rigging process then I am confident that this will be my pipeline.

Skeletal animation experiment

One of the next things I want to figure out is how I’ll handle the character animations. I’ve been using the tiny dungeon sprites from Oryx Design Lab, and I had been thinking that skeletal animation might help bring them to life in an interesting way. I didn’t quite know how I would do this so I did some research and there are a ton of options to try out, from Creature to Spine2D, to Maya, and even Unity itself supports animation from within the editor. Here is my first test:

I brought the 16×16 sprite into Maya and slapped it onto an image plane, scaling it up 100 times until each pixel was 1 grid unit, and then I made a 1×1 polygon plane for each pixel. I ended up using a planar projection and using the sprite as a texture, but I think it may be more efficient to either use vertex colors or a tiny 1D texture that has the 8 colors the sprite has in it.

This animation is just a simple waving idle, so I want to do another test with more action like a run or an attack. I like where it is going so I want to see if I can take it to the limit as well, with FX and everything. Then I want to see if I can streamline the setup process by automating the manual steps I did to turn the pixels into polygons. Cheers!

Unity3D Extension method example

Extension methods are awesome for extending the functionality of existing classes. What is really cool is that if you use an IDE that supports autocompletion, your extension methods will show up when using the classes you extend.

For this example, let’s suppose that you want to extend Unity’s AnimationClip to support the idea of adding an “OnAnimationEnd” event. When the animation clip ends, a callback will be called.

using UnityEngine;

public static class AnimationClipExtensions
{
    public static void AddOnAnimationEndEvent (this AnimationClip animationClip, string onAnimationEndCallbackName)
    {
        AddOnAnimationEndEvent (animationClip, onAnimationEndCallbackName, 0, 0.0f, "", null);
    }

    public static void AddOnAnimationEndEvent (this AnimationClip animationClip, string onAnimationEndCallbackName, int intParameter)
    {
        AddOnAnimationEndEvent (animationClip, onAnimationEndCallbackName, intParameter, 0.0f, "", null);
    }

    public static void AddOnAnimationEndEvent (this AnimationClip animationClip, string onAnimationEndCallbackName, float floatParameter)
    {
        AddOnAnimationEndEvent (animationClip, onAnimationEndCallbackName, 0, floatParameter, "", null);
    }

    public static void AddOnAnimationEndEvent (this AnimationClip animationClip, string onAnimationEndCallbackName, string stringParameter)
    {
        AddOnAnimationEndEvent (animationClip, onAnimationEndCallbackName, 0, 0.0f, stringParameter, null);
    }

    public static void AddOnAnimationEndEvent (this AnimationClip animationClip, string onAnimationEndCallbackName, Object objectReferenceParameter)
    {
        AddOnAnimationEndEvent (animationClip, onAnimationEndCallbackName, 0, 0.0f, "", objectReferenceParameter);
    }

    private static void AddOnAnimationEndEvent (this AnimationClip animationClip, string onAnimationEndCallbackName, int intParameter, float floatParameter, string stringParameter, Object objectReferenceParameter)
    {
        AnimationEvent animEvent = new AnimationEvent ();
        animEvent.time = animationClip.length;
        animEvent.functionName = onAnimationEndCallbackName;
        animEvent.intParameter = intParameter;
        animEvent.floatParameter = floatParameter;
        animEvent.stringParameter = stringParameter;
        animEvent.objectReferenceParameter = objectReferenceParameter;
        animEvent.messageOptions = SendMessageOptions.DontRequireReceiver;
        animationClip.AddEvent (animEvent);
    }
}

Now that we have a few extension methods you can test it out in a component.

using UnityEngine;
using Assets.Scripts.Util;

public class AnimClipExtensionsTest : MonoBehaviour
{
    public AnimationClip testClip;

    void Start()
    {
        Debug.Assert(testClip != null);
        testClip.AddOnAnimationEndEvent("OnAnimationEnd");
        
        var animationComponent = GetComponent<Animation>();

        Debug.Assert(animationComponent != null);

        animationComponent.AddClip(testClip, "testClip");
        animationComponent.Play("testClip");
    }

    void OnAnimationEnd()
    {
        Debug.Log("OnAnimationEnd() was called!");
    }
}

Unity3D AssetPostprocessor Example

In Unity3D, you’ll often find yourself repeating a lot of simple tasks on prefabs if you make changes to the source content after you’ve placed instances of the prefab in the editor; stuff like turning off the renderer for some meshes, or adding colliders and scripted components. Unity provides a mechanism to automate much of this work with the AssetPostProcessor class.

In your Maya scenes, every mesh, bone, etc are all GameObjects in Unity. When you save your Maya scenes, it triggers them to be re-imported in Unity and when that happens, the AssetPostProcessor’s OnPostprocessGameObjectWithUserProperties() method will get called once for every GameObject in the Maya scene. If any of those GameObjects have custom attributes added to them, each attribute will have its attribute name and attribute value in the arrays passed into OnPostprocessGameObjectWithUserProperties.

Ok. So what is all this code? The examples I have seen usually have something like this inside the OnPostprocessGameObjectWithUserProperties method:

if (userPropertyName == "AddMeshCollider")
{
    ...
}
else if (userPropertyName == "AddSphereCollider")
{
    ...
}

There is nothing wrong with that code, but my preference is to separate out the logic that handles what to do for each user property into its own class, and never touch the OnPostprocessGameObjectWithUserProperties method again.

To do that, we can use the Attribute class and C# reflection. We’ll create an ImportTaskAttribute that takes a name in its constructor. That name will correspond to the user property name (the custom attribute name in Maya.)

All classes that are marked up with that attribute will get collected by an ImportTaskCollector class which we’ll use to fetch them and then call their Execute method to do the work.

using System.Linq;
using UnityEngine;
using UnityEditor;
using System;
using System.Collections;
using System.Collections.Generic;
using System.Reflection;

This is the ImportTaskAttributeClass. The TaskName property will hold the name matching the user property.

[AttributeUsage(AttributeTargets.Class, Inherited = true, AllowMultiple = false)]
public class ImportTaskAttribute : Attribute
{
    public string TaskName;
    
    public ImportTaskAttribute(string taskName)
    {
        TaskName = taskName;
    }
}

This interface is the contract for all of the import tasks. And the concrete class below is what we’ll inherit from.

public interface IPostProcessGameObjectWithUserPropertiesTask
{
    GameObject ImportedGameObject {get; set;}
    string UserPropertyName {get; set;}
    object UserPropertyValue {get; set;}
    
    bool ExecuteTask();
    void PostExecuteTask();
}

public class PostProcessGameObjectWithUserPropertiesTask : IPostProcessGameObjectWithUserPropertiesTask
{
    public GameObject ImportedGameObject {get; set;}
    public string UserPropertyName {get; set;}
    public object UserPropertyValue {get; set;}
    public object UserData {get; set;}
    
    public virtual bool ExecuteTask() { return false; }

    public virtual void PostExecuteTask() {}
}

This is the ImportTaskCollector. Its job is to find all classes marked up with the ImportTaskAttribute.

public sealed class ImportTaskCollector
{
    private Dictionary<string, object> _importTasks = new Dictionary<string, object>();
    
    public ImportTaskCollector()
    {
        Assembly assembly = typeof(IPostProcessGameObjectWithUserPropertiesTask).Assembly;
        Type target = typeof(IPostProcessGameObjectWithUserPropertiesTask);        
        var importTaskTypes = assembly.GetTypes()
                            .Where(type => target.IsAssignableFrom(type));

        foreach (Type importTaskType in importTaskTypes)
        {   
            if (importTaskType.IsAbstract || importTaskType.IsGenericType)
            {
                continue;
            }
 
            var importTaskInstance = Activator.CreateInstance(importTaskType);
            var importTaskTypeAttributes = Attribute.GetCustomAttributes(importTaskType);

            var importTaskTypeAttribute = importTaskTypeAttributes
                .SingleOrDefault(attr => attr as ImportTaskAttribute != null) as ImportTaskAttribute;
            
            if (importTaskTypeAttribute != null)
            {
                _importTasks.Add(importTaskTypeAttribute.TaskName, importTaskInstance); 	
            }
        }
    }
    
    public IPostProcessGameObjectWithUserPropertiesTask GetTask(string taskName)
    {
        if (_importTasks.ContainsKey(taskName))
        {
            return _importTasks[taskName] as IPostProcessGameObjectWithUserPropertiesTask; 
        }
        else
        {
            return null;
        }
    }
}

Finally, this is our custom AssetPostprocessor.

public class AssetImport : AssetPostprocessor
{
    private readonly ImportTaskCollector _importTaskCollector;
    
    public AssetImport()
    {
        _importTaskCollector = new ImportTaskCollector();
    }
    
    void OnPostprocessGameObjectWithUserProperties(GameObject g, String[] userPropertyNames, System.Object[] userPropertyValues)
    {
        for (int propertyPairIndex = 0; propertyPairIndex < userPropertyNames.Length; propertyPairIndex++)
        {
            var userPropertyName = userPropertyNames[propertyPairIndex];
            var userPropertyValue = userPropertyValues[propertyPairIndex];
            
            IPostProcessGameObjectWithUserPropertiesTask importTask = _importTaskCollector.GetTask(userPropertyName);
            
            if (importTask != null)
            {
                importTask.ImportedGameObject = g;
                importTask.UserPropertyName = userPropertyName;
                importTask.UserPropertyValue = userPropertyName;
                
                if (importTask.ExecuteTask())
                {
                    importTask.PostExecuteTask();
                }
            }
        }
    }
}

Ok, with all of that in place, here is an example of how you would use it:

[ImportTaskAttribute("AddMeshCollider")]
public class AddMeshColliderTask : PostProcessGameObjectWithUserPropertiesTask
{
    public bool ExecuteTask()
    {
        ImportedGameObject.AddComponent<MeshCollider>();
        return true;
    }
}

Then, if you add an attribute named “AddMeshCollider” to any mesh in your maya scene, your task will get run for that game object and a MeshCollider will be added.

But we can do better. We can make a generic AddComponentTask where the generic type parameter is the Component we want to add.

public class AddComponentTask<T> : PostProcessGameObjectWithUserPropertiesTask where T : Component
{
    public override bool ExecuteTask()
    {
        UserData = ImportedGameObject.AddComponent<T>();    

        return UserData != null;
    }
}

[ImportTask("AddMeshCollider")]
public class AddMeshColliderTask : AddComponentTask<MeshCollider>
{
	// Nothing to do, ExecuteTask() gets called on AddComponentTask<T>
	// and T is MeshCollider in this case.
}

Now, what if we wanted to add a CapsuleCollider and then set the height and radius from within Maya? The UserData property holds the component we just added, and now that code lives in the AddComponenTask‘s Execute method. We don’t want to keep duplicating the code for adding a component, so this is where the PostExecute method comes into play.

[ImportTask("AddCapsuleCollider")]
public class AddCapsuleColliderTask : AddComponentTask<CapsuleCollider>
{
	public override void PostExecuteTask()
	{
		var capsule = UserData as CapsuleCollider;
		var capsuleData = UserPropertyValue as Vector2?;
			
		if (capsule != null && capsuleData.HasValue)
		{
			capsule.height = capsuleData.Value.x;
			capsule.radius = capsuleData.Value.y;
		}
	}
}

As always, if you’ve got any questions, shoot me an email at jspataro@gmail.com