If you’ve been following the updates on the Away3D blog, you’ll have noticed the updated roadmap mentioning the dev branch on Github. This branch is basically where we’re working to get things towards Beta, so take a look if you’re curious to see where we’re headed. I personally advise anyone to use this branch if you’re starting out with a new project but make a snapshot of the revision you’re working with. Some things will still change and might very well break your code

We’ll put up some proper blog posts introducing new features as we get to Beta, but for now I’ll quickly explain what I’ve personally been working on, and how I broke your existing code I’ve also went ahead and updated the source code for the demos in previous blog posts to match the dev branch, so you can see how it differs concretely.

Death to BitmapMaterial! All hail TextureMaterial!

One of the biggest changes, I think. Favouring composition over inheritance, we deprecated BitmapMaterial, VideoMaterial, MovieMaterial etc. They have been replaced by a single TextureMaterial, which accepts a Texture2DBase object. In practice, this will for instance be a BitmapTexture (VideoTexture etc are still in development). This way, when supporting new texture types you don’t need to extend every type of material that needs to extend this material type, which is especially a mess when you start creating custom materials (and need to extend/duplicate those to support all possible texture types). The same applies for cube maps (fe: BitmapCubeTexture), the normal and specular maps that are set on the default materials, and the view’s backgroundImage (now simply View3D::background). It’s a big change that might annoy many of you, but it’s necessary. With things like ATF support coming up (and who knows what else), things would simply become unmanageable and error-prone otherwise.

Furthermore, there are some “special” convenience textures that can be used for the default materials. For instance, these materials expect a specular map to have the specular strength on the red channel, and the specular power (gloss) on the green. SpecularBitmapTexture allows you to pass two greyscale BitmapData objects (gloss is optional) and composites the data correctly. When using texture splatting, you can use SplatBlendBitmapTexture, which takes 3 BitmapData objects containing the blending value for each splatting layer and places each on the red, blue and green channels as expected by TerrainDiffuseMethod. However, in both cases, it’s usually better to do these things in your offline asset preparation stage and use simpler texture objects instead.

Light Picking

Another rather big change for those working with lights, but one that offers great benefits. Instead of assigning the lights as a static array as before, materials now expect a LightPickerBase object. Right now, that means StaticLightPicker, which in turn accepts the array of lights. Why this extra object? This way, you can create a DynamicLightPicker object that selects the most important lights from the EntityCollector, allowing different lights to be used without reassigning the light array (and as a result potentially invalidating the material). As light collection is often game-engine dependent, providing our own dynamic light picker is not the highest priority. At least it’s good to know the possibility is there, right?

Disposal

Before, most dispose(…) methods accepted a “deep” parameter, which caused “sub-assets” (Geometry of a Mesh, BitmapData of a BitmapTexture, etc) to be disposed as well. While in some cases this saves you from writing a trivial few lines of disposal code, in many cases it just is an open door to invalid state (accidentally disposing a BitmapData used by another BitmapTexture) and ambiguity (what will be cleared, and what will remain uncleaned?). Allowing an object to destroy objects it did not create is poor resource management and generally bad practice in my opinion. Hence the new credo: you clean up what you create!

Ambient lighting

There have been some changes in how ambient lighting works. Before, the ambient and ambientColor of the materials dictated how much ambient light is coming from the lights, rather than how much ambient light is actually reflected by the material. That has been changed, and lights now have ambient and ambientColor properties as well. As a result, ambient light now functions similar to diffuse and specular light. The lights emit it, the material reflects it. It’s usually best to only set ambient light properties on DirectionalLight objects, since ambient light is global. PointLight objects can get culled if they’re not affecting anything in the frustum and their ambient contribution would be dropped as a result.

Other changes and new features

• Big refactor on how the materials and animations are compiled to facilitate building custom materials
• Slight restructuring of the render flow to allow more intricate custom renderers
• Light probes (default materials only support convoluted cube maps at this point)
• Reduced shadow swimming with shadow mapping
• RefractionEnvMapMethod for environment-map based refraction mapping
• AnisotropicSpecularMethod for anisotropic specular highlights
• Shadow mapping for point lights (HardShadowMapMethod only)
• AlphaMaskMethod to influence the material’s alpha, optionally based on a secondary UV set
• Light map methods: DiffuseLightMapMethod to apply light maps as diffuse light, and LightMapMethod to apply it on the final shaded result
• WrapDiffuseMethod to perform a very cheap fake way for subsurface scattering, as outlined in GPU Gems #1

I hope to scrape together some time to write some things about these new features as soon as possible. A recurring promise, I know, but bear with me here

It’s time to elaborate on the previous blog post’s topic and investigate one of the most important scene graph nodes: the Mesh. It’ll probably be the object you’ll be working with most, and it allows a form of flexibility that can really provide a benefit to your memory usage and performance. That is, of course, if you know how. I’ll talk more about performance and memory usage next time, for now it’s just important to understand how Mesh works.

Meshes and Geometries

Meshes and Geometry objects are closely related. Geometries provide the – you guessed it – geometry of a 3D object: the vertices, triangle indices, UV coordinates, vertex normals, and what have you. Mesh objects are there to give a Geometry a place in the scene graph (and as such, a position in 3D space), as well as link it to a material. Why bother with the distinction, you may wonder. Why not just place the geometry data inside the Mesh class and be done with it? In many cases, you’d want to use the same geometry in several places. Different monsters of the same type throughout a level, for instance. The Geometry object allows you to save memory and limit the amount of data that’s uploaded to the GPU.

Both Meshes and Geometry mirror each other in that they both contain “sub”-objects (SubMesh and SubGeometry, respectively). Each SubMesh object links to a corresponding SubGeometry object in the Mesh’s Geometry object. Each SubGeometry provides the vertex and triangle data for each part that will make up the entire object. Confused? Check the graph below. The reason for this subdivision is mainly so multiple materials can be used within a single Mesh. Because of how the GPU issues draw commands, materials cannot be assigned to individual triangles in the model. Instead, several SubGeometries are used, and each can be rendered with a different material. This is achieved by assigning a material to the corresponding SubMesh. SubMesh materials are optional; if not provided, the main Mesh object’s material is used for rendering. In other words, the SubMesh material property overrides the Mesh material property for the corresponding SubGeometry.

Time for a practical example. A car Mesh can refer to a Geometry object containing a SubGeometry for the car body and one for the windows. This way, a metallic BitmapMaterial can be used for the car body, and a transparent ColorMaterial can be used for the windows, by assigning the materials to the SubMesh objects.

The scene graph inheritance structure (black arrows) and the Mesh/Geometry architecture (white arrows)

The Scene Graph in Action

If you’re still a bit confused even after looking at the magnificent chart above (yes, that is the same one as in the previous post – sue me), a demo will definitely help. And what way to better illustrate a hierarchical scene graph than one illustrating a blatant lack of inspiration as well: a mini solar system! Not everything in the source is as pragmatic as it could be, but as it’s done for purely illustrative purposes, I’ll forgive myself just this once. Play around with the source, and things should start making more sense.

Demo

Source

And that’s it for now! Any questions? shoot!

Update

All sources for this post have been updated to use the dev branch of Away3D 4.0: https://github.com/away3d/away3d-core-fp11/tree/dev

I’m planning some future blog posts dealing with tips to get better performance out of your Away3D 4.0 (FP11) projects. When working with the GPU, it’s easy to get unexpected slowdowns due to inefficient content. There are a lot of common mistakes and misconceptions that I see popping up time and time again, and I reckon it’s a good idea to try and rid the world of them. Before that, it’s important to understand one of the most central aspects of the engine: the scene graph. It forms the basis of many of the performance tips that will follow, so despite the seemingly trivial nature of the subject, it is important to explain things in proper detail.

The scene graph is essentially the 3D equivalent of the Flash display list. If you’ve worked with Away3D before, or any other 3D engine for that matter, it’s nothing new; every version of Away3D has had a scene graph, even if it was never been called that way, and it’s simply the Scene3D object and all its children: ObjectContainer3D, Mesh, Sprite3D, … It’s the building blocks you use to construct your 3D scene in a hierarchical way that feels natural. There are some differences with older versions of the engine, especially how Mesh objects are constructed, so let’s step through the different objects.

Scene graph objects

The scene graph is made up of objects (nodes) that form a tree data structure. Nodes can be added as a child to other nodes, which makes their transformation (position, rotation and scale) relative to that of their parents’.

• Scene3D: Essentially, this is the root node of a scene graph. It wraps a root ObjectContainer3D and links it to the spatial partitioning system (more on that in a future post). Whenever a View3D is created, an empty Scene3D is created by default if one is not passed along. Since it’s a root node by design, a Scene3D object cannot be added as a child to other containers.
• ObjectContainer3D: Comparable to Flash’s DisplayObjectContainer, it is the most basic scene graph node. It can be added as a child to other ObjectContainer3Ds (or subclasses), and in turn it can be a parent of other ObjectContainer3D (or subclass) objects. Despite the name, child nodes aren’t necessarily “contained” by the container in the most literal sense. It merely implies that the child objects’ transformation is relative to that of the parent, much like Flash Sprite objects that are a child of a DisplayObjectContainer. Move or rotate the parent, and the child will move or rotate along. For instance, a rider object can be a child of a horse object so that when the horse moves, the rider will always be in the correct place without having to explicitly update its position. It does not mean – assuming your game is within the bounds of the morally acceptable – that the rider is inside the horse. This may seem like a distinction too trivial to even point out, but it’s a misconception that has managed to confuse a good few people in the past. The results are often wastefully constructed scene graphs and superfluous transformation updates, simply because of this misinterpretation. Every scene graph object that you manipulate to generate your scene (that excludes Scene3D itself), extends ObjectContainer3D.
• Entity: While it’s an abstract class and you should never use it directly, it’s important enough to know of its existence, especially if you’re looking into creating your own scene graph objects. It forms the base for any object that has a “physical presence”. Entities are collected in the render loop, and are dealt with differently depending on the concrete subclass.
• Mesh: The most typical renderable 3D object, consisting out of a Geometry that defines vertices, triangles, and all that jazz. It also provides the material with which the object is rendered. Mesh objects will be the central subject of the next blog post, so I’ll keep it brief here.
• Sprite3D: A so-called “billboard”, basically a 2-triangle plane that always faces the camera. Remember the monsters in old shooters like Doom or Duke Nukem 3D? Sprites, baby!
• SkyBox: A special case scene graph object, used for faking the sky or environment in a scene. As it’s always supposed to be “as far away as possible”, it can’t be moved and will always center itself around the camera and size itself so it’ll fit within the camera frustum. There’s not supposed to be more than one SkyBox in the scene.
• PointLight/DirectionalLight: These are light objects that can be used for material shading and casting shadows (DirectionalLight only). Traditionally, lights weren’t part of the scene graph in Away3D, but now they can be added in order to make lights dependent on other objects’ position (fe: the light on a miner’s hat). However, because directional lights are “infinitely far away” to approximate very distance light sources such as the sun, their position is in fact irrelevant. It’s recommended to add them to the scene directly. However, the position in combination with lookAt could be used to create sun cycles, but yeah let’s not go there now
• Camera3D: Cameras are used to render the scene to a view, and don’t necessarily need to be added to the scene graph (by default, they aren’t). However, it can be convenient if you want to make your camera’s position and orientation depend on another object (a rigid chase camera for instance), which is also a change from older versions of the engine.

The scene graph inheritance structure (black arrows) and the Mesh/Geometry architecture (white arrows)

See, not that different from what you probably already know! However, the way Meshes are constructed, and how they relate to Geometry objects has changed considerably, and can be an important aspect when creating efficient content. And that’s… for the next blog post!

Molehill, Adobe’s new API to leverage the GPU for rendering, was made public some time ago in the form of an “incubator” Flash Player release, and along with it we released an early pre-alpha version of Away3D 4.0, codenamed “Broomstick”. I’ve been working on the new engine for quite some time now, and since the release I hadn’t had the time to post any more information aside from what was shown on the blog post. Time to change that, I’d say!
Before you do anything else, you’ll need to install the Incubator Flash Player, because the demos will be using that. Secondly, there’s no guarantee that anything related to Away3D 4.0 will be exactly the same in the final release, as it is of course an early alpha. Finally, source for all demos is in the usual Away3D repository. They’re a bit messy, since they were actually just quick test files to see if everything still works

Subsurface scattering

Subsurface scattering is basically what happens to light when it travels through a translucent surface. Instead of either simply reflecting off a surface or passing through it, the light will enter the material, reflect a good couple of times before exiting the surface again and reaching the eye. This behaviour causes a general blurring of the diffuse lighting on an object and allows light to shimmer through less “thick” regions. Just think about how a candle’s flame shines through the wax.

There’s a few rendering techniques that perform subsurface scattering to some extent. A popular approach is to render the diffuse lighting to a texture and simply blur it slightly. However, I find that this approach doesn’t allow light to travel through an object and so I opted for another approach: using depth maps. Similar to shadow mapping, a depth map is rendered from the point of view of the light, and when rendering, we compare depths of the rendered pixel to the value in the depth map. Instead of using this to determine whether a pixel is in shadow or not, we can use the difference between these values to determine the “thickness” of the object, or how far light has to travel through it to be able to reach the eye (see my amateurish schematic on the right ).

Depending on this distance, we can colour the pixel differently. We define a colour the light gets by traveling through the object (this depends on the actual material), and the final pixel’s colour ranges from this “scatter colour” to the material’s (texture) colour, depending on how thick it is.

This technique can be used to make materials look like wax, such as in this demo.

Advanced Skin Rendering

Skin is in fact a translucent object, so we can use subsurface scattering to increase the realism, as usual rendering techniques often create a harsh or clay-like effect. Instead, subsurface scattering softens the general shading and allows light to travel through more translucent regions such as the ears, softer parts of the nose, etc.
To further increase the realism, the specular highlights are modulated using a fresnel term. As with most objects in reality, the reflectivity of an object changes depending on the view angle, and with it the strength of the highlights. When observing skin head-on, there’s usually not a strong direct light reflection, but it can usually be perceived on shallow angles.
The result of both can be seen here.

In Away3D 4.0

First of all, to get started using Broomstick, check out this article by John Lindquist. He did a great job explaining how to get started!
Default materials in Away3D 4.0 are currently implemented using “methods”, which are properties of a material that define how the shaders work in a modular fashion. This way, there’s no need for a billion variation of Material classes for each combination. For subsurface scattering, we need to change the diffuseMethod property of a material and assign an instance of SubsurfaceScatteringDiffuseMethod. For the fresnel specular highlights, we assign an instance of FresnelSpecularMethod to the specularMethod property. It’s all in the source, so knowing this, you should be able to make sense of what’s going on in there

Demos

In case you skipped through the rest of the article, here’s a demo recap. Loading times may be long, as the models are pretty big

Wax Statue : Illustrating subsurface scattering to generate a material resembling wax.
Head rendering: Using subsurface scattering and a specular fresnel term to increase realism in skin rendering. Press any key to toggle the subsurface scattering, so you can see the difference. Note the light shining through the ears, for example.