Intro to BAScene framework for Mac

Scene Kit
You’re making a scene!

Thursday, 7 March, 13

Who am I?
• ambivalent coder in high school
• graduated with an English degree in 1996
• became a Mac fanatic; learned C
• hyped up for Rhapsody (OS X+Cocoa)
• back to school for Comp Sci in 2000
• now work as full-time iOS developer

Motivations
Why am I building another 3D library?


Microserfs

• 1995

• Douglas Coupland

• Oop!

• Virtual LEGO


Microsoft employees leave to form a start-up in Silicon Valley. His vision for Oop! was
compelling. I wanted it, and still do. The ideas in the book burrowed into my subconscious.
And I wanted to be part of the software development world.

3D
• 3D scenes are interesting
• Some things are naturally 3-dimensional
• We experience a 3D world every day
• 3D provides a sense of realism
• 3D is creeping into app design through the
side door


“Making a scene” means to attracts attention. That’s a good thing!
Apps: We have pseudo-3D icons, interfaces, pseudo-3D animations
let’s get 3D out in the open in a friendly way

3D is Too Hard

• The barrier to entry for 3D is too high.
• 3D math is too complicated.
• 3D graphics API are too complicated.
• Creating 3D content is too complicated.
• Can we make it easier?


Vectors, transformation matrices, projective geometry. Ouch!
OpenGL state, primitives, buffers, shader programs.
I just want to stick some boxes together.

Hide Complexity
• Reduce or eliminate need for OpenGL
• Replace OpenGL state with Obj-C classes
• Use abstractions that feel more natural
• Provide necessary types and functions
• Take care of math drudge work
• Make it easier to make fun apps

Still missing some fundamental features.

Virtual Toys
Not your old LEGO set


Not about big-budget 3D games.

Example: Sim City
• Build a city

• Build networks:

• roads

• power

• Build an economy

• Unleash havoc


OPTIONAL

Example: Minecraft
• Explore a virtual world

• Build things:

• buildings

• roads

• railways

• farms

• monster traps

• microprocessors !?


OPTIONAL: Don’t waste time on this!

Beyond Games
• Games market is mature and saturated
• Interactive entertainment is bigger
• Games are too limiting; too constraining
• Toys give more freedom to explore
• Toys let you make a world in your image
• Virtual toys scale up cheaply

Virtual toys have a lot of potential. The market could grow a lot.
Examples: Sim City, Sims, Minecraft
Toys are for experimentation and self-directed learning.
Virtual toys are not as fun as real games, but they have qualities real toys lack.
With networked software, you can

Concepts


If you’re already a 3D developer, please

Scene Kit Concepts
• A scene is made of props on a virtual stage
• A scene is integrated into a workﬂow:
• assemble props and arrange the scene
• capture an image (“paint it”)
• update the scene
• capture a new image, etc.

the stage is a conceptual container, the virtual world
in

Design Patterns
• Is a scene a model or a view or both?
• depends on your point of view
• could say it’s a model of a view
• classic MVC provides a view of a model
• in a simulation, there is another model
• scenes are require tools to build

OPTIONAL

Camera

• point of view
• field of view, etc.
• “style” of the image
• fill style, blur, etc.
• delegates drawing


POV: orientation, depth of field, field of view, dimensions, aspect ratio, focus point

Scene Hierarchy

• Arrangement
• Stage > Partition > Group > Prop
• Construction
• Prop > Prototype > Mesh > Polygon >
Point > Tuple


Prop

• a “physical” object

• instance of prototype

• make many copies that
share the same
geometry data


Prototype

• Collection of meshes

• meshes can be shared

• each mesh can have a
customized appearance
that is unique to that
prototype


Transform is used to position the mesh in the prototype’s local coordinate space.
I didn’t make this model!

Mesh

• Collection of polygons


Polygon

• Closed, ﬂat shape

• Composed of points


Point
• Fundamental geometric
concept

• Collection of tuples

• location

• orientation (normal)

• colour

• texture coordinates


A tuple is a 3-element vector interpreted as a spatial co-ordinate (cartesian space, colour
space, texture space).
Textures may only need 1 or 2 elements. This picture doesn’t tell you much.

Classes and Interfaces
Object model, data types, and functions


Here I’ll begin to review the concepts in reverse order

Base Types
• Structures
• point, matrix, size, region, triangle ++
• vector types often union’ed with an array
(e.g.: volume for size)
• some have integer and ﬂoat variations
• string transformation functions

a volume is a union of a size and an array of elements
add picture of code deﬁning Volume and Size types

typedef struct { typedef struct {
! CGFloat x; ! NSUInteger w;
! CGFloat y; ! NSUInteger h;
! CGFloat z; ! NSUInteger d;
} BAPointf; } BASizei;

typedef BAPointf BARotation3; typedef struct {
! CGFloat w;
typedef union { ! CGFloat h;
! BAPointi p; ! CGFloat d;
! NSInteger i[3]; } BASizef;
} BALocationi;
typedef union {
typedef union { ! BASizei s;
! BAPoint4f p; ! NSUInteger i[3];
! CGFloat i[4]; } BAVolumei;
} BALocationf;
typedef union {
typedef union { ! BASizef s;
! BARotation3 r; ! CGFloat i[3];
! CGFloat i[3]; } BAVolumef;
} BAOrientationf;


Utilities
• Functions for operating on structures
• Imitates functions from NSGeometry.h
• Simple operations like creation, midpoints
• Complex stuff like matrix math
• NSColor to struct transformation
• useful drawing functions for debugging

Managed Object Model
Custom NSManagedObject subclasses


Model: Geometry

Model: Composition

Geometric Entities

• Point, Prototype and Mesh
• support construction from element arrays
• along with Group, support ﬂattening back
to element arrays


Mesh

• Represent complex geometric shapes
• As part of a prototype, support:
• appearance properties
• spatial transformation
• library of simple shapes provided


Composites

• Mesh, Prototype, Prop and Group
• can be identiﬁed and loaded by name
• organization and re-use
• have bounding boxes and intersection tests


Other
• BAScene class does some high-level work
• manages object model and context
• BASceneView: custom OpenGL view
• BACameraSetup: view to control camera
• BAResourceStorage: caches GL data
• BATexture: handles GL texture stuff

BATexture has an equivalent in GLKit, but Scene Kit is compatible back to 10.5

Alternatives
• Quartz Composer
• if you don’t want or need Objective-C:
• Ogre3D, Irrlicht, Unity, Unreal
• for iOS (could be ported to Mac OS X):
• iSGL3D - developer has abandoned
• Cocos3d (based on Cocos2d) - young

Quartz Composer really has a different design and usage model. I’ve never really used it.
There is no open-source development targeting 3D on Mac OS X.
Should not need to use C++ or some bizarre C library to have fun with 3D programming.
The commercial stuff is good if you want to do polished-looking 3D games.

Caveats
• Missing a lot of things
• Work progressing slowly
• I’m lazy and life is full of distractions
• Not available, not even open source
• When it’s sufﬁcient, I’ll share SDK
• release source code at some point

Needs support for creating texture mapping; animations; and shaders.
If you want to try it, just ask me for it.

Contact me

• bgulanowski@gmail.com


Thank You

Time for demos and sample code


Intro to BAScene framework for Mac

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