Objeck Documentation

Bundle

OpenGL 3.3 core rendering on top of SDL2. Builds on sdl2.obl for the window and context; this bundle is the GL side. Compile with -lib sdl2. Layers, thinnest first: GLWindow (window and context), GL (state), Shader, Mesh, Texture2D, Light, RenderTarget, Material, Frustum, ShadowMap, PointShadow, Overlay, Transform, and Box/Scene. All public, so nothing is capped. Targets the 3.3 core profile, forward-compatible: the highest common denominator across the desktop platforms Objeck ships, since macOS caps at 4.1 core. GLES-only hardware is out of scope by construction. See docs/opengl.md for setup, a minimal program, why the calls are coarse-grained, and how to add one.

Track

How a value changes over time. The other half of animation. Transform->SetParent says how parts move TOGETHER; a Track says how anything moves at all -- a lid opening, a platform rising, a light dimming, a door swinging, a camera pushing in. It holds keys and reads a value back at any time between them:

Why a track rather than a tween

A from-to pair with a duration covers the easy case and then stops: an animation that goes out, waits, and comes back is three of them plus the bookkeeping to sequence them. Keys are that for free, and reduce to the easy case when there are two of them.

What it does not do

One FLOAT. Not a vector, not a colour, not a quaternion -- three tracks make a position and four make a colour, and keeping it scalar is what lets it drive anything at all rather than the specific things somebody thought of. It has no clock of its own either: Sample takes a time, so the caller decides whether that is wall time, a paused time, or one running backwards. Rotation between two ANGLES here is not the same as rotating between two orientations -- interpolating yaw, pitch and roll separately is fine for a hinge or a turntable and wrong for anything tumbling freely, which needs quaternions this bundle does not have.

Example

swing := Track->New();
swing->Add(0.0, 0.0);
swing->Add(1.5, 90.0);
swing->SetEasing(Easing->EASE_IN_OUT);
...
door->SetYaw(swing->Sample(elapsed)->ToRadians());

Add #

Add a key. Inserted in time order, so keys can be added in any order. Adding a second key at exactly the same time replaces the first rather than creating a step nothing can land between.

method : public : Add(time:Float, value:Float) ~ Nil

Parameters

Name	Type	Description
time	Float	when, in seconds from the start
value	Float	what the track reads at that moment

GetCount #

method : public : GetCount() ~ Int

Return

Type	Description
Int	how many keys the track holds

GetDuration #

The time of the last key, which is how long the track runs for.

method : public : GetDuration() ~ Float

Return

Type	Description
Float	seconds, or 0 for an empty track

GetEasing #

method : public : GetEasing() ~ Int

Return

Type	Description
Int	the current easing mode

GetKeyTime #

method : public : GetKeyTime(index:Int) ~ Float

Parameters

Name	Type	Description
index	Int	0 to GetCount() - 1

Return

Type	Description
Float	the time of that key, or 0 if out of range

GetKeyValue #

method : public : GetKeyValue(index:Int) ~ Float

Parameters

Name	Type	Description
index	Int	0 to GetCount() - 1

Return

Type	Description
Float	the value of that key, or 0 if out of range

IsLoop #

method : public : IsLoop() ~ Bool

Return

Type	Description
Bool	whether the track loops

New # constructor

An empty track. Sampling one with no keys returns 0.

New()

New # constructor

A track that runs from one value to another -- the common case, spelled directly.

New(duration:Float, )

Parameters

Name	Type	Description
duration	Float	how long it takes, in seconds

Sample #

Read the value at a moment. Before the first key returns the first value and after the last returns the last, so a track is safe to sample at any time without the caller clamping -- unless it loops, in which case time wraps.

method : public : Sample(time:Float) ~ Float

Parameters

Name	Type	Description
time	Float	seconds from the start

Return

Type	Description
Float	the value there

SetEasing #

How the value moves BETWEEN keys. LINEAR by default. The eased modes are what stop machine-driven motion reading as machine-driven: almost nothing in the world starts and stops at full speed, and EASE_IN_OUT is the difference between a lid opening and a lid teleporting through its arc.

method : public : SetEasing(easing:Int) ~ Nil

Parameters

Name	Type	Description
easing	Int	an Easing

SetLoop #

Whether time wraps past the last key. Off by default, which HOLDS the last value -- right for a door that opens once. On wraps back to the start, for anything cyclic. Note a looping track jumps at the wrap unless its first and last values match.

method : public : SetLoop(loop:Bool) ~ Nil

Parameters

Name	Type	Description
loop	Bool	true to wrap

Shape #

Bend 0..1 according to the easing mode.

method : private : Shape() ~ Float

Parameters

Name	Type	Description