BansheeEngine/SceneView.txt

TODO:
 - Core thread gets stuck on shutdown when OpenGL is used...Somewhere in kernel

Weekend:
 - Set up grid material and hook it up to renderer (+ actually instantiate it in EditorApplication)
 
 - Fix up shader so I can reference two different gpu vars with a single shader var (e.g. DX11 sampler variables will have different names than DX9 or GL sampler variables)
 - You can create a resource handle to invalid resource type. Add a security feature to prevent that, at least in debug mode?
 - When unloading unused resources I should do it recursively so it unloads any new ones that might have been released during the first unload
 - Ensure that resource handles only have a single mData (and fix Resources::unloadAllUnused)

 - Think about picking implementation and possibly Handles implementation

TODO - Think about:
 - How will I allow user from C# to draw gizmos and handles?
 - Unity uses immediate mode
 - I should probably focus more on implementing a nice C# drawing interface so I don't constantly have to go and use C++
    - Although this might be overkill for this point - I think even Unitys handles/gizmos are C++ in the end

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Handles

 - Make a few different base handle types:
   - Slider 1D (e.g. for movement using an arrow cap)
   - Slider 2D (e.g. for movement in 2D using a plane render)
   - Similar for scale/rotation handles  (see Unity for its implementations of those)

Handles should have colliders which will be queries whenever user input is detected in scene view
If any handle is hit the input will not proceed further (e.g. no picking will be done) and that handle control
will become active.

Base handle types should just be positioned in space and then return value every frame as user moves them.
 - This way they can also easily be used from C# for custom user-made stuff

TODO - Think about this
See for inspiration: http://docs.unity3d.com/ScriptReference/Handles.html

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Picking

TODO - Think about this

Picking
 - Create core thread class that accepts a screen coordinate and a camera and it determines object at its position
 - System then renders all visible objects with diferent colors 
 - Image then needs to be read back to determine what was hit
 - Result is returned via async op
 - Needs to support multi-select where I draw a rectangle on screen
 - NOTE: I will also need to render gizmos which I assume will all be within a single buffer. This might require special care since normally I can color each buffer with a different color, which won't work in this case.
     - Similar issue might happen with particles and other systems

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Rendering selection

Get the mesh from the selected Renderable
Draw that same mesh again using a shader that grays out the original
The second mesh will likely need to use depth bias (sloped depth bias too?)

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Grid

Generate grid of X size around Y point
Normally Y is (0, 0, 0) but we should be able to move it with camera
There will be minor and major axes with slightly different color (and thickness?)
Instead of pixel perfect lines draw 2D quads (Using DrawHelper which has thick line support)

Mesh can be static, I can just move its origin by length of the major line (+ maybe have a fadeout in shader with 1 invisible major line so the movement is not noticeable)
Material is retrieved from builtin materials list

This can be drawn directly using the draw list and not a renderable

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Gizmos

GizmoSetups
 - Determines what to display for a certain component (or a SceneObject) itself

GizmoManager
 - Every frame goes through all game objects and create/removes their gizmos. It keeps a cached version of all gizmos
 - It keeps a list of gizmo descriptors
 - A "diff" of this list is sent to Core thread every frame

GizmosRenderer
 - Batches all gizmos into a single buffer and renders them with a single call
 - It might be a bit problematic if custom textures are used for gizmos
    - Just don't batch those?

When picking GizmosRenderer can draw the gizmos as normal but using a special shader.

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Need to allow the user to specify custom gizmos.
 - Have a set of methods like Gizmos.DrawSphere, DrawIcon, DrawLine, DrawCube, DrawFrustum, etc.
 - Have a CustomGizmo attribute which you can attach to a method
 - That method can then call above methods
 - Additionally in the attribute you can specify when is the gizmo displayed: Active, Selected, NotSelected, SelectedOrChild
 - And an option if gizmo can be picked or not
 - These methods will somehow automatically be registered with the GizmoSetups