Brush Editor

Introduction

The Brush Editor is basically a simple Blueprint Editor to edit UOdysseyBrush assets.
UOdysseyBrush are used ILIAD’s PaintEngine as brushes to draw in the canvas.

Modules

The Brush Editor files are based in 2 modules :

  • OdysseyBrush : Which contains the UOdysseyBrush class representing the asset, aswell as all the blueprint node functions provided by the asset.

  • OdysseyBrushEditor : Contains minimal files to open a simple Blueprint Editor when opening a UOdysseyBrush asset.

OdysseyBrush Module

In the OdysseyBrush Module you can find :

  • The UOdysseyBrush asset class

  • The UOdysseyBrush Blueprint Nodes provided through Blueprint Function Libraries, Enums, Structures, Classes.

  • The UOdysseyBrush overrides structure

OdysseyBrushEditor Module

Todo

do it

UOdysseyBrush Asset

The UOdysseyBrush asset class is declared in Developer/OdysseyBrush/Classes/OdysseyBrushBlueprint.h.
The class itself is extremely simple, and is just a basic blueprint class containing nothing.
When created UOdysseyBrush is assigned a Blueprint Parent Class : UOdysseyBrushAssetBase acting like if UOdysseyBrush was deriving from it.

UOdysseyBrushAssetBase is declared in Developer/OdysseyBrush/Classes/OdysseyBrushAssetBase.h.

UOdysseyBrushAssetBase provides the methodes ILIAD will use to retrieve the rectangles affected by a Stamp or adding a new “Drawing State” when using the brush, etc…
Moreover, it provides all nodes which directly linked with the Brush behaviour :

  • Stylus Inputs for (interpreted each Step of the stroke)

  • Paint Engine Modifiers

  • Paint Engine Events and Actions

Blueprint Workflow

To be able to draw on a pixel block, UOdysseyBrush relies on the Stamp node, which will stamp down the given block using the given parameters on the destination block the PaintEngine is editing.
UOdysseyBrush also needs some entry points to know when to call Stamp. Those entry points are events :

  • OnSelected : Triggered when the brush is selected (when opening an editor, or the brush is changed in the editor BrushSelector).

  • OnTick : Triggered 60 times per seconds

  • OnStrokeBegin : Triggered a stroke begins (on stylus down basically)

  • OnStrokeEnd : Triggered a stroke ends (on stylus up basically)

  • OnSubStrokeBegin : Triggered a sub stroke begins, a sub stroke is the whole part of the stroke that is drawn between two stylus positions.

  • OnSubStrokeEnd : Triggered a sub stroke ends, a sub stroke is the whole part of the stroke that is drawn between two stylus positions.

  • OnStep : Triggered at each step generated by the interpolation between two stylus position when the stroke has begun.

  • OnStateChanged : Triggered when the state of the brush or the PaintEngine changes (color changed, modifier changed, blendmode changed, etc…)

../../_images/BrushEditorStroke.jpg

Additional Blueprint Nodes

When editong an UOdysseyBrush asset, the user need some nodes to edit more than just the Brushes parameters.
The user need some node to edit pixel blocks, colors, execute specific mathematic functions, define rectangles for pixel blocks, etc …
All those nodes are dispatched in several files under the Proxies folder :

  • OdysseyBrushBlending : contains all the enums to manage pixel block blending

  • OdysseyBrushBlock : contains the pixel block structure and all the basic nodes to edit the pixel blocks (see Odyssey Block Reference)

  • OdysseyBrushColor : contains the class representing a color and all its nodes

  • OdysseyBrushFormat : contains all the enums to manage picel formats

  • OdysseyBrushMath : contains additional Mathematic nodes

  • OdysseyBrushPivot : contains all the classes, structures, enums, to manage pixel block pivot points

  • OdysseyBrushRect : contains a Rectangle class made to define rectangle zones on pixel blocks

  • OdysseyBrushTransform : contains all Transformations nodes (Matrices, scale, shear, etc…)

Odyssey Block Reference

Odyssey Block Reference is a structure wrapping a pixel block.
It keeps the block alive and tracks dependencies between blocks, in order to keep alive all the blocks the ULIS library needs to work on.

Note

Odyssey Block Reference are not really references, it just wraps a block, and each node returning a Odyssey Block Reference actually returns a new object of this structure.