[API Review] RT-28129: event coordinates with perspective camera

Chien Yang chien.yang at oracle.com
Fri Feb 1 11:12:14 PST 2013

Yes we do, texCoord (texture coordinate) is a commonly used term in the 
computer graphics world, for example, OpenGL has methods such as 
glTexCoord4f(x, y, z, w ),  and glTexCoordPointer(4,GL_FLOAT,0,0).

- Chien

On 2/1/2013 11:01 AM, Richard Bair wrote:
> Only thing that got my attention was: getIntersectedTexCoord
> Is the rest of the 3D API using shortened names like "tex" and "coord" 
> as well?
> Richard
> On Feb 1, 2013, at 10:57 AM, Chien Yang <chien.yang at oracle.com 
> <mailto:chien.yang at oracle.com>> wrote:
>> Looks good to me. This proposed change will also provide a consistent 
>> picking framework for 2D and 3D primitives.
>> Thanks,
>> - Chien
>> On 2/1/2013 8:51 AM, Pavel Safrata wrote:
>>> Hello,
>>> this is related to the 3D support planned for FX8, yet it is a 
>>> bugfix of an existing issue.
>>> With perspective camera, events delivered to any node that's not 
>>> lying flat on the XY plane contain wrong local coordinates - they 
>>> ignore the projection transformations. It's enough to rotate a 
>>> rectangle along X axis and the coordinates become useless.
>>> http://javafx-jira.kenai.com/browse/RT-28129
>>> Solution to this problem requires API changes, because we need to 
>>> compute in 3D to get proper numbers. So I propose to add a "double 
>>> getZ()" method to all picking-based events, with the following 
>>> semantics: the event's getSceneX(), getSceneY() values still 
>>> represent the 2D coordinates of the mouse in the window content 
>>> pixels (screen coordinates minus window position and decorations); 
>>> the getX(), getY(), getZ() represent the hit point in the local 3D 
>>> space (which may now be different even for scene because of the 
>>> perspective transform). If no node is picked, the hit point with the 
>>> scene will be found on the projection plane. Note that nothing 
>>> changes for the 2D case, for the 3D case we now have correct 3D 
>>> coordinates instead of a complete nonsense.
>>> There is one more issue - how to pass the correct coordinates to the 
>>> event constructors. Instead of creating more construrctors with the 
>>> three additional coordinates, I propose to use a concept called 
>>> PickResult which was briefly discussed earlier and will soon be part 
>>> of a 3D API review. In short, it is an object that contains 
>>> information about the pick for the event - the picked node, local 
>>> coordinates of the hit and some 3D-specific stuff. For proper 3D 
>>> support, it will anyway be necessary to pass the PickResult to the 
>>> events and allow access to it; once this is done, the event can 
>>> compute the coordinates from it. So I propose adding PickResult to 
>>> the event constructors. Note that they've not been released yet, so 
>>> we can modify them instead of adding new ones. Also note that for 
>>> convenience of 2D use-cases, the constructors will accept a null 
>>> PickResult and in this case compute PickResult values based on the 
>>> passed event target and scene coordinates (which is sufficient for 
>>> 2D case).
>>> Side note for those who remember the previous 3D API discussion: the 
>>> PickResult is no longer restricted to 3d shapes, it is present 
>>> always, with the 3D-specific fields having null values where not 
>>> applicable.
>>> Summary of this proposal:
>>> Affected classes: MouseEvent, MouseDragEvent, DragEvent, 
>>> GestureEvent, ContextMenuEvent and TouchPoint
>>> new methods: getZ(), getPickResult() (and extended semantics of 
>>> event local coordinates for 3D case)
>>> modified methods: added PickResult to all constructors
>>> Concrete description of the PickResult and the proposed picking API 
>>> can be found here:
>>> https://wikis.oracle.com/display/OpenJDK/Picking3dAPI
>>> Thanks,
>>> Pavel

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