V-up texture coordinate support

[Chien Yang]

Hi August,

      Thanks for the feedback. You are correct in both approaches, i. e. 
convert the geometric data or rotate the camera and flip the V. You 
implemented the former approach and our loader opted the later. We 
understand that this V-up feature can be very useful to loader 
developers like you. We will add the V-up option in the next FX 8 update 
release.

- Chien


On 10/22/2013 2:45 AM, August Lammersdorf, InteractiveMesh wrote:
> My JavaFX 3D model importers convert geometric data to the JavaFX 3D 
> coordinate sytem to support the default camera model (viewing into the 
> screen along the +Z-axis). A Y-up right-handed coordinate system (e.g. 
> COLLADA-, OBJ-, X3D-exports from modelling tools) is mapped as 
> follows: +Y -> -Y, +X -> +X, +Z -> -Z. This includes the adjustment of 
> all transforms and also the v-flipping of the texture coordinates: v 
> -> 1 - v. In this case I prefer converted texture coordinates stored 
> in the TriangelMesh instead of converting them 'backstage'.
>
> Alternatively, I consider providing an ImportOption to omit this 
> conversions if someone wants to simulate a Y-up right-handed 
> coordinate system in JavaFX. This would result in TriangelMesh points 
> and texture coordinates consistent with the imported file. Now an 
> internal v-flipping is needed to avoid upside-down textures because 
> the corresponding texture coordinates are typically v-up oriented. Right?
>
> Simulating a Y-up right-handed coordinate system in JavaFX is 
> discussed in "Getting Started with JavaFX 3D Graphics/Camera/Y-down 
> versus Y-up" 
> (http://docs.oracle.com/javafx/8/3d_graphics/camera.htm#CJAHFAHB). 
> Doesn't this approach require an immediate availability of a 
> v-flipping feature?
>
> August
>
> Am Donnerstag, den 17.10.2013, 15:08 +0200 schrieb Chien Yang 
> <chien.yang at oracle.com>:
>> Hi all,
>>
>>      Java images are defined such that (0, 0) references the top left
>> most pixel of the image. In JavaFX, the texture coordinate system for
>> 3D objects is defined with its U axis increasing from left to right
>> and the V axis increasing from top to bottom. Hence a texture
>> coordinate of (0, 0) references pixel (0, 0), which is the top left
>> corner of the texture, and a texture coordinate of (1, 1) references
>> the bottom right corner of the texture. This system matches the layout
>> of the image, which is stored such that the top-most row of pixels
>> ends up in memory in row 0. It also matches with the default 3D
>> coordinate system used in JavaFX where the X axis increases from left
>> to right and the Y axis increases from top to bottom.
>>
>>      We understand that this V-down coordinate system maybe confusing
>> or hard to work with for some 3D content developers when using models
>> that are defined with Y-up. We could add a V-up option (as a boolean
>> property of Shape3D). If set, we would flip the texture coordinates
>> when rendering, such that:  V' = 1 - V.
>>
>>     However it is very late in this release to consider any more
>> changes, so our plan is to add this option in a post FX 8 release if
>> it turns out to be needed. Please let us know right away if there is a
>> compelling need for V-up support in the FX 8 release.
>>
>> - Kevin and Chien
>