[x3d-public] Problem with inverted polygons/normals: actually texture transparency

[Don Brutzman]

Patrick: really great.  Thank you.

Your replacement version is uploaded and checked in (25% smaller), Shay D Pixel has become less shy and is fully with us now.  8)

http://x3dGraphics.com/examples/X3dForAdvancedModeling/ShayDPixel/pixelModel_BaseColor.png

The first .png version was converted from original .tga Targa image using latest GIMP.  If further image scrutiny is desired by anyone, all original .tga images now available at
http://x3dgraphics.com/examples/X3dForAdvancedModeling/ShayDPixel/images/originals/

(No good deed goes unpunished!) Request: who is writing up the specification feedback issue?

	Web3D Standards Comment Form
	http://www.web3d.org/content/web3d-standards-comment-form


On 11/8/2017 7:51 AM, Roy Walmsley wrote:
> Patrick,
> 
> Great spot. Thank you.
> 
> That also explains the behaviour of my Coin3D viewer. It saves transparent objects to render after opaque objects, and I had it set to sort transparent objects by distance.
> 
> All the best,
> 
> Roy

On 11/8/2017 7:45 AM, Michalis Kamburelis wrote:
> 2017-11-08 16:27 GMT+01:00 Patrick Dähne <pdaehne at gmail.com>:
>> As soon as the texture file contains an alpha channel, X3D browsers classify shapes with that texture as transparent shapes. Rendering transparent shapes is difficult. Browsers handle transparent shapes differently. Instant Player and X3DOM write transparent objects to the depth buffer. Most other browser don’t. In this special case, the result of Instant Player and X3DOM looks better than result of other browsers, but that is pure coincidence. None of the browsers is wrong or right.
> 
> And view3dscene looks at the texture contents to decide whether to use
> alpha testing (which doesn't have problems with ordering) or alpha
> blending (which is indeed tricky, but can represent partial
> transparency). It can be overridden by "alphaChannel" field,
> https://castle-engine.sourceforge.io/x3d_implementation_texturing_extensions.php#section_ext_alpha_channel_detection
> .
> 
> Regards,
> Michalis

> -----Original Message-----
> From: x3d-public [mailto:x3d-public-bounces at web3d.org] On Behalf Of Patrick Dähne
> Sent: 08 November 2017 15:27
> To: X3D Graphics public mailing list <x3d-public at web3d.org>
> Subject: Re: [x3d-public] Problem with inverted polygons/normals
> 
>> Am 07.11.2017 um 16:17 schrieb Don Brutzman <brutzman at nps.edu>:
>>
>> Initial draft version of an interesting new model is available at
>>
>> 	Shay D Pixel Version 2
>> 	http://x3dgraphics.com/examples/X3dForAdvancedModeling/ShayDPixel/ShayDPixelVersion2Index.html
>>
>> This version was exported from an .fbx version using Okino Nugraf.  Original at
>>
>> 	http://x3dgraphics.com/examples/X3dForAdvancedModeling/ShayDPixel/pixel_v2.fbx
>>
>> It looks OK in several players (such as Instant Reality and X3DOM) but polygon ordering appears reversed in X_ITE.  Adjusting the solid field hasn't helped.  Perhaps a normal issue?
>>
>> Wondering if anyone else can figure out what is going on here, screenshot attached for clarity.  TIA for all help.
> 
> 
> The texture of the model contains an alpha channel. Remove the alpha channel from the texture, and everything looks right.
> 
> As soon as the texture file contains an alpha channel, X3D browsers classify shapes with that texture as transparent shapes. Rendering transparent shapes is difficult. Browsers handle transparent shapes differently. Instant Player and X3DOM write transparent objects to the depth buffer. Most other browser don’t. In this special case, the result of Instant Player and X3DOM looks better than result of other browsers, but that is pure coincidence. None of the browsers is wrong or right.
> 
> Bye,
> 
> Patrick

all the best, Don
-- 
Don Brutzman  Naval Postgraduate School, Code USW/Br       brutzman at nps.edu
Watkins 270,  MOVES Institute, Monterey CA 93943-5000 USA   +1.831.656.2149
X3D graphics, virtual worlds, navy robotics http://faculty.nps.edu/brutzman