Created attachment 176263 [details]
negative z-coordinate of light
Open the attached documents in Word and in LibreOffice. Notice, that the maximum of the lighting is at different positions.
The problem is, that Word interprets a positive z-direction of the light as being a light coming from the side of the observer. But LibreOffice interprets a positive z-direction as coming form the opposite side.
Unfortunately neither [MS-ODRAW] nor ODF specify the orientation of the z-axis in the coordinate system of an extruded custom shape. Therefore an immediate fix is not possible. We might need to change the model for ODF or the import/export filter.
I currently try to clarify it:
Created attachment 176264 [details]
positive z-coordinate of light
Created attachment 176265 [details]
compare case negative
Created attachment 176266 [details]
Created attachment 176267 [details]
rtf source for case negative
I have used the attached rtf document, to create the doc files. An rtf document has a human readable source and so allows to set values directly.
To get a suitable rtf document start with a new document in Word, insert a custom shape -here a circle- and save it to rtf format. That converts the circle to a shape compatible with the MS binary formats. You then get an UI in Word, which has the similar settings than the "3D Settings" dialog in LibreOffice.
Then I have used Word to generate the doc files.
Import of extruded shapes in a rtf document is not implemented in LibreOffice. Therefore a direct compare of the rtf documents is not possible.
Created attachment 176268 [details]
rtf source for case positive
Created attachment 177130 [details]
Proof, that z-axis points towards observer
I'm sure now, that in MS Office the z-axis points towards observer. For screenshots and calculations see the attached files.
Created attachment 177131 [details]
Test file with non-default settings as mentioned in previous attachment
Created attachment 177132 [details]
Test file in doc format, so that you can open it directly in LO
I can confirm with Version: 18.104.22.168.alpha0+ / LibreOffice Community
Build ID: c13db6e792cc347ffff4585f23866f195651f21f
CPU threads: 4; OS: Linux 5.11; UI render: default; VCL: gtk3
Locale: cs-CZ (cs_CZ.UTF-8); UI: en-US
Calc: threaded Jumbo
Regina Henschel committed a patch related to this issue.
It has been pushed to "master":
tdf#145700 Improve lighting in extruded custom shapes
It will be available in 7.4.0.
The patch should be included in the daily builds available at
https://dev-builds.libreoffice.org/daily/ in the next 24-48 hours. More
information about daily builds can be found at:
Affected users are encouraged to test the fix and report feedback.
The here introduced invalid range for draw:extrusion-specularity is tracked in bug 147580.