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IDProjectCategoryView StatusDate SubmittedLast Update
0028253Community[OCCT] OCCT:Visualizationpublic2016-12-20 16:192016-12-22 11:32
ReporterTimo 
Assigned Tobugmaster 
PrioritynormalSeverityminor 
StatusclosedResolutionduplicate 
PlatformOSOS Version
Product Version[OCCT] 7.1.0 
Target VersionFixed in Version 
Summary0028253: Incorrect treatment of transparency if a spline face overlaps itself in 3D view
DescriptionWhen a spline face is strongly bent it can occur that some part of the face is in front of another part of the face in the 3D view. In this case, if transparency is used, there occur ugly artefacts.

The problem does not occur if two different faces are behing each other.

Also, it could not be reproduced with simple geometry like box or sphere. So, it might be specific to more complex surfaces.
Steps To Reproducepload ALL
restore shell.brep s
vinit
vdisplay s
vfit
vsetdispmode s 1
vsettrans s 0.4
TagsNo tags attached.
Test case numberNot needed
Attached Filespng file icon transparency artefacts.png (93,860 bytes) 2016-12-20 16:19
? file icon shell.brep (322,579 bytes) 2016-12-20 16:20

- Relationships
duplicate of 0027716closedbugmaster Community Visualization - incorrect treatment of multiple transparent objects in 3D view 
duplicate of 0027925closedbugmaster Open CASCADE Visualization - implement order-independent transparency algorithm within rasterization rendering 

-  Notes
(0061927)
kgv (developer)
2016-12-20 16:33

Dear bugmaster,

please close the issue as duplicate of 0027716.
(0061928)
Timo (developer)
2016-12-20 16:35
edited on: 2016-12-20 16:35

0027716 seems to be a slightly different problem because it is about different objects behind each other, where I'm speaking about different parts of the same object behind each other. But maybe it has the same reason.
I cannot see 0027925, so cannot comment on that.

(0061929)
kgv (developer)
2016-12-20 16:43
edited on: 2016-12-20 16:45

> 0027716 seems to be a slightly different problem because
> it is about different objects behind each other,
> where I'm speaking about different parts
> of the same object behind each other.
Scenarios are different but the reason is the same - order-dependent transparency without any ordering.

Issue with several transparent objects can be worked around more simple (sorting objects)
than issues within the single transparent object
(which would require sorting triangles - and even this sorting might be not enough in case of their intersection).

General-purpose order-independent transparency algorithms can solve issues within both scenarios.


- Issue History
Date Modified Username Field Change
2016-12-20 16:19 Timo New Issue
2016-12-20 16:19 Timo Assigned To => kgv
2016-12-20 16:19 Timo File Added: transparency artefacts.png
2016-12-20 16:20 Timo File Added: shell.brep
2016-12-20 16:32 kgv Relationship added duplicate of 0027716
2016-12-20 16:32 kgv Relationship added duplicate of 0027925
2016-12-20 16:33 kgv Note Added: 0061927
2016-12-20 16:33 kgv Assigned To kgv => bugmaster
2016-12-20 16:33 kgv Status new => feedback
2016-12-20 16:33 kgv Resolution open => duplicate
2016-12-20 16:35 Timo Note Added: 0061928
2016-12-20 16:35 Timo Note Edited: 0061928 View Revisions
2016-12-20 16:43 kgv Note Added: 0061929
2016-12-20 16:45 kgv Note Edited: 0061929 View Revisions
2016-12-20 16:45 kgv Note Edited: 0061929 View Revisions
2016-12-20 16:45 kgv Note Edited: 0061929 View Revisions
2016-12-22 11:32 apn Test case number => Not needed
2016-12-22 11:32 apn Status feedback => closed
2016-12-22 11:32 apn Target Version 7.2.0 =>


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