View Issue Details
| ID | Project | Category | View Status | Date Submitted | Last Update |
|---|---|---|---|---|---|
| 0028253 | Community | OCCT:Visualization | public | 2016-12-20 16:19 | 2020-07-14 14:41 |
| Reporter | Timo | Assigned To | bugmaster | ||
| Priority | normal | Severity | minor | ||
| Status | closed | Resolution | fixed | ||
| Product Version | 7.1.0 | ||||
| Fixed in Version | 7.2.0 | ||||
| Summary | 0028253: Incorrect treatment of transparency if a spline face overlaps itself in 3D view | ||||
| Description | When 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 Reproduce | pload ALL restore shell.brep s vinit vdisplay s vfit vsetdispmode s 1 vsettrans s 0.4 | ||||
| Tags | No tags attached. | ||||
| Test case number | Not needed | ||||
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transparency artefacts.png (93,860 bytes) |
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shell.brep (322,579 bytes) |
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Dear bugmaster, please close the issue as duplicate of 0027716. |
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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. |
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> 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. |
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Reported issue still exists in OCCT 7.4.0. |
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Dear Matthias, please elaborate what exactly doesn't work as expected in use case. Rendering semitransparent objects requires sorting and order-independent transparency (OIT) techniques. Within the current state (since 0027925 linked to the bug), OCCT implements one such OIT technique - Weighted OIT eliminating the main artifacts of unordered transparency at the cost of blurry transparency and a little bit slower framerate. There are other OIT techniques available in a wild providing better visual quality at lower framerate, which are currently not available in OCCT 3D Viewer. OCCT 3D Viewer also provides Ray-Tracing engine, which handles transparency more naturally. OIT is disabled by default in OCCT 3D Viewer, so that application experiencing artifacts should enable it explicitly. pload VISUALIZATION MODELING restore shell.brep s vinit View1 vdisplay -dispMode 1 s vaspects s -setTransparency 0.4 vfit vrenderparams -oit 0 |
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Thank you Kirill, it was unclear to me, that it's not a default, but has to be activated explicitly. There is a comment on the bottom of 0027925: *Patch also simplifies processing of transparent objects for standard method: rendering priority of transparent graphical structures is managed automatically, therefore there is no need to care about it at application's side.* The issue can be closed. Thanks again! |
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> Patch also simplifies processing of transparent objects for standard method Previously opaque and transparent objects have not been sorted, so that it was easy to draw something completely broken like opaque object overriding transparent one. The sorting have to be done manually via priorities (like it was done in AIS_Shape). Now transparent presentations are implicitly drawn after opaque ones, so that this specific kind of issue does no more occur (but it is irrelevant to the issue of combining several transparent presentations). |
| 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 | |
| 2016-12-20 16:43 | kgv | Note Added: 0061929 | |
| 2016-12-20 16:45 | kgv | Note Edited: 0061929 | |
| 2016-12-20 16:45 | kgv | Note Edited: 0061929 | |
| 2016-12-20 16:45 | kgv | Note Edited: 0061929 | |
| 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 => |
| 2020-07-10 13:41 | Matthias | Note Added: 0093082 | |
| 2020-07-10 13:41 | Matthias | Status | closed => feedback |
| 2020-07-10 13:41 | Matthias | Resolution | duplicate => reopened |
| 2020-07-10 14:45 | kgv | Note Added: 0093087 | |
| 2020-07-10 14:45 | kgv | Assigned To | bugmaster => Matthias |
| 2020-07-10 14:46 | kgv | Note Edited: 0093087 | |
| 2020-07-10 14:46 | kgv | Note Edited: 0093087 | |
| 2020-07-10 14:47 | kgv | Note Edited: 0093087 | |
| 2020-07-10 16:15 | Matthias | Note Added: 0093091 | |
| 2020-07-10 16:15 | Matthias | Assigned To | Matthias => bugmaster |
| 2020-07-10 16:15 | Matthias | Resolution | reopened => fixed |
| 2020-07-10 16:20 | kgv | Note Added: 0093092 | |
| 2020-07-10 16:20 | kgv | Note Edited: 0093092 | |
| 2020-07-10 16:21 | kgv | Note Edited: 0093092 | |
| 2020-07-10 16:21 | kgv | Note Edited: 0093092 | |
| 2020-07-14 14:41 | bugmaster | Status | feedback => closed |
| 2020-07-14 14:41 | bugmaster | Fixed in Version | => 7.2.0 |
