View Issue Details
| ID | Project | Category | View Status | Date Submitted | Last Update |
|---|---|---|---|---|---|
| 0023236 | Community | OCCT:Visualization | public | 2012-07-02 18:45 | 2014-02-27 18:18 |
| Reporter | Pawel | Assigned To | Pawel | ||
| Priority | normal | Severity | minor | ||
| Status | closed | Resolution | won't fix | ||
| Platform | Windows | OS | VC++ 2005 | ||
| Product Version | 6.5.3 | ||||
| Summary | 0023236: Visualization - transparency for XCAFPrs_AISObject not computed correctly | ||||
| Description | For transparent XCAFPrs_AISObjects it does not seem to matter which one is front. OCCT seems to calculate the pixel color value only once. Look at the DRAW reproducer and the attached pictures. It doesn't matter whether the grey boxes are in front of the green ones or behind them. | ||||
| Steps To Reproduce | Draw reproducer: ReadStep D test.step XShow D vfit vsetdispmode 1 XSetTransparency D 0.5 Rotate the view now. | ||||
| Additional information and documentation updates | This issue might be related to 23123 | ||||
| Tags | No tags attached. | ||||
| Test case number | |||||
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document.png (10,387 bytes) |
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view_from_behind.png (10,063 bytes) |
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view_from_front.png (9,588 bytes) |
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Issue 23123 does not solve this problem. |
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Dear bugmaster, please close the issue as out of future plans. |
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Just to clarify the reason why this issue should be closed, I remind once again that the OpenGL rasterizer in OCCT currently implements only good old simplified transparency mechanism based on alpha blending. This technique is known as order-dependent, i.e. the results depends on the order in which primitives are drawn. Spatial relations between transparent objects (overlapping in the view) do not matter - that leads to incorrect visual results when the actual Z order in the eye space differs from the drawing order (in other words, when the front object is drawn first). There are methods that propose reasonable trade-off between the frame rate and correctness of transparency, e.g. depth peeling. Currently, we do not have plans to implement any advanced transparency algorithms, however, we are ready to consider such a request on a commercial base. Meanwhile, OCCT ray tracing renderer can be recommended when it is critical to obtain better visual results, because it implements physically correct transparency algorithm. |
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OCCT ray tracing renderer can be recommended when it is critical to obtain better visual results |
| Date Modified | Username | Field | Change |
|---|---|---|---|
| 2012-07-02 18:45 | Pawel | New Issue | |
| 2012-07-02 18:45 | Pawel | Assigned To | => bugmaster |
| 2012-07-02 18:45 | Pawel | File Added: document.png | |
| 2012-07-02 18:45 | Pawel | File Added: view_from_behind.png | |
| 2012-07-02 18:45 | Pawel | File Added: view_from_front.png | |
| 2012-07-02 18:49 | Pawel | File Added: test.step | |
| 2012-07-09 20:31 | Pawel | Note Added: 0020885 | |
| 2014-02-17 15:09 | kgv | Note Added: 0027922 | |
| 2014-02-17 15:09 | kgv | Status | new => feedback |
| 2014-02-17 15:09 | kgv | Resolution | open => won't fix |
| 2014-02-17 15:09 | kgv | Summary | Transparency for XCAFPrs_AISObject not computed correctly => Visualization - transparency for XCAFPrs_AISObject not computed correctly |
| 2014-02-19 10:07 |
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Note Added: 0027956 | |
| 2014-02-19 10:10 |
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Note Edited: 0027956 | |
| 2014-02-27 18:18 | bugmaster | Note Added: 0028057 | |
| 2014-02-27 18:18 | bugmaster | Status | feedback => closed |
| 2014-02-27 18:18 | bugmaster | Assigned To | bugmaster => Pawel |