MantisBT
Mantis Bug Tracker Workflow

View Issue Details Jump to Notes ] Issue History ] Print ]
IDProjectCategoryView StatusDate SubmittedLast Update
0028177Community[OCCT] OCCT:Visualizationpublic2016-11-30 14:072018-03-25 12:01
ReporterMarkus 
Assigned Tokgv 
PrioritynormalSeverityminor 
StatusnewResolutionopen 
PlatformOSOS Version
Product Version[OCCT] 7.1.0 
Target Version[OCCT] 7.4.0*Fixed in Version 
Summary0028177: Visualization - MSAA has no effect on clipping planes when using built-in GLSL programs
DescriptionIf MSAA is activated and a clipping plane used in the Samples, the edges at the clipping plane are not anti-aliased.

However, in Draw they are anti-aliased.

What is the difference? Or what can be the reason why it isn't working in the samples.
Steps To Reproduce- Open the Viewer3d sample
- Click on the button for "overlapped boxes"
- Switch on and adjust model clipping so that the box is clipped
- Switch on antialiasing
=> the edges at the clipping plane are not anti-aliased. The others are. See appended images.

However, in Draw it works:

pload ALL
vinit
vclipplane create pln1
vclipplane change pln1 equation 1 0 0 -0.1
vclipplane set pln1 view Driver1/Viewer1/View1
box b 100 100 100
vdisplay b
vsetdispmode 1
vfit
vrotate 10 10 10
vclipplane change pln1 equation 1 0 0 -0.5
vrenderparams -msaa 4

TagsNo tags attached.
Test case number
Attached Filespng file icon without MSAA.png (10,320 bytes) 2016-11-30 14:07
png file icon with MSAA.png (11,377 bytes) 2016-11-30 14:08
png file icon Draw 7.0 without MSAA.png (4,814 bytes) 2016-11-30 14:52
png file icon Draw 7.0 with MSAA.png (5,085 bytes) 2016-11-30 14:52

- Relationships
related to 0028487closedbugmaster Open CASCADE Visualization, TKOpenGl - add option for rendering with lower resolution 
child of 0027748newkgv Open CASCADE Visualization - clipping and capping improvements 

-  Notes
(0060918)
kgv (developer)
2016-11-30 14:12

> However, in Draw it works
There is no visual difference in Draw - the aliasing is same.
(0060920)
Timo (developer)
2016-11-30 14:52

Sorry, it worked in OCCT 7.0.
It doesn't work anymore in OCCT 7.1.
(0060924)
kgv (developer)
2016-11-30 15:14
edited on: 2016-11-30 15:14

The difference is that fixed-function pipeline is not used by default anymore since OCCT 7.1.0.
You can enable it temporarily as a workaround if this issue is critical for you.

(0060925)
Timo (developer)
2016-11-30 15:21

Thanks, it is not critical but it would be good to fix it.
(0060927)
kgv (developer)
2016-11-30 15:28
edited on: 2016-11-30 15:29

It is in TODO list (0027748):
> 1) Hardware supporting gl_ClipDistance
> (GLSL1.3 on desktop; APPLE_clip_distance
> or GL_EXT_clip_cull_distance on OpenGL ES)
> might show better performance since it allows
> skipping Fragment Shader if entire primitive (e.g. triangle)
> is behind the clipping plane(s).

Although there might be some another workaround for it, which is not clear for now.

Technically the problem is caused by *discard* command called to apply clipping plane within Fragment Shader.
So that entire pixel is either clipped or not,
making MSAA buffer samples equal from clipping planes point of view.


- Issue History
Date Modified Username Field Change
2016-11-30 14:07 Timo New Issue
2016-11-30 14:07 Timo Assigned To => kgv
2016-11-30 14:07 Timo File Added: without MSAA.png
2016-11-30 14:08 Timo File Added: with MSAA.png
2016-11-30 14:12 kgv Note Added: 0060918
2016-11-30 14:52 Timo Note Added: 0060920
2016-11-30 14:52 Timo File Added: Draw 7.0 without MSAA.png
2016-11-30 14:52 Timo File Added: Draw 7.0 with MSAA.png
2016-11-30 15:14 kgv Note Added: 0060924
2016-11-30 15:14 kgv Note Edited: 0060924 View Revisions
2016-11-30 15:15 kgv Summary MSAA does not work at clipping plane in samples but it works in Draw => Visualization - MSAA has no effect on clipping planes when using built-in GLSL programs
2016-11-30 15:20 kgv Relationship added child of 0027748
2016-11-30 15:21 Timo Note Added: 0060925
2016-11-30 15:28 kgv Note Added: 0060927
2016-11-30 15:29 kgv Note Edited: 0060927 View Revisions
2016-11-30 15:29 kgv Note Edited: 0060927 View Revisions
2017-05-31 15:37 Timo Reporter Timo => Markus
2017-07-20 11:32 kgv Target Version 7.2.0 => 7.3.0
2018-03-13 14:37 kgv Target Version 7.3.0 => 7.4.0*
2018-03-25 12:01 kgv Relationship added related to 0028487


Copyright © 2000 - 2018 MantisBT Team
Powered by Mantis Bugtracker