How to anti-alias in vtkRenderWindow

Support
1 
     The vtkRenderWindow contains a collection of vtkRenderers, and parameters that control rendering features such as stereo, anti-aliasing, motion blur and focal depth.

I have an image followed.

saw
saw800×320 6.62 KB
. How could I do it with anti-aliasing operation in vtkRenderWindow? Demo code is better.

2

@carlusst
You could try this, but it depends on the hardware.

.... setup actors, mapper, renderer ...
vtkNew<vtkRenderWindow> renWin;
renWin->AddRenderer(yourRenderer);
renWin->SetMultiSamples(4); // add this to your code.
.... setup interaction and start event loop ....
3

You can enable FXAA by flipping a switch in the renderer: UseFXAAOn(). It is simple and fast but it just a 2D image post-processing operation, therefore it removes all kinds of details from your rendered image. There are many parameters that you can tune though, so there is a good chance that the image quality will be overall better than without using anti-aliasing at all.

4

Thank jaswantp. I will try it according to your step.

5

Thanks Andras for your advice.I am reading FXAA . It should be powerful. Could it be limited by hardware?

6

It is all just 2D software post-processing, so it is quite limited in what it can do, but it is fully hardware-independent and does not interfere with 3D rendering passes.

7

UseFXAAOn() is a function in C code. But how to use it in Python ?

8

Is it unavailable in python wrappings?

9

All VTK methods are Python-wrapped (maybe except a few cases that use special argument types).

>>> ren = vtk.vtkRenderer()
>>> ren.UseFXAAOn()
>>> ren.GetUseFXAA()
True
10

FXAA is fast and does a decent job, but some people don’t like its visual results. Skyrim, a game from Bethesda, uses FXAA and is criticized for its blurry looks by some of its users. I let this up to the user (choose FXAA, MSAA or none). I personally find MSAA better. Just try each and choose the one that you feel right.

2 Likes
11

FXAA can be good for artistic visualization, where accurate colors and sizes are not crucial. I would consider risky to use FXAA for scientific visualization, as it alters the information: it blurs objects as if they had equal importance, while in correct anti-aliasing what is in front should never be altered by what is behind (unless it is semi-transparent).

For example, see discoloration in the purple line as it goes above green and blue background:

image
image1735×645 308 KB

Discourse scales down the image in the post, so you can only see the difference in the zoomed-in red circles, or if you click on the image, download the full resolution image, and view it on your screen 1:1 (without any rescaling).

2 Likes
12

If have any other functions in VTK beside FAXX?

13

You can do true antialiasing, with multisampling (MSAA) - see vtkRenderWindow::SetMultiSamples(). If you use a GUI toolkit then you may need to enable MSAA in the application and/or embedding rendering widget, too.

14

I did it with multisampling,but no effect is seen.

15

This is exactly what is hard with hardware MSAA. It depends on the hardware, operating system, type of render window, etc. Do you embed the render window into a GUI toolkit (Qt, wxWidgets, …) or it is a plain vtkRenderWindow? How many samples did you set? You may get some hints about what goes wrong if you run your code step by step in a debugger.

16

Hi, carlusst,

To use MSAA properly, you must call these BEFORE creating the viewer widget (assuming you’re using Qt):

vtkOpenGLRenderWindow::SetGlobalMaximumNumberOfMultiSamples ( 8 );
QSurfaceFormat::setDefaultFormat ( QVTKOpenGLWidget::defaultFormat() );

Then you call:

vtkwidget->GetRenderWindow()->SetMultiSamples( 4 );

I hope this casts some linght on MSAA usage.

regards,

Paulo