Need help with proper motion blur

Forums Technical Discussion Need help with proper motion blur

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mickyblue: Member; 217 posts; Joined: Sept. 2009; Offline

Jan. 23, 2012 5:46 a.m.

Hi,

I can't find a way to render proper (jitter free) motionblur for a simple test object.
Please take a look at the enclosed test file.

Thanks

Attachments:
motionblur.hipnc (108.9 KB)


bollili: Member; 205 posts; Joined: Dec. 2009; Offline

Jan. 23, 2012 4:51 p.m.

Hi,

if you put the blast after the trail sop, it should work.
The problem you experience is due to the changing point numbers, caused by the deleted points.

Cheers


mickyblue: Member; 217 posts; Joined: Sept. 2009; Offline

Jan. 24, 2012 5:07 a.m.

thanks bollili!

but are there any opportunities to make it work without joining the subnet?
Maybe saving the point order from a first frame. to an attribute so that they become fixed, and dont cause a jumping v attribute?


bollili: Member; 205 posts; Joined: Dec. 2009; Offline

Jan. 24, 2012 5:22 a.m.

You could put $PT into an attribute for the grouped points (attribute create sop), delete points (your blast node) and then sort by expression using your created attribute (sort sop). This should prevent the point numbers to jump around…


mickyblue: Member; 217 posts; Joined: Sept. 2009; Offline

Jan. 25, 2012 7:57 a.m.

thanks bollili,

But I'm still intrested in finding a way to reproduce a working v attribute.
Cause I use geos from other apps too.

I try to relate to that thing with a knew topic.


circusmonkey: Member; 2624 posts; Joined: Aug. 2006; Offline

Jan. 25, 2012 2:58 p.m.

Hi mickyblue ,
If you had changing point counts any render engine's motion blur would fail to work correctly. Just implement bollili's advise.

rob

Gone fishing


mickyblue: Member; 217 posts; Joined: Sept. 2009; Offline

Jan. 25, 2012 4:53 p.m.

Hi rob,

I did look for bollilis advice and it works in this test case.
So what to do with imported geometry, with not having the possibility to create addtional attributes etc…

So is there no way to get some motionblur for a fluid like mesh!?


circusmonkey: Member; 2624 posts; Joined: Aug. 2006; Offline

Jan. 25, 2012 5:06 p.m.

I did look for bollilis advice and it works in this test case.
So what to do with imported geometry, with not having the possibility to create addtional attributes etc…

I really dont see the problem, every single job I have ever done involves adding / changing something about the imported assets I get from another department. I just suck all the geometry into a new object level node and go from there. Feel free to explain the workflow you are using with a scene file.

rob

Gone fishing


mickyblue: Member; 217 posts; Joined: Sept. 2009; Offline

Jan. 26, 2012 9:10 a.m.

Hi Rob,

thanks for support!
Enclosed is a simple test hip with an appendant obj sequenz.
Well there is nothing big to explain, I try to get some motionblur.

Attachments:
motionblur.zip (213.7 KB)


circusmonkey: Member; 2624 posts; Joined: Aug. 2006; Offline

Jan. 26, 2012 5:45 p.m.

Hi,
Look at the file I have given you in the fix geo node, thats a way of getting a consistent point number. But you have a bigger problem you have geometry popping on and off . You are never going to get correct motion blur with that happening, as on the first frame the geo appears there will be no motion blur as there is no v value from the prior frame plus the time blend sop will not work either ( read the help for it ). You are going to have to re think how you are approaching your project.

rob

Attachments:
fluidBlur_rsefix.hipnc (119.1 KB)

Gone fishing


mickyblue: Member; 217 posts; Joined: Sept. 2009; Offline

Jan. 27, 2012 4:31 a.m.

thanks Rob!

Last clarifing notes for me …

Good to have a your appreciation on this.
So I finally know that there is no workaround after I write out the fluid geo. I can't import a Geo sequnenze with changing PT (Like fluid meshes) and expect working Motionbur!

Fluids tend to change their PT some merge some die. So the popping that apperars here and there is because of this right!?… So there definitely have to have a velocity attribute before I import the mesh sequenze! right!?

Thanks


circusmonkey: Member; 2624 posts; Joined: Aug. 2006; Offline

Jan. 27, 2012 3:30 p.m.

Hi,
The same problems exist if you want to send Houdini geo to maya , then render it in MR or Renderman , the point count cannot change and you cannot have geometry popping on and off as per your example. There certainly are ways to to pass attributes off to geometry like v via point clouds or taking base data and transferring it over to new geometry. My best advice is to get making small tests and continually revise how to achieve the goal. Sometimes things are just better done in one 3d package.

rob

Gone fishing


mickyblue: Member; 217 posts; Joined: Sept. 2009; Offline

Jan. 29, 2012 9:51 a.m.

thanks!


mickyblue: Member; 217 posts; Joined: Sept. 2009; Offline

Jan. 29, 2012 9:52 a.m.

thanks!


ragupasta: Member; 349 posts; Joined: Aug. 2006; Offline

Jan. 30, 2012 1:47 a.m.

circusmonkey
Sometimes things are just better done in one 3d package.

rob

This is sound advice. Doesn't always work this way, but it's nice when it does.

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