Tips on volumetric strand render

[Morten Bartholdy]

I am doing glowing trails using strands and it is working pretty much like I want it - see attached greenish trails with glowing tips. I have one snag though - the client really likes the look seen in the attached Trapcode still (the multi clored one) - much like lightpainting with long exposure time, so overlapping trails and especially bends in the trail become brighter by the exposure effect.

 

So my question is, is there a way to achieve something similar with MR and volumetric rendering of strands? Currently I am piping a gradient with high values for the glowing tip into the ambient slot of the Particle Volume Cloud, which would not provide the look my client likes :/

 

I would very much like to avoid finding an AE artist to do this in Trapcode since I need these trails to fly in between and behind 3D objects in the scene, and preferably also reflect in the surfaces of said objects.

 

Any tips are much appreciated!

 

Cheers - Morten

 

 

[Chris Chia]

You could achieve this in compositing inside FX Tree.

[Morten Bartholdy]

Thanks for the suggestion, but I am not sure how you would do that Chris - if I comp a trail onto itself with screen or additive the whole trail will get brighter - the thing I am looking for is for the trail to render additive out of the 3D render, so where a trail covers itself it will get brighter.

Morten

[Thomas Volkmann]

Did you take a look at emRPC?  http://www.mootzoid.com/wb/pages/softimagexsi/emrpc4.php

Won't work with the reflections though (but maybe you can use your mentalray strands for subtle reflections?)

Morten Bartholdy <x...@colorshopvfx.dk> hat am 2. Mai 2013 um 14:14 geschrieben:

[Leonard Koch]

I would subdivide the strands pretty highly and then from every of those strand positions shoot a ray towards the camera that stops n number of times along the way to check for other strand positions close to it and if it finds any increases the brightness of the color at the originating strand position.

It is kind of computationally expensive, but since it's just something you slab on at the end before rendering it doesn't really matter.

[Schoenberger]

Hi

 

Have you taken a look at the sample scene that come with XSI?

Just one particle per color trail and then textured.

www.BinaryAlchemy.de/ftp_file/BAMD_TrailGlass8.mov

www.BinaryAlchemy.de/ftp_file/BAMD_TrailSpiral_A02.mov

 

 

 

Holger Schönberger
technical director
The day has 24 hours, if that does not suffice, I will take the night

 

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From: softimag...@listproc.autodesk.com [mailto:softimag...@listproc.autodesk.com] On Behalf Of Morten Bartholdy

Sent: Thursday, May 02, 2013 10:58 AM

To: soft...@listproc.autodesk.com
Subject: Tips on volumetric strand render

[Schoenberger]

Another Example (no sample scene).

Afaik 3 Particle trails together:

http://www.binaryalchemy.de/develop/shd_vol/vid/PT_Trail_follow_low.mov

 

 

Holger Schönberger
technical director
The day has 24 hours, if that does not suffice, I will take the night

 

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From: softimag...@listproc.autodesk.com [mailto:softimag...@listproc.autodesk.com] On Behalf Of Morten Bartholdy
Sent: Thursday, May 02, 2013 10:58 AM
To: soft...@listproc.autodesk.com
Subject: Tips on volumetric strand render

[Matt Morris]

If your trail is semi-transparent then it would naturally be additive over itself. The bends in the trail could be a harder nut to crack, could maybe do something related to the density of points along a curve?

--
www.matinai.com

[Morten Bartholdy]

I actually started by revising the TrailSpiral scene. The trail glass sort of does what I need, but I couldn't figure out how to move a particle along a path trailing the strand behind it in a controllable manner, plus I still don't get the additive render look like with lightpainting - see:  https://vimeo.com/40768255

MB

[Morten Bartholdy]

Holger, I recall seeing this one in your Volume Shaders package, but have no clue where to find the Particle Cache loader . I have BaVolume installed - should I install  Volume Shader version 3.7.21?

Morten

[Schoenberger]

For this example, all you need is installed with XSI.

The cache loader is required in case you do not have the trail in ICE.

 

> but I couldn't figure out how to move a particle along a path trailing the strand behind it in a controllable manner

The trail does only copy the last position at that frame of the particle in an array.

Afaik there are no compounds to modify this array, but I am not sure, have not worked with ICE in a long time.

There are strands and strand trails in ICE. I do not know why they seperated them.

Strand trails are exported to support the trail settings in the particle shader.

 

 

>plus I still don't get the additive render look like with lightpainting

Replicate the real world.

Put the color of the particle shader into ambient of the volume shader.

Increase the ambient slider to 10. Set the diffuse slider to 0.

Shadow density to 0, global density to a something very low as you do not want to block anything by the "volume".

 

 

Holger Schönberger
technical director
The day has 24 hours, if that does not suffice, I will take the night

 

From: softimag...@listproc.autodesk.com [mailto:softimag...@listproc.autodesk.com] On Behalf Of Morten Bartholdy

Sent: Thursday, May 02, 2013 3:51 PM
To: soft...@listproc.autodesk.com
Subject: RE: Tips on volumetric strand render