Cineversity

Hello again

I’m having a weird issue with rendering hair…
The setup is using Xparticles, with a Trail object, and using hair to render the trails.
What happens to my hair alpha pass is what you can see in the attached, looks like undersampling or noise?

Thanks for any tips
Alex

Here is a slightly bigger image as Cineversity won’t let me upload bigger images
https://www.dropbox.com/s/69y6p2k62qm1yw0/2016-02-01_18h40_35.png?dl=0

Hi Alex,

Would you mind sending me a Scene file? Since you use Dropbox already, and you might not share it public-ally, send me the link to my Cineversity PM.  The X-Particles team gave me license for a few month, so I can have a look at your file natively.

All the best

Thanks for the scene-file, Alex.

If I get the problem correctly, the question that the scene files “tells” me, is: How to get the X-Particles xpTrail to work with Hair via Cinema 4D with Arnold. Well, I had to get the trial from Arnold to even see what is going on, hence the delay in answering.

The simple answer (for me) would be, to give you that link
https://support.solidangle.com/display/AFCUG/Hair+object
and hope you get something. ;o)

In short, with my 10 minutes of Arnold experience so far, what I get is that it needs to be rendered as “Curve”, and this curve has parameters. These parameters can be set up in the Object Manager>Tags, C4D to A Tags> Arnold Parameters. This Tag needs to sit on the xpTrail for example.
If you click on that Tag and inside of the Attribute Manager, you can set up Curve Thickness and the sample rate. There are more parameter, but I think you get these perhaps faster than I get them, as I guess you work so far longer with Arnold than I do.
The fast answer that I get to work here is with the Standard Render. Which would allow to a certain degree for a Multi-pass solution. Hair in Standard, and anything else in Arnold. (If Arnold is the key.

Even faster, to take an N-Gon Spline in a Sweep [NURBS] and drive this with the two xpTrail and an C4D material>Luminance, if I get it right, set up with a colorful Gradient. This would allow for more options, e.g., depth, etc.

Please let me know if the guess with Arnold was wrong and your question is purely to the Standard render.

(BTW, you mentioned that the rendering will be in 4K, presumably UHD. If that is the case, check the colorspace, as it was set to sRGB, which is close to REC709, but not at all to REC2020. Since UHD has HDR and a wide color gamut as option, this should be considered, so the project will not look as dull as HD-REC709 stuff will—in comparison.)

All the best

Hi Sassi

Thanks so much for looking into this with so much detail.  I’m not sure why Arnold was turned on, I’m not using it on this shot…I was using the standard renderer as I can’t get hair multipass with the Physical renderer.  I may have made a mistake, but the file I sent you should have been setup to use the standard renderer?

What my problem is coming from is that when I set up the multipass for Hair, my passes have a lot of “dirt” in the hair, as you can see in the pictures I uploaded.  It looks like a sampling issue, but I can’t tell, because the hair looks good in the beauty pass.

I could use your method to create a mesh around the spline, or even x-particle’s own spline mesher, but I was using hair because it gives me all the hair deformation options in case I need them…I also assumed hair might be faster to render than geometry?

Thanks again
Alex

Hi Alex,

When I opened the scene, I was warned that some plug-ins are missing. So, I assumed… OK, no Arnold, but was fund to get an idea about. My wish is always to get the reduced files that shows the problem.

=======
Hair-Multi-Pass:
The only thing that looks really problematic is the alpha channel. Set the Backlit-Color in the same way the Color channel is in the Hair Material. From the Multi-pass, take “Hair Back Illumination” and the Hair Illumination, and combine these two, this should give you a proper Alpha for this project. I saw that the Brightness was set to 200%, perhaps to fight the “dirt”.

My suggestion copy the Hair Material, while at 100% or lower, and place them to the xpTrail, as “Blend” Add mode. BUT: for each copy set the Hair Thickness about 5-10% less, which should help to keep a good AA, while allowing for enough Illumination to keep a great line. Use the Material>Thickness>“Curve” to set the lower values, that will allow you to set later new values at once for all, and keep the progression based on the curve. Anti-Alias is not working very well with way over 100% values.
Waht happens to the Multipass-alpha seems more a question for the support, here I can only offer the way I have described above.

The only problems that I see, are based on the xpTrail when they intersect with the rest of the model. XP allows for individual treatment. This can be fixed and is not based on any software.

If you do all of that only based on the additional options of hair, perhaps have a look here as well:
https://player.vimeo.com/video/146617317
So far I can tell, the xpTrail works with C4D Deformers. Even MoGraph Effectors set to Deform [point] will work. I guess XP has a lot more to offer as well.

I have tried to use the Hair Render Tag, but none of the options there will give me anything that would be less or better.

The xpTrail was set to “Not seen by camera”, seemed to have no influence on Hair and xpTrail, though.

I tried as well (Render Settings>>Hair> Pixel and Vertex, but also, no change, I get an result. Check the manual for that, it has a nice and clear image to show the difference.

From the Manual
Hair and the Physical Renderer

Even though Hair can be used in conjunction with the Physical Renderer it does, however, bear several disadvantages:

Rendering hair takes much longer (because hairs are calculated internally as polygons)
Hair looks slightly different
Hair Multi-Passes are not supported

============

My best guess besides all of the above: set up a fresh scene, with just the very few absolute needed items, and go from there (explore the options). If there is something that will not work, please share.
Other wise I hope to have given an alternatives to Hair, with the Vimeo link above.

Let me know if that works for you.

All the best

Hi Sassi

Thanks a lot for this super thorough answer.

Great idea to combine the hair tags!  I’ll try that.  I like the curve idea, awesome way to keep the relationship procedural!

I’ll also try to use a sweep or the x particles spline mesher and compare the speed with hair rendering.  I always think hair is super fast to render, but maybe that is only when you have tons and tons of it.

Great to know that I can use other deformers on the xp Trail!  That helps a lot.

And yes, thanks for pointing out the intersection, I’ll fix that…

Thanks again, as always, I’m very grateful for the wisdom you so kindly share.

Alex

You are very welcome, Alex. I really love to dive into things like that.

I hope there is something on the end that will support the project.

Yes, the Spline-Mesher is great, and so is the xpTrail-Deformer.

Isn’t it great that there are so many ways?

Yes hair can be an advantage, but it has some limitations from time to time, it’s a balance act.

My best wishes!