(semi) transparent materials when mixing FLIP fluids ?

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MichielvanderZanden: Member; 11 posts; Joined: Sept. 2016; Offline

Jan. 7, 2017 2:03 p.m.

Hi there everybody,

I have managed to make 3 FLIP Fluid colors mix within one Material. Basically by following two tutorials about Mixing Fluids: by Peter Quint http://vimeo.com/55764136 [vimeo.com] (from 13:39 min) and a webinar by Jeff Wagner http://vimeo.com/182074285 [vimeo.com] , from 39:20 min. With some extra help on this forum, it worked out and all looks nice.

BUT, now I would like to make an hairgel-like, semi-transparent mix of colors. Trying out different materials, it seems impossible to do this. It's like the Cd point attribute is overruling opacity? I'm using the Plastic material right now, but also when I try BasicLiquid, there's no opacity visible.

I also saw this ( http://www.sidefx.com/forum/topic/14223/ [sidefx.com] ) post on the forum, basically the same question, but it's still not working for me.

Happy to hear from you! Thanks in advance!

(image: my render with normal opaque colors)

Edited by MichielvanderZanden - Jan. 7, 2017 14:06:48


Enivob: Member; 2658 posts; Joined: June 2008; Offline

Jan. 7, 2017 3:13 p.m.

Have you tried setting the Opacity Scale, on the Opacity tab, for the Diffuse Surface of the Mantra Shader to 0? I have had to lower this to 0 to get texture based alpha to work. Perhaps it can work for you too? Even though the name is “scale” it seems to act like a “sum” instead of a multiply. When 1 no alpha/opacity gets through.

Edited by Enivob - Jan. 7, 2017 15:15:17

Using Houdini Indie 20.5
Windows 11 64GB Ryzen 16 core.
nVidia 3060RTX 12BG RAM.


MichielvanderZanden: Member; 11 posts; Joined: Sept. 2016; Offline

Jan. 9, 2017 5:07 a.m.

Thanks Enivob, but it didn't work out. I've put a screenshot underneath, my settings are as you described?
I'm using a mid-grey texture to get a semi-transparent effect.
Note that I have used point colors (Cd attributes) to get 3 different colors within one material. Maybe I have to add something there?

Anybody?


Enivob: Member; 2658 posts; Joined: June 2008; Offline

Jan. 9, 2017 9:36 a.m.

I guess the next question is what does your opacity map look like and do you have UVs on your fluid? Mapping only works if you have UVs. If you drop down a UV Quickshade node you can visualize your UV layout in the viewport.

Edited by Enivob - Jan. 9, 2017 09:38:00

Using Houdini Indie 20.5
Windows 11 64GB Ryzen 16 core.
nVidia 3060RTX 12BG RAM.


MichielvanderZanden: Member; 11 posts; Joined: Sept. 2016; Offline

Jan. 9, 2017 10:03 a.m.

Hi Enivob, thanks for your reply. Actually I didnt use UV's. Oops.

The image I want to use for opacity is just a square flat grey colored jpeg.

- I've found the UV Quickshade node, but where do I have to connect it?
- See my node settings in images underneath

Thanks in advance!


Enivob: Member; 2658 posts; Joined: June 2008; Offline

Jan. 9, 2017 12:50 p.m.

Check out Jeff's webinar on FLIP fluid [vimeo.com] ~1:19:09. He talks about adding UVs to flip using a RestSolver inside a VOP. This is after you have enabled the dual rest checkbox.

Using Houdini Indie 20.5
Windows 11 64GB Ryzen 16 core.
nVidia 3060RTX 12BG RAM.


MichielvanderZanden: Member; 11 posts; Joined: Sept. 2016; Offline

Jan. 9, 2017 6:34 p.m.

Hi Enivob, thanks again.. I followed everything from the webinar. Also enabling the dual rest checkbox etc. It doesn't work out.


Enivob: Member; 2658 posts; Joined: June 2008; Offline

Jan. 10, 2017 9:27 a.m.

If your scene is non-client work can you post it?

Using Houdini Indie 20.5
Windows 11 64GB Ryzen 16 core.
nVidia 3060RTX 12BG RAM.


MichielvanderZanden: Member; 11 posts; Joined: Sept. 2016; Offline

Jan. 10, 2017 2:44 p.m.

Of course! You you'll find 2 files: one with no trial and and error opacity settings and another where I tried to. Thanks a lot!

Attachments:
forum__22(RENDER)DIKKE_VARIANT_TR_settings_.hiplc (2.2 MB)
forum__22(RENDER)DIKKE_VARIANT_TR_settings(FORUM)2_.hiplc (2.2 MB)


Enivob: Member; 2658 posts; Joined: June 2008; Offline

Jan. 10, 2017 6:13 p.m.

Hmm..after playing around with your file and basically rebuilding it I can get some UVs transferred but they certainly look stretched. I tried out Jeff Wagner's dual rest approach and it does seem to be broken on 15.5.673. Even he experiences a problem in the video.

But a basic box project after surfacing allows some UV work. In this example a companion set of particles is generated from the original source volumes. UVs are attribute transferred to the particle points and travel through the entire FLIP system back out to surfacing.

Edited by Enivob - Jan. 10, 2017 18:14:31

Attachments:
Untitled-1.jpg (76.0 KB)
ap_particle_assist_FLIP_UVs.hipnc (2.1 MB)

Using Houdini Indie 20.5
Windows 11 64GB Ryzen 16 core.
nVidia 3060RTX 12BG RAM.


Enivob: Member; 2658 posts; Joined: June 2008; Offline

Jan. 10, 2017 8:35 p.m.

Here is more like what I was suggesting, modifying your original file. Use a MantraSurface, not the Principled shader which lacks opacity support, and apply a map to the Opacity channel. In this image the checkerboard pattern can clearly be seen removing part of the fluid. But the UVs are stretched so is the checkboard patterns removal capabilities. Try playing around with other projection or UV generation techniques.

Edited by Enivob - Jan. 10, 2017 20:36:27

Attachments:
Untitled-1.jpg (58.9 KB)
ap_DIKKE_VARIANT_TR_settings_.hipnc (1.2 MB)

Using Houdini Indie 20.5
Windows 11 64GB Ryzen 16 core.
nVidia 3060RTX 12BG RAM.


MichielvanderZanden: Member; 11 posts; Joined: Sept. 2016; Offline

Jan. 12, 2017 5:21 a.m.

Thanks a lot for your efforts to help me out Enivob!! I'll dig in your files later this weekend, I'll let you know.

I also found this video: https://vimeo.com/130118827 [vimeo.com] … this is more or less the effect I would like to achieve. 3 semi-transparent colors blending in one Fuid sim.


Dave Stewart: Member; 39 posts; Joined: May 2014; Offline

Sept. 27, 2017 8:19 p.m.

MichielvanderZanden
Thanks a lot for your efforts to help me out Enivob!! I'll dig in your files later this weekend, I'll let you know.

I also found this video: https://vimeo.com/130118827 [vimeo.com] … this is more or less the effect I would like to achieve. 3 semi-transparent colors blending in one Fuid sim.

Just saw this, have you figured it out? I created the paste sim you posted above, it was tricky to get it to work. I created a separate volume with density and Cd, color transferred from the sim points. So the sim mesh is 100% refractive and reveals the colored volume beneath. Only way I could get it to look decent…

–Dave

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