Smoke Material transparency or opacity

   304   5   1
User Avatar
Member
264 posts
Joined: 5月 2014
Offline
Am I missing something? In the Basic Smoke material, I don't see any slider for transparency or opacity. Any clue?

Attached is a pic of my current render, I want this smoke to be more transparent.

Thanks
Gz
Edited by Grendizer - 2021年3月7日 05:45:53

Attachments:
Material_Smoke_Transparency.jpg (110.7 KB)

Houdini advanced newbie
User Avatar
Member
2012 posts
Joined: 6月 2008
Offline
You could render it out and fade it back in a composite, or adjust your density. Density is essentially transparency for a volume, right?

Try using a VolumeWrangle at the end of your network and type.
// Fifty percent reduction.
@density *=0.5;
if you link the value to a slider you could animate the value up and down.
@density *= ch("opacity");
Edited by Enivob - 2021年3月7日 08:59:48
Using Houdini Indie
Ubuntu 18.04 48GB Ryzen 16 core.
nVidia 1070GTX 8BG RAM
User Avatar
Member
264 posts
Joined: 5月 2014
Offline
Thanks for your help.

I didn't need the VolumeWrangle because I already had a DOP Network in my scene. So what I did is this:
DOP Network > Node Volume source > tab "volume" > operation 1 > Source volume = density, Target field = density, Scale = put here a value that will multiply the density, such as 0.25.

The Density solution is not perfect because it doesn't just increase the transparency of the smoke, it also alters its shape. I'd like the shape to remain exactly the same while becoming half visible. Check attached pics.
So the best solution might be the compositing one.
Edited by Grendizer - 2021年3月7日 12:17:50

Attachments:
Volume Dop network Density Scales exp.jpg (432.3 KB)

Houdini advanced newbie
User Avatar
Member
613 posts
Joined: 12月 2006
Offline
Yes, don't alter the density in your sim. This affects threshold lookups and your sim will look different. In general, the values going into pyro should be normailized 0-1.

Either do what Enviob suggested, or adjust the density in your shader, or use a Volume mix SOP which gives you a ramp to remap the denisty field.
Sean Lewkiw
Lost Boys Montreal
User Avatar
Member
264 posts
Joined: 5月 2014
Offline
Hello mr CatFish, thanks for the tips!

After some more test back in the basicsmoke shader , I found out that the "density Scale" slider does what I was looking for!

By the way, how can I check the density value in my volume nodes? For example when I select a volumevop then go to the Geometry Spreadsheet, the "points" mode shows nothing, and the "primitive" mode only shows "0 density".
Houdini advanced newbie
User Avatar
Member
4366 posts
Joined: 9月 2011
Online
Grendizer
By the way, how can I check the density value in my volume nodes

A good way to get an idea of the values in a region is to use volume slice.
  • Quick Links