Symbolic Posted October 27, 2008 Share Posted October 27, 2008 Hi, I have just started to explore volumes. It seems to be different than the usual Houdini logic... especially in terms of attributes. So I was trying to add color to a simple smoke system. This topic was my starting point: http://forums.odforce.net/index.php?showto...hl=Color+Volume I also used this topic: http://forums.odforce.net/index.php?showto...Maya-like+Fluid It kind of worked, so I have some questions. Sorry if they are silly... but I am confused about some of the things It looks like that: I use the point-cloud technique to transfer colors to the volume: The VOP network from the examples looks like that: So the density gets multiplied with the color coming from the points. I am loosing the colors since the density goes down. What is the way of keeping the color always there and constant? I can add a multiplication with an animated slider just to increase the strenght over time... But is there a more efficient way? Also... It seems like after the gassadvect and the gasssolver are introduced to the DOP network so that the SCATTERED points are stable, it is no more possible to get a good volume render. So the setup is good only for the point clouds. When it comes to rendering the volume it just jitters alot. So for now I had to split the workflow. (1) Point Cloud generator The DOPs network and the SOPs network for the point cloud generator looks like that: There are some other things going on in these screenshots, but in practice it is the scatter technique mentioned in the volume tutorials on Side Effects. (2) Applying the point colors to the volume The DOPs network and the SOPs network for coloring the volume looks like that: The VOP network attached above is used in this second stage. So is this the correct way of approaching the issue... at least one of them? Cheers. Once again sorry if this is a silly question... just trying to wrap it up... Quote Link to comment Share on other sites More sharing options...
rdg Posted October 27, 2008 Share Posted October 27, 2008 I would have thought that you add the color through volumeMIXSOPs and import them into your shader using one of the volume from file VOPs ... But this is just guessing ... Quote Link to comment Share on other sites More sharing options...
Symbolic Posted October 27, 2008 Author Share Posted October 27, 2008 I would have thought that you add the color through volumeMIXSOPs and import them into your shader using one of the volume from file VOPs ...But this is just guessing ... Hi rdg, Yes "volumemix" works quite good in simple situations. The examples on Side Effects are focusing on that. But in my case... I would like to depend on point attributes. Another way of doing this is getting metaballs involved and relying entirely on point attributes... But I am just trying to make it work with this approach (no metaballs yet). Cheers. Quote Link to comment Share on other sites More sharing options...
Symbolic Posted October 27, 2008 Author Share Posted October 27, 2008 (edited) Ow... I knew I have been silly. So it is just a matter of replacing the "density" with a constant multiplier... and it will keep the color the same all the way through. ... or fitting the range of the density from (1 to 0) to (1 to 0.6) ... or (density + (-density)) * Cd anyway... just the usual VOPs operations... sorry I was a bit quick to ask the question. So it looks like that: Although I am still not sure about the SCATTER (Point Cloud) / Volume VOP workflow. Any ideas? Edited October 27, 2008 by Symbolic Quote Link to comment Share on other sites More sharing options...
Symbolic Posted October 28, 2008 Author Share Posted October 28, 2008 (edited) Well... I have noticed that I am getting jitters in my renders when transferring "Cd" attribute from point cloud on my volumes. What might be causing this? smoke_jitter.mov Edited October 28, 2008 by Symbolic Quote Link to comment Share on other sites More sharing options...
Allegro Posted October 28, 2008 Share Posted October 28, 2008 (edited) Well... I have noticed that I am getting jitters in my renders when transferring "Cd" attribute from point cloud on my volumes. What might be causing this? smoke_jitter.mov If you take a look at the file I posted in http://forums.odforce.net/index.php?showto...hl=Color+Volume you'll see that I use a stationary grid of points for vop level transfer of the color to volumes. I *think* that because your points are moving around each frame your voxels may be having a hard time figuring out what color they should be. Additionally, the reason I fill the entire container with points in the first place, is that you'll have pre-multiplication issues with your colors. Right now, as your density diminishes, so does your color. You likely want color everywhere in your volume so that your colors aren't turning black at the edges. edit: You may also want to take a look at http://www.sidefx.com/exchange/info.php?fi...p;versionid=529 which has dop level coloring of the volumes. Edited October 28, 2008 by Allegro Quote Link to comment Share on other sites More sharing options...
Symbolic Posted October 28, 2008 Author Share Posted October 28, 2008 Hi Allegro, Thank you very much. Yes you are right, the setup was for a static volume... So the points are moving and as they move they affect different voxels... so this creates the jitter. But there must be a workflow making it possible to dynamically color a volume through a point cloud. I will have a look at the "Smoke Bomb" example meanwhile. What I am trying to achieve is... having the smoke get colored as it passes around the poles... I managed to do this with the points... But I could not transfer the color from points on to the volume... So maybe metaballs is the only solution... cheers. Quote Link to comment Share on other sites More sharing options...
Symbolic Posted October 30, 2008 Author Share Posted October 30, 2008 Should I totally abandon the concept of trying to color the volume with attributes, points... anything? Or are there any suggestions? Cheers. Quote Link to comment Share on other sites More sharing options...
Allegro Posted October 30, 2008 Share Posted October 30, 2008 Should I totally abandon the concept of trying to color the volume with attributes, points... anything? Or are there any suggestions?Cheers. it'd help if you could attach a version of your file that I could take a look at Quote Link to comment Share on other sites More sharing options...
Symbolic Posted October 31, 2008 Author Share Posted October 31, 2008 Hi Allegro, I will pack a file as soon as possible. Thanks. Quote Link to comment Share on other sites More sharing options...
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