stig_olsen Posted March 24, 2014 Share Posted March 24, 2014 Hi, I have tried to use the for each sop and attrib create to center the chunks points, but it does not work for me. I want the points to be centered because I want to emit smoke (smoke trails) from the mids of the points. Can someone please take a look at my project and tell me what I have done wrong? And, its possible it is easier ways to do this also? Stig center_points.hipnc Quote Link to comment Share on other sites More sharing options...
onkel_eilert Posted March 24, 2014 Share Posted March 24, 2014 Hey. Here is what i would do. center_points_FIX.hipnc Quote Link to comment Share on other sites More sharing options...
stig_olsen Posted March 24, 2014 Author Share Posted March 24, 2014 Thanks!And I guess that will work with a point sop position centroid expression as well.Stig Quote Link to comment Share on other sites More sharing options...
LPriest Posted March 26, 2014 Share Posted March 26, 2014 A better way to emit smoke would be from scattered points on the inside faces of fractured geometry. Why do you want to emit from the centers ? Quote Link to comment Share on other sites More sharing options...
stig_olsen Posted March 26, 2014 Author Share Posted March 26, 2014 Hi, Mainly because its told to do so in one of the tutorials I have seen, but I didnt question it because it makes sense that emitting from one single point makes more controlable / thinner trails than from a geometry piece? How do I set it up your way and what is the benefits? Stig Quote Link to comment Share on other sites More sharing options...
LPriest Posted March 27, 2014 Share Posted March 27, 2014 I've attached a faster way to computer the centers, avoid for each where you can, it's incredibly slow and you'll start to see massive performance drops when you start using very large numbers of geometry. If you are using houdini 13 the derbis source SOP does what you want, it's an implementation of something most studios have been doing for a while where you scatter points on debris and trigger emission based on how far the pieces separate from each other. In your scene just drop the node down and plug in the result of the RBD sim and set the rest frame to 25, then just put the result into a fluid source using Cd to drive the density. Other useful ways you could change this node is to do the emission based on the change in acceleration which is a bit like impact detection. It's not really about the benefits it's more about what the disadvantages of emitting from centers are. At the simplest level would smoke/ dust emit from the center of a piece of debris? Probably not .. By emitting from the centers your don't get any sense of angular velocity from your emission velocities so a piece spinning around won't appropriately carry its velocities through to your emission. Also because you're emitting from centers if you are using the debris pieces as collision objects the desnity will be killed when it's inside the colliders so you will get very strange or no denisity when you try and do this. Is controlling the thickness of trails something you really want for debris especially if you loose all of the above. And even if you do need to do this there are other ways of controlling it for example you can control the scatter in the debris source with an attribute. centerDemo.hipnc Quote Link to comment Share on other sites More sharing options...
stig_olsen Posted March 28, 2014 Author Share Posted March 28, 2014 Thank you, it makes sense! So you mean that I should really emit the smoke trails direcly from my chunks geometry? Stig Quote Link to comment Share on other sites More sharing options...
stig_olsen Posted March 28, 2014 Author Share Posted March 28, 2014 LPriest, can you please take a look at why my trails doesnt look like trails? Im really struggling with this! Stig center_points_v10.hipnc Quote Link to comment Share on other sites More sharing options...
stig_olsen Posted March 28, 2014 Author Share Posted March 28, 2014 Sorry... this is the correct project file! Not the one in the above post. stig center_points_v11.hipnc Quote Link to comment Share on other sites More sharing options...
stig_olsen Posted March 31, 2014 Author Share Posted March 31, 2014 What I can see is that it doesnt really generate trails, but emit smoke in all the directions the shunk rotate. It looks a bit strange, as I guess trails should make a trail starting from where the chunks get thrown to where it ends. Stig Quote Link to comment Share on other sites More sharing options...
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