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Technical Discussion » Overcoming a double transform from dop network within a geometry node.
- iamnelsonlim
- 39 posts
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Thanks Tomas for confirming my suspicion. At the moment, sounds like it is probably still best for setups to have dopnets that are separate objects.
Technical Discussion » Overcoming a double transform from dop network within a geometry node.
- iamnelsonlim
- 39 posts
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Hi guys,
I wanted to pick your brains about overcoming double transforms that happen when you place a dop network within a geometry node.
As a matter of workflow, I have found over the years that trying to contain my setups within a small set of or single geometry node has been beneficial for clarity. That something that Jeff covered also in this webinar. https://vimeo.com/272793390 [vimeo.com]
However, when you do something like that, if you need to place a transform on the geometry node or parent it to a null with a transform, inevitably, it will cause the dop network within to receive a double transform. Once from the geometry node itself and a second time when the data from the geometry node is fed into the dopnetwork via opinputpath().
I've attached a simple smoke scene to illustrate what I mean.
The pyro_doubletransformed node is being translated 8 units to on the x instead of 4 units.
Is there a simple/elegant way to avoid this from happening?
I wanted to pick your brains about overcoming double transforms that happen when you place a dop network within a geometry node.
As a matter of workflow, I have found over the years that trying to contain my setups within a small set of or single geometry node has been beneficial for clarity. That something that Jeff covered also in this webinar. https://vimeo.com/272793390 [vimeo.com]
However, when you do something like that, if you need to place a transform on the geometry node or parent it to a null with a transform, inevitably, it will cause the dop network within to receive a double transform. Once from the geometry node itself and a second time when the data from the geometry node is fed into the dopnetwork via opinputpath().
I've attached a simple smoke scene to illustrate what I mean.
The pyro_doubletransformed node is being translated 8 units to on the x instead of 4 units.
Is there a simple/elegant way to avoid this from happening?
Edited by iamnelsonlim - Sept. 11, 2019 19:12:58
Technical Discussion » Forced Matte Objects in image planes
- iamnelsonlim
- 39 posts
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I was wondering if anyone figured out a good workflow for this issue? It's hard to use the normal/Pz pass if force matte objects are still included in it.
Technical Discussion » Atmospheric fog/dust setup
- iamnelsonlim
- 39 posts
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Because this is most likely going to be a pretty large volume, I would first attempt to do this with pop particles that are fed to the ‘volume rasterize particles’ node.
I've included a quick example. Hope it helps.
I've included a quick example. Hope it helps.
Edited by iamnelsonlim - Sept. 21, 2016 15:58:06
Technical Discussion » Guided FLIP simulations
- iamnelsonlim
- 39 posts
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Hi guys,
I am wondering if it's possible to simulate a thin layer of ocean from any given geometry mesh in houdini?
I am referencing a feature that is similar to bifrost's guided simulations.
https://www.youtube.com/watch?v=zeZNAsq5m0c [youtube.com]
From what I see, the closest shelf tool setup would be the wave layer tank. However, the wave layer tank uses an output(phase,freq, amplitude volumes) from an ocean spectrum node that is fed into the wave tank node. Is there a way, it can take in any geometry mesh as an input source instead?
I have very specific ocean shapes and so I have geometry that I need to place into a flip sim as I will have a boat that travels through the ocean as well and will be making wakes and splashes.
Thanks in advance for any tips!
I am wondering if it's possible to simulate a thin layer of ocean from any given geometry mesh in houdini?
I am referencing a feature that is similar to bifrost's guided simulations.
https://www.youtube.com/watch?v=zeZNAsq5m0c [youtube.com]
From what I see, the closest shelf tool setup would be the wave layer tank. However, the wave layer tank uses an output(phase,freq, amplitude volumes) from an ocean spectrum node that is fed into the wave tank node. Is there a way, it can take in any geometry mesh as an input source instead?
I have very specific ocean shapes and so I have geometry that I need to place into a flip sim as I will have a boat that travels through the ocean as well and will be making wakes and splashes.
Thanks in advance for any tips!
Technical Discussion » Whitewater and suspended foam particles
- iamnelsonlim
- 39 posts
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I posed my question to sidefx and John Lynch gave me a good reply that diagnosed what the problem was, how to fix it proper and how to fix it quickly in my situation.
I thought I would post it hear for anyone else facing this issue in the future as it is fairly easy to fall into this problem if using custom emitters for your flip sims.
I thought I would post it hear for anyone else facing this issue in the future as it is fairly easy to fall into this problem if using custom emitters for your flip sims.
I believe your issue is with your emission geometry.
Normally if you use something like FluidSource, you will be creating both particles and a “surface” SDF that represents the emission geometry. The FLIP Solver setup uses this via the SourceVolume DOP to merge in the new particles, *and* to merge in the surface SDF of the emission geometry so that the final FLIP surface field represents the full fluid including the newly emitted fluid. This last step is necessary because emission happens last in each timestep.
Having an accurate surface SDF coming out of FLIP is important for whitewater since it uses it for depth testing. Unfortunately it's a little too easy to provide incorrect (or missing) values when creating a custom emitter, as you have done here. You are only creating particles, which is generally fine, but since you don't actually create a surface SDF, you are giving the FLIP solver invalid values for the surface field in the SourceVolume DOP. These flow through to the whitewater depth testing and lead to stuck particles when it can't figure out where in the fluid the whitewater particles are.
There's an easy fix: just set the Source Volume operation on source_surface_from_splash_emitter to None, which will disable the merging of the (non-existing) surface SDF field. We should probably handle this situation better by default.
A couple of useful debugging tips for these kind of issues: turn on the Surface guide for the FLIP sim. It should be a smooth (if low-res) representation of the fluid. Without this fix it's blocky due to the invalid values.
Also you can clear the Delete Internal Attributes parameter on the Whitewater Solver and look at the values for “depth” on all the particles. If you see a lot of particles with a constant value of zero, that's usually a sign of a bad surface SDF.
Technical Discussion » Whitewater and suspended foam particles
- iamnelsonlim
- 39 posts
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Technical Discussion » Whitewater and suspended foam particles
- iamnelsonlim
- 39 posts
- Offline
Hi guys,
I have been bumping into a peculiar issue on the whitewater setup from the shelf tools, where I seem to have white water particles that ‘stick’ in the air for a moment before coming down.
I have tried a number of ways to tackle this issue but have not been successful. Mainly, I have isolated the issue down to when the foam particles transit into spray. That seems to be when they hang around for a bit before gravity brings them down.
I'm probably not doing something right, as I am relatively new to using the white water setup from the shelf.
Has anyone bumped into something like this before? I have a scene file where I have this issue replicated.
I have been bumping into a peculiar issue on the whitewater setup from the shelf tools, where I seem to have white water particles that ‘stick’ in the air for a moment before coming down.
I have tried a number of ways to tackle this issue but have not been successful. Mainly, I have isolated the issue down to when the foam particles transit into spray. That seems to be when they hang around for a bit before gravity brings them down.
I'm probably not doing something right, as I am relatively new to using the white water setup from the shelf.
Has anyone bumped into something like this before? I have a scene file where I have this issue replicated.
Edited by iamnelsonlim - July 5, 2016 16:52:32
Technical Discussion » Maelstrom RnD
- iamnelsonlim
- 39 posts
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Hey Yash,
Thanks for the help and advise. I'm really thankful. This has been helpful in understanding the different ways we can manipulate flip fluids with custom fields.
This is a great starting point to dive further into.
Thanks!
Thanks for the help and advise. I'm really thankful. This has been helpful in understanding the different ways we can manipulate flip fluids with custom fields.
This is a great starting point to dive further into.
Thanks!
Technical Discussion » Maelstrom RnD
- iamnelsonlim
- 39 posts
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Hi guys,
I'm trying out a couple of fluid RnD sims with custom velocity fields. Currently, I am trying to create a large maelstrom in the ocean and I haven't been able to get my custom velocity field to generate the type of swirl to create a a maelstrom. The fluid are rotating, but it doesn't seem to generate the vortex swirl I was hoping.
My scene scale is large at 500x350x400m wave tank size. I have a custom velocity volume field which is basically a cross product of position against {0,1,0} to get the swirl direction.
I think I am missing out on a thing or two to get the effect I want. Hopefully, someone can shed some light for me?
Thanks.
I'm trying out a couple of fluid RnD sims with custom velocity fields. Currently, I am trying to create a large maelstrom in the ocean and I haven't been able to get my custom velocity field to generate the type of swirl to create a a maelstrom. The fluid are rotating, but it doesn't seem to generate the vortex swirl I was hoping.
My scene scale is large at 500x350x400m wave tank size. I have a custom velocity volume field which is basically a cross product of position against {0,1,0} to get the swirl direction.
I think I am missing out on a thing or two to get the effect I want. Hopefully, someone can shed some light for me?
Thanks.
Technical Discussion » Will SideFx every allow installation on two computers?
- iamnelsonlim
- 39 posts
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Admittedly, this isn't as easy as what Adobe's CC has done for users to work from home or work,, but might be worth a try.
Sounds like you'll want to get a floating license and install the license server on your laptop. That way, your license server goes with you wherever your laptop is.
Have your desktop houdini installation look to your laptop for the license server. It would help if you have setup a hostname for laptop in your home network. That way you can check out a license on your workstation whenever you are at home/work so long as your have your laptop turned on and on the same network.
I know at least one person who has that setup.
Sounds like you'll want to get a floating license and install the license server on your laptop. That way, your license server goes with you wherever your laptop is.
Have your desktop houdini installation look to your laptop for the license server. It would help if you have setup a hostname for laptop in your home network. That way you can check out a license on your workstation whenever you are at home/work so long as your have your laptop turned on and on the same network.
I know at least one person who has that setup.
Technical Discussion » Reading attributes from a houdini alembic file into Maya
- iamnelsonlim
- 39 posts
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Hi guys,
I'm trying to read point data from an alembic export of an ocean surface from houdini.
I have cusp, cuspdir, v, uv and foam attributes that are generated by the ocean spectrum node and exported into the abc file.
However, I'm not sure how to read them into maya to drive some vray shader parameter. I haven't used maya a lot either, so it could just be me.
After bringing in the abc file, I see some of that data in the “Extra Attributes” But it doesn't seem to make sense to me.
I read around about using the Maya SOuP plugins to read the point attributes, but I'm hoping there is a more direct way without resorting to an additional plugin that the community might know about?
Thanks in advance!
I'm trying to read point data from an alembic export of an ocean surface from houdini.
I have cusp, cuspdir, v, uv and foam attributes that are generated by the ocean spectrum node and exported into the abc file.
However, I'm not sure how to read them into maya to drive some vray shader parameter. I haven't used maya a lot either, so it could just be me.
After bringing in the abc file, I see some of that data in the “Extra Attributes” But it doesn't seem to make sense to me.
I read around about using the Maya SOuP plugins to read the point attributes, but I'm hoping there is a more direct way without resorting to an additional plugin that the community might know about?
Thanks in advance!
Technical Discussion » Non-unit scales on camera?
- iamnelsonlim
- 39 posts
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Thanks guys,
That is really helpful information.
I used the method of a null node and was able to extract the transformations on a few frames across the timeline and it does seem that my scale stays pretty much at 1.0, 1.0, 1.0 throughout the frame range.
So I'm still not quite sure I understand the message about non-unit scales on the camera.
That is really helpful information.
I used the method of a null node and was able to extract the transformations on a few frames across the timeline and it does seem that my scale stays pretty much at 1.0, 1.0, 1.0 throughout the frame range.
So I'm still not quite sure I understand the message about non-unit scales on the camera.
Technical Discussion » Non-unit scales on camera?
- iamnelsonlim
- 39 posts
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Thanks keyframe.
That explaination helps to make sense of that message.
Since it's an alembic camera that I brought in, I wasn't able to see any rotation translation or scale changes. Is there a way to read that information?
That explaination helps to make sense of that message.
Since it's an alembic camera that I brought in, I wasn't able to see any rotation translation or scale changes. Is there a way to read that information?
Technical Discussion » Non-unit scales on camera?
- iamnelsonlim
- 39 posts
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Hi guys,
I was wondering if anyone has bumped into this message from mantra?
I've imported an alembic camera from maya in this case. I'm not quite sure what this message means. Is there a way to specify units on the camera? Also, the camera is not being scaled.
I do have units set to cm in houdini (instead of the default metres) if that is of any consequence.
It's not affecting my renders, but I'm curious to know more about this.
Thanks!
I was wondering if anyone has bumped into this message from mantra?
mantra: Camera has non-unit scales, which may affect certain shading (i.e. volumes)
I've imported an alembic camera from maya in this case. I'm not quite sure what this message means. Is there a way to specify units on the camera? Also, the camera is not being scaled.
I do have units set to cm in houdini (instead of the default metres) if that is of any consequence.
It's not affecting my renders, but I'm curious to know more about this.
Thanks!
Technical Discussion » Particle fluid surface with a shrinking pscale
- iamnelsonlim
- 39 posts
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Hi guys,
I was trying to use the particle fluid surface node today by meshinga trail of points that have a pscale that was decreasing with the complement of the normalised age. I noticed that the fluid surface did not seem take into account the decreasing pscale of the points once they have been meshed.
Is this something to be expected? Just curious.
I had to use a vdb from points sop instead to achieve the look.
I was trying to use the particle fluid surface node today by meshinga trail of points that have a pscale that was decreasing with the complement of the normalised age. I noticed that the fluid surface did not seem take into account the decreasing pscale of the points once they have been meshed.
Is this something to be expected? Just curious.
I had to use a vdb from points sop instead to achieve the look.
Technical Discussion » How do you work on scenes with assets in feet?
- iamnelsonlim
- 39 posts
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Hey Koen,
Thanks for that tip.
I was actually wondering how such a big change in the scale would affect the solvers and it did worry me if certain parameters did not scale properly, I would only find out too late.
I wanted to avoid scaling everything down. But I guess that's the only way. As suggested by arctor, I would have to parent everything to null and scale it down. I'm going to have to test how cameras would react to this as well.
Thanks
Nelson
Thanks for that tip.
I was actually wondering how such a big change in the scale would affect the solvers and it did worry me if certain parameters did not scale properly, I would only find out too late.
I wanted to avoid scaling everything down. But I guess that's the only way. As suggested by arctor, I would have to parent everything to null and scale it down. I'm going to have to test how cameras would react to this as well.
Thanks
Nelson
Technical Discussion » How do you work on scenes with assets in feet?
- iamnelsonlim
- 39 posts
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A follow up question to this.
Is there way to set the default length units to feet for a facility. Such as an environment variable?
Thanks
Is there way to set the default length units to feet for a facility. Such as an environment variable?
Thanks
Technical Discussion » How do you work on scenes with assets in feet?
- iamnelsonlim
- 39 posts
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Thanks for all the replies.
1. Change the Unit Length to Feet. That seems to be a good way to do this.
I noticed that the dop gravity force will automatically have it's unit scaled from -9.81 to -32.174. And other solvers have similar conversions also if weights was changed from kg to pounds for instance.
This seems the better approach then parenting and scaling everything down as I'll need to scale everything back up to feet again if I need to export the geometry out to other packages.
Thanks!
1. Change the Unit Length to Feet. That seems to be a good way to do this.
I noticed that the dop gravity force will automatically have it's unit scaled from -9.81 to -32.174. And other solvers have similar conversions also if weights was changed from kg to pounds for instance.
This seems the better approach then parenting and scaling everything down as I'll need to scale everything back up to feet again if I need to export the geometry out to other packages.
Thanks!
Technical Discussion » How do you work on scenes with assets in feet?
- iamnelsonlim
- 39 posts
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Hi guys,
I'm curious if anyone has had to deal with receiving a scene where geometry/assets/cameras/lights that are in US customary scale(e.g. feet),
but you had to bring it into houdini for simulation and then later export it back out in the same US customary scale?
So far, I've been eyeballing my simulation number's to get sims that look and feel correct for the scale, but I was wondering if there was any more scientific and methodical system of doing this. Perhaps, some way to convert the entire scene from feet into metres when first ingested and then some way to convert the entire scene back into feet when exporting the results? Wanted to see if any of you folks out there have had to deal with this problem so far and what did you find helpful?
Thanks!
I'm curious if anyone has had to deal with receiving a scene where geometry/assets/cameras/lights that are in US customary scale(e.g. feet),
but you had to bring it into houdini for simulation and then later export it back out in the same US customary scale?
So far, I've been eyeballing my simulation number's to get sims that look and feel correct for the scale, but I was wondering if there was any more scientific and methodical system of doing this. Perhaps, some way to convert the entire scene from feet into metres when first ingested and then some way to convert the entire scene back into feet when exporting the results? Wanted to see if any of you folks out there have had to deal with this problem so far and what did you find helpful?
Thanks!
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