Youy are so clear and concise - this has to be one of the best Houdini tutorials I've followed. Thanks! Nice to see another Houdini girly too there arent many of us!
I must have watched a dozen videos that were all either not exactly what I wanted or outdated. Then i found your channel and it had everything, exactly as I needed. So clear and engaging too. Really impressed by how easy to understand you make it. Big fan.
@@VoxelFX You're welcome. I ran into some problems I'm hoping you could help me out with. 1st of all, how would I go about telling Houdini to only start simulating at a specific frame other than frame 1? Say I have an animated Can with fluid and want the fluid to start being emitted on frame 100. I toggled the brain icon as you instructed, but noticed that it still simulates all the other frames. 2nd, once I finally have my setup ready, how do I go about converting the particles to mesh so I can start shedding and rendering? Overall, it was an awesome tutorial!!
@@AcerKanyiki4 Here's a link that might also help to answer the 2nd question: ua-cam.com/video/UQXS12sj9IA/v-deo.html 1. The brain icon disables the simulation for the entire scene, which is helpful if you want to work on the models or add keyframes without waiting ages for the simulation to re-simulate. If you want to change the start frame of your simulation select the "AutoDopNetwork" (OBJ level). You will find the "Start frame" option in the "Simulation" tab. You simply type the frame number you want your simulation to start. 2. If you use the shelf tools, the network for meshing will be set up automatically. You can find it in the OBJ level, it's called "particle_fluid" Then, display the "surface_cache" node or the "RENDER" null to see the meshed liquid. However, when you render your scene, Houdini will automatically read data from that node, so the liquid should be cached ok. :) Let me know if it helped! :D
@@VoxelFX Thanks for the reply. The tips were invaluable! But I saw that I can also change the frame start from within the DOP network (Fluid Particles - on the Creations Tab). I'm not sure if it's the correct way, but it seems to work just fine. Please advise. The scene that I'm working on is for a Soda Can that's supposed to pour liquid into a glass. I went through the entire setup successfully, and have officially hit an unbreakable wall. I have literally spent hours on this with zero success. The fluid is filling up nicely and I've managed to tighten up the voxels to keep the fluid in the container. But the action of tightening up the voxels also seems to be restricting the fluid from flowing out of the Can through the hole. I couldn't understand why, so I loosened the voxels for the top part of the Can and completely reduced the offset, re-simulated and the fluid is behaving as expected. I've tinkered with as many settings as described in the video for the top part of the Can to let the fluid through and it's not working at all. Please help! I've included a link to my g-drive with the .hip file for examination. I'll grant you permission once you request entry: drive.google.com/file/d/1Kp2Dpd6vaExEp58MTfwma4S1E6Az-71Y/view?usp=sharing Please live any helpful notes in the file if you see fit. Much thanks!
@Aser Kanyiki You can change the start frame in either place as they are linked. There are always several ways to do one thing, in my other tutorial I showed a way to do it with VEX: ua-cam.com/video/HIJuYzNyTCg/v-deo.html Regarding the simulation, there are several more things that will help you in a situation like this: 1. Make sure your collision geometry is good quality (meaning: no holes, good topology, extruded walls); this way you will save a lot of time fixing it in the simulation. Also remember that the simulated geometry doesn’t have to be the same as the one you use for rendering, so you can have slightly bigger extrusions or lower polycount to make the scene simulate faster. 2. Check the particle separation. In short, each water droplet has a specified size, so if the single particle size (particle separation) is bigger than the hole in the geometry, it will not go through. So lowering the particle separation might also help. 3. Increase the substeps. By increasing the substeps you’ll allow Houdini to make more precise calculations, so small holes and interaction between the particles and the colliders will be better. In your case, it was a mixture of all. I’ve sent you the new scene with notes via email. Hope it helped 😊
Hi mahdiw mousavi, there are several things that might be happening here. 1. Check your collider geometry, make sure it is closed (watertight). If you are not sure, do the following after your created/imported 3D model. - "VDB from polygons" and adjust the Voxel Size to get a bit more detail, e.g. 0.08 - "Convert VDB" and change the "Convert to" option to "Polygons" - Use this as your static collider 2. If it is still not working, make sure to check the collision geometry in your DOP Network "Static Object" node. - StaticObject/Collisions/RBD Solver/Volume/ switch on "Collision Guide" to see the blue representation of the object - Adjust the "Division Size" if needed 3. If this still doesn't work, use "Collision Separation" - DOP network/FLIP object/Properties/Collision Separation - Set the value to something a bit lower than your Particle Separation*Grid Scale Let me know if any of this helped and then we can troubleshoot further. :)
Hi, I recently started studying Houdini and found your channel. You are better than any courses! Thank you for your tutorials! I have a question. What if I import an alembic, and the model will have its own animation, which I baked in another program. Will it be a deformable object or an animation (for collision)? And what about models with skeletal animation?
Thank you Demgreart! I’m happy to hear the videos have helped 😊 Answering your question, for any moving object you’ll use the “Deforming Object” shelf tool or if you create the collision object manually, then tick the “Use Deforming Geometry” option on the “Static Object” node in the DOP network. It doesn’t matter if the geometry is animated in Houdini or any other software (though sometimes you’ll have to prep it). Although, it can be a topic for a separate tutorial… In terms of the naming, you’d call any moving model that comes from a different software a “deforming” geometry too. It becomes an “animated” geometry if you add keyframes on the OBJ level in Houdini, in which case you’ll also have to use the “Use Object Transform” option on the “Static object” node in the DOP network. At least when we talk in the context of FLIP simulations. Here’s a video that explains it in a bit more detail: www.sidefx.com/tutorials/bullet-collisions-in-houdini-deforming-vs-animated/
So unbelievably helpful! I was banging my head against the wall with this sim b/c the water was going through the collider and this solved it. That's a great feeling. Thanks!
Thanks for noting :) In most examples that's the case. But this is because most models are on 0 in Y axis, so we don't see the difference. If the model is, for example, 5 in Y, it returns -5. (let me know if I'm not missing something) :)
I have clicked icon "create Static Object" twice. Nodes are duplicated. Iam so confusing. So I deleted all those nodes. But the Warning sign appear. Finally, i have to do all over again (i fogot to undo). Houdini is dangerous for me if i dont really understand it clearly. (English is not my main language xD). Btw, thank you so much for making these tutorials!
Don't worry, Houdini is difficult and it takes time to get used to it. :) When you are not sure if the shelf tool worked, it's best to check if any new nodes are added in the AutoDopNetwork before clicking on the tool again. There's also a description of current actions at the bottom left side of the screen. Just take your time and you'll get used to it soon! :)
@@VoxelFX Nope it's static! But I've run into the same problem when the collider was moving. Like putting the liquid in a glass bottle and animating the bottle.
If it's static, it should be easier. :) Just make sure the VDB of your container is watertight. You can do it by displaying the "Collision guide" in the "static object" node in DOP network. If you can see gaps, the liquid will go through them. You need to reduce the "Division size" until the blue visualization of your collider is accurate.
@@VoxelFX Thanks for your reply. I have checked my collision guide and it looks solid. I've run my division size down to 0.012 but there are still a couple of particles that just penetrates my collider...
@@p73ccw It's hard to tell without seeing the actual scene, but sometimes if the liquid has very high velocity, it can go through the walls. In this case you'd need to increase the substeps on the dopnetwork under the "simulation" tab. A lighter thing to do fix it, especially if it's just a couple of particles that are going through the collider, is removing them post-sim. For that you need to switch on the "Add ID Attribute" option in your FLIPsolver/Particle Motion/Behavior. Then, delete the unwanted particles based on their id.
Youy are so clear and concise - this has to be one of the best Houdini tutorials I've followed. Thanks! Nice to see another Houdini girly too there arent many of us!
I must have watched a dozen videos that were all either not exactly what I wanted or outdated. Then i found your channel and it had everything, exactly as I needed. So clear and engaging too. Really impressed by how easy to understand you make it. Big fan.
Thank you Luke, I'm very happy to hear that! :D
This was amazingly informative, especially the part about avoiding collision issues. Thanks so much!!!
Exactly what I needed. Thanks a bunch! Subbed.
I'm happy to hear that! Thank you ^_^
@@VoxelFX You're welcome. I ran into some problems I'm hoping you could help me out with. 1st of all, how would I go about telling Houdini to only start simulating at a specific frame other than frame 1? Say I have an animated Can with fluid and want the fluid to start being emitted on frame 100. I toggled the brain icon as you instructed, but noticed that it still simulates all the other frames. 2nd, once I finally have my setup ready, how do I go about converting the particles to mesh so I can start shedding and rendering? Overall, it was an awesome tutorial!!
@@AcerKanyiki4
Here's a link that might also help to answer the 2nd question: ua-cam.com/video/UQXS12sj9IA/v-deo.html
1. The brain icon disables the simulation for the entire scene, which is helpful if you want to work on the models or add keyframes without waiting ages for the simulation to re-simulate. If you want to change the start frame of your simulation select the "AutoDopNetwork" (OBJ level). You will find the "Start frame" option in the "Simulation" tab. You simply type the frame number you want your simulation to start.
2. If you use the shelf tools, the network for meshing will be set up automatically. You can find it in the OBJ level, it's called "particle_fluid" Then, display the "surface_cache" node or the "RENDER" null to see the meshed liquid. However, when you render your scene, Houdini will automatically read data from that node, so the liquid should be cached ok. :)
Let me know if it helped! :D
@@VoxelFX Thanks for the reply. The tips were invaluable! But I saw that I can also change the frame start from within the DOP network (Fluid Particles - on the Creations Tab). I'm not sure if it's the correct way, but it seems to work just fine. Please advise.
The scene that I'm working on is for a Soda Can that's supposed to pour liquid into a glass. I went through the entire setup successfully, and have officially hit an unbreakable wall. I have literally spent hours on this with zero success. The fluid is filling up nicely and I've managed to tighten up the voxels to keep the fluid in the container. But the action of tightening up the voxels also seems to be restricting the fluid from flowing out of the Can through the hole.
I couldn't understand why, so I loosened the voxels for the top part of the Can and completely reduced the offset, re-simulated and the fluid is behaving as expected. I've tinkered with as many settings as described in the video for the top part of the Can to let the fluid through and it's not working at all. Please help! I've included a link to my g-drive with the .hip file for examination. I'll grant you permission once you request entry:
drive.google.com/file/d/1Kp2Dpd6vaExEp58MTfwma4S1E6Az-71Y/view?usp=sharing
Please live any helpful notes in the file if you see fit. Much thanks!
@Aser Kanyiki
You can change the start frame in either place as they are linked. There are always several ways to do one thing, in my other tutorial I showed a way to do it with VEX: ua-cam.com/video/HIJuYzNyTCg/v-deo.html
Regarding the simulation, there are several more things that will help you in a situation like this:
1. Make sure your collision geometry is good quality (meaning: no holes, good topology, extruded walls); this way you will save a lot of time fixing it in the simulation. Also remember that the simulated geometry doesn’t have to be the same as the one you use for rendering, so you can have slightly bigger extrusions or lower polycount to make the scene simulate faster.
2. Check the particle separation. In short, each water droplet has a specified size, so if the single particle size (particle separation) is bigger than the hole in the geometry, it will not go through. So lowering the particle separation might also help.
3. Increase the substeps. By increasing the substeps you’ll allow Houdini to make more precise calculations, so small holes and interaction between the particles and the colliders will be better.
In your case, it was a mixture of all. I’ve sent you the new scene with notes via email.
Hope it helped 😊
Thank you 🌟
Now I finally see why the collision failed with so many other tutorials. Thank you so much for going into detail with Houdini's functionality.
thanks for your help but my glass doesnt fill with the particles i dont know why???
Hi mahdiw mousavi, there are several things that might be happening here.
1. Check your collider geometry, make sure it is closed (watertight). If you are not sure, do the following after your created/imported 3D model.
- "VDB from polygons" and adjust the Voxel Size to get a bit more detail, e.g. 0.08
- "Convert VDB" and change the "Convert to" option to "Polygons"
- Use this as your static collider
2. If it is still not working, make sure to check the collision geometry in your DOP Network "Static Object" node.
- StaticObject/Collisions/RBD Solver/Volume/ switch on "Collision Guide" to see the blue representation of the object
- Adjust the "Division Size" if needed
3. If this still doesn't work, use "Collision Separation"
- DOP network/FLIP object/Properties/Collision Separation
- Set the value to something a bit lower than your Particle Separation*Grid Scale
Let me know if any of this helped and then we can troubleshoot further. :)
Particle Radius Scale / Grid Scale >= 0.866
this is soo! helpfull
Hi, I recently started studying Houdini and found your channel. You are better than any courses! Thank you for your tutorials! I have a question. What if I import an alembic, and the model will have its own animation, which I baked in another program. Will it be a deformable object or an animation (for collision)? And what about models with skeletal animation?
Thank you Demgreart! I’m happy to hear the videos have helped 😊
Answering your question, for any moving object you’ll use the “Deforming Object” shelf tool or if you create the collision object manually, then tick the “Use Deforming Geometry” option on the “Static Object” node in the DOP network. It doesn’t matter if the geometry is animated in Houdini or any other software (though sometimes you’ll have to prep it).
Although, it can be a topic for a separate tutorial…
In terms of the naming, you’d call any moving model that comes from a different software a “deforming” geometry too. It becomes an “animated” geometry if you add keyframes on the OBJ level in Houdini, in which case you’ll also have to use the “Use Object Transform” option on the “Static object” node in the DOP network. At least when we talk in the context of FLIP simulations.
Here’s a video that explains it in a bit more detail: www.sidefx.com/tutorials/bullet-collisions-in-houdini-deforming-vs-animated/
i found a best channel with interesting topic Thanks
Veryy well explained, thankss, you cleared a lot of doubts that I had, excellent for beginners :D
So unbelievably helpful! I was banging my head against the wall with this sim b/c the water was going through the collider and this solved it. That's a great feeling. Thanks!
-$YMIN = $YMAX
Thanks for noting :) In most examples that's the case. But this is because most models are on 0 in Y axis, so we don't see the difference. If the model is, for example, 5 in Y, it returns -5. (let me know if I'm not missing something) :)
You are amazing!!!!!!!!!
I have clicked icon "create Static Object" twice. Nodes are duplicated. Iam so confusing. So I deleted all those nodes. But the Warning sign appear. Finally, i have to do all over again (i fogot to undo). Houdini is dangerous for me if i dont really understand it clearly. (English is not my main language xD). Btw, thank you so much for making these tutorials!
Don't worry, Houdini is difficult and it takes time to get used to it. :)
When you are not sure if the shelf tool worked, it's best to check if any new nodes are added in the AutoDopNetwork before clicking on the tool again. There's also a description of current actions at the bottom left side of the screen. Just take your time and you'll get used to it soon! :)
@@VoxelFX Thanks, i'll keep this in mind.
thank you for your tutorial!!!
Subbed
I have followed all the exact steps of your tutorial, but some of my particles still seem to penetrate the collider. What's the fix??
Hey Chris Jang :) is your collider moving?
@@VoxelFX Nope it's static! But I've run into the same problem when the collider was moving. Like putting the liquid in a glass bottle and animating the bottle.
If it's static, it should be easier. :) Just make sure the VDB of your container is watertight. You can do it by displaying the "Collision guide" in the "static object" node in DOP network. If you can see gaps, the liquid will go through them. You need to reduce the "Division size" until the blue visualization of your collider is accurate.
@@VoxelFX Thanks for your reply. I have checked my collision guide and it looks solid. I've run my division size down to 0.012 but there are still a couple of particles that just penetrates my collider...
@@p73ccw It's hard to tell without seeing the actual scene, but sometimes if the liquid has very high velocity, it can go through the walls. In this case you'd need to increase the substeps on the dopnetwork under the "simulation" tab. A lighter thing to do fix it, especially if it's just a couple of particles that are going through the collider, is removing them post-sim. For that you need to switch on the "Add ID Attribute" option in your FLIPsolver/Particle Motion/Behavior. Then, delete the unwanted particles based on their id.