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This hip was inspired by Brushstroke Tools in Blender. brushstroke_fire.zip 20 brushstrokes are included. I made them in Krita (free software). I used these presets (also free): https://krita-artists.org/t/memileo-brushes/53579 https://krita-artists.org/t/memileo-impasto-brushes/92952

Here are some ideas using this on curves (if I understood correctly) shift_points_along_curve.hipnc

Hi magicians, I'm finishing a tutorial about how to create hard surface helmets procedurally in Houdini, here's a previz:

Maybe try with Target Forward Vector, a bit hard blend, for a smooth edge need to make something else. paint_alignment_v02.hiplc

https://forums.odforce.net/topic/52360-heightfields-guided-by-pyro/#comment-238377 you have endless Way to make this .

Yeah, but only works on straigth line @Aizatulin's file is awesome!

I do not think a discord is the right thing for odforce, as Marc mentioned, the info get lost easily. Even though you can search etc still is not as nice as having it in a forum.

I would like to increase the curviness of a given curve in post. Do you know other methods to this problem? This seems to work nicely, but maybe there are better ways to do it.(?) increase_curvature_in_post.hiplc

true i think then your setup is already good and simple to use. you could also extend the curves to fix the issue in my setup ... but guess thats then already too much

interesting one, though it doesn't seems to be 100% correct for example here the normals don't follow the curvature properly adjusting the Search Radius can help, but it has to be larger than the length of a segment in the line (this can be problematic if the distribution of points are not uniform in the line (and if you can't apply resample for some reason)) but thanks, it's an interesting and simple approach indeed.

avoid_force_super_simple.hip thats maybe simpler

Wow that thread is really helpful thank you for sharing that

if you mean Those Swirls .its just Texture that its being advected and Rest uv by movement of particles(to volumes) that you can map to -P.y . just volumes . @korbendalas

Hi, Here's a hipfile for this: drive_ocean_amplitude.hiplc

I'm not proud of this definitely not the best approach, (especially that it doesn't stop at the end ) but maybe can give you ideas. curtain_thingy.hiplc

Upskilling. Tried new stuff. Demo in below link!! For More info: https://www.linkedin.com/posts/chandrakanth-santharam-6b8b3527_houdini-template-manger-10-activity-7333552173038845952-0RUG?utm_source=share&utm_medium=member_desktop&rcm=ACoAAAWvTKwBN4lVJ6vJC07NTnwyTd6gViVRL4U Cheers!!

The funny thing is that I tried the Target Forward Vector, but somehow failed to have success... This method is really nice, thank you very much @fencer!

I came across this effect on behance and I wanna remake it , I'm still a a beginner , so bare with me , I made a classic Flip setup with gas stick on collision and surface tension , I animated the viscosity and surface tension I also added some negative divergence to make the fluid implode a little ( it did gave a good effect at the beginning so I stuck with it , idk if its a good idea ) . I wanna get a natural tear from the start and these small strands , mine feels elastic . Ref Mine any help will be appreciated . caramel_tear_test01.hipnc

Hey John Fraiser, Hopefully, this is what you meant. It is a continuous curve that you can carve from the beginning to the end. The seam is adjustable with a curve and thickness. You can just make it straight if you need it like that For every connected primitive, you make a gap (blast away some points), for example between point 350 and 375, then you use sort sop to shift the point order by -375. That way, your numbering starts and ends where the gap is. After that is done for every loop you can use the add sop to make one continuous curve. tstOdForceSippet.hipnc

Most likely fracturing setup structure is not correct, starts from polyextrude without volume. Check some more examples of this technique. See an example of a simple way to make a metal ship rbd. SPACESHIP_CRASH_020_v01.hiplc

This is pretty much the same as it always has been: Who's Online 10 Members, 0 Anonymous, 89 Guests However this is a good question, what can we do to generate more excitement on the forums? Is anyone interested in running challenges? Unfortunately I have a studio to run now, which is quite all encompassing, but we're happy to support any good ideas! M

Here's a little hda for creating point(s) on polylines. It is designed to work only on polylines with 2 points! If your polyline has multiple segments, it can/will give you weird unexpected results. TIP: Type "popo" in the TAB menu to find it fast. sipi-point_on_polyline-0.0.3.hda

quick flipbook gif of how the shot is looking. I'll re-animate Thanos soon enough. Also gonna be covered in lighting when Hulk hits the ground with his fist. would be nice to figure out how to get those pieces to 'splay' outwards a bit more as they fall so i dont end up with a cloud at the bottom of the shot - but i think i can figure that out using this active_age attribute now thanks for all your help on this

Anyone who's interested, I managed to find out that I have to convert the images like this: (e.g. using Houdini COPernicus or Nuke) (in the Write node you can choose Utility - Linear - sRGB as well) Or! You can save this step by setting ACES Output Transform in Davinci to sRGB (Linear) - CSC at export. Probably this is the easiest way. Best wishes, Attila

After a hiatus, DASH::package returns. Version 5.1 is an extensive rollout of fixes and new nodes that demonstrate composed applications of Dot and Cross Product operations: Linear Algebra, geometric relationships, rotation matrices, etc. Release: https://github.com/probiner/DASH/releases/tag/v5.1.0 Cheers

Use the Snippet VOP

Spent some time to make vellum snow simulation and Karma XPU render. Reflection volume pas Karma CPU.

I've developed a Houdini Hipfile Diff Tool to address the challenge of tracking changes in Houdini hipfiles. This tool, inspired by 'git diff', offers a dual-view comparison, visual indicators for changes, synchronized navigation, and a search feature. It's tailored for the Houdini environment using hython 3.9. The tool is open-source and available on my GitHub:https://github.com/golubevcg/hip_file_diff_tool I also have a small article on my website about this tool: https://golubevcg.com/post/comparing_hipfiles_in_houdini:_the_diff_tool Feedback and collaboration are welcome. If you encounter any bugs or issues, please don't hesitate to send me a message. Let's refine our Houdini tools together.

make of those stairs VDB and use this on Pop wrangle (input 2 ) on first points that you want to use) float volSample = volumesample(1,0,@P); vector volGrad = normalize(volumegradient(1,0,@P)); @P -= volGrad * volSample;//adjust Position @v += @force * @Timeinc;//Force to V @force = 0;//Force to be 0 vector vVertical = volGrad * dot(@v, volGrad); vector vHorizontal = @v - vVertical; @v = vHorizontal;

Hi art3mis, We used all those options before and it depends on what you are exporting. Alembic for vellum cloth is not great for optimisation later on and VAT was constantly loaded in memory which gave us problems during optimisation as well. We ended up using dembones for our baked cloth simulation and in the end was a lot lighter on the system. RBD to FBX was used extensively through out our production. That was great since we can optimise the the simulation right before it was baked and it doesn't change the rbd sim at all. Another issue with Alembic is that it doesn't handle a 2nd UV channel. Glen

Houdini was getting bored doing hours of simulation, so I gave him something to play with. - Done in Houdini, script in VEX, rendered using Karma.

You can achieve this by writing this sort of code inside a Primitive Wrangle: string cam = chs("cam"); float near = 0; float far = -0.01; vector pnear = fromNDC ( cam, set ( 0.5, 0.5, near ) ); vector pfar = fromNDC ( cam, set ( 0.5, 0.5, far ) ); vector dir = -normalize ( pfar - pnear ); vector n = normalize ( primuv ( 0, "N", @primnum, 0.5 ) ); if ( dot ( n, dir ) < ch("threshold") ) i@group_fresnel = 1;

Dopsmotor.rar

There are so many nice example files on this website that I am often searching for. I wanted to use this page as a link page to other posts that I find useful, hopefully you will too. This list was started years ago, so some of the solutions may be dated. Displaced UV Mapped Tubes Particles Break Fracture Glue Bonds Render Colorized Smoke With OpenGL Rop Moon DEM Data Creates Model Python Script Make A Belly Bounce Helicopter Dust Effect Conform Design To Surface Benjamin Button Intro Sequence UV Style Mapping UV Box and Multiple Projection Styles Ping Pong Frame Expression Instance vs. Copy (Instance Is Faster) Particle Bug Swarm Over Vertical and Horizontal Geometry Rolling Cube Rounded Plexus Style Effect Pyro Smoke UpRes Smoke Trails From Debris Align Object Along Path Fading Trail From Moving Point Swiss Cheese VDB To Polygons Get Rid Of Mushroom Shape In Pyro Sim A Tornado Ball Of Yarn Particles Erode Surface Unroll Paper Burrow Under Brick Road Non Overlapping Copies Build Wall Brick-By-Brick FLIP Fluid Thin Sheets Smoke Colored Like Image Volumetric Spotlight Moving Geometry Using VEX Matt's Galaxy Diego's Vortex Cloud Loopable Flag In Wind Eetu's Lab <--Must See! Wolverine's Claws (Fracture By Impact) Houdini To Clarisse OBJ Exporter Skrinkwrap One Mesh Over Another Differential Growth Over Surface Blazing Fast OpenCL Smoke Solver [PYTHON]Post Process OBJ Re-Write Upon Export Rolling Clouds Ramen Noodles Basic Fracture Extrude Match Primitive Number To Point Number Grains Activate In Chunks Fracture Wooden Planks Merge Two Geometry Via Modulus Fill Font With Fluid DNA Over Model Surface VDB Morph From One Shape To Another Bend Font Along Curve Ripple Obstacle Across 3D Surface Arnold Style Light Blocker Sphere Dripping Water (cool) Exploded View Via Name Attribute VEX Get Obj Matrix Parts eetu's inflate cloth Ice Grows Over Fire Flying Bird As Particles DEM Image To Modeled Terrain Pyro Temperature Ignition Extrude Like Blender's Bevel Profile Particles Flock To And Around Obstacles BVH Carnegie Mellon Mocap Tweaker (python script) Rolling FLIP Cube Crowd Agents Follow Paths Keep Particles On Deforming Surface Particle Beam Effect Bendy Mograph Text Font Flay Technique Curly Abstract Geometry Melt Based Upon Temperature Large Ship FLIP Wake (geo driven velocity pumps) Create Holes In Geo At Point Locations Cloth Blown Apart By Wind Cloth Based Paper Confetti Denim Stitching For Fonts Model A Raspberry Crumple Piece Of Paper Instanced Forest Floor Scene FLIP pushes FEM Object Animated Crack Colorize Maya nParticles inside an Alembic Path Grows Inside Shape Steam Train Smoke From Chimney Using Buoyancy Field On RBDs In FLIP Fluid Fracture Along A Path COP Based Comet Trail eetu's Raidal FLIP Pump Drip Down Sides A Simple Tornado Point Cloud Dual Colored Smoke Grenades Particles Generate Pyro Fuel Stick RBDs To Transforming Object Convert Noise To Lines Cloth Weighs Down Wire (with snap back) Create Up Vector For Twisting Curve (i.e. loop-d-loop) VDB Gowth Effect Space Colonization Zombie L-System Vine Growth Over Trunk FLIP Fluid Erosion Of GEO Surface Vein Growth And Space Colonization Force Only Affects Particle Inside Masked Area Water Ball External Velocity Field Changes POP particle direction Bullet-Help Small Pieces Come To A Stop Lightning Around Object Effect Lightning Lies Upon Surface Of Object Fracture Reveals Object Inside Nike Triangle Shoe Effect Smoke Upres Example Julien's 2011 Volcano Rolling Pyroclastic FLIP Fluid Shape Morph (with overshoot) Object Moves Through Snow Or Mud Scene As Python Code Ramp Scale Over Time Tiggered By Effector Lattice Deforms Volume Continuous Geometric Trail Gas Enforce Boundary Mantra 2D And 3D Velocity Pass Monte Carlo Scatter Fill A Shape Crowd Seek Goal Then Stop A Bunch Of Worms Potential Field Lines Around Postive and Negative Charges Earthquake Wall Fracture Instance Animated Geometry (multiple techniques) Flip Fluid Attracted To Geometry Shape Wrap Geo Like Wrap3 Polywire or Curve Taper Number Of Points From Second Input (VEX) Bullet Custom Deformable Metal Constraint Torn Paper Edge Deflate Cube Rotate, Orient and Alignment Examples 3D Lines From 2D Image (designy) Make Curves In VEX Avalanche Smoke Effect Instant Meshes (Auto-Retopo) Duplicate Objects With VEX Polywire Lightning VEX Rotate Instances Along Curved Geometry Dual Wind RBD Leaf Blowing Automatic UV Cubic Projection (works on most shapes) RBD Scatter Over Deforming Person Mesh FLIP Through Outer Barrier To Inner Collider (collision weights) [REDSHIFT] Ground Cover Instancing Setup [REDSHIFT] Volumetric Image Based Spotlight [REDSHIFT] VEX/VOP Noise Attribute Planet [REDSHIFT] Blood Cell Blood Vessel Blood Stream [REDSHIFT] Light Volume By Material Emission Only [REDSHIFT] Python Script Images As Planes (works for Mantra Too!) [REDSHIFT] MTL To Redshift Material [REDSHIFT] Access CHOPs In Volume Material [REDSHIFT] Mesh Light Inherits Color [REDSHIFT] Color Smoke [REDSHIFT] FBX Import Helper [REDSHIFT] Terrain Instancer Height Field By Feature Dragon Smashes Complex Fractured House (wood, bricks, plaster) Controlling Animated Instances Road Through Height Field Based Terrain Tire Tread Creator For Wheels Make A Cloth Card/Sheet Follow A NULL Eye Veins Material Matt Explains Orientation Along A Curve Mesh Based Maelstrom Vortex Spiral Emit Multiple FEM Objects Over Time Pushing FEM With Pyro Spiral Motion For Wrangle Emit Dynamic Strands Pop Grains Slope, Peak and Flat Groups For Terrains Install Carnegie Mellon University BVH Mocap Into MocapBiped1 Ramp Based Taper Line Fast Velocity Smoke Emitter Flip Fill Cup Ice Cubes Float [PYTHON]Export Houdini Particles To Blender .bphys Cache Format [PYTHON] OP UNHIDE ALL (opunhide) Collision Deform Without Solver or Simulation Mograph Lines Around Geometry Waffle Cornetto Ice Cream Cone Ice Cream Cone Top Unroll Road Or Carpet Burning Fuse Ignites Fuel or Painted Fuel Ignition Painted Fuel Combustion Small Dent Impact Deformation Particle Impact Erosion or Denting Of A Surface Helicopter Landing Smoke And Particles Radial Fracture Pieces Explode Outwards Along Normal Tangent Based Rocket Launch Rolling Smoke Field Tear/Rip FLIP (H12 still works in H16) Rain Flows Over Surface Rains Water Drip Surface Splash Smoke Solver Tips & Tricks Folding Smoke Sim VEX Generated Curve For Curling Hair Copy and Align One Shape Or Object To The Primitives Of Another Object (cool setup) A Better Pop Follow Curve Setup FEM Sea Cucumber Moves Through Barrier Fracture Cloth Smoke Confinement Setup Merge multiple .OBJ directly Into A Python Node Blood In Water Smoke Dissipates When Near Collision Object Whirlpool Mesh Surface Whirlpool Velocity Motion For FLIP Simple Bacteria Single Point Falling Dust Stream Flames Flow Outside Windows Gas Blend Density Example Localized Pyro Drag (smoke comes to a stop) Granular Sheet Ripping Post Process An Export (Post Write ROP Event) Corridor Ice Spread or Growth Set Velocity On Pieces When Glue Bonds Break Water Drops Along Surface Condensation Bottle Grains Snow or Wet Sand Starter Scene A Nice Little Dissolver Turn An Image Into Smoke Fading Ripples Grid Example Stranger Things Wall Effect Face Through Rubber Wall [PYTHON]Create Nurbs Hull Shelf Tool [PYTHON] Ramp Parameter [PYTHON] On Copy OF HDA or Node Select Outside Points Of Mesh, Honor Interior Holes Sparks Along Fuse With Smoke Umbrella Rig Melt FLIP UVs Tire Burn Out Smoke Sim Flip or Pyro Voxel Estimate Expression Motorcycle or Dirt Bike Kicks Up Sand Particles Push Points Out Of A Volume [PYTHON]Cellular Automata Cave Generator Punch Dent Impact Ripple Wrinkle VEX Rotate Packed Primitive Via Intrinsic Kohuei Nakama's Effect FLIP Fluid Inside Moving Container Particles Avoid Metaball Forces FLIP Divergence Setup FLIP Transfer Color Through Simulation To Surface Morph Between Two Static Shapes As Pyro Emits Constraint Based Car Suspension Pyro Smoke Gas Disturbs Velocity Wire Solver Random Size Self Colliding Cables Fast Cheap Simple Collision Deform CHOP Based Wobble For Animated Character Slow Motion FLIP Whaitewater Avoid Stepping In Fast Pyro Emission Fast Car Tires Smoke FLIP Fluid Fills Object Epic Share Of Softbody/Grain Setups (Must see!) Balloon, Pizza, Sail, Upres Shirt, Paint Brush Create Pop Grain Geometry On-The-Fly In A DOPs Solver Varying Length Trails VEX Based Geometry Transform Determine Volume Minimum and Maximum Values Grain Upres Example Animated pintoanimation For Cloth Sims Batch Render Folder Of OBJ files Vellum Weaving Cloth Fibers Knitting Kaleidoscopic Geometry UV Image Map To Points Or Hair Color Particles Like Trapcode Particular Flat Tank Boat Track With Whitewater Orthographic Angle Font Shadow Select Every Other Primitive or Face? Printer Spits Out Roll Of Paper Unroll Paper, Map, Plans, Scroll Simple Vellum L-System Plant Basic Cancer Cell 2D Vellum Solution Vellum Animated Zero Out Stiffness To Emulate Collapse Whitewater On Pre Deformed Wave [PYTHON] Menu Callback Change Node Color Extruded Voronoi With Scale Effector Multi Material RBD Building Fracture House Collapse Spin Vellum Cloth Whirlpool Vortex Trippy Organic Line Bend Design Logo Based Domino Layout Delete Outer Fracture Pieces, Keeping Inside Pieces UV Mapped Displaced Along Length Curly Curves Slow Particle Image Advection Nebula Saw Through VDB Like Butter Fuel Based Rocket Launch With Smoke Fuel Based Rocket Launch With Smoke [upres] Deform Pyro Along Path Bend Pyro Gas Repeat Solver With RBD Collision Raining Fuel Fire Bomb City Video Tutorial Pyro Cluster Setup (Animated Moving Fuel Source) [PYTHON] Mantra .MTL File Reader (creates new materials) Pyro Dampen By Distance FLIP Fluid Sweeps Away Crowd Ragdoll Gas Repeat Solver X-Men Mystique Feather Effect Camera Frustum Geometry Culling Vellum Extrude Shape Into Cloth Wire Web Constraint Setup Pyro Smoke Font Dissolve "Up In Smoke" Helicopter Landing With Vellum Grass and Dust or Smoke Another Thin Sheet Fluid Setup Color Rain Drops Over Surface Dual Smoke Object Wand Battle Custom GasDisturb node (easy to use) Hair Driven Grass Example File Pyro Smoke With Masked Turbulence Align High Resolution Mesh With Low Resolution RBD Simulation Streaky Portal Effect Height From Luma Cracking Glass Dome, Fracture VEX Noise Types FLIP Waterwheel Fracture Brick Wall Using UVs Vellum Stacked Torn Membranes Terrain Topographical Line Curves Prepare RBD Fracture For Unreal Alembic Export Growing Ivy Solver Fix For Intermittent FLIP Surfacing Issue Extensive RBD Fracturing Thread With HIP Files Peter Quint's Pop Streams Particle Example Fracture Geometry To Release Flip Fluid Inside Procedurally Reverse Normals Vellum Culling Voronoi Shape To Shape Transition Animated Scattering Accessing Parametric UVs On A Surface Organic Hallways/Corridors Through A Mesh Smoke Particle Dissolve Along One Axis Expanding Vellum Rings That Collide With One Another Read, Fetch, or Get SOP Attribute Inside Of DOPS Broad Splash When Object Enters Water Blendshape Crowd Example [PYTHON] Replace Packed Intrinsic Geometry From Another Source Rip/Tear Part Of Paper To Reveal And Roll Up After Effects Text Styles Cabling Mesh Surface Hanging Wires Or Cables Use Python Inside a Font Sop Brand Accurate Textures Using Karma XPU hScript asCode Microscopic Hair USD Attribute Equivalents For Preview Shader (i.e. Cd mangle) Vellum Peel Effect SOP Pyro Control Field Gas Disturbance Repair Geometry Self Intersection FLIP Follows Curve Long Winded Guide To Houdini Instancing Disable Simulations On Startup Tutorial HIP Library Use Google To Discover Attached HIP Files Useful Websites: Tokeru Houdini Houdini Vex Houdini Python Houdini Blueprints FX Thinking Rich Lord HIP Files iHoudini Qiita Ryoji Toadstorm Blog Eetu's HIP Of The Day Video Tutorials: Peter Quint Rohan Dalvi Ben Watts Design Yancy Lindquist Contained Liquids Moving Fem Thing Dent By Rigid Bodies Animating Font Profiles Swirly Trails Over Surface http://forums.odforce.net/topic/24861-atoms-video-tutorials/ http://forums.odforce.net/topic/17105-short-and-sweet-op-centric-lessons/page-5#entry127846 Entagma Johhny Farmfield Vimeo SideFX Go Procedural

and I made it work inheritVel_Test_v02.hip

pointdeform has built-in piece attribute, that you can use to embed each piece individually. This will create new problem on itself, as it will cause little cracks in the beginning, which you can fix by blending between the two methods. vellum_ballon_pop_fix.hiplc

During the last 3 weeks, a did some Rnd and published my results on vimeo . Some people asked me to share my files here, so here we are i hope it will help!

maybe this? not exhaustively tested tho...that's your job. ts_delete_internal_bubbles_withPig_fix.hiplc

You can set the Operation of the divergence field to Subtract and the smoke will move away from the divergence field, instead of being drawn in. Upres on right. Animating the scale of the volume might not be the best approach. All that does is increase or decrease the value in the area of the divergence field. To expang and area, you might try want to animate the scale of the divergence field shape at the SOP level and leave the DOP scale set to a constant. That way, when you expand the size from zero and up, the field size area of effect will grow, not the strength. ap_UPRES_smoke_divergence_040220.hiplc

if you unlock the POP force node and go into the noise_force VOP, you can see on the right how it combines the force every frame, there are two bind nodes: one to bring the force into the vop, and second to output it. Between them there is an add node and it combines the force with a calculation from the current frame. If you want to kill the additional force you are adding on one axis, you could drop down multiply node and multiply it with a constant vector - for example (1,1,0), that way it will only add the force on x and y axis.

you can specify formatting in Print VOP in similar way as in printf() function, see the example ts_formatted_print_vop.hip

Here, the pops one: bacteria_simple_pops.hipnc

First off shifting the vertex order will actually change the way the geometry is constructed. Just so you know. Adding to the post above, you can use the Primitive SOP's Face/Hull tab to reverse the vertex sort (reversing the primitive normals to boot) or shift the vertex number. Any of these shifts will keep the point order intact. If you want to reconstruct the primitive using any vertex sort driven by the point sort order, you can use the Add SOP. First press the toggle to just keep the points. Then in the Polygons Tab choose the Group option. Now your vertex order will match the point order, as messed up as you want it to be. If you have multiple primitives to reconstruct, use the Connectivity SOP to create a partition attribute and use the "By Attribute" option in the Add menu parameter. There are a bunch of other ways to reconstruct primitives from re-sorted vertices but the Add SOP is the easiest to use driven by the point order. playing_with_vertex_order.hip

I know this turned into vex based solutions, but in case anybody interested, Polyframe SOP offers direct way of calculating gradient vectors from attribute http://www.sidefx.com/docs/houdini13.0/nodes/sop/polyframe just change the style to Attribute Gradient

no, thats two different things even if it seems to be the same at a first glance. well, there are some similarities, for example both are tangent vectors but the definition and how the gradient get calculated is very different. a vector pointing to the max-value-point of its surrounding is just like a very rough approximation of the gradient but not the same! to get the gradient you´ll usually need to calculate partial derivatives (differentiate a function). in your case there is no function so you have to solve it nummerically. anyway, attached is a file where you can see the difference. i did´nt calculate derivatives in the example, instead i used the fact that the gradient is allways perpedicular to the contour line of an value. that way you do not have to care about boundary conditions ... btw. instead of primneighbours(...) you want to use pointneighbours(...) to get the string. with higher polycounts i would stay away from that expression since it will be slow and is not really needed ... hth. petz gradient.hipnc

I've wanted to tackle mushroom caps in pyro sims for a while. Might as well start here... Three things that contribute greatly to the mushroom caps: coarse sub-steps, temperature field and divergence field. All of these together will comb your velocity field pretty much straight out and up. Turning on the velocity visualization trails will show this very clearly. If you see vel combed straight out, you are guaranteed to get mushrooms in that area. If you are visualizing the velocity, best to adjust the visualization range by going forward a couple frames and adjusting the max value until you barely see red. That's your approximate max velocity value. Off the shelf pyro explosion on a hollow fuel source sphere at frame 6 will be about 16 Houdini units per second and the max velocity coincides with the leading edge of the divergence filed (if you turn it on for display, you'll see that). So Divergence is driving the expansion, which in turn pushes the velocity field and forms a pressure front ahead of the explosion because of the Project Non-Divergent step that assumes the gas is incompressible across the timestep, that is where where divergence is 0. I'm going to get the resize field thingy out of the way first as that is minor to the issue but necessary to understand. Resizing Fields Yes, if you have a huge explosion with massive velocities driven by a rapidly expanding divergence field, you could have velocities of 40 Houdini units per second or higher! Turning off the Gas Resize will force the entire container to evaluate which is slow but may be necessary in some rare cases, but I don't buy that. What you can do is, while watching your vel and divergence fields in the viewport, adjust the Padding parameter in the Bounds field high enough to keep ahead of the velocity front as that is where you hope for some nice disturbance, turbulence and confinement to stir around the leading edge of the explosion. or... Use several fields to help drive the resizing of the containers. Repeat: Use multiple fields to control the resizing of your sim containers. Yep, even though it says "Reference Field" and the docs say "Fluid field..", you can list as many fields in this parameter field that you want to help in the resizing. In case you didn't know. Diving in to the Resize Container DOP, there is a SOP Solver that contains the resizing logic that constructs a temporary field called "ResizeField", importing the fields (by expanded string name from the simulation object which is why vector fields work) with a ForEach SOP, each field in turn, then does a volume bound with the Volume Bounds SOP on all the fields together using the Field Cutoff parameter. Yes there is a bit of an overhead in evaluating these fields for resizing, but it is minor compared to having no resizing at all, at least for the first few frames where all the action and sub-stepping needs to happen. Default is density and why not, it's good for slower moving sims. Try using density and vel: "density vel". You need both as density will ensure that the container will at least bound your sources when they are added. Then vel will very quickly take over the resizing logic as it expands far more rapidly than any other field in the sim. Then use the Field Cutoff parameter to control the extent of the container. The default here is 0.005. This works for density as this field is really a glorified mask: either 0 or 1 and not often above 1. Once you bring the velocity field in to the mix, you need to adjust the Field Cutoff. Now that you have vel defined along side density, this Field Cutoff reads as 0.005 Houdini units per second wrt the vel field. Adjust Field Cutoff to suit. Start out at 0.01 and then go up or down. Larger values give you smaller, tighter containers. Lower values give you larger padding around the action. All depends on your sim, scale and velocities present. Just beware that if you start juicing the ambient shredding velocity with no Control Field (defaults to temperature with it's own threshold parameter so leave there) to values above the Field Cutoff threshold, your container will zip to full size and if you have Max Bounds off, you will promptly fill up your memory and after a few minutes of swapping death, Houdini will run out of memory and terminate. Just one of the things to keep in mind if you use vel as a resizing field. Not that I've personally done that... The Resolution Scale is useful to save on memory for very large simulations, which means you will be adjusting this for large simulations. The Gas Resize Field DOP creates a temporary field called ResizeBounds and the resolution scale sets this containers resolution compared to the reference fields. Remember from above that this parameter is driving the Volume Bound SOP's Bounding Value. Coarser values leads to blurred edges but that is usually a good thing here. Hope that clears things up with the container resizing thing. Try other fields for sims if they make sense but remember there is an overhead to process. For Pyro explosions, density and vel work ok. For combustion sims like fire, try density and temperature where buoyancy contributes a lot to the motion.