i would use hair curves or ribbon geo trail to art direct the trail. if trail are straight i would then worldcenter the head of the trail for the pyro sim. and then inject density / speed created from trail in a sparse grid. trail ribbon going the after burn way is really old school in houdini. BUT if you really want that you need a cvex vollume shader that pcopen per point attribute at rendertime. this might be useful to achieve what you want : https://www.orbolt.com/asset/SideFX::pointcloudvolume

i would try to feed the render engine directly without doing any intermediate step inside maya. if you use arnold render, i recommand per frame alembic sequence and direct load with the arnold stand-in for geo, points, curves. https://docs.arnoldrenderer.com/display/A5AFMUG/An+Introduction+to+Stand-ins and arnold volume for vdb loading. https://docs.arnoldrenderer.com/display/A5AFMUG/Volume

a small exemple that might be useful with it. extrude.hiplc

Great stuff Vince i didn't know this tool exist , very interesting especially the zRemesher + Blendshape connection.

ahah great guys ! whisky it is ! for quad remeshing algo , the best imo is zbrush cause it give you the ability to draw topology guides directly from cv's. quad remesher from exoside is in second place. and i think this is the same guys that coded the two. at least in the early Zbrush release. but the big plus is that you can run it throw SOPs procedurally, and Zbrush can't match that.

ahah this exercices is really addictive ! i finally got something good enough , i have refactor a lot just polyexpand + quad remesher , i think you have enough to mimic the reference, the only part that need extra work is how you compute the displacement map, where you need to precisly evaluate edgedist instead of my old school att transfer. expand_remesh_003.hiplc

That's cool vince ! the hardest part would be to relax the edge loop in v direction in order to have a match topology between each patch for merge. Quad remesher is nice , it cost a litlle but it offer remeshing qulaity you can't match with vanillia houdini tool. I try to combine polyexpand + area isolation with voronoi + quad remesher. it's not bad , but the topology is not perfect like the reference. i really feel that poly is clunky for those kind of work, i really prefer nurbs for that kind of stuff. for exemple just the clean flat topology is hard to get, and we haven't even talk about beveling between each torus. I'm curious to see if some modeling expert can come with a fully working solution. Cheers expand_remesh.hiplc

Polyexpand is also interesting but not perfect. this question is a good rubik's cube for the brain I would probably go for a polyexpand + quad remesher path, but this problem need some love if you really want to get a clean edgeflow polyexpand.hipl c

for a houdini workflow, i think that working on a flat shell, where you focus on your flat torus shell, that you merge and cut, would be the first part, then you create your hard edge group and try to keep clean Cd for each torus, you send it to quad remesher with edge and Cd constrain. i don't see how you could procedurally generate a clean topo shell without quad remesher ? remesh / labs instant mesh / vdb convert / height field convert none of them will give you clean quad flow. i would also try to create 2 types of flat guiding cv's corresponding to the edge loop of the higher part of the roof and also the doors entry then i would deform those 2 curves as main controler guide of the form and compute the deformation of the flat shell according to their position from the guided cv's in vex or with deformers. EDIT: even quadremesher doesn't sound good enough to get very precise and accurate flat topo polyexpand 2d might be a good idea in that regard. deform_02.hiplc you can be very close to your ref, but imo where houdini will suck is for the fillet tool , when you use a nurbs modeler, the intersect function of a nurbs modeler, then curves fillet at intersection will be very hard to replicate. and often what create the beauty of those models , is the clean mathematical fillet patch between two shapes. i am not sure you will get those nice fillet interp and holes between shapes easily.

vdb smooth is the best i see at the moment Volume_Deform.hiplc

For an exotic approach i would definitly give heightfield a try, with half-torus gradient influence convert as heightmap. then curvature analysis mask and blend mask. You could also height project a reference half-poly torus then merge them with heightfield tools. you can then convert to vdb , or convert to poly with booleans for holes. for the clean poly like topology across the roof i would give a try with quad remesher on the very dense geo generated from heightfield / vdb with colors per torus and color vertex guided topology. heightfield.hiplc

i don't know if it helps , i guess not cause my setup is very trivial, but for those kind of fx where you need fire propagation, i would art direct all the whole setup in SOP using points and just release the whole art directed point cloud into pyro solve. more precisly i would convert all the scene that need to be burn to point cloud, then connect each point with an edge thanks to adjacent pieces nodes, then use the edge transport connected to a trigger group that would evolve dynamically. fire_test.hipnc

For those who have the time to investigate i agree with antoine that meshlab would give the best toolset for the job, and even more. cause it can be use in command line, it work under windows or linux env, and function can be call in python inside houdini. compute_normal_for_point_clouds https://pymeshlab.readthedocs.io/en/latest/filter_list.html?highlight=point normal#compute_normal_for_point_clouds generate_surface_reconstruction_screened_poisson https://pymeshlab.readthedocs.io/en/latest/filter_list.html?highlight=poisson#generate_surface_reconstruction_screened_poisson

with the command line tool PoissonRecon from my link i get the following result. the utility is pretty straightforward, and can be call directly from houdini like the Labs tools. surfacing.zip

i don't think that you have a default tool for surface reconstruction from a point cloud. If you really need accurate result you need to check Poisson surface reconstruction algorithm. https://hhoppe.com/poissonrecon.pdf Implementing this in vex might be hard and slow there is a thread that talk about this : I would find a good binary executable that do poisson surface reconstruction, and that can be call with a command line , then link it to houdini by taking exemple of what they do in the Labs Instant Meshes nodes. https://www.cs.jhu.edu/~misha/Code/PoissonRecon/Version13.72/#EXECUTABLES there is also a Labs AliceVision Meshing nodes , that might be interesting to check before , cause it might be able to already do this. i have never try it.