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Fireandsmoke

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About Fireandsmoke

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  • Name
    JHeks
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    Sydney, Australia
  1. Vector maths basics

    But how would you define the direction of the green vector, because without the point of A as a reference, how are we to know by reading the green vectors coordinates that the origin is the tip of A?
  2. Vector maths basics

    I'm learning a bit about basic vector maths. I'm getting a bit confused by vector direction. My understanding thus far is that a vector will always get it's direction based on its relationship to origin (i.e. draw a line between 0,0 and x,y and that's your vector direction). But then I have seen some Houdini tutorials which talk about adding one vector to the tip of the other to get a vector which has a direction which is not based on its relationship to origin, but rather to the tip of the previous point. Is this possible, and if so how is this determined, given that a vector only has the coordinates of a single point in space? Example in my attached picture of A+B, where I was told that the result would be the green vector. Though based on my understanding of vectors I would have thought this would always result in the dotted blue line.
  3. Copy Stamping using the new ForEach workflow

    Thanks Andr1. This is a little different to what I was proposing which was to change the actual branching of each pattern, but is interesting nonetheless. I've been trying to decipher your hip, can you elaborate a little on what you are doing by isolating the back face and applying the pivot? I'm a bit lost getting that part. Thanks for providing that example. Thanks Toadstorm. I'm surprised by this, I would have thought it would be a common technique.. I suppose it is not a very efficient way of doing things.
  4. Copy Stamping using the new ForEach workflow

    Thanks David, nice video. I am familiar with those techniques for stamping static objects. Where it is not working for me is that I'm trying to copy solvers, and use the same technique to vary a seed which randomises the pattern of each trail. However for some reason, it doesnt work, all the trails still appear the same (see project file). Do you know why this may be? Also, I noticed in your vimeo comments you replied that you weren't sure whether for each loops are more efficient than stamping. I believe that whilst there may not be much gain just comparing to for each loops, the benefit comes from being able to use for each loops inside compile blocks, which are significantly faster. Jeff Wagner talks about it here at around the 45min mark:
  5. I'm following recommendations to avoid use of the copy stamp SOP. I have a trail effect which I've created with a solver sop which I want to copy to points on a grid, using a forEach and a CopytoPoints. But I want to vary the randomise seed of each of my trails so they appear different. How can I pass on an attribute with a unique value per point which will "stamp" the trail, allowing me to apply a unique seed to each copy? Thanks for the advice. polyextrude_solver_foreach.hiplc
  6. Rand value in Group Expression

    anim, thank you! Exactly that. I was watching the geo spreadsheet totally lost as to why the grouping wasn't moving beyond the first frame. So if I were to summarise this into a rule for my future self, Hscript expressions, which must be used in backticks to work in a VEX context, will always only return a single value. If it's not too low level to explain, why is this?
  7. Rand value in Group Expression

    Thanks guys. So what I am trying to achieve is quite simple in theory but not working for me so far, and I think I can see why... I start with a box, which I run into a solver. Inside the solver I have a very basic setup which takes the previous frame into a Group Expression which randomly selects one of the last four prims, and then a poly extrude to extrude that selected prim. So the effect should be that the end of the object grows a new extruded face each time, like a twisty branch growing. Displaying the primitive numbers, I think I can see why this isnt working. For some reason when the extrude is running through the solver, it shifts the primitive numbers around every iteration. Whereas if I were to take a box and extrude it a few times manually, all existing primitive numbers hold their original position, and 4 new numbers are created each time you extrude and create 4 new polys. Can anybody explain the logic of why this is happening inside the solver? Thanks! polyextrudesolver_project.hiplc
  8. Rand value in Group Expression

    Thanks bhouse will give this a try tonight. Regarding the backticks, symeks post just mentions backticks need to be used when writing expressions in fields which expect hscript. This is Vex input so does this also apply as a blanket rule in Vex? Symek has confused me a bit, he categorises those expressions like npoints () as being different to Hscript, Ive always thought of those expressions as being Hscript expressions.
  9. Using a Group Expression SOP I can find the last prim of my geo with @primnum==`nprims(0)`-1 If I want that selection to change randomly between, say the last 4 prims, why does the following not work: @primnum==`nprims(0)`-rand(@Frame)*4 Also, is the reason I require backticks for the nprims expression above because it is a hscript expression in a VEX context? Thanks
  10. Render Cd in Packed prims

    Thank you kindly!
  11. I have a grid with random coloured points, copy a bunch of cubes onto it using a copy to points and select "pack and instance". Why do all the cubes inherit the Cd and show it in the view port, yet when I render, they do not show Cd? How can I get around this? Thanks
  12. Hi, I've been struggling to work this out for hours, wondering if somebody can put me out of my misery and give me some direction. I basically have created a simple solver setup which grows a wiggly line using an Add and randomly transforming the position of the last point on the line. I'm trying to copy this wiggly line to points using a Copy to Points and For Each loop, but can not work out how to get the randomness of the line be different for every copy. I thought maybe I could create an attribute based on the iteration value which could be used as a seed, but it's not working for me. Would really love some input on this, Thanks a lot, much appreciated Growingline_Solver.hiplc
  13. Alembic geo not working with Boolean

    It was the conversion to poly that I was missing, thanks so much.
  14. That has worked, thanks very much!
  15. I'm playing with this volumetric video capture (a mesh I'm importing as an alembic file - download at the bottom of this page http://www.depthkit.tv/demodata/) I'm trying to create a layered outline effect intersecting a stack of grids with the model and using the Seam operation of the Boolean SOP, but none of the boolean functions work with this mesh at all. Are there rules as to what kind of files play nice with the boolean sop? I tired exporting the alembic as a .bgeo but same issue.. Cheers
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