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matt

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About matt

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    Peon

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    http://mattebb.com

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  • Name
    Matt
  • Location
    Sydney, Australia
  1. Differential curve growth

    Just saw this thread - very cool stuff here! The laplacian growth mentioned earlier is actually pretty simple. Find the laplacian of a sdf (which emphasises high curvature 'pointy bits'), and advect along the volume gradient direction where the laplacian is higher. You can even get away with just adding a constant value to the sdf to push it out rather than doing a proper fancy advection. The trick is in fiddling around with processing fields to keep them smooth, and also adding in some fun custom stuff - eg. also multiply that displacement also by the dot product of the gradient and another vector field.
  2. Digging up an old thread here, this may be of interest http://mattebb.com/weblog/weighted-randomness-in-vex/
  3. Houdini 14 Wishlist

    Re. global vs separated node contexts: While I agree sometimes the diving in and out of multiple levels of subnetworks can become a chore, the one thing I really do like about Houdini is that the segmentation does in fact make some things simpler and more predictable. Unlike Maya where you can have any kind of data going between any kind of inconsistently named inputs and outputs, with Houdini I always know what is travelling through. For example in SOPs, I know that a node connection always represents a geometry stream, with a detail and a bunch of primitives and points (etc). In Maya there are so many different data types, inputs and outputs that you can't get as good a picture of what's going on in a network - you have to go in a lot more detail and examine exactly what data is going where. I know there's probably a whole spectrum of alternate possibilities for node network systems as well, but I just want to mention that sometimes forcing things to be simpler and consistent (even if it means a bit more segmentation) is not necessarily a bad thing.
  4. oh thanks! I should give it a more thorough look to see what the deal is there.
  5. Well if you'er talking about calculating the Mie function at render time, you may as well just precalculate some versions in an offline process (in mieplot or something) for a few different droplet sizes. I don't know the maths involved but I bet it's pretty complex - not the sort of thing I'd really want to code from scratch in a shadeop or something.
  6. no, I would have loved to have been there! henyey-greenstein is reasonably simple[1], perhaps a bit cheaper than to the cost (using this method) of a texture lookup? Probably not by much... To properly calculate the Mie function from scratch is very heavy though - it goes right back to first principles (distribution of droplet sizes) and runs the physics through that. AFAIK it can take something like mieplot on the order of hours to calculate the full 180 degrees.. [1] (1 - g*g) / pow(1 + g*g - 2*g*costheta, 1.5f);
  7. I did some work today converting simulated Mie phase function data [1] into a form usable for integration into a vop net shader - an exr file. This can be useful for rendering clouds, faithfully reproducing atmospheric optic effects like fogbows and glories. I've made a detailed writeup on my blog, and there's a demo on vimeo too: http://mattebb.com/weblog/rendering-clouds-with-the-mie-phase-function/ cheers [1] http://evasion.imag.fr/~Antoine.Bouthors/research/phd/thesis/tables/fitted_data_usage.html
  8. edge grouping supported on H12.1.30

    That's the best news of the 12.1 release Hopefully it does mean better edge support in 13, too.
  9. Spherical Harmonics in VOPs

    Thanks! Jesse: Yeah, took sweet time I know, but finally... eetu: There are lots of things it can be useful for - I saw the blog of a Maya char TD who was using SH to mix several different 0blend shapes based on the angle between bones. Anything that involves values that vary by angle! aghourab: Well, I understand the concepts but not really the detailed math The code is mostly this paper translated into VEX: http://www.cs.columbia.edu/~cs4162/slides/spherical-harmonic-lighting.pdf
  10. I've done a bit of experimenting, and implemented some VOPs which can be used to generate and evaluate spherical harmonics inside a VOP net. I've written up some info on what this is all about here: http://mattebb.com/weblog/spherical-harmonics-in-vops/ and you can download the OTL and a hip here: http://mattebb.com/projects/houdini/houdini_sh_otl_hipnc.v001.zip Or just check the video - hope it's understandable! I have ideas for some more more practical usage for these tools in mind, will update here if I can get time to do it!
  11. new color scheme ..

    What caught my eye in that screenshot is not the colours but the new big ramp parameter editor! One of my favourite additions in h12 - seriously!
  12. Silver necklace, 3D printed

    rapidprototype.com.au
  13. I recently used Houdini to model a necklace for my girlfriend's birthday. It's in a few pieces, which I got 3D printed and cast in sterling silver - I've done this once before in Houdini to make a ring, but wanted to try something different this time. The design is inspired by an islamic tile pattern we saw recently while travelling in Turkey, which I re-created procedurally, then randomly broke it up and distorted the parts. The final model was then brought into Blender for cleaning up the mesh, making it watertight, adding sprues for the casting process, and exporting to STL. I think it's really fun working this way - It's not purely generative or mathematical (which I find can easily get cliched, like obvious fractal patterns), but it's a bit like parameterising the visual design, so that there can still be an element of chance and unpredictability. the finished print: Some WIP shots: cheers
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