t file** - ply file with just x,y,z locations. I got it from a 3d scanner. Here is how first few lines of file looks like - ply format ascii 1.0 comment VCGLIB generated element vertex 6183 property float x property float y property float z end_header -32.3271 -43.9859 11.5124 -32.0631 -43.983 11.4945 12.9266 -44.4913 28.2031 13.1701 -44.4918 28.2568 13.4138 -44.4892 28.2531 13.6581 -44.4834 28.1941 13.9012 -44.4851 28.2684 ... ... ... In case you need the data - please email me on **nisha.m234@gmail.com**. **Algorithm:** I am trying to find principal curvatures for extracting the ridges and valleys. The steps I am following is: 1. Take a point x 2. Find its k nearest neighbors. I used k from 3 to 20. 3. average the k nearest neighbors => gives (_x, _y, _z) 4. compute covariance matrix 5. Now I take eigen values and eigen vectors of this covariance matrix 6. I get u, v and n here from eigen vectors. u is a vector corresponding to largest eigen value v corresponding to 2nd largest n is 3rd smallest vector corresponding to smallest eigen value 7. Then for transforming the point(x,y,z) I compute matrix T T = [ui ] [u ] [x - _x] [vi ] = [v ] x [y - _y] [ni ] [n ] [z - _z] 8. for each i of the k nearest neighbors:<br> [ n1 ] [u1*u1 u1*v1 v1*v1] [ a ]<br> [ n2 ] = [u2*u2 u2*v2 v2*v2] [ b ] <br> [... ] [ ... ... ... ] [ c ] <br> [ nk ] [uk*uk uk*vk vk*vk]<br> Solve this for a, b and c with least squares 9. this equations will give me a,b,c 10. now I compute eigen values of matrix [a b b a ] 11. This will give me 2 eigen values. one is Kmin and another Kmax. **My Problem:** The output is no where close to finding the correct Ridges and Valleys. I am totally Stuck and frustrated. I am not sure where exactly I am getting it wrong. I think the normal's are not computed correctly. But I am not sure. I am very new to graphics programming and so this maths, normals, shaders go way above my head. Any help will be appreciated. **PLEASE PLEASE HELP!!** **Resources:** I am using Visual Studio 2010 + Eigen Library + ANN Library. **Other Options used** I tried using MeshLab. I used ball pivoting triangles remeshing in MeshLab and then applied the polkadot3d shader. If correctly identifies the ridges and valleys. But I am not able to code it. **My Function:** //the function outputs to ply file void getEigen() { int nPts; // actual number of data points ANNpointArray dataPts; // data points ANNpoint queryPt; // query point ANNidxArray nnIdx;// near neighbor indices ANNdistArray dists; // near neighbor distances ANNkd_tree* kdTree; // search structure //for k = 25 and esp = 2, seems to got few ridges queryPt = annAllocPt(dim); // allocate query point dataPts = annAllocPts(maxPts, dim); // allocate data points nnIdx = new ANNidx[k]; // allocate near neigh indices dists = new ANNdist[k]; // allocate near neighbor dists nPts = 0; // read data points ifstream dataStream; dataStream.open(inputFile, ios::in);// open data file dataIn = &dataStream; ifstream queryStream; queryStream.open("input/query.
pts", ios::in);// open data file queryIn = &queryStream; while (nPts < maxPts && readPt(*dataIn, dataPts[nPts])) nPts++; kdTree = new ANNkd_tree( // build search structure dataPts, // the data points nPts, // number of points dim); // dimension of space while (readPt(*queryIn, queryPt)) // read query points { kdTree->annkSearch( // search queryPt, // query point k, // number of near neighbors nnIdx, // nearest neighbors (returned) dists, // distance (returned) eps); // error bound double x = queryPt[0]; double y = queryPt[1]; double z = queryPt[2]; double _x = 0.0; double _y = 0.0; double _z = 0.0; #pragma region Compute covariance matrix for (int i = 0; i < k; i++) { _x += dataPts[nnIdx[i]][0]; _y += dataPts[nnIdx[i]][1]; _z += dataPts[nnIdx[i]][2]; } _x = _x/k; _y = _y/k; _z = _z/k; double A[3][3] = {0,0,0,0,0,0,0,0,0}; for (int i = 0; i < k; i++) { double X = dataPts[nnIdx[i]][0]; double Y = dataPts[nnIdx[i]][1]; double Z = dataPts[nnIdx[i]][2]; A[0][0] += (X-_x) * (X-_x); A[0][1] += (X-_x) * (Y-_y); A[0][2] += (X-_x) * (Z-_z); A[1][0] += (Y-_y) * (X-_x); A[1][1] += (Y-_y) * (Y-_y); A[1][2] += (Y-_y) * (Z-_z); A[2][0] += (Z-_z) * (X-_x); A[2][1] += (Z-_z) * (Y-_y); A[2][2] += (Z-_z) * (Z-_z); } MatrixXd C(3,3); C <<A[0][0]/k, A[0][1]/k, A[0][2]/k, A[1][0]/k, A[1][1]/k, A[1][2]/k, A[2][0]/k, A[2][1]/k, A[2][2]/k; #pragma endregion EigenSolver<MatrixXd> es(C); MatrixXd Eval = es.eigenvalues().real().asDiagonal(); MatrixXd Evec = es.eigenvectors().real(); MatrixXd u,v,n; double a = Eval.row(0).col(0).value(); double b = Eval.row(1).col(1).value(); double c = Eval.row(2).col(2).value(); #pragma region SET U V N if(a>b && a>c) { u = Evec.row(0); if(b>c) { v = Eval.row(1); n = Eval.row(2);} else { v = Eval.row(2); n = Eval.row(1);} } else if(b>a && b>c) { u = Evec.row(1); if(a>c) { v = Eval.row(0); n = Eval.row(2);} else { v = Eval.row(2); n = Eval.row(0);} } else { u = Eval.row(2); if(a>b) { v = Eval.row(0); n = Eval.row(1);} else { v = Eval.row(1); n = Eval.row(0);} } #pragma endregion MatrixXd O(3,3); O <<u, v, n; MatrixXd UV(k,3); VectorXd N(k,1); for( int i=0; i<k; i++) { double x = dataPts[nnIdx[i]][0];; double y = dataPts[nnIdx[i]][1];; double z = dataPts[nnIdx[i]][2];; MatrixXd X(3,1); X << x-_x, y-_y, z-_z; MatrixXd T = O * X; double ui = T.row(0).col(0).value(); double vi = T.row(1).col(0).value(); double ni = T.row(2).col(0).value(); UV.row(i) << ui * ui, ui * vi, vi * vi; N.row(i) << ni; } Vector3d S = UV.colPivHouseholderQr().solve(N); MatrixXd II(2,2); II << S.row(0).value(), S.row(1).value(), S.row(1).value(), S.row(2).value(); EigenSolver<MatrixXd> es2(II); MatrixXd Eval2 = es2.eigenvalues().real().asDiagonal(); MatrixXd Evec2 = es2.eigenvectors().real(); double kmin, kmax; if(Eval2.row(0).col(0).value() < Eval2.row(1).col(1).value()) { kmin = Eval2.row(0).col(0).value(); kmax = Eval2.row(1).col(1).value(); } else { kmax = Eval2.row(0).col(0).value(); kmin = Eval2.row(1).col(1).value(); } double thresh = 0.0020078; if (kmin < thresh && kmax > thresh ) cout << x << " " << y << " " << z << " " << 255 << " " << 0 << " " << 0 << endl; else cout << x << " " << y << " " << z << " " << 255 << " " << 255 << " " << 255 << endl; } delete [] nnIdx; delete [] dists; delete kdTree; annClose(); } Thanks, NISHA…
bject of this edition focuses on the investigation of interactions between the environment and the human being, made through objects, mechanisms and architectures able to interact with who makes use of them. The aim of digitalMed IV is drawing a catalogue of projects/prototypes to insert them in an urban context, and to outline new future-cities profile.
PURPOSES AND TERMS:
The digitalMed Summer School IV edition aims to organize the flows of information, in which the city is absorbed, to adapt projects and to make them useful, no invasives, and suitable to establish an information exchange.
The concepts of slow cities and smart cities are directed by all types procedures, from immaterial to materia, from information to the built. This is the iter that we will follow to reinvent the relationship between man, environment and cities.
Through learning by-doing educational procedure, participants will acquire not only new metodologies and means, but also concrete cases where testing these ones. In this way, new acquired information won’t remain simple educational exercises, but will be notable elements in the portfolio participants.
TOPICS:
The planning approach of digitalMed Summer School IV edition will supply to participants all the technic knowledges and theoretical bases in order to work.
The first days of workshop will focus on the outline of a shared vocabulary that allows to work from shared meanings. This phase is characterized by subjects occurring in the contemporary architecture such as computational design, digital fabrication and data driven, then systems, like Arduino, which allow the interaction with objects, and fields like permaculture and social innovation that nowadays contribute to the realignment of environment and city’ ideas.
The participants will have the opportunity to learn the use of software for the parametric planning, like Grasshopper, and to test interactions between real information and virtual data (and viceversa) through the use of Arduino.
PREREQUISITES:
The workshop is open both to the students and to the professionals. It needs a basic knowledge of Rhinoceros 3D program. All the participants have to bring their own laptop. The programs for installing will be communicated during the registration act.
HOW TO REGISTER:
To register to the Summer School DigitalMed 2013 you must send an e-mail to info@medaarch.com, with the object: “Iscrizione DIGITALMED2013”.
The mail has to contain:
Name; surname; profession; telephone; e-mail.
After the reception of the above-mentioned e-mail, the participants will be contacted by phone, as well as by e-mail, to be informed about payment methods
Registrations are to be construed when the payment will be effective.
DEADLINE: Registrations to the workshop close on July 19 h18:00.
INFO:
Organizational Segretary digitalMed IV
Dott.ssa Francesca Luciano
Web site: www.medaarch.com
e-mail: info@medaarch.com
tel : +39 392 5149075
fb: mediterranean Fab Lab
tw: @medfablab
…
ake a network of lines (i.e. a graph) and make a Plankton Mesh, from which you can use Cytoskeleton to make a solid mesh (and then smooth it with Weaverbird).
Works with ngons (polygons with 3 or more sides). Other examples I found only worked with tris and quads.
Works on open or closed surfaces
While these examples start with a surface, you could start with a network of lines and make a patch surface
This is meant for 2D networks/surfaces. I haven't attempted filling a 3D volume. My guess is this wouldn't work as it would require a non-manifold mesh that Plankton wouldn't handle.
Note similar results could be achieved with the following:
TSplines
MeshDual (dual of a tri mesh, not as much freedom/control)
Working backwards, here is the GhPython script from Will Pearson that builds a Plankton Mesh from vertices and faces. The vertices are a list of 3D coordinates, the faces are a tree a lists, with each list containing the indices of vertices that form a closed loop. From Will, "Plankton only handles manifold meshes, i.e. meshes which have a front and a back. This orientation is determined by the "right-hand rule" i.e. if the vertices of a face are ordered counter-clockwise then the face normal will be out of the page/screen."
# V: list of Point3d # F: tree of int
import Grasshopper appdata = Grasshopper.Folders.DefaultAssemblyFolder
import clr clr.AddReferenceToFileAndPath(appdata + "Plankton.dll")
import Plankton
pmesh = Plankton.PlanktonMesh()
for pt in V: pmesh.Vertices.Add(pt.X, pt.Y, pt.Z)
for face in F.Branches: face = list(face)[:-1] pmesh.Faces.AddFace(face)
These vertices and faces are precisely the output from Starling. Starling takes in a list of Polylines which form the (properly oriented) face loops.
The polyline face loops can be generated...
Directly from Panels on a surface using LunchBox
Using any network of lines/curves on a surface (curves will need to be converted to polylines before Starling)
The latter was achieved using the Surface Split command, then converting the face edges (converted to curves) into polyline loops to represent faces.
…
onstrates the following:
1. The definition's functionality employing HumanUI for the custom user interface.
2. Color based segmentation in manual and auto modes.
3. The evaluation of the definition's ability to handle different point cloud data sets.
This definition performs color based segmentation in two modes.
A manual mode, that implements the Delta-E CIE 2000 color difference formula, for targeted feature detection. An auto mode, that employs a simple RGB Color Range algorithm for quicker preliminary results.
RGB to XYZ to CIELab conversion and Delta-E scripts were based on Colormine's project code from github. Results have been compared and verified with the results of http://colormine.org/color-converter and http://colormine.org/delta-e-calculator/Cie2000.
Each stored class is charted and can be accessed through the UI, as shown at 2:30, where Delta-E CIE 2000, in CieLab color space, output results were found to be in perceptive conformity with human eyes, far superior to the preliminary RGB implementation.
Initial definition versions could process highly subsampled clouds in acceptable timings. Further research showed that employing the multithread processing of Volvox components, bundling the Delta E formula with the RGB to CIE lab color conversion script, per color segmentation calculations for a one million points point cloud would go down from 23 (c# script component) and 8 (vb script component) seconds to approx. 1 second (volvox script cloud component), thus allowing the segmentation of less subsampled point clouds.
I would like to thank Heumann A. and Zwierzycki M. who provided direct support with HumanUI and Volvox. Also Grasshopper3d forum users Maher S. and Segeren P., who contributed with Rhino viewport manipulation scripts.
More on Volvox:
http://papers.cumincad.org/cgi-bin/works/Show?_id=ecaade2016_171&sort=DEFAULT&search=ecaade%20volvox&hits=2629
http://www.food4rhino.com/app/volvox
http://duraark.eu/
HumanUI:
http://www.food4rhino.com/app/human-ui?page=1&ufh=&etx=
ColorMine:
https://github.com/THEjoezack/ColorMine…
ns about them.
It's a direction for Kangaroo I very much intend to continue developing - and I am still getting to grips with the possibilities and experimenting with how different optimization and fairing forces work in combination with one another, so I would value your input and experience.
For those interested in some background reading material -
[1] http://www.cs.caltech.edu/~mmeyer/Research/FairMesh/implicitFairing.pdf
[2] http://mesh.brown.edu/taubin/pdfs/taubin-eg00star.pdf
[3] http://www.pmp-book.org/download/slides/Smoothing.pdf
[4] http://graphics.stanford.edu/courses/cs468-05-fall/slides/daniel_willmore_flow_fall_05.pdf
[5] http://www.evolute.at/technology/scientific-publications.html
[6] http://www.math.tu-berlin.de/~bobenko/recentpapers.html
[7] http://spacesymmetrystructure.wordpress.com/2011/05/18/pseudo-physical-materials/
[8] http://www.evolute.at/technology/scientific-publications/34.html
[9] http://www.evolute.at/software/forum/topic.html?id=18
At the moment the Laplacian smoothing is uniformly weighted, which tends to even out the edge lengths as well as smoothing the form, which is sometimes desirable, and sometimes not. It also tends to significantly shrink meshes when the edges are not fixed.
I plan to try some of the other weighting possibilities, such as Fujiwara or cotangent weighting (see [1] and [3]), as well as other fairing approaches, such as Taubin smoothing [2], Willmore flow[4], and so on. This also has applications in the simulation of bending of thin shells.
Planar quad panels are often desirable, but I'm finding that planarization forces alone are sometimes unstable, or cause undesirable crumpling, so need to be combined with some sort of fairing/smoothing, but the different types have quite different effects, and the balance is sometimes tricky.
There's also the whole issue of meshes which are circular (I posted a demo of circularization on the examples page), or conical (this one still isn't working quite right yet), and their relationship with principal curvature grids and placement of irregular vertices, all of which is rather different when the whole form is up for change, rather than having a fixed target surface [7].
I'm also trying to get to grips with ways of making surfaces of planar hexagons, which need to become concave in regions of negative Gaussian curvature (see this discussion)
and I hope to release soon a component for calculating CP meshes, as described in [8], which I think could have many exciting construction implications.
While there are a number of well developed smoothing algorithms, their main area of application so far seems to be in processing and improving 3D scan data, so using them in design in this way is somewhat new territory. There can be structural, fabrication or performance reasons for certain types of smoothness, but of course the aesthetic reasons are also often important, and I think there are some interesting discussions to be had here about the aesthetics of smoothness.
Anyway, that's enough rambling from me, hopefully something there triggers some discussion - I'm really keen to hear about how all of you envision these tools might be used and developed.
…
g-in, brief theory of complex systems, introduction to multi-agent systems and non-linear design, flocking, Boid library, basic examples - brownian motion, adhesion, separation, alignment, geometry following.-----------------------TIME: first session10am – GMT, London11am – Paris, Brussels, Rome, Vienna, Budapest, Bratislava, Warsaw9pm - Sidney7pm – Tokyo6pm – Beijing, Shanghai, Shenzhen, Hong Kong, Taipei3:30pm – Mumbai3pm – Karachi2pm - Samara1pm – Baghdad, Moscow, St Petersburg12pm – Istanbul, Athens, Helsinki, Cairo, JohannesburgTIME: second session3pm – GMT, London4pm – Paris, Brussels, Rome, Vienna, Budapest, Bratislava, Warsaw7pm – Dubai, Abu Dhabi, Baku6:30pm – Tehran6pm – Baghdad, Moscow, St Petersburg5pm – Istanbul, Athens, Helsinki, Cairo, Johannesburg1pm – Rio de Janeiro, São Paulo, Montevideo12pm – Buenos Aires, Santiago10am – Toronto, New York City, Bogota, Lima9am – Mexico City7am – Los AngelesWEBINARSThe rese arch Grasshopper® sessions are unique for their thorough explanation of all the features, which creates a sound foundation for your further individual development or direct use in the practice. The webinars are divided into four groups: Essential, Advanced, Iterative and Architectural. If you are a Rhinoceros 3D or Grasshopper® newcomer, you are advised to take all the Essential sessions before proceeding to the next level. If none of the proposed topics suit your needs or if you require special treatment, you can request a custom-tailored 1on1 session. All sessions are held entirely in English.The webinars are series of on-line live courses for people all over the world. The tutor broadcasts the screen of his computer along with his voice to the connected spectators who can ask questions and comment in real time. This makes webinars similar to live workshops and superior to tutorials.…
Added by Jan Pernecky at 3:36pm on February 17, 2015
instead of ballooning outwards, just puffing upwards.
THIS WILL WORK! Creating the mesh springs is only three seconds for 200X200 and the Unary Force is still milliseconds. Only Kangaroo takes an initiation time then cycles rapidly (0.5 seconds each) and it only takes a few cycles, maybe a dozen or two.
There is considerable 3D aliasing from the 2D mesh crudeness.
Now, to best Laurent's scheme, let's double down to 400X400. First I disable Kangaroo, and the timer. The preparation takes...FOREVER....and...ever...4.6 minutes to cull the points is all, a trivial step there is likely a better strategy for than finding the ones on the inside then using those to cull duplicates from the whole collection. The springs only took 12 seconds and the forces again milliseconds.
Kangaroo, to initialize takes...after hitting the reset button to start it...over 15 minutes and counting...well 400X400 is 160K vertices and Rhino tends to bog down at 30K points...but it was done in 30 minutes. Then I enable the timer and each cycle takes...uh...it's not in any error mode but nothing is happening past a very faint first automatic cycle that shows in the mesh...yet no CPU power is being used by Rhino...well...it's simply not running...ah, well, there's just a dummy delay of another 5 minutes and then the cycles take 2.7 seconds...what a stupid delay that was not using CPU power.
Now that it's cycling, can I change the stiffness in real time, usually I can...well, no, I seem to be back in the 5 minute delay, but not the 30 minutes interface-locking one...still waiting. Here is a 1/4 scale height model of the above output:
Time's up, life goes on. The aliasing and slow speed make it unworkable except for little logos or something. Some math and parallel processing are needed?
…
Added by Nik Willmore at 5:51pm on February 21, 2016
this was about some boring building I wouldn't respond ... but here we are talking sardines.
Here's my take on that matter:
1. The 4 C# first create/use a nurbs, then define some random planes (and transformations) and then (a) either they place some humble stripes or ... er ... (b) sardines as instance definitions (NOTE: Load Rhino file first).
2. All important decisions are the ones in yellow groups.
3. You control what you get via this (priority on stripes or sardines? that's the 1M Q):
4. If you decide for sardines (the right thing to do) then you must ENABLE the Sardiniser(C)(tm)(US patent pending) as follows:
5. The vodkaFactor on that Sardiniser C# adds some spice in the sardine placement (it does that by altering the priority on the "composite" transformation in use: first randomly rotate then planeToPlane .... or the other thing?).
6. Only the finest Da Morgada sardines are used in this definition:
7. Spot the WARNING in the filter related with what sardine to choose > do it wrong and no hard disk on your workstation > no risk no fun > sorry Amigos, he he.
8. 1M question for you all: why placing sardines (it's real-time you know) is WAY faster than creating these humble stripes?
9. Although the sardines are placed in real time as regards your CPU ... the critical factor is your GPU (display mode: rendered).
10.Still WIP (dancing sardines in the next update).
have some sardine fun, best, Lord of SardineLand…
r ideal surface so they add up where lots of points or lines cluster and create rather unintuitive bulges form a 3D modeler's perspective, here done with Millipede's Geometry Wrapper:
I've learned to do marching tetrahedra or cubes in Python to create the surface as needed from a implicit ( f(x,y,z) = 0 ) mathematical equation based on raw trigonometry but am not yet sure how to define an equation for Rhino user created input items like this or find a way to make marching cubes accept such input let alone one that doesn't treat each geometry item as an electric charge with so little decay.
This would afford an old school "organic" modeling paradigm that T-Splines replaced, but the T-Spines pipe command can't do nearby lines right either, which just makes overlapping junk. Metaballs and lines are not as elegant in that there is a real "dumb clay" aspect to the result that affords little natural structure beyond just smoothing, but still, if it works at all that beats T-Splines, and then I can feed the crude mesh result into Kangaroo MeshMachine to afford surface tension relaxation that will add elegant form to it.
I need both quick hacks and some help on how to deeply approach the mathematics of the required isosurface, now that I can think in Python better than ever.
I got a hint the other day here, about using a different power of fall-off but am not sure how to do the overall task mathematically:
"and just as with point based potentials, one can use different power laws for the distance, function, resulting it different amounts of rounding at the junctions. Below is with a 1/d^3 law for comparision with the above 1/d" - Daniel Piker
http://www.grasshopper3d.com/forum/topics/meshes?commentId=2985220%3AComment%3A1324050
He also included this link about bulging:
http://paulbourke.net/geometry/implicitsurf/
Am I supposed to create an actual implicit equation for my assigned points and lines and use that with marching cubes to surface it? If so, how do I define that equation, at all, and then how to control bulging too?
…
edit 29/04/14 - Here is a new collection of more than 80 example files, organized by category:
KangarooExamples.zip
This zip is the most up to date collection of examples at the moment, and collects t