How are the control points connected in a NURBS surface? - maya
I'm trying to learn how to deal with NURBS surfaces for a project. Basically I wan't to build a geometry in some 3D program with NURBS, then export the geometry, and run some simulations with it. I have figured out the NURBS curve, and I do think I mostly understand how surfaces work, but what I don't get is how the control points are connected. Apparently you don't need any topology matrix as with polygons? When I export NURBS surfaces from Maya, in the file format .ma, which is plain text file, I can see the knot vectors, and then just a list of points. No topology information. How does this work? How can you reconstruct the NURBS surface without knowing how the points are connected to each other? The exported file is written below:
//Maya ASCII 2013 scene
//Name: test4.ma
//Last modified: Sat, Jan 26, 2013 07:21:36 PM
//Codeset: UTF-8
requires maya "2013";
requires "stereoCamera" "10.0";
currentUnit -l centimeter -a degree -t film;
fileInfo "application" "maya";
fileInfo "product" "Maya 2013";
fileInfo "version" "2013 x64";
fileInfo "cutIdentifier" "201207040330-835994";
fileInfo "osv" "Mac OS X 10.8.2";
fileInfo "license" "student";
createNode transform -n "loftedSurface1";
setAttr ".t" -type "double3" -0.68884794895562784 0 -3.8172687581953233 ;
createNode nurbsSurface -n "loftedSurfaceShape1" -p "loftedSurface1";
setAttr -k off ".v";
setAttr ".vir" yes;
setAttr ".vif" yes;
setAttr ".covm[0]" 0 1 1;
setAttr ".cdvm[0]" 0 1 1;
setAttr ".dvu" 0;
setAttr ".dvv" 0;
setAttr ".cpr" 4;
setAttr ".cps" 4;
setAttr ".cc" -type "nurbsSurface"
3 3 0 0 no
8 0 0 0 1 2 3 3 3
11 0 0 0 1 2 3 4 5 6 6 6
54
0.032814107781307778 -0.01084889661073064 -2.5450696958149557
0.032814107781308312 -0.010848896610730773 -1.6967131305433036
0.032824475105651972 -0.010848896610730714 -0.0016892641735144487
0.032777822146102309 -0.01084889661073018 2.5509821204222565
0.032948882997777158 -0.010848896610730326 5.3256822304677218
0.032311292550627417 -0.010848896610730283 7.5033561343333179
0.034690593487551526 -0.010848896610730296 11.39484483093603
0.014785648001686571 -0.010848896610730293 11.972583607988943
-0.00012526283089935193 -0.010848896610730293 12.513351622510489
0.87607723187763198 -0.023973071493875439 -2.5450696958149557
0.87607723187766595 -0.023973071493876091 -1.6967131305433036
0.87636198619878247 -0.023973071493875821 0.00026157734839016289
0.87508059175355446 -0.023973071493873142 2.5441541750955903
0.87977903805225144 -0.023973071493873861 5.3510431702524812
0.86226664730269065 -0.02397307149387367 7.4087403205209448
0.9276177640022375 -0.023973071493873725 11.747947146400762
0.39164345444212556 -0.023973071493873704 12.72679599298271
-0.003344290659457324 -0.023973071493873708 13.356608602511475
2.7585407036097025 0.080696275184513055 -2.5450696958149557
2.7979735813230628 0.036005680442686323 -1.6988092981025378
2.7828331201271896 0.05438167150027777 0.0049374879309111996
2.6143679292284574 0.23983328019207673 2.5309327393956176
2.67593270347135 0.19013709747074492 5.3992530024698517
2.5981387973985108 0.20347021966427298 7.2291224273514345
2.8477496474469728 0.19983391361149261 12.418208886861429
1.1034136098865515 0.20064198162322153 14.474560637904968
-0.010126299867110311 0.20064198162322155 15.133224682698101
4.5214126649737496 0.45953483463333544 -2.5450696958149557
4.6561826938778452 0.23941045408996731 -1.7369291398229287
4.6267725925384751 0.29043329565744253 0.025561242784985394
3.9504978751410711 1.3815767918640129 2.5159293599869446
4.1596851721552888 1.0891788615080038 5.438642765250469
3.9992107014958198 1.1676270867254697 7.0865667556376426
4.4319212871194775 1.1462321162116154 12.949041810935984
1.6384310220676352 1.1509865541035829 15.927795222282771
-0.015643773215464073 1.1509865541035829 16.578582772395933
5.2193823159440154 3.0233786192453191 -2.5450696958149557
5.2193823159440162 3.0233786192453196 -1.6967131305433036
5.2218229691816047 3.0233786192453191 0.0091618497226043649
5.2108400296124504 3.0233786192453196 2.5130032217858407
5.251110808032692 3.0233786192453191 5.4667467111172652
5.1010106339208772 3.0233786192453191 6.9770771103715621
5.6611405519478906 3.0233786192453205 13.358896446133507
2.0430537629341199 3.0233786192453183 17.059047057656215
-0.019924192630756767 3.0233786192453191 17.6998820408444
5.1365144716134976 5.4897102753589557 -2.5450696958149557
5.1365144716134994 5.4897102753589566 -1.6967131305433036
5.1389093836131625 5.4897102753589566 0.0089946049919694682
5.1281322796146718 5.4897102753589566 2.5135885783430627
5.1676483276091361 5.4897102753589548 5.4645725296190131
5.0203612396297714 5.4897102753589566 6.9851884798073476
5.5699935435527692 5.4897102753589566 13.328625149888618
2.0133428487217855 5.4897102753589557 16.975388787391935
-0.01960785732642523 5.4897102753589557 17.617014800296868
;
select -ne :time1;
setAttr ".o" 1;
setAttr ".unw" 1;
select -ne :renderPartition;
setAttr -s 2 ".st";
select -ne :initialShadingGroup;
setAttr ".ro" yes;
select -ne :initialParticleSE;
setAttr ".ro" yes;
select -ne :defaultShaderList1;
setAttr -s 2 ".s";
select -ne :postProcessList1;
setAttr -s 2 ".p";
select -ne :defaultRenderingList1;
select -ne :renderGlobalsList1;
select -ne :hardwareRenderGlobals;
setAttr ".ctrs" 256;
setAttr ".btrs" 512;
select -ne :defaultHardwareRenderGlobals;
setAttr ".fn" -type "string" "im";
setAttr ".res" -type "string" "ntsc_4d 646 485 1.333";
select -ne :ikSystem;
setAttr -s 4 ".sol";
connectAttr "loftedSurfaceShape1.iog" ":initialShadingGroup.dsm" -na;
// End of test4.ma
A NURBS surface is allays topologically square with points of degree+spans in u direction and (degree-1)+spans+1* in v direction. (a single NURBS surface is like one face of a polygon only more complicated)
The first 2 attributes in ".cc" are the degree in direction, and the next two lines define the knots each individual value represents a span. Duplicates are just weights so the point is repeated x times so:
8 0 0 0 1 2 3 3 3
Means there 8 knots (in this case in U direction) with 0 1 2 3 spans for a total of 6 points so it's a single span curve of third degree in U direction. The example has 9 points in V direction thus 7*9 = 54 points in total
This is not enough however, for NURBS to be even remotely useful. You must implement trim curves which are curves that lay on the UV parametrization of the surface and they can clip the individual NURBS to different shape.
In practice however maya users rely on manual quilting. Quilts** are the higher order NURBS equivalent of a mesh, that most nurbs modelers use as a concept. To handle these its often not enough to have even the trim curves. As trim curves cannot be reliably transported between applications, without sewing. Thus many applications rely on actually telling what the spatial history of said surface to surface quilt collections topographical connection is. So be prepared to make your own intersection algorithms etc., etc., for any meaningful NURBS compatibility.
For more on the mathematical underpinning info see Wikipedia, wolfram etc.
* If I remember correctly something like that.
** Quilts have different names in different applications due to simultaneous discovery on in several different language areas.
NURBS surfaces' CVs are always laid out in a grid. The number of CVs in a nurbs surface can be computed using the degree of the surface and the number of knots in each direction. Then the CVs are just presented in some specific order, typically row-major.
Let's look at your example. I'm mostly just guessing the format, so you'll want to check my assumptions.
3 3 0 0 no
It looks like you have a bicubic surface. It's not periodic in either direction (that is, you have a sheet rather than a cylinder or torus). Your CVs are non-rational, meaning they're [x,y,z] instead of [xw,yw,zw,w].
In other words, the format of that first line appears to be:
[degree in s] [degree in t] [periodic in s] [periodic in t] [rational]
Next up, one knot vector has 8 knot values, and the other has 11. For a degree 3 non-periodic nurbs, the number of CVs is num_knots - 2. So, you have 6 x 9 CVs in this surface.
The first 6 CVs are in the first row. The next 6 are in the next row, etc.
If you're looking for more information on NURBS, I'd recommend this text for theory. For maya specific stuff, they have some decent documentation in the maya API.
Related
How can I read a string from PDF file in C?
I want to create a program that process the edit distance from two file, My code works with strings read from a txt file. But now I want to read strings from PDF DOC exc. How can I read strings from this files? I tryed with the func fread but it not works.
This is the code that i wrote:
void method () {
FILE *file;
char *str;
if ((file = fopen("C:/Users/latin/Desktop/prova.pdf", "rb")) == NULL) {
printf("Error!\n");
}
fread(&str,18,1,file);
printf("%s",str);
}
prova.pdf is a PDF file that contains this string : ciaoCiao merendina .
It is possible to do this in plain C. Adobe did it. Artifex did it. Others have done it. But as commented, it is a ton of work. But I can outline the steps to give you a feel for what's involved. First you could read the "Magic Number" at the start and check that it is actually a PDF. It should start with %PDF- followed by a version number. But apparently many PDF producers don't conform to this requirement. Next, you need to skip to the very end of the file and read backwards, looking for something like: startxref 1581 %%EOF That number is the byte-offset of the start of the X-Reference table which lists the binary offsets of all the "objects" in the file. An object can be a Page or a Font or a Content Stream or many other things. Looking at the X-Reference table, you'll see something like this: xref 0 4 0000000000 65535 f 0000000010 00000 n 0000000063 00000 n 0000000127 00000 n 0000000234 00000 n trailer << /Root 1 0 R /Size 4 >> The line /Root 1 0 R tells you which object is the root of the document tree. You'll need to examine this object to find the top-level Pages object which looks like this: 2 0 obj << /Kids [ 3 0 R ] /Type /Pages /Count 1 >> endobj The Kids element here contains a reference to the first Page object which looks like this: 3 0 obj << /Contents [ 4 0 R ] /MediaBox [ 0.0 0.0 612.0 792.0 ] /Type /Page /Parent 2 0 R >> endobj Then you'll need to find the Contents object referenced here. A Content stream, if it's not encrypted or compressed, will show you the drawing commands and text commands being drawn to the page. 5 0 obj << /Length 15660 >> stream BT F1 10.0 Tf 30.0 750.0 Td (<< ) Tj ET BT F1 10.0 Tf 50.0 738.0 Td (/) Tj ET BT F1 10.0 Tf 56.0586 738.0 Td (astring) Tj ET BT F1 10.0 Tf 86.7852 738.0 Td ( ) Tj ET BT F1 10.0 Tf 89.2852 738.0 Td (\() Tj ET BT F1 10.0 Tf 92.6133 738.0 Td (this string data) Tj ET [...lots more commands follow...] endstream endobj Text commands will always be bracketed by BT ... ET. In here, you can finally see the strings wrapped in parens. But you'll have to pay attention to the coordinates 30.0 750.0 Td of each string to figure out which ones are part of the same logical line. If the PDF was created from a word processor, it is likely to contain text in this form but with lots of caveats. It might have re-encoded fonts and the text strings will no longer represent ASCII characters but just positions in the font's encoding vector. If the PDF was created from a scanned document, it may just contain images of the pages with no text content at all unless it has gone through a conversion involving OCR.
Filter rows of files conditional on multiple arrays values
I have a number of files (N>1000) with qtl summary data e.g. lets assume the first file is made of six lines (in reality they are all GWAs/imputed files with >10M SNPs)
cat QTL.1.txt
Chr Rs BP beta se pvalue
11 rs11224233 134945522 0.150216 0.736939 0.962375
11 rs4616056 134945709 0.129518 0.371824 0.910326
11 rs11823417 134945710 0.103462 0.41737 0.845826
11 rs80294507 134945765 0.150336 0.735363 0.961403
11 rs61907173 134946034 0.104531 0.158224 0.884548
11 rs147621717 134946277 0.105365 0.196168 0.86476
I would like to filter each of these datasets based on chromosome and positions of a list of genes (my list has 100 genes but now lest assume it has 2); therefore creating N_QTL*N_Genes files. I would like to go through each gene/position for each QTL. The Chromosome, positions and name of the genes are stored in four arrays and I would like to read iteratively these arrays and save the output for each qtl file for each gene.
What I have done so far doesnt work and I know awk is not the best way to do this:
declare -a array1
declare -a array2
declare -a array3
declare -a array4
array1=(11 11) #chromosome
array2=(134945709 134945765) #start gene position
array3=(134946034 134946277) #end gene position
array4=(A B) # gene name
for qtl in 1; do # in reality it would be for qtl in 1 1000
for ((i=0; i<${#array1[#]}; i++)); do
cat QTL.$qtl.txt | awk '$1=='array1[$i]' && $3>='array2[$i]' &&
$3<='array3[$i]' {print$0}' > Gene.${array4[$i]}_QTL.$qtl.txt;
done;
done
within awk $1 is the chromosome and $3 the position- so therefore filtering based on these.
So my expected output for QTL.1.txt for Gene A would be
cat Gene.A_QTL.1.txt
Chr Rs BP beta se pvalue
11 rs4616056 134945709 0.129518 0.371824 0.910326
11 rs11823417 134945710 0.103462 0.41737 0.845826
11 rs80294507 134945765 0.150336 0.735363 0.961403
11 rs61907173 134946034 0.104531 0.158224 0.884548
And for QTL.1.txt for Gene B would be
cat Gene.B_QTL.1.txt
Chr Rs BP beta se pvalue
11 rs80294507 134945765 0.150336 0.735363 0.961403
11 rs61907173 134946034 0.104531 0.158224 0.884548
11 rs147621717 134946277 0.105365 0.196168 0.86476
I end up with empty files as probably the way I ask these columns to be filtered based on the values of the arrays doesnt work.
Any help very much appreciated!
Thank you in advance
Mixing bash and awk for parsing files is not always the best way forward.
Here a solution with awk only.
Assume you have the information assigned to your bash array in a file:
$ cat info
11 134945765 154945765 Gene1
12 134945522 174945522 Gene2
You could use the following awk script to perform a lookup with the data file:
awk 'NR==FNR{
for(i=2;i<=NF;i++)
a[$1,i]=$i
next
}
a[$1,2]<=$3 && a[$1,3]>=$3{
print $0 > a[$1,4]"_QTL"
}' info QTL.1.txt
This will create a file with the following content:
$ cat Gene1_QTL
11 rs80294507 134945765 0.150336 0.735363 0.961403
11 rs61907173 134946034 0.104531 0.158224 0.884548
11 rs147621717 134946277 0.105365 0.196168 0.86476
Maybe not exactly what you're looking at, but yet I hope this is helpful...
You might want to do the following if multiple genes are located in the same chromosome (using gene name instead of chr as Key):
awk 'NR==FNR{
chr[$4]=$1;
start[$4]=$2;
end[$4]=$3;
}
NR!=FNR{
for (var in chr){
name=var"_"FILENAME;
if(chr[var]==$1 && start[var] <=$3 && end[var]>=$3){
print $0 > name;
}
}
}' info QTL
How to extract organized palette from image/video with FFMPEG+Imagemagick?
I use FFMPEG and Imagemagick to extract the color palette from an image or video with a Windows batch file, :: get current folder name for %%* in (.) do set CurrDirName=%%~nx* :: get current filename for /R %1 %%f in (.) do ( set CurrFileName=%%~nf ) ffmpeg -i "%1" -vf palettegen "_%CurrFileName%_temp_palette.png" convert "_%CurrFileName%_temp_palette.png" -filter point -resize 4200%% "_%CurrFileName%_palette.png" del "_%CurrFileName%_temp_palette.png" This outputs something like, I need this to have better transition throughout the color blocks though, like all blues from darkest to lightest then transitioning to greens, yellows etc. like, Is there a way/switch to create this with either Imagemagick/FFMPEG?
I don't like working on Windows, but I wanted to show you a technique you could use. I have therefore written it in bash but avoided nearly all Unix-y stuff and made it very simple. In order to run it on Windows, you would only need ImageMagick and awk and sort which you can get for Windows from here and here.
I'll demonstrate using an image of random data that the script creates on around the third line:
Here is the script. It is pretty well commented and should convert easily enough to Windows if you like what it does.
#!/bin/bash
# Create an initial image of random data 100x100
convert -size 100x100 xc:gray +noise random image.png
# Extract unique colours in image and convert to HSL colourspace and thence to text for "awk"
convert image.png -unique-colors -colorspace hsl -depth 8 txt: | awk -F"[(), ]+" '
!/^#/{
H=$3; S=$4; L=$5 # Pick up HSL. For Hue, 32768=180deg, 65535=360deg. For S&L, 32768=50%, 65535=100%
NGROUPS=4 # Change this according to the number of groups of colours you want
bin=65535/NGROUPS # Calculate bin size
group=int(int(H/bin)*bin) # Split Hue into NGROUPS
printf "%d %d %d %d\n",group,H,S,L
}' > groupHSL.txt
# Sort by column 1 (group) then by column 4 (Lightness)
sort -n -k1,1 -k4,4 < groupHSL.txt > groupHSL-sorted.txt
# Reassemble the sorted pixels back into a simple image, 16-bit PNM format of HSL data
# Discard the group in column 1 ($1) that we used to sort the data
awk ' { H[++i]=$2; S[i]=$3; L[i]=$4 }
END {
printf "P3\n"
printf "%d %d\n",i,1
printf "65535\n"
for(j=1;j<=i;j++){
printf "%d %d %d\n",H[j],S[j],L[j]
}
}' groupHSL-sorted.txt > HSL.pnm
# Convert HSL.pnm to sRGB.png
convert HSL.pnm -set colorspace hsl -colorspace sRGB sRGB.png
# Make squareish shape
convert sRGB.png -crop 1x1 miff:- | montage -geometry +0+0 -tile 40x - result.png
If I set NGROUPS to 10, I get:
If I set NGROUPS to 4, I get:
Note that, rather than using pipes and shell tricks, the script generates intermediate files so you can easily see each stage of the processing in order to debug it.
For example, if you run this:
convert image.png -unique-colors -colorspace hsl -depth 8 txt: | more
you will see the output that convert is passing to awk:
# ImageMagick pixel enumeration: 10000,1,255,hsl
0,0: (257,22359,1285) #015705 hsl(1.41176,34.1176%,1.96078%)
1,0: (0,0,1542) #000006 hsl(0,0%,2.35294%)
2,0: (41634,60652,1799) #A2EC07 hsl(228.706,92.549%,2.7451%)
3,0: (40349,61166,1799) #9DEE07 hsl(221.647,93.3333%,2.7451%)
4,0: (31868,49858,2056) #7CC208 hsl(175.059,76.0784%,3.13725%)
5,0: (5140,41377,3341) #14A10D hsl(28.2353,63.1373%,5.09804%)
6,0: (61423,59367,3598) #EFE70E hsl(337.412,90.5882%,5.4902%)
If you look at groupHSL-sorted.txt, you will see how the pixels have been sorted into groups and then increasing lightness:
0 0 53456 10537
0 0 18504 20303
0 0 41377 24158
0 0 21331 25700
0 0 62708 28270
0 0 53199 31354
0 0 23130 32896
0 0 8738 33410
0 0 44204 36494
0 0 44204 36751
0 0 46260 38293
0 0 56283 40606
0 0 53456 45489
0 0 0 46517
0 0 32896 46517
0 0 16191 50372
0 0 49601 55769
0 257 49601 11565
0 257 42148 14392
0 257 53713 14649
0 257 50115 15677
0 257 48830 16191
Windows is particularly awkward at quoting things - especially scripts in single quotes like I use above for awk. I would suggest you extract the two separate awk scripts into separate files something like this:
script1.awk
!/^#/{
H=$3; S=$4; L=$5 # Pick up HSL. For Hue, 32768=180deg, 65535=360deg. For S&L, 32768=50%, 65535=100%
NGROUPS=4 # Change this according to the number of groups of colours you want
bin=65535/NGROUPS # Calculate bin size
group=int(int(H/bin)*bin) # Split Hue into NGROUPS
printf "%d %d %d %d\n",group,H,S,L
}
and
script2.awk
{ H[++i]=$2; S[i]=$3; L[i]=$4 }
END {
printf "P3\n"
printf "%d %d\n",i,1
printf "65535\n"
for(j=1;j<=i;j++){
printf "%d %d %d\n",H[j],S[j],L[j]
}
}
Then the two lines in the main script will become something like:
convert image.png -unique-colors -colorspace hsl -depth 8 txt: | awk -F"[(), ]+" -f script1.awk > groupHSL.txt
and
awk -f script2.awk groupHSL-sorted.txt > HSL.pnm
MEL code:Create a cube that high is 1, weight is 2 and d is 2
I have to run MEL script, but I am not sure. This is my code: polyCube -w 2 -h 1 -d 2; setAttr "pCube1.rotateY" 45; setAttr "pCube1.translateY" 5; I am trying to create a cube that high is 1, weight is 2 and d is 2 that will stay at y = 45. Am I wrong? Any suggestions?
Tried your code and it appears to work fine. What are you having trouble with?
A few notes: If you want to create multiple cubes with this, the name is going to change. To handle this, you can get the object name of the newly created poly cube. Another good practice is to wrap your code in curly braces { // my code } to avoid issues with variable scope.
{
string $myCube[] = `polyCube -w 2 -h 1 -d 2`;
setAttr ($myCube[0]+".rotateY") 45;
setAttr ($myCube[0]+".translateY") 5;
print($myCube); // outputs string array with object name and node name
}
Gnuplot: import x-axis from file
I have two files 'results.dat' and 'grid.dat'. The results.dat contains per row a different data set of y values. 1 325.5 875.4 658.7 365.5 2 587.5 987.5 478.6 658.5 3 987.1 542.6 986.2 458.7 The grid.dat contains the corresponding x values. 1 100.0 200.0 300.0 400.0 How can I plot with gnuplot the grid.dat as x values und a specific line of results.dat as corresponding y values? E.g. line 3: 1 100.0 987.1 2 200.0 542.6 3 300.0 986.2 4 400.0 458.7 Thanks in advance.
Thats quite similar to the recent question Gnuplot: plotting the maximum of two files. In your case it is also not possible to do it with gnuplot only.
You need an external tool to combine the two files on-the-fly, e.g. with the following python script (any other tool would also do):
""" selectrow.py: Select a row from 'results.dat' and merge with 'grid.dat'."""
import numpy as np
import sys
line = int(sys.argv[1])
A = np.loadtxt('grid.dat')
B = np.loadtxt('results.dat', skiprows=(line-1))[0]
np.savetxt(sys.stdout, np.c_[A, B], delimiter='\t')
And then plot the third line of results.dat with
plot '< python selectrow.py 3' w l