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• Box 2d basic questions

  - by philipp

  I am a bit new to box2d and I am developing an game with type and letters. I am using an svg font and generate the box2d bodies direct from the glyphs path definition, using the convex hull of them. I also have an decomposition routine the decomposes this hull if necessary. All this it is more or less working, except that I got some strange errors which definitely are caused by the scale factors. The problem is caused by two factors: first: the world scale of box2d, second: the the precision of curve-approximation of the glyph vectors. So through scaling down the input vertices for box2d, it happens that they become equal caused by numerical precision, what causes errors in box2d. Through scaling the my glyphs a bit up, this goes away. I also goes away if I chose a different world scale factor, but this slows down the whole animation quite much! So if my view port is about 990px * 600px and i want to animate Glyphs in box2d which should have a size from about 50px * 50px up to 300px * 300px, which scale factor of the b2world should i choose? How small should the smallest distance from on vertex to another be, while approximating the glyph vectors? Thanks for help greetings philipp EDIT:: I continued reading the docs of box2d and after rethinking of the units system, which is designed to handle object from 0.1 up to 10 meters, I calculated a scale factor of 75. So Objects 600px width will are 8 meters wide in box2d and even small objects of about 20px width will become 0.26 meters width in box2d. I will go on trying with this values, but if there is somebody out there who could give me a clever advice i would be happy!

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• C# vector class - Interpolation design decision

  - by Benjamin

  Currently I'm working on a vector class in C# and now I'm coming to the point, where I've to figure out, how i want to implement the functions for interpolation between two vectors. At first I came up with implementing the functions directly into the vector class... public class Vector3D { public static Vector3D LinearInterpolate(Vector3D vector1, Vector3D vector2, double factor) { ... } public Vector3D LinearInterpolate(Vector3D other, double factor { ... } } (I always offer both: a static method with two vectors as parameters and one non-static, with only one vector as parameter) ...but then I got the idea to use extension methods (defined in a seperate class called "Interpolation" for example), since interpolation isn't really a thing only available for vectors. So this could be another solution: public class Vector3D { ... } public static class Interpolation { public static Vector3D LinearInterpolate(this Vector3D vector, Vector3D other, double factor) { ... } } So here an example how you'd use the different possibilities: { var vec1 = new Vector3D(5, 3, 1); var vec2 = new Vector3D(4, 2, 0); Vector3D vec3; vec3 = vec1.LinearInterpolate(vec2, 0.5); //1 vec3 = Vector3D.LinearInterpolate(vec1, vec2, 0.5); //2 //or with extension-methods vec3 = vec1.LinearInterpolate(vec2, 0.5); //3 (same as 1) vec3 = Interpolation.LinearInterpolation(vec1, vec2, 0.5); //4 } So I really don't know which design is better. Also I don't know if there's an ultimate rule for things like this or if it's just about what someone personally prefers. But I really would like to hear your opinions, what's better (and if possible why ).

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• Multiplayer Network Game - Interpolation and Frame Rate

  - by J.C.

  Consider the following scenario: Let's say, for sake of example and simplicity, that you have an authoritative game server that sends state to its clients every 45ms. The clients are interpolating state with an interpolation delay of 100 ms. Finally, the clients are rendering a new frame every 15ms. When state is updated on the client, the client time is set from the incoming state update. Each time a frame renders, we take the render time (client time - interpolation delay) and identify a previous and target state to interpolate from. To calculate the interpolation amount/factor, we take the difference of the render time and previous state time and divide by the difference of the target state and previous state times: var factor = ((renderTime - previousStateTime) / (targetStateTime - previousStateTime)) Problem: In the example above, we are effectively displaying the same interpolated state for 3 frames before we collected the next server update and a new client (render) time is set. The rendering is mostly smooth, but there is a dash of jaggedness to it. Question: Given the example above, I'd like to think that the interpolation amount/factor should increase with each frame render to smooth out the movement. Should this be considered and, if so, what is the best way to achieve this given the information from above?

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• Looking for algorithms regarding scaling and moving

  - by user1806687

  I've been bashing my head for the past couple of weeks trying to find algorithms that would help me accomplish, on first look very easy task. So, I got this one object currently made out of 5 cuboids (2 sides, 1 top, 1 bottom, 1 back), this is just for an example, later on there will be whole range of different set ups. I have included three pictures of this object(as said this is just for an example). Now, the thing is when the user scales the whole object this is what should happen: X scale: top and bottom cuboids should get scaled by a scale factor, sides should get moved so they are positioned just like they were before(in this case at both ends of top and bottom cuboids), back should get scaled so it fits like before(if I simply scale it by a scale factor it will leave gaps on each side). Y scale: sides should get scaled by a scale factor, top and bottom cuboid should get moved, and back should also get scaled. Z scale: sides, top and bottom cuboids should get scaled, back should get moved. Here is an image of the example object (a thick walled box, with one face missing, where each wall is made by a cuboid): Front of the object: Hope you can help,

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• How to move the rigidbody at the position of the mouse on release

  - by Edvin

  I'm making a "Can Knockdown" game and I need the rigidbody to move where the player released the mouse(OnMouseUp). Momentarily the Ball moves OnMouseUp because of rigidbody.AddForce(force * factor); and It moves toward the mousePosition but doesn't end up where the mousePosition is. Here's what I have so far in the script. var factor = 20.0; var minSwipeDistY : float; private var startTime : float; private var startPos : Vector3; function OnMouseDown(){ startTime = Time.time; startPos = Input.mousePosition; startPos.z = transform.position.z - Camera.main.transform.position.z; startPos = Camera.main.ScreenToWorldPoint(startPos); } function OnMouseUp(){ var endPos = Input.mousePosition; endPos.z = transform.position.z - Camera.main.transform.position.z; endPos = Camera.main.ScreenToWorldPoint(endPos); var force = endPos - startPos; force.z = force.magnitude; force /= (Time.time - startTime); rigidbody.AddForce(force * factor); }

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• How to update a QPixmap in a QGraphicsView with PyQt

  - by pops

  I am trying to paint on a QPixmap inside a QGraphicsView. The painting works fine, but the QGraphicsView doesn't update it. Here is some working code: #!/usr/bin/env python from PyQt4 import QtCore from PyQt4 import QtGui class Canvas(QtGui.QPixmap): """ Canvas for drawing""" def __init__(self, parent=None): QtGui.QPixmap.__init__(self, 64, 64) self.parent = parent self.imH = 64 self.imW = 64 self.fill(QtGui.QColor(0, 255, 255)) self.color = QtGui.QColor(0, 0, 0) def paintEvent(self, point=False): if point: p = QtGui.QPainter(self) p.setPen(QtGui.QPen(self.color, 1, QtCore.Qt.SolidLine)) p.drawPoints(point) def clic(self, mouseX, mouseY): self.paintEvent(QtCore.QPoint(mouseX, mouseY)) class GraphWidget(QtGui.QGraphicsView): """ Display, zoom, pan...""" def __init__(self): QtGui.QGraphicsView.__init__(self) self.im = Canvas(self) self.imH = self.im.height() self.imW = self.im.width() self.zoomN = 1 self.scene = QtGui.QGraphicsScene(self) self.scene.setItemIndexMethod(QtGui.QGraphicsScene.NoIndex) self.scene.setSceneRect(0, 0, self.imW, self.imH) self.scene.addPixmap(self.im) self.setScene(self.scene) self.setTransformationAnchor(QtGui.QGraphicsView.AnchorUnderMouse) self.setResizeAnchor(QtGui.QGraphicsView.AnchorViewCenter) self.setMinimumSize(400, 400) self.setWindowTitle("pix") def mousePressEvent(self, event): if event.buttons() == QtCore.Qt.LeftButton: pos = self.mapToScene(event.pos()) self.im.clic(pos.x(), pos.y()) #~ self.scene.update(0,0,64,64) #~ self.updateScene([QtCore.QRectF(0,0,64,64)]) self.scene.addPixmap(self.im) print('items') print(self.scene.items()) else: return QtGui.QGraphicsView.mousePressEvent(self, event) def wheelEvent(self, event): if event.delta() > 0: self.scaleView(2) elif event.delta() < 0: self.scaleView(0.5) def scaleView(self, factor): n = self.zoomN * factor if n < 1 or n > 16: return self.zoomN = n self.scale(factor, factor) if __name__ == '__main__': import sys app = QtGui.QApplication(sys.argv) widget = GraphWidget() widget.show() sys.exit(app.exec_()) The mousePressEvent does some painting on the QPixmap. But the only solution I have found to update the display is to make a new instance (which is not a good solution). How do I just update it?

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• ANOVA with 3 fixed factors in R

  - by TKBell

  Im trying to run a model with a response variable p and 3 fixed factors to get ANOVA. this is how my code looks like : #run it as 3 fixed factor model p1=c(37,38,37,41,41,40,41,42,41) p2=c(42,41,43,42,42,42,43,42,43) p3=c(30,31,31,31,31,31,29,30,28) p4=c(42,43,42,43,43,43,42,42,42) p5=c(28,30,29,29,30,29,31,29,29) p6=c(42,42,43,45,45,45,44,46,45) p7=c(25,26,27,28,28,30,29,27,27) p8=c(40,40,40,43,42,42,43,43,41) p9=c(37,38,37,41,41,40,41,42,41) p10=c(35,34,34,35,35,34,35,34,35) p = cbind(p1,p2,p3,p4,p5,p6,p7,p8,p9,p10) partnumber=c(rep(1,9),rep(2,9),rep(3,9),rep(4,9),rep(5,9),rep(6,9),rep(7,9),rep(8,9),rep(9,9),rep(10,9)) test=c(rep(c(rep(1:3,3)),10)) inspector = rep(c(rep(1,3),rep(2,3),rep(3,3)),10) fpartnumber = factor(partnumber) ftest = factor(test) finspector = factor(inspector) model=lm(p~fpartnumber*ftest*finspector) summary(model) anova(model) but when I run it I get this error : it says my variable length for fpartnumber is different , but when I checked the length of each variable and is 90. What is going on ? model=lm(y~fpartnumber*ftest*finspector) Error in model.frame.default(formula = yang ~ fpartnumber * ftest * finspector, : variable lengths differ (found for 'fpartnumber')

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• Recognizing terminals in a CFG production previously not defined as tokens.

  - by kmels

  I'm making a generator of LL(1) parsers, my input is a CoCo/R language specification. I've already got a Scanner generator for that input. Suppose I've got the following specification: COMPILER 1. CHARACTERS digit="0123456789". TOKENS number = digit{digit}. decnumber = digit{digit}"."digit{digit}. PRODUCTIONS Expression = Term{"+"Term|"-"Term}. Term = Factor{"*"Factor|"/"Factor}. Factor = ["-"](Number|"("Expression")"). Number = (number|decnumber). END 1. So, if the parser generated by this grammar receives a word "1+1", it'd be accepted i.e. a parse tree would be found. My question is, the character "+" was never defined in a token, but it appears in the non-terminal "Expression". How should my generated Scanner recognize it? It would not recognize it as a token. Is this a valid input then? Should I add this terminal in TOKENS and then consider an error routine for a Scanner for it to skip it? How does usual language specifications handle this?

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• Return call from ggplot object

  - by aL3xa

  I've been using ggplot2 for a while now, and I can't find a way to get formula from ggplot object. Though I can get basic info with summary(<ggplot_object>), in order to get complete formula, usually I was combing up and down through .Rhistory file. And this becomes frustrating when you experiment with new graphs, especially when code gets a bit lengthy... so searching through history file isn't quite convenient way of doing this... Is there a more efficient way of doing this? Just an illustration: p <- qplot(data = mtcars, x = factor(cyl), geom = "bar", fill = factor(cyl)) + scale_fill_manual(name = "Cylinders", value = c("firebrick3", "gold2", "chartreuse3")) + stat_bin(aes(label = ..count..), vjust = -0.2, geom = "text", position = "identity") + xlab("# of cylinders") + ylab("Frequency") + opts(title = "Barplot: # of cylinders") I can get some basic info with summary: > summary(p) data: mpg, cyl, disp, hp, drat, wt, qsec, vs, am, gear, carb [32x11] mapping: fill = factor(cyl), x = factor(cyl) scales: fill faceting: facet_grid(. ~ ., FALSE) ----------------------------------- geom_bar: stat_bin: position_stack: (width = NULL, height = NULL) mapping: label = ..count.. geom_text: vjust = -0.2 stat_bin: width = 0.9, drop = TRUE, right = TRUE position_identity: (width = NULL, height = NULL) But I want to get code I typed in to get the graph. I reckon that I'm missing something essential here... it's seems impossible that there's no way to get call from ggplot object!

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• Sorting in Lua, counting number of items

  - by Josh

  Two quick questions (I hope...) with the following code. The script below checks if a number is prime, and if not, returns all the factors for that number, otherwise it just returns that the number prime. Pay no attention to the zs. stuff in the script, for that is client specific and has no bearing on script functionality. The script itself works almost wonderfully, except for two minor details - the first being the factor list doesn't return itself sorted... that is, for 24, it'd return 1, 2, 12, 3, 8, 4, 6, and 24 instead of 1, 2, 3, 4, 6, 8, 12, and 24. I can't print it as a table, so it does need to be returned as a list. If it has to be sorted as a table first THEN turned into a list, I can deal with that. All that matters is the end result being the list. The other detail is that I need to check if there are only two numbers in the list or more. If there are only two numbers, it's a prime (1 and the number). The current way I have it does not work. Is there a way to accomplish this? I appreciate all the help! function get_all_factors(number) local factors = 1 for possible_factor=2, math.sqrt(number), 1 do local remainder = number%possible_factor if remainder == 0 then local factor, factor_pair = possible_factor, number/possible_factor factors = factors .. ", " .. factor if factor ~= factor_pair then factors = factors .. ", " .. factor_pair end end end factors = factors .. ", and " .. number return factors end local allfactors = get_all_factors(zs.param(1)) if zs.func.numitems(allfactors)==2 then return zs.param(1) .. " is prime." else return zs.param(1) .. " is not prime, and its factors are: " .. allfactors end

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• Why doesn't interface inheritance work when writing shell extensions in c#?

  - by Factor Mystic

  According to this article about writing shell extensions in .Net, inheriting the shell interfaces as you might naturally do when writing code doesn't work. I've observed this in my own code as well. Doesn't work: public interface IPersist { // stuff specific only to IPersist } public interface IPersistFolder : IPersist { // stuff specific only to IPersistFolder } Does work: public interface IPersistFolder { // stuff specific to IPersist only // stuff specific to IPersistFolder only } The article notes this fact: Lo and behold, it worked! Notice that I've abandoned any idea that IPersistFolder is inherited from anything at all and just included the stubs from IPersist right in its definition. In all candor, I can't tell you why this is but it definitely works just fine and shouldn't give you any problems. So my I'll ask the question this guy didn't know; why didn't the original code work?

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• Using a 64bit Linux kernel, can't see more than 4GB of RAM in /proc/meminfo

  - by Chris Huang-Leaver

  I'm running my new computer which has 8GB of RAM installed, which is visable from BIOS page, does not show in /proc/meminfo uname -a Linux localhost 3.0.6-gentoo #2 SMP PREEMPT Sat Nov 19 10:45:22 GMT-- x86_64 AMD Phenom(tm) II X4 955 Processor AuthenticAMD GNU/Linux The result of /proc/meminfo is as follows: (thans Andrey) MemTotal: 4021348 kB MemFree: 1440280 kB Buffers: 23696 kB Cached: 1710828 kB SwapCached: 4956 kB Active: 1389904 kB Inactive: 841364 kB Active(anon): 1337812 kB Inactive(anon): 714060 kB Active(file): 52092 kB Inactive(file): 127304 kB Unevictable: 32 kB Mlocked: 32 kB SwapTotal: 8388604 kB SwapFree: 8047900 kB Dirty: 0 kB Writeback: 0 kB AnonPages: 492732 kB Mapped: 47528 kB Shmem: 1555120 kB Slab: 267724 kB SReclaimable: 177464 kB SUnreclaim: 90260 kB KernelStack: 1176 kB PageTables: 12148 kB NFS_Unstable: 0 kB Bounce: 0 kB WritebackTmp: 0 kB CommitLimit: 10399276 kB Committed_AS: 3293896 kB VmallocTotal: 34359738367 kB VmallocUsed: 317008 kB VmallocChunk: 34359398908 kB AnonHugePages: 120832 kB HugePages_Total: 0 HugePages_Free: 0 HugePages_Rsvd: 0 HugePages_Surp: 0 Hugepagesize: 2048 kB DirectMap4k: 23552 kB DirectMap2M: 3088384 kB DirectMap1G: 1048576 kB I have tried using mem=8G as a kernel boot parameter, I read a post about setting HIGHMEM64G to yes, before realising that only applies to 32bit kernels. Trying dmindecode -t memory SMBIOS 2.7 present. Handle 0x0026, DMI type 16, 23 bytes Physical Memory Array Location: System Board Or Motherboard Use: System Memory Error Correction Type: Multi-bit ECC Maximum Capacity: 32 GB Error Information Handle: Not Provided Number Of Devices: 4 Handle 0x0028, DMI type 17, 34 bytes Memory Device Array Handle: 0x0026 Error Information Handle: Not Provided Total Width: 64 bits Data Width: 64 bits Size: 4096 MB Form Factor: DIMM Set: None Locator: DIMM0 Bank Locator: BANK0 Type: <OUT OF SPEC> Type Detail: Synchronous Speed: 1333 MHz Manufacturer: Manufacturer0 Serial Number: SerNum0 Asset Tag: AssetTagNum0 Part Number: Array1_PartNumber0 Rank: Unknown Handle 0x002A, DMI type 17, 34 bytes Memory Device Array Handle: 0x0026 Error Information Handle: Not Provided Total Width: Unknown Data Width: 64 bits Size: No Module Installed Form Factor: DIMM Set: None Locator: DIMM1 Bank Locator: BANK1 Type: Unknown Type Detail: Synchronous Speed: Unknown Manufacturer: Manufacturer1 Serial Number: SerNum1 Asset Tag: AssetTagNum1 Part Number: Array1_PartNumber1 Rank: Unknown Handle 0x002C, DMI type 17, 34 bytes Memory Device Array Handle: 0x0026 Error Information Handle: Not Provided Total Width: 64 bits Data Width: 64 bits Size: 4096 MB Form Factor: DIMM Set: None Locator: DIMM2 Bank Locator: BANK2 Type: <OUT OF SPEC> Type Detail: Synchronous Speed: 1333 MHz Manufacturer: Manufacturer2 Serial Number: SerNum2 Asset Tag: AssetTagNum2 Part Number: Array1_PartNumber2 Rank: Unknown Handle 0x002E, DMI type 17, 34 bytes Memory Device Array Handle: 0x0026 Error Information Handle: Not Provided Total Width: Unknown Data Width: 64 bits Size: No Module Installed Form Factor: DIMM Set: None Locator: DIMM3 Bank Locator: BANK3 Type: Unknown Type Detail: Synchronous Speed: Unknown Manufacturer: Manufacturer3 Serial Number: SerNum3 Asset Tag: AssetTagNum3 Part Number: Array1_PartNumber3 Rank: Unknown

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• resize image in asp.net

  - by alina

  I have this code to resize an image but the image doesn't look so good: public Bitmap ProportionallyResizeBitmap(Bitmap src, int maxWidth, int maxHeight) { // original dimensions int w = src.Width; int h = src.Height; // Longest and shortest dimension int longestDimension = (w > h) ? w : h; int shortestDimension = (w < h) ? w : h; // propotionality float factor = ((float)longestDimension) / shortestDimension; // default width is greater than height double newWidth = maxWidth; double newHeight = maxWidth / factor; // if height greater than width recalculate if (w < h) { newWidth = maxHeight / factor; newHeight = maxHeight; } // Create new Bitmap at new dimensions Bitmap result = new Bitmap((int)newWidth, (int)newHeight); using (Graphics g = Graphics.FromImage((System.Drawing.Image)result)) g.DrawImage(src, 0, 0, (int)newWidth, (int)newHeight); return result; }

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• T-Sql Modify Insert SProc To Update If Exists.

  - by Goober

  Scenario I have a stored procedure written in T-Sql that I use to insert data into a table as XML. Since the data gets updated regularly, I want the rows to be updated if they already exist (Aside from when the application is first run, they will always exist). Question Below is the code of my Insert Sproc, however I cannot seem to workout the Update side of the stored procedure & would appreciate some help. CODE set ANSI_NULLS ON set QUOTED_IDENTIFIER ON go ALTER PROCEDURE [dbo].[INS_Curve] ( @Curve varchar(MAX) ) AS DECLARE @handle int exec sp_xml_preparedocument @handle OUTPUT, @Curve INSERT INTO CurveDB..tblCurve(LoadID,BusinessDate, Factor) SELECT LoadID,BusinessDate, Factor FROM OPENXML(@handle, 'NewDataSet/Table1',2) WITH( LoadID int, BusinessDate DateTime, Factor float ) exec sp_xml_removedocument @handle

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• How can I read this url in Rebol ?

  - by Rebol Tutorial

  when trying to read this kind of url URL: http://v4.lscache2.c.youtube.com/videoplayback?ip=0.0.0.0&sparams=id,expire,ip,ipbits,itag,algorithm,burst,factor,oc:U0dWSlhTVF9FSkNNNl9QTVhJ&algorithm=throttle-factor&itag=34&ipbits=0&burst=40&sver=3&expire=1275886800&key=yt1&signature=89195E808CB3FBBC7BDE7298A1DC0613D7987F00.D3064112E8F479C523F8DF4FBFDF392CE48167C2&factor=1.25&id=34e01ad39b34b5c9& I get this error read/binary url connecting to: v4.lscache2.c.youtube.com ** User Error: Error. Target url: http://v4.lscache2.c.youtube.com/videoplayback?ip=0.0.0.0&sparams=id,expire,ip,ipbits, itag,algorithm... ** Near: read/binary url

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• Getting Factors of a Number

  - by Dave

  Hi Problem: I'm trying to refactor this algorithm to make it faster. What would be the first refactoring here for speed? public int GetHowManyFactors(int numberToCheck) { // we know 1 is a factor and the numberToCheck int factorCount = 2; // start from 2 as we know 1 is a factor, and less than as numberToCheck is a factor for (int i = 2; i < numberToCheck; i++) { if (numberToCheck % i == 0) factorCount++; } return factorCount; }

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• Are high powered 3D game engines better at 2D games than engines made for 2D

  - by Adam

  I'm a software engineer that's new to game programming so forgive me if this is a dumb question as I don't know that much about game engines. If I was building a 2D game am I better off going with an engine like Torque that looks like it's built for 2D, or would higher powered engines like Unreal, Source and Unity work better? I'm mainly asking if 2D vs 3D is a large factor in choosing an engine. For the purpose of comparison, let's eliminate variables by saying price isn't a factor (even though it probably is). EDIT: I should probably also mention that the game we're developing has a lot of RTS and RPG elements regarding leveling up

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• Registrar with good security, DNS hosting, and DNSSEC and IPv6 resolvers?

  - by semenko

  I'm looking to move my domains away from GoDaddy, but I'm having a tough time finding anyone with comparable features at a (even remotely) similar price. I've looked at the usual suggestions (NameCheap, Gandi.net, etc.), but they all seem to lack many of the GoDaddy feature base. I'm looking for: DNSSEC IPv6 Resolvers (dig pdns01.domaincontrol.com AAAA; etc. ) SSL-Logins by default HTTP-only login cookies No stupid password restrictions Two-factor authentications No DNS record limits Rough DNS statistics (queries/day, etc.) Audit trails GoDaddy has all of these, except two-factor, for $3/month. See http://www.godaddy.com/domains/dns-hosting.aspx I can't seem to find any other registrar that supports even a few of these. Is there a registrar that offers comparable features? Or, barring that, a DNS hosting service that offers similar features? (AWS Route53 doesn't offer DNSSEC or IPv6)

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• Does it help to be core programmer of a product (product meant for social good ) for getting into Ph. D. in top university in USA say top 20?

  - by Maddy.Shik

  Hey i am working upon a product as core developer which will be launched in USA market in few months if successful. Can this factor improve my chance to get Ph.D. in good university(say top 20 in US). Normally good universities like CMU, standford, MIT, Cornell are more interested in student's profile like research work, under graduate school etc. I am not passed out from very good university its ranked in top 20 of India only. Neither did i do research work till now. But being one of founding member of company and developing product for same, i want to know if this factor can help and to what extent. For university with ranking lower than 20 what matters most is GRE General score and GPA but i guess top university must be appreciating a person's real efforts.

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• Does it help to be core programmer of a product (meant for social good) for getting into a PhD program at a top university?

  - by Maddy.Shik

  Hey i am working upon a product as core developer which will be launched in USA market in few months if successful. Can this factor improve my chances for getting accepted into a PhD program at a top university (say top 20 in US)? Normally good universities like CMU, Standford, MIT, Cornell are more interested in student's profile like research work, undergraduate school, etc. I am now passed out from very good university it's ranked in top 20 of India only. Neither did I do research work till now. But being one of founding member of company and developing product for same, I want to know if this factor can help and to what extent.

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• Why does multiplying texture coordinates scale the texture?

  - by manning18

  I'm having trouble visualizing this geometrically - why is it that multiplying the U,V coordinates of a texture coordinate has the effect of scaling that texture by that factor? eg if you scaled the texture coordinates by a factor of 3 ..then doesn't this mean that if you had texture coordinates 0,1 and 0,2 ...you'd be sampling 0,3 and 0,6 in the U,V texture space of 0..1? How does that make it bigger eg HLSL: tex2D(textureSampler, TexCoords*3) Integers make it smaller, decimals make it bigger I mean I understand intuitively if you added to the U,V coordinates, as that is simply an offset into the sampling range, but what's the case with multiplication? I have a feeling when someone explains this to me I'm going to be feeling mighty stupid

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• PCF shadow shader math causing artifacts

  - by user2971069

  For a while now I used PCSS for my shadow technique of choice until I discovered a type of percentage closer filtering. This method creates really smooth shadows and with hopes of improving performance, with only a fraction of texture samples, I tried to implement PCF into my shader. This is the relevant code: float c0, c1, c2, c3; float f = blurFactor; float2 coord = ProjectedTexCoords; if (receiverDistance - tex2D(lightSampler, coord + float2(0, 0)).x > 0.0007) c0 = 1; if (receiverDistance - tex2D(lightSampler, coord + float2(f, 0)).x > 0.0007) c1 = 1; if (receiverDistance - tex2D(lightSampler, coord + float2(0, f)).x > 0.0007) c2 = 1; if (receiverDistance - tex2D(lightSampler, coord + float2(f, f)).x > 0.0007) c3 = 1; coord = (coord % f) / f; return 1 - (c0 * (1 - coord.x) * (1 - coord.y) + c1 * coord.x * (1 - coord.y) + c2 * (1 - coord.x) * coord.y + c3 * coord.x * coord.y); This is a very basic implementation. blurFactor is initialized with 1 / LightTextureSize. So the if statements fetch the occlusion values for the four adjacent texels. I now want to weight each value based on the actual position of the texture coordinate. If it's near the bottom-right pixel, that occlusion value should be preferred. The weighting itself is done with a simple bilinear interpolation function, however this function takes a 2d vector in the range [0..1] so I have to convert my texture coordinate to get the distance from my first pixel to the second one in range [0..1]. For that I used the mod operator to get it into [0..f] range and then divided by f. This code makes sense to me, and for specific blurFactors it works, producing really smooth one pixel wide shadows, but not for all blurFactors. Initially blurFactor is (1 / LightTextureSize) to sample the 4 adjacent texels. I now want to increase the blurFactor by factor x to get a smooth interpolation across maybe 4 or so pixels. But that is when weird artifacts show up. Here is an image: Using a 1x on blurFactor produces a good result, 0.5 is as expected not so smooth. 2x however doesn't work at all. I found that only a factor of 1/2^n produces an good result, every other factor produces artifacts. I'm pretty sure the error lies here: coord = (coord % f) / f; Maybe the modulo is not calculated correctly? I have no idea how to fix that. Is it even possible for pixel that are further than 1 pixel away?

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• Oracle NoSQL Database Exceeds 1 Million Mixed YCSB Ops/Sec

  - by Charles Lamb

  We ran a set of YCSB performance tests on Oracle NoSQL Database using SSD cards and Intel Xeon E5-2690 CPUs with the goal of achieving 1M mixed ops/sec on a 95% read / 5% update workload. We used the standard YCSB parameters: 13 byte keys and 1KB data size (1,102 bytes after serialization). The maximum database size was 2 billion records, or approximately 2 TB of data. We sized the shards to ensure that this was not an "in-memory" test (i.e. the data portion of the B-Trees did not fit into memory). All updates were durable and used the "simple majority" replica ack policy, effectively 'committing to the network'. All read operations used the Consistency.NONE_REQUIRED parameter allowing reads to be performed on any replica. In the past we have achieved 100K ops/sec using SSD cards on a single shard cluster (replication factor 3) so for this test we used 10 shards on 15 Storage Nodes with each SN carrying 2 Rep Nodes and each RN assigned to its own SSD card. After correcting a scaling problem in YCSB, we blew past the 1M ops/sec mark with 8 shards and proceeded to hit 1.2M ops/sec with 10 shards.  Hardware Configuration We used 15 servers, each configured with two 335 GB SSD cards. We did not have homogeneous CPUs across all 15 servers available to us so 12 of the 15 were Xeon E5-2690, 2.9 GHz, 2 sockets, 32 threads, 193 GB RAM, and the other 3 were Xeon E5-2680, 2.7 GHz, 2 sockets, 32 threads, 193 GB RAM.  There might have been some upside in having all 15 machines configured with the faster CPU, but since CPU was not the limiting factor we don't believe the improvement would be significant. The client machines were Xeon X5670, 2.93 GHz, 2 sockets, 24 threads, 96 GB RAM. Although the clients had 96 GB of RAM, neither the NoSQL Database or YCSB clients require anywhere near that amount of memory and the test could have just easily been run with much less. Networking was all 10GigE. YCSB Scaling Problem We made three modifications to the YCSB benchmark. The first was to allow the test to accommodate more than 2 billion records (effectively int's vs long's). To keep the key size constant, we changed the code to use base 32 for the user ids. The second change involved to the way we run the YCSB client in order to make the test itself horizontally scalable.The basic problem has to do with the way the YCSB test creates its Zipfian distribution of keys which is intended to model "real" loads by generating clusters of key collisions. Unfortunately, the percentage of collisions on the most contentious keys remains the same even as the number of keys in the database increases. As we scale up the load, the number of collisions on those keys increases as well, eventually exceeding the capacity of the single server used for a given key.This is not a workload that is realistic or amenable to horizontal scaling. YCSB does provide alternate key distribution algorithms so this is not a shortcoming of YCSB in general. We decided that a better model would be for the key collisions to be limited to a given YCSB client process. That way, as additional YCSB client processes (i.e. additional load) are added, they each maintain the same number of collisions they encounter themselves, but do not increase the number of collisions on a single key in the entire store. We added client processes proportionally to the number of records in the database (and therefore the number of shards). This change to the use of YCSB better models a use case where new groups of users are likely to access either just their own entries, or entries within their own subgroups, rather than all users showing the same interest in a single global collection of keys. If an application finds every user having the same likelihood of wanting to modify a single global key, that application has no real hope of getting horizontal scaling. Finally, we used read/modify/write (also known as "Compare And Set") style updates during the mixed phase. This uses versioned operations to make sure that no updates are lost. This mode of operation provides better application behavior than the way we have typically run YCSB in the past, and is only practical at scale because we eliminated the shared key collision hotspots.It is also a more realistic testing scenario. To reiterate, all updates used a simple majority replica ack policy making them durable. Scalability Results In the table below, the "KVS Size" column is the number of records with the number of shards and the replication factor. Hence, the first row indicates 400m total records in the NoSQL Database (KV Store), 2 shards, and a replication factor of 3. The "Clients" column indicates the number of YCSB client processes. "Threads" is the number of threads per process with the total number of threads. Hence, 90 threads per YCSB process for a total of 360 threads. The client processes were distributed across 10 client machines. Shards KVS Size Clients Mixed (records) Threads OverallThroughput(ops/sec) Read Latencyav/95%/99%(ms) Write Latencyav/95%/99%(ms) 2 400m(2x3) 4 90(360) 302,152 0.76/1/3 3.08/8/35 4 800m(4x3) 8 90(720) 558,569 0.79/1/4 3.82/16/45 8 1600m(8x3) 16 90(1440) 1,028,868 0.85/2/5 4.29/21/51 10 2000m(10x3) 20 90(1800) 1,244,550 0.88/2/6 4.47/23/53

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• Help with Boost Spirit ASTs

  - by Decmac04

  I am writing a small tool for analyzing simple B Machine substitutions as part of a college research work. The code successfully parse test inputs of the form mySubst := var1 + var2. However, I get a pop-up error message saying "This application has requested the Runtime to terminate it in an unusual way. " In the command prompt window, I get an "Assertion failed message". The main program is given below: // BMachineTree.cpp : Defines the entry point for the console application. // /*============================================================================= Copyright (c) 2010 Temitope Onunkun =============================================================================*/ /////////////////////////////////////////////////////////////////////////////// // // UUsing Boost Spririt Trees (AST) to parse B Machine Substitutions. // /////////////////////////////////////////////////////////////////////////////// #define BOOST_SPIRIT_DUMP_PARSETREE_AS_XML #include <boost/spirit/core.hpp> #include <boost/spirit/tree/ast.hpp> #include <boost/spirit/tree/tree_to_xml.hpp> #include "BMachineTreeGrammar.hpp" #include <iostream> #include <stack> #include <functional> #include <string> #include <cassert> #include <vector> #if defined(BOOST_SPIRIT_DUMP_PARSETREE_AS_XML) #include <map> #endif // Using AST to parse B Machine substitutions //////////////////////////////////////////////////////////////////////////// using namespace std; using namespace boost::spirit; typedef char const* iterator_t; typedef tree_match<iterator_t> parse_tree_match_t; typedef parse_tree_match_t::tree_iterator iter_t; //////////////////////////////////////////////////////////////////////////// string evaluate(parse_tree_match_t hit); string eval_machine(iter_t const& i); vector<string> dx; string evaluate(tree_parse_info<> info) { return eval_machine(info.trees.begin()); } string eval_machine(iter_t const& i) { cout << "In eval_machine. i->value = " << string(i->value.begin(), i->value.end()) << " i->children.size() = " << i->children.size() << endl; if (i->value.id() == substitution::leafValueID) { assert(i->children.size() == 0); // extract string tokens string leafValue(i->value.begin(), i->value.end()); dx.push_back(leafValue.c_str()); return leafValue.c_str(); } // else if (i->value.id() == substitution::termID) { if ( (*i->value.begin() == '*') || (*i->value.begin() == '/') ) { assert(i->children.size() == 2); dx.push_back( eval_machine(i->children.begin()) ); dx.push_back( eval_machine(i->children.begin()+1) ); return eval_machine(i->children.begin()) + " " + eval_machine(i->children.begin()+1); } // else assert(0); } else if (i->value.id() == substitution::expressionID) { if ( (*i->value.begin() == '+') || (*i->value.begin() == '-') ) { assert(i->children.size() == 2); dx.push_back( eval_machine(i->children.begin()) ); dx.push_back( eval_machine(i->children.begin()+1) ); return eval_machine(i->children.begin()) + " " + eval_machine(i->children.begin()+1); } else assert(0); } // else if (i->value.id() == substitution::simple_substID) { if (*i->value.begin() == (':' >> '=') ) { assert(i->children.size() == 2); dx.push_back( eval_machine(i->children.begin()) ); dx.push_back( eval_machine(i->children.begin()+1) ); return eval_machine(i->children.begin()) + "|->" + eval_machine(i->children.begin()+1); } else assert(0); } else { assert(0); // error } return 0; } //////////////////////////////////////////////////////////////////////////// int main() { // look in BMachineTreeGrammar for the definition of BMachine substitution BMach_subst; cout << "/////////////////////////////////////////////////////////\n\n"; cout << "\t\tB Machine Substitution...\n\n"; cout << "/////////////////////////////////////////////////////////\n\n"; cout << "Type an expression...or [q or Q] to quit\n\n"; string str; while (getline(cin, str)) { if (str.empty() || str[0] == 'q' || str[0] == 'Q') break; tree_parse_info<> info = ast_parse(str.c_str(), BMach_subst, space_p); if (info.full) { #if defined(BOOST_SPIRIT_DUMP_PARSETREE_AS_XML) // dump parse tree as XML std::map<parser_id, std::string> rule_names; rule_names[substitution::identifierID] = "identifier"; rule_names[substitution::leafValueID] = "leafValue"; rule_names[substitution::factorID] = "factor"; rule_names[substitution::termID] = "term"; rule_names[substitution::expressionID] = "expression"; rule_names[substitution::simple_substID] = "simple_subst"; tree_to_xml(cout, info.trees, str.c_str(), rule_names); #endif // print the result cout << "Variables in Vector dx: " << endl; for(vector<string>::iterator idx = dx.begin(); idx < dx.end(); ++idx) cout << *idx << endl; cout << "parsing succeeded\n"; cout << "result = " << evaluate(info) << "\n\n"; } else { cout << "parsing failed\n"; } } cout << "Bye... :-) \n\n"; return 0; } The grammar, defined in BMachineTreeGrammar.hpp file is given below: /*============================================================================= Copyright (c) 2010 Temitope Onunkun http://www.dcs.kcl.ac.uk/pg/onun Use, modification and distribution is subject to the Boost Software License, Version 1.0. (See accompanying file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt) =============================================================================*/ #ifndef BOOST_SPIRIT_BMachineTreeGrammar_HPP_ #define BOOST_SPIRIT_BMachineTreeGrammar_HPP_ using namespace boost::spirit; /////////////////////////////////////////////////////////////////////////////// // // Using Boost Spririt Trees (AST) to parse B Machine Substitutions. // /////////////////////////////////////////////////////////////////////////////// //////////////////////////////////////////////////////////////////////////// // // B Machine Grammar // //////////////////////////////////////////////////////////////////////////// struct substitution : public grammar<substitution> { static const int identifierID = 1; static const int leafValueID = 2; static const int factorID = 3; static const int termID = 4; static const int expressionID = 5; static const int simple_substID = 6; template <typename ScannerT> struct definition { definition(substitution const& ) { // Start grammar definition identifier = alpha_p >> (+alnum_p | ch_p('_') ) ; leafValue = leaf_node_d[ lexeme_d[ identifier | +digit_p ] ] ; factor = leafValue | inner_node_d[ ch_p( '(' ) >> expression >> ch_p(')' ) ] ; term = factor >> *( (root_node_d[ch_p('*') ] >> factor ) | (root_node_d[ch_p('/') ] >> factor ) ); expression = term >> *( (root_node_d[ch_p('+') ] >> term ) | (root_node_d[ch_p('-') ] >> term ) ); simple_subst= leaf_node_d[ lexeme_d[ identifier ] ] >> root_node_d[str_p(":=")] >> expression ; // End grammar definition // turn on the debugging info. BOOST_SPIRIT_DEBUG_RULE(identifier); BOOST_SPIRIT_DEBUG_RULE(leafValue); BOOST_SPIRIT_DEBUG_RULE(factor); BOOST_SPIRIT_DEBUG_RULE(term); BOOST_SPIRIT_DEBUG_RULE(expression); BOOST_SPIRIT_DEBUG_RULE(simple_subst); } rule<ScannerT, parser_context<>, parser_tag<simple_substID> > simple_subst; rule<ScannerT, parser_context<>, parser_tag<expressionID> > expression; rule<ScannerT, parser_context<>, parser_tag<termID> > term; rule<ScannerT, parser_context<>, parser_tag<factorID> > factor; rule<ScannerT, parser_context<>, parser_tag<leafValueID> > leafValue; rule<ScannerT, parser_context<>, parser_tag<identifierID> > identifier; rule<ScannerT, parser_context<>, parser_tag<simple_substID> > const& start() const { return simple_subst; } }; }; #endif The output I get on running the program is: ///////////////////////////////////////////////////////// B Machine Substitution... ///////////////////////////////////////////////////////// Type an expression...or [q or Q] to quit mySubst := var1 - var2 parsing succeeded In eval_machine. i->value = := i->children.size() = 2 Assertion failed: 0, file c:\redmound\bmachinetree\bmachinetree\bmachinetree.cpp , line 114 I will appreciate any help in resolving this problem.

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• Optimizing Disk I/O & RAID on Windows SQL Server 2005

  - by David

  I've been monitoring our SQL server for a while, and have noticed that I/O hits 100% every so often using Task Manager and Perfmon. I have normally been able to correlate this spike with SUSPENDED processes in SQL Server Management when I execute "exec sp_who2". The RAID controller is controlled by LSI MegaRAID Storage Manager. We have the following setup: System Drive (Windows) on RAID 1 with two 280GB drives SQL is on a RAID 10 (2 mirroed drives of 280GB in two different spans) This is a database that is hammered during the day, but is pretty inactive at night. The DB size is currently about 13GB, and is used by approximately 200 (and growing) users a day. I have a couple of ideas I'm toying around with: Checking for Indexes & reindexing some tables Adding an additional RAID 1 (with 2 new, smaller, HDs) and moving the SQL's Log Data File (LDF) onto the new RAID. For #2, my question is this: Would we really be increasing disk performance (IO) by moving data off of the RAID 10 onto a RAID 1? RAID 10 obviously has better performance than RAID 1. Furthermore, SQL must write to the transaction logs before writing to the database. But on the flip side, we'll be reducing both the size of the disks as well as the amount of data written to the RAID 10, which is where all of the "meat" is - thereby increasing that RAID's performance for read requests. Is there any way to find out what our current limiting factor is? (The drives vs. the RAID Controller)? If the limiting factor is the drives, then maybe adding the additional RAID 1 makes sense. But if the limiting factor is the Controller itself, then I think we're approaching this thing wrong. Finally, are we just wasting our time? Should we instead be focusing our efforts towards #1 (reindexing tables, reducing network latency where possible, etc...)?

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