Is there a way to separate an object by material?
Splitting pieces of a mesh into a new object
How bad for TeX is omitting braces {}, even if the result is the same? Sometimes writing braces and omitting them produces the same result:  \tilde{\psi}  \mathrm{e}^{\mathrm{i} \pi}   vs  \tilde \psi   \mathrm e^{\mathrm i \pi}   Or (taken from Werner's comment below)   \frac{1}{2} vs \frac12   If that's the case, how bad for the quality of my code is omitting them? Of course, if one compiles a pair of formulas, there is no difference. But, since I ignore how TeX works, my point is: if one writes long codes with these habits,   doesn't TeX go somehow crazy because I'm not writing as it expects?   For instance, does it have any effect on how fast are long documents compiled? Any reason to keep them? Does the shebang determine the shell which runs the script? Whenever I am given a system type with a certain transfer function, I am always asked to proceed to find out the 1. impulse response and 2. step response of the system. My question is, what is so special about these two response types that other responses, like for example parabolic response, is not what I am asked to find out? Name for these kinds of "sayings"? Javascript Date: next month I need to amend my return but I already received check from IRS with my refund. Should I cash it out now or wait until I amend my return? I need to amend my return, but I have already received a check from IRS (they approved my return that I need to amend). Should I cash out this check and then amend my return, or should I dispose this check and wait for a check from an amended return? Please add close flags, duplicate links and review data to the public data dump It is easily checked that $\displaystyle\sum_{i\ =\ 0}^{n}\left(\, -1\,\right)^{i} \binom{n}{i} = 0$, for example by appealing to the binomial theorem.  I'm trying to figure out what happens with the truncated sum $\displaystyle\sum_{i\ =\ 0}^{D}\left(\, -1\,\right)^{i}\binom{n}{i}$.  How far away from $0$ can this get, as a function of $D$ ?.  I'm mostly interested in the case of when $D \ll n$, such as $D \sim \,\sqrt{\,n\,}\,$.  Thanks ! What's the best way to store class variables in PHP? I currently have my PHP class variables set up like this:  class someThing {      private $cat;     private $dog;     private $mouse;     private $hamster;     private $zebra;     private $lion;      //getters, setters and other methods }   But I've also seen people using a single array to store all the variables:  class someThing {      private $data = array();      //getters, setters and other methods }   Which do you use, and why? What are the advantages and disadvantages of each? BSOD: Driver State Power Failure For the past two weeks, I've been getting this BSOD error on my Lenovo laptop. I have even reset my laptop ("rest this PC"), but it's still happening.  My laptop details:     I have the latest Nvidia driver for my Nvidia Geforce MX150: 431.60 released on 23 Jul 2019.  I have the latest BIOS for my laptop: 8TCN53WW15  released on 15 Jul 2019.     I have run WhoCrashed, it says it says the problem was caused by some driver which could not be identified. If I get to know the problematic driver I will update/uninstall it.  How can I analyze my dump files, so that I can find the problematic driver?  Edit 1: If you get "Oops there was a problem with the network" on google drive page while accessing dump files, just click on download. They will be downloaded. I don't know what's causing this. The keyboard I am trying to create has a lot of Unicode and looks like this:   Being unsuccessful with the following tutorial:    (There are a few errors in the tutorial, and it uses imprecise language such as "Cutting" things instead of "Deleting" them, and it is formatted strangely)   I was wondering if anybody would be so kind to provide a better tutorial with step by step instructions? Limits, find a limit that exist in absolute value but not outside the absolute value. Exporting QGIS contour attributes in DXF file? I have a .tiff data file that generates contours in QGIS. I save it as .dxf. The contours don't have any attributes or data. That's bad, because I want to make a 3D landscape in Revit using the information.   How do a save/export the contour lines from QGIS so that they have a z-elevation attribute or at least some information?    I ticked the attributes box when extracting the contours, but the attributes doesn't show in the dxf. Xpath expression with multiple predicates How do I prove this function is bijective? $$ v(s,p)=2^{p-1}(2s-1). $$ The domain is natural numbers and the codomain is also the natural numbers.  And this one: $$ f(s)=2s-1. $$ The domain is the natural numbers, and the codomain is the odd numbers in the natural numbers.  With this one I would do this to show it's injective: $$ \begin{align} v(s)&amp;=v(s_1)\\ \implies 2s-1&amp;=2s_1-1\\ \implies (2s_1)/2&amp;=(2s_2)/2\\ \implies s=s_1 \end{align} $$ So it's injective since if $v(s)=v(s_1)$ then $s=s_1$.  And to show it's surjective $f(s)=y$: $$ \begin{align} y&amp;=2s-1\\ \implies s&amp;=(y+1)/2 \end{align} $$ Then the function must be surjective since every $y$ is the same as the codomain for $f$.  Am I correct? Shuffling questions in exam Where is .bashrc? Is there an elegant way to have performant, natural sorting in a MySQL database?  For example if I have this data set:   Final Fantasy Final Fantasy 4 Final Fantasy 10 Final Fantasy 12 Final Fantasy 12: Chains of Promathia Final Fantasy Adventure Final Fantasy Origins Final Fantasy Tactics   Any other elegant solution than to split up the games' names into their components    Title: "Final Fantasy" Number: "12" Subtitle: "Chains of Promathia"   to make sure that they come out in the right order? (10 after 4, not before 2).  Doing so is a pain in the a** because every now and then there's another game that breaks that mechanism of parsing the game title (e.g. "Warhammer 40,000", "James Bond 007") Let $A$ be a commutative ring, $I$ an ideal of $A$ and $M$ an module over $A$. Is it true that $\operatorname{Ann}(M/IM) = \operatorname{Ann}(M) + I$?    One inclusion is certainly true, but I don't know about the other one. If the above statement does not hold in general, does it perhaps for finitely generated modules? If you visit a chat room attached to a beta site while logged out, the log in message is all but unreadable, being dark grey on a dark blue background. For example, visit  while logged out or in private browsing mode.