I use sky texture as world as part of my lightning setup. How do I render with transparent background while keeping the light emitted by sky texture?
I would like to render an animation as a series of .png images with transparent backgrounds for use in a video. Is this possible?
Why are Only Real Things Measurable? Why can't we measure imaginary numbers? I mean, we can take the projection of a complex wave to be the "viewable" part, so why are imaginary numbers given this immeasurable descriptor? Namely with operators in quantum mechanics, why must measurable quantities be Hermitian, and consequently real? A little look through an etymology dictionary shows that the root is Latin gigas with adjective form gigant.  So in its derivation to English, why did the second "g" get retained in gigantic but was dropped from giant?  I have an inkling that the word giant may have travelled through French on its way to English, where it may have been pronounced "gee-yant" or "jee-yant" with a change to the second "g" that was then dropped when taken into English.  However, the "g" is retained as a hard "g" in gigantic. Detecting the system DPI/PPI from JS/CSS? I'm working on a kind of unique app which needs to generate images at specific resolutions according to the device they are displayed on. So the output is different on a regular Windows browser (96ppi), iPhone (163ppi), Android G1 (180ppi), and other devices. I'm wondering if there's a way to detect this automatically.  My initial research seems to say no. The only suggestion I've seen is to make an element whose width is specified as "1in" in CSS, then check its offsetWidth (see also ). Makes sense, but iPhone is lying to me with that technique, saying it's 96ppi.  Another approach might be to get the dimensions of the display in inches and then divide by the width in pixels, but I'm not sure how to do that either. Converting transparent gif / png to jpeg using java Can blender use the Alpha channel of an image as transparency on a plane? Why can I only change my Stack Overflow name once every 30 days? I have a  on Stack Overflow. I recently decided to change the name on my profile. I did this, but I made a spelling mistake! I wrote "Kryton" instead of "Kryten"! When I tried to fix this, a message came back saying that I can only change my profile name every 30 days. Why? Is there any way I can fix my profile name? Note: If you're looking for a simple explanation as to why comments aren't required on downvotes, see .   I used to get "upset" (though that is too strong a term) when I got downvoted without comment. If my answer isn't good enough then I'd like to know why. Not only does it improve the answer for the OP but it improves my knowledge too.  Where the down-vote has been explained I've found it useful &amp; it has improved my answer, or forced me to delete the answer if it was totally wrong.  So is there any way we can encourage people to leave a comment? Perhaps they don't lose rep if they explain their down-vote?  I must admit though that I haven't always explained my down-vote either so you could call me a hypocrite. I've also grown a thicker skin over the months of using SO (it seems to have come with the higher rep score ;-)), so I'm less bothered about this now. I have a Toshiba satellite A-200 laptop with a Vista OS on it with 4 NTFS partitions  (C:) Vista  (D:) Entertainment  (E:) Work  (F:) Sources   and I wanted to start using Ubuntu instead. So I tried it first from the live CD and everything was OK and all the partitions were shown and working and so I decided to install Ubuntu to replace Vista on the (C:) drive. After I did that I can no longer find my folders and files on the (D:), (E:), (F:) partitions and the only file system that is shown is one 198 GB although my HDD is 320 GB.  I can't access the lost data on the remaining 120 GB which I hope is still there and not totally lost  I am now working from the live CD but I am unable to install testdisk. Can I recover the Vista partitions by the product recovery CD to get my laptop back to the factory settings? Can I recover the NTFS partitions using a recovery program for Windows or will that make the problem worse?   I need these data badly as I don't have a backup for them. Equation of a line maintaining equal ratio distance between two points. Say I have two points. One at $A = (0, 0)$ and another at $B = (0, 10)$. I wish to derive an equation for a line that, for any point $P$ on the line, would equal a set ratio for the distance $P$ to $A$ and $P$ to $B$.  This is easy if the predetermined ratio for $A:B$ is $1:1$. I would create a line from $A$ to $B$, find its midpoint, then create an orthogonal line at the midpoint. Then at any $P$ on the line I know that the ratio distances from $P$ to $A$ and $B$ will be $1:1$.  But what if the ratio for $A:B$ is something like $11:18$?  This is for a positioning algorithm I am implementing - not for homework :)  EDIT: Note - If an exact formula is not possible, an approximation of the line out to $\pm 200$ from $A$ or $B$ is acceptable as values further from $A$ and $B$ will not be utilized anyway. A linear equation for the final result/approximation is ideal for speed in running multiple computations. How does the twitter bot work? I'm a begginer in blender, so please forgive me if the question looks silly to you!  Almost all the objects in my scene disappeared (except 2) as if I deleted them by mistake. The thing is all the objects are still listed in the right side graph. The all have the eye button activated, but yet nothing is visible anymore! As I don't have a backup file, I simply can't find any tricks to fix this...  Thank you for you help! If $[\cdot]$ denotes greatest integer function, then what is the value of natural number $n$ satisfying the equation $$[\log_21]+[\log_22]+[\log_23]+\dots[\log_2n]=1538 ?$$   My try:  Note that  $$0+1\times2+2\times2^2+3\times2^3+4\times2^4+5\times2^5+6\times2^6+7\times2^7=1538$$  But the answer is $$n=\sum_{i=0}^72^i=255.$$  How is it derived? How to center a listing? I'm trying to get some console output in my homework. I put it in a listings environment but I want it to be centered horizontally on the page.  The only thing I get centered is the caption ;-/  \begin{minipage}{1\textwidth} \begin{center} \begin{lstlisting}[caption={Ausgabe des C-Programms},label={ggt_c_ausgabe}] a  |  b  |  q  |  u  |  s  |  v  |  t   ---------------------------------------- 78 |  21 |   1 |     |   1 |   1 |  -1  21 |  15 |   3 |   1 |  -3 |  -1 |   4  15 |   6 |   1 |  -3 |   4 |   4 |  -5   6 |   3 |   2 |   4 | -11 |  -5 |  14   3 |     |   2 | -11 |  26 |  14 | -33  ---------------------------------------- \end{lstlisting} \end{center} \end{minipage} What could be the reason covid19 death data shows strong periodic trends? The covid19 death data for US shows strong periodic trends. It does not make sense to me that people die periodically.   What could be the reason to having such data? I thought it might be the reporting artifacts, for example, people always update data at Monday, but the period seems to be 3-4 days. Firefox: Downloading files with drag and drop Rubik's Cube Combination Could anyone explain why the number of legal or reachable combinations of a $3\times 3\times 3$ Rubik's Cube is $1/12\mbox{th}$ of the total. I understood the logic behind the total number of combinations: $8! \cdot 2^{12} + 3^{12} \cdot 12!$. What I am not able to understand is why do we divide this quantity by $2 \cdot 3\cdot 2$. I don't have any idea about parity or group/set theory. Is there another possible explanation for it? I'm practicing proofs and given the following statement:  Let $\Sigma$ be an alphabet, $\epsilon$ the empty word and $\sigma:\Sigma^{*}\rightarrow\Sigma^{*}$ an operation which for $a\in\Sigma$ and $w\in\Sigma^{*}$ is defined as $$\sigma(\epsilon)=\epsilon,\\\sigma(wa)=a\sigma(w).$$  I would like to prove through induction that $\sigma$ is equal to the word reversal operation $rev$ meaning that $\sigma(w)=rev(w)=w_{n}...w_{1}$ for every $w=w_{1}...w_{n}\in\Sigma^{*}$.  My suggestion is as follows:  For $w=\epsilon$ we have $$\sigma(w)=\sigma(\epsilon)=\epsilon=rev(\epsilon)=rev(w).$$  Let $w=xa$ with $x\in\Sigma^{*}$ and $a\in\Sigma$, then $$\sigma(x)=x_{n}...x_{1}=rev(x).$$  Thus we also have $$\sigma(w)=\sigma(xa)=\sigma(x_{1}...x_{n}a)=a\sigma(x_{1}...x_{n})=ax_{n}\sigma(x_{1}...x_{n-1})=...=ax_n...x_{1}=rev(x_{1}...x_{n}a)=rev(xa)=rev(w).$$  Does that constitute a correct and sufficient proof? If not, I would very much appreciate your feedback. Can you attack with different weapons using Extra Attack? The fighter's  feature (PHB, p. 72) says:     Beginning at 5th level, you can attack twice, instead of once, whenever you take the Attack action on your turn.   Assuming I am holding two different weapons, and don't want to spend my bonus action on Two-Weapon Fighting, can I attack once with each weapon? As you can see, the off-topic page isn&#39;t quite right...    Could this (minor) issue be fixed? Add folder to PATH How to add something to PATH ? I have added like   PATH=$PATH:/home/example export PATH   and it works until I restart , after that when  I type env in PATH there is no /home/example.