math

问题 I have a large list of items, each item has a weight. I'd like to select N items randomly without replacement, while the items with more weight are more probable to be selected. I'm looking for the most performing idea. Performance is paramount. Any ideas? 回答1: If you want to sample items without replacement, you have lots of options. Use a weighted-choice-with-replacement algorithm to choose random indices. There are many algorithms like this. One of them is WeightedChoice , described later

问题 I have a large list of items, each item has a weight. I'd like to select N items randomly without replacement, while the items with more weight are more probable to be selected. I'm looking for the most performing idea. Performance is paramount. Any ideas? 回答1: If you want to sample items without replacement, you have lots of options. Use a weighted-choice-with-replacement algorithm to choose random indices. There are many algorithms like this. One of them is WeightedChoice , described later

问题 From my understanding, the atan2() function exists in programming languages because atan() itself cannot always determine the correct theta since the output is restricted to -pi/2 to pi/2. If this is the case, then the same problem applies to both asin() and acos() , both of whom also have restricted ranges, so then why are there no asin2() and acos2() functions? 回答1: First off, note that the syntaxes of the two arctan functions are atan(y/x) and atan2(y, x) . This distinction is important,

问题 Below is what I have so far. At the moment, the player moves, and all I want it to do now is face the mouse cursor at all times (think Hotline Miami or other top-down games). I've used some code involving atan2 that I found online, but I barely understand what it does (finds the distance between the player and mouse somehow...) and my character just spins wildly offscreen until I get an 'Out of memory' error. Any help would be much appreciated, I've looked all over the internet and can't find

问题 Below is what I have so far. At the moment, the player moves, and all I want it to do now is face the mouse cursor at all times (think Hotline Miami or other top-down games). I've used some code involving atan2 that I found online, but I barely understand what it does (finds the distance between the player and mouse somehow...) and my character just spins wildly offscreen until I get an 'Out of memory' error. Any help would be much appreciated, I've looked all over the internet and can't find

问题 Below is what I have so far. At the moment, the player moves, and all I want it to do now is face the mouse cursor at all times (think Hotline Miami or other top-down games). I've used some code involving atan2 that I found online, but I barely understand what it does (finds the distance between the player and mouse somehow...) and my character just spins wildly offscreen until I get an 'Out of memory' error. Any help would be much appreciated, I've looked all over the internet and can't find

问题 Below is what I have so far. At the moment, the player moves, and all I want it to do now is face the mouse cursor at all times (think Hotline Miami or other top-down games). I've used some code involving atan2 that I found online, but I barely understand what it does (finds the distance between the player and mouse somehow...) and my character just spins wildly offscreen until I get an 'Out of memory' error. Any help would be much appreciated, I've looked all over the internet and can't find

问题 Below is what I have so far. At the moment, the player moves, and all I want it to do now is face the mouse cursor at all times (think Hotline Miami or other top-down games). I've used some code involving atan2 that I found online, but I barely understand what it does (finds the distance between the player and mouse somehow...) and my character just spins wildly offscreen until I get an 'Out of memory' error. Any help would be much appreciated, I've looked all over the internet and can't find

问题 More a maths question then a programming one, but I need to code camera rotation and I have no idea how. The maths are a bit to abstract for me to do out of the blue. The camera's rotation is done with quaternions, all I really want is a sample to study or just an article about the subject but I can't find anything. 回答1: here is something i wrote in opengl. the basic algorithm should be the same in any language. the things you need are: the up vector of unit length (where up is defined if you

问题 More a maths question then a programming one, but I need to code camera rotation and I have no idea how. The maths are a bit to abstract for me to do out of the blue. The camera's rotation is done with quaternions, all I really want is a sample to study or just an article about the subject but I can't find anything. 回答1: here is something i wrote in opengl. the basic algorithm should be the same in any language. the things you need are: the up vector of unit length (where up is defined if you