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  • Normal map applied as diffuse textures looks wrong

    - by KaiserJohaan
    Diffuse textures works fine, but I am having problem with normal maps, so I thought I'd tried to apply the normal maps as the diffuse map in my fragment shader so I could see everything is OK. I comment-out my normal map code and just set the diffuse map to the normal map and I get this: http://postimg.org/image/j9gudjl7r/ Looks like a smurf! This is the actual normal map of the main body: http://postimg.org/image/sbkyr6fg9/ Here is my fragment shader, notice I commented out normal map code so I could debug the normal map as a diffuse texture "#version 330 \n \ \n \ layout(std140) uniform; \n \ \n \ const int MAX_LIGHTS = 8; \n \ \n \ struct Light \n \ { \n \ vec4 mLightColor; \n \ vec4 mLightPosition; \n \ vec4 mLightDirection; \n \ \n \ int mLightType; \n \ float mLightIntensity; \n \ float mLightRadius; \n \ float mMaxDistance; \n \ }; \n \ \n \ uniform UnifLighting \n \ { \n \ vec4 mGamma; \n \ vec3 mViewDirection; \n \ int mNumLights; \n \ \n \ Light mLights[MAX_LIGHTS]; \n \ } Lighting; \n \ \n \ uniform UnifMaterial \n \ { \n \ vec4 mDiffuseColor; \n \ vec4 mAmbientColor; \n \ vec4 mSpecularColor; \n \ vec4 mEmissiveColor; \n \ \n \ bool mHasDiffuseTexture; \n \ bool mHasNormalTexture; \n \ bool mLightingEnabled; \n \ float mSpecularShininess; \n \ } Material; \n \ \n \ uniform sampler2D unifDiffuseTexture; \n \ uniform sampler2D unifNormalTexture; \n \ \n \ in vec3 frag_position; \n \ in vec3 frag_normal; \n \ in vec2 frag_texcoord; \n \ in vec3 frag_tangent; \n \ in vec3 frag_bitangent; \n \ \n \ out vec4 finalColor; " " \n \ \n \ void CalcGaussianSpecular(in vec3 dirToLight, in vec3 normal, out float gaussianTerm) \n \ { \n \ vec3 viewDirection = normalize(Lighting.mViewDirection); \n \ vec3 halfAngle = normalize(dirToLight + viewDirection); \n \ \n \ float angleNormalHalf = acos(dot(halfAngle, normalize(normal))); \n \ float exponent = angleNormalHalf / Material.mSpecularShininess; \n \ exponent = -(exponent * exponent); \n \ \n \ gaussianTerm = exp(exponent); \n \ } \n \ \n \ vec4 CalculateLighting(in Light light, in vec4 diffuseTexture, in vec3 normal) \n \ { \n \ if (light.mLightType == 1) // point light \n \ { \n \ vec3 positionDiff = light.mLightPosition.xyz - frag_position; \n \ float dist = max(length(positionDiff) - light.mLightRadius, 0); \n \ \n \ float attenuation = 1 / ((dist/light.mLightRadius + 1) * (dist/light.mLightRadius + 1)); \n \ attenuation = max((attenuation - light.mMaxDistance) / (1 - light.mMaxDistance), 0); \n \ \n \ vec3 dirToLight = normalize(positionDiff); \n \ float angleNormal = clamp(dot(normalize(normal), dirToLight), 0, 1); \n \ \n \ float gaussianTerm = 0.0; \n \ if (angleNormal > 0.0) \n \ CalcGaussianSpecular(dirToLight, normal, gaussianTerm); \n \ \n \ return diffuseTexture * (attenuation * angleNormal * Material.mDiffuseColor * light.mLightIntensity * light.mLightColor) + \n \ (attenuation * gaussianTerm * Material.mSpecularColor * light.mLightIntensity * light.mLightColor); \n \ } \n \ else if (light.mLightType == 2) // directional light \n \ { \n \ vec3 dirToLight = normalize(light.mLightDirection.xyz); \n \ float angleNormal = clamp(dot(normalize(normal), dirToLight), 0, 1); \n \ \n \ float gaussianTerm = 0.0; \n \ if (angleNormal > 0.0) \n \ CalcGaussianSpecular(dirToLight, normal, gaussianTerm); \n \ \n \ return diffuseTexture * (angleNormal * Material.mDiffuseColor * light.mLightIntensity * light.mLightColor) + \n \ (gaussianTerm * Material.mSpecularColor * light.mLightIntensity * light.mLightColor); \n \ } \n \ else if (light.mLightType == 4) // ambient light \n \ return diffuseTexture * Material.mAmbientColor * light.mLightIntensity * light.mLightColor; \n \ else \n \ return vec4(0.0); \n \ } \n \ \n \ void main() \n \ { \n \ vec4 diffuseTexture = vec4(1.0); \n \ if (Material.mHasDiffuseTexture) \n \ diffuseTexture = texture(unifDiffuseTexture, frag_texcoord); \n \ \n \ vec3 normal = frag_normal; \n \ if (Material.mHasNormalTexture) \n \ { \n \ diffuseTexture = vec4(normalize(texture(unifNormalTexture, frag_texcoord).xyz * 2.0 - 1.0), 1.0); \n \ // vec3 normalTangentSpace = normalize(texture(unifNormalTexture, frag_texcoord).xyz * 2.0 - 1.0); \n \ //mat3 tangentToWorldSpace = mat3(normalize(frag_tangent), normalize(frag_bitangent), normalize(frag_normal)); \n \ \n \ // normal = tangentToWorldSpace * normalTangentSpace; \n \ } \n \ \n \ if (Material.mLightingEnabled) \n \ { \n \ vec4 accumLighting = vec4(0.0); \n \ \n \ for (int lightIndex = 0; lightIndex < Lighting.mNumLights; lightIndex++) \n \ accumLighting += Material.mEmissiveColor * diffuseTexture + \n \ CalculateLighting(Lighting.mLights[lightIndex], diffuseTexture, normal); \n \ \n \ finalColor = pow(accumLighting, Lighting.mGamma); \n \ } \n \ else { \n \ finalColor = pow(diffuseTexture, Lighting.mGamma); \n \ } \n \ } \n"; Here is my wrapper around a texture OpenGLTexture::OpenGLTexture(const std::vector<uint8_t>& textureData, uint32_t textureWidth, uint32_t textureHeight, TextureFormat textureFormat, TextureType textureType, Logger& logger) : mLogger(logger), mTextureID(gNextTextureID++), mTextureType(textureType) { glGenTextures(1, &mTexture); CHECK_GL_ERROR(mLogger); glBindTexture(GL_TEXTURE_2D, mTexture); CHECK_GL_ERROR(mLogger); GLint glTextureFormat = (textureFormat == TextureFormat::TEXTURE_FORMAT_RGB ? GL_RGB : textureFormat == TextureFormat::TEXTURE_FORMAT_RGBA ? GL_RGBA : GL_RED); glTexImage2D(GL_TEXTURE_2D, 0, glTextureFormat, textureWidth, textureHeight, 0, glTextureFormat, GL_UNSIGNED_BYTE, &textureData[0]); CHECK_GL_ERROR(mLogger); glGenerateMipmap(GL_TEXTURE_2D); CHECK_GL_ERROR(mLogger); glBindTexture(GL_TEXTURE_2D, 0); CHECK_GL_ERROR(mLogger); } OpenGLTexture::~OpenGLTexture() { glDeleteBuffers(1, &mTexture); CHECK_GL_ERROR(mLogger); } And here is the sampler I create which is shared between Diffuse and normal textures // texture sampler setup glGenSamplers(1, &mTextureSampler); CHECK_GL_ERROR(mLogger); glSamplerParameteri(mTextureSampler, GL_TEXTURE_MAG_FILTER, GL_LINEAR); CHECK_GL_ERROR(mLogger); glSamplerParameteri(mTextureSampler, GL_TEXTURE_MIN_FILTER, GL_LINEAR_MIPMAP_NEAREST); CHECK_GL_ERROR(mLogger); glSamplerParameteri(mTextureSampler, GL_TEXTURE_WRAP_S, GL_REPEAT); CHECK_GL_ERROR(mLogger); glSamplerParameteri(mTextureSampler, GL_TEXTURE_WRAP_T, GL_REPEAT); CHECK_GL_ERROR(mLogger); glSamplerParameterf(mTextureSampler, GL_TEXTURE_MAX_ANISOTROPY_EXT, mCurrentAnisotropy); CHECK_GL_ERROR(mLogger); glUniform1i(glGetUniformLocation(mDefaultProgram.GetHandle(), "unifDiffuseTexture"), OpenGLTexture::TEXTURE_UNIT_DIFFUSE); CHECK_GL_ERROR(mLogger); glUniform1i(glGetUniformLocation(mDefaultProgram.GetHandle(), "unifNormalTexture"), OpenGLTexture::TEXTURE_UNIT_NORMAL); CHECK_GL_ERROR(mLogger); glBindSampler(OpenGLTexture::TEXTURE_UNIT_DIFFUSE, mTextureSampler); CHECK_GL_ERROR(mLogger); glBindSampler(OpenGLTexture::TEXTURE_UNIT_NORMAL, mTextureSampler); CHECK_GL_ERROR(mLogger); SetAnisotropicFiltering(mCurrentAnisotropy); The diffuse textures looks like they should, but the normal looks so wierd. Why is this?

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  • storing data for maps database

    - by Timigen
    I am working on an application that displays choropleth maps. These maps are of all different types, some display state by county, country by state/province, or world by country. How should I handle storing the map information in the database? My Thoughts: I won't need to do queries to find POI inside a region, so I don't think there is a need to use spatial datatypes. I am considering storing a map as a geoJSON object (I am using JS mapping library that accepts geoJSON). The only issue is what if I want a map of the US northeast. Then I would have geoJSON for the US and a separate one for the US northeast, which would be redundant. Would it make sense to have a shape database where I had each state then when I needed a map of the US I could query for each state, and when I needed a map of the US Northeast I could again query for what I need? Note: I am not concerned with storing the data for each region, just the region itself. I will query for the data on the fly for the specific region.

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  • Microsoft Assessment and Planning (MAP) Toolkit 5.0 Beta

    - by Lara Rubbelke
    Do you know where SQL Server is installed - everywhere it is installed? Do you really know where SQL Server is installed? Are you looking for a tool that will help you discover any rogue instances so you can better manage these instances? The Beta 2 for the Microsoft Assessment and Planning (MAP) Toolkit 5.0 is now open. Join the beta review program and help influence the development of the toolkit. To participate, register for the MAP Toolkit 5.0 Beta 2 at Microsoft Connect. The MAP Toolkit 5.0...(read more)

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  • Microsoft Assessment and Planning (MAP) Toolkit 5.0 Beta

    - by Lara Rubbelke
    Do you know where SQL Server is installed - everywhere it is installed? Do you really know where SQL Server is installed? Are you looking for a tool that will help you discover any rogue instances so you can better manage these instances? The Beta 2 for the Microsoft Assessment and Planning (MAP) Toolkit 5.0 is now open. Join the beta review program and help influence the development of the toolkit. To participate, register for the MAP Toolkit 5.0 Beta 2 at Microsoft Connect. The MAP Toolkit 5.0...(read more)

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  • Hide individual regions on a territory map

    - by Paul
    I have a map of adjacent irregularly-shaped territories. It happens to be a county map, but that's not important. In the game, the player only sees a few to start, and as he progresses to new territories, the ones adjacent to it are revealed. It's a territory-scale fog-of-war. I'm using Unity3D, and my inclination is to make a set of planes, each of which has an image of a single territory on it, and then arrange them manually like a jigsaw puzzle. It then is fairly easy to respond to a click on each region and also to mark the planes as visible or invisible, or even do clever things like fade or zoom on individual regions. This sounds like an arduous task, and if we need to change the visual design of the territories, we'd have to cut up the main map all over again into each of the individual pieces. Does anyone have a more elegant solution to this problem?

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  • Google I/O 2012 - A Master Class in Map Styling

    Google I/O 2012 - A Master Class in Map Styling Scott Shawcroft, Jonah Jones Custom Styled Maps allow developers to customize the look and feel of the underlying Google Maps tiles. This makes it really easy to make a great looking map. You can tailor your map to your message, to your color scheme, or to help emphasize your data. In this class, master maps designers will help you build beautiful, elegant styles that make your maps work for you. For all I/O 2012 sessions, go to developers.google.com From: GoogleDevelopers Views: 23 0 ratings Time: 38:21 More in Science & Technology

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  • Whole map design vs. tiles array design

    - by Mikalichov
    I am working on a 2D RPG, which will feature the usual dungeon/town maps (pre-generated). I am using tiles, that I will then combine to make the maps. My original plan was to assemble the tiles using Photoshop, or some other graphic program, in order to have one bigger picture that I could then use as a map. However, I have read on several places people talking about how they used arrays to build their map in the engine (so you give an array of x tiles to your engine, and it assemble them as a map). I can understand how it's done, but it seems a lot more complicated to implement, and I can't see obvious avantages. What is the most common method, and what are advantages/disadvantages of each?

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  • Collisions on complex map 2D

    - by waxx
    I'm currently thinking about collision and map system that I want to use in my next game and I'm kind of puzzled. Maps are going to be somewhat complex with lots of irregularities and thus tiling is out of question. I thought about an editor where you'd draw rectangles on the map that would represent areas that are collidable with and then saving such "collision map" with only black/white gfx. Or maybe should I save exact rectangles data with their x/y/width/height into some text file and go from there? What would you recommend? Thanks.

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  • How to create reproducible probability in map generation?

    - by nickbadal
    So for my game, I'm using perlin noise to generate regions of my map (water/land, forest/grass) but I'd also like to create some probability based generation too. For instance: if(nextInt(10) > 2 && tile.adjacentTo(Type.WATER)) tile.setType(Type.SAND); This works fine, and is even reproduceable (based on a common seed) if the nextInt() calls are always in the same order. The issue is that in my game, the world is generated on demand, based on the player's location. This means, that if I explore the map differently, and the chunks of the map are generated in a different order, the randomness is no longer consistent. How can I get this sort of randomness to be consistent, independent of call order? Thanks in advance :)

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  • 3d js map rendering

    - by gotha
    In the past I've done a 2D tile map using HTML, CSS and Javascript. Now I have the task of creating a 3D version using the same technologies - think of it like a space map where all planets have x/y/z positions. Currently, I have no idea to do this. Is there an existing library or something I can modify to do my job? If not, what method of rendering the map should I use? It needs to be as browser independent as possible, so I can't use webgl, flash or canvas. I'm considering plain JS & HTML or SVG (using Raphael for compatibility).

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  • libgdx - collision detection with tiled map java

    - by user2875021
    currently, I am working on a 2d rpg game which is similar to final fantasy 1-4. I can load up a tiled map and the sprite can walk freely on the map. However, I will like to create a wall for it to stop walking through it. I created three tiled layer Background, Collision, Overhead and one Collision object layer with rectangles only. "How do I handle collisions with the object layer in the tiled map?" "Do I have to create every single rectangle that is in the object layer with Rectangle rectangle = new Rectangle() and rectangle.set(x, y, width, height)in the code?" Thank you very much in advance. Any help is greatly appreciated!

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  • overriding big popup on directions Google Maps

    - by Glycerine
    I've happily implemented v2 of Google maps to my site without a hitch, I also successfully perform a drive directions using GDirections.load(). What I need to do is stop the popup of the mini map when you select a particular step in the routing directions. So when the user clicks on say "step 3", instead of the default popup showing a mini map, I'd like to add a custom icon to that position. Hope it makes sense Thanks in advance guys.

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  • Removing Directions markers from the Google Maps API V3

    - by anonymous
    To remove a normal marker from a map, I understand you simply call marker.setMap(null), but when implementing the Google Maps directions services, it automatically adds markers A and B onto the map ( calculating directions from point A to point B ). I do not have control over these markers, so I cannot remove them in the normal way. So how can I remove these markers (I have custom markers on the map instead)?

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  • jQuery update Google Map

    - by Beardy
    I am trying to update a google map v3 with jQuery and at the moment it loads the map but when .preview is clicked the map scaled to the width and height and then goes grey. $('.preview').click(function(){ var width = $('#width').val(); var height = $('#height').val(); $('#map').css({ 'width':width, 'height':height }); var mapElement = document.getElementById('map'); var updateOptions = { zoom: 6 } var map = new google.maps.Map(mapElement, updateOptions); });

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  • OpenGL/GLSL: Render to cube map?

    - by BobDole
    I'm trying to figure out how to render my scene to a cube map. I've been stuck on this for a bit and figured I would ask you guys for some help. I'm new to OpenGL and this is the first time I'm using a FBO. I currently have a working example of using a cubemap bmp file, and the samplerCube sample type in the fragment shader is attached to GL_TEXTURE1. I'm not changing the shader code at all. I'm just changing the fact that I wont be calling the function that was loading the cubemap bmp file and trying to use the below code to render to a cubemap. You can see below that I'm also attaching the texture again to GL_TEXTURE1. This is so when I set the uniform: glUniform1i(getUniLoc(myProg, "Cubemap"), 1); it can access it in my fragment shader via uniform samplerCube Cubemap. I'm calling the below function like so: cubeMapTexture = renderToCubeMap(150, GL_RGBA8, GL_RGBA, GL_UNSIGNED_BYTE); Now, I realize in the draw loop below that I'm not changing the view direction to look down the +x, -x, +y, -y, +z, -z axis. I really was just wanting to see something working first before implemented that. I figured I should at least see something on my object the way the code is now. I'm not seeing anything, just straight black. I've made my background white still the object is black. I've removed lighting, and coloring to just sample the cubemap texture and still black. I'm thinking the problem might be the format types when setting my texture which is GL_RGB8, GL_RGBA but I've also tried: GL_RGBA, GL_RGBA GL_RGB, GL_RGB I thought this would be standard since we are rendering to a texture attached to a framebuffer, but I've seen different examples that use different enum values. I've also tried binding the cube map texture in every draw call that I'm wanting to use the cube map: glBindTexture(GL_TEXTURE_CUBE_MAP, cubeMapTexture); Also, I'm not creating a depth buffer for the FBO which I saw in most examples, because I'm only wanting the color buffer for my cube map. I actually added one to see if that was the problem and still got the same results. I could of fudged that up when I tried. Any help that can point me in the right direction would be appreciated. GLuint renderToCubeMap(int size, GLenum InternalFormat, GLenum Format, GLenum Type) { // color cube map GLuint textureObject; int face; GLenum status; //glEnable(GL_TEXTURE_2D); glActiveTexture(GL_TEXTURE1); glGenTextures(1, &textureObject); glBindTexture(GL_TEXTURE_CUBE_MAP, textureObject); glTexParameterf(GL_TEXTURE_CUBE_MAP, GL_TEXTURE_MIN_FILTER, GL_LINEAR); glTexParameterf(GL_TEXTURE_CUBE_MAP, GL_TEXTURE_MAG_FILTER, GL_LINEAR); glTexParameterf(GL_TEXTURE_CUBE_MAP, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE); glTexParameterf(GL_TEXTURE_CUBE_MAP, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE); glTexParameterf(GL_TEXTURE_CUBE_MAP, GL_TEXTURE_WRAP_R, GL_CLAMP_TO_EDGE); for (face = 0; face < 6; face++) { glTexImage2D(GL_TEXTURE_CUBE_MAP_POSITIVE_X + face, 0, InternalFormat, size, size, 0, Format, Type, NULL); } // framebuffer object glGenFramebuffers(1, &fbo); glBindFramebuffer(GL_FRAMEBUFFER, fbo); glFramebufferTexture2D(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT0, GL_TEXTURE_CUBE_MAP_POSITIVE_X, textureObject, 0); status = glCheckFramebufferStatus(GL_FRAMEBUFFER); printf("%d\"\n", status); printf("%d\n", GL_FRAMEBUFFER_COMPLETE); glViewport(0,0,size, size); for (face = 1; face < 6; face++) { drawSpheres(); glFramebufferTexture2D(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT0,GL_TEXTURE_CUBE_MAP_POSITIVE_X + face, textureObject, 0); } //Bind 0, which means render to back buffer, as a result, fb is unbound glBindFramebuffer(GL_FRAMEBUFFER, 0); return textureObject; }

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  • IRC newbie needs detailed "How To" directions for freenode.net connection with OS X IRC app

    - by Johnny Utahh
    Newbie IRC user here. Trying to get connected on freenode.net, preferably with a native Mac OS X client (I'm running 10.6.8), or at least something with a good "OS X feel." Also seeking a client that comes "well regarded" in Mac community (eg, Linkinus reflects outstanding Apple App Store user ratings). Thus far have found it remarkably difficult to "get started from scratch" with ANY client. All attempted clients (Colloquy, Textual, Linkinus) experience some sort of "* Notice -- You need to identify via SASL to use this server" error. I see this freenode SASL-friendly client list; am I really limited to only these clients? This "IRC-freenode startup" procedure has been far more difficult than I had originally anticipated. Why can't I just do this and have it "just work"? Bottom line: looking for a "chapter and verse"/cookbook description of how to get started with freenode.net IRC chat rooms on Mac OS. Need reference to known-working client, and then exact directions on how to get connected to a chat room with a nickname.

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  • Alternative to google map api, so that I can use it on a HTTPS/SSL encrypted website.

    - by Zeeshan Rang
    I have a question regarding map api. I was using the the google map api in my website before. But since I have encryption the site using HTTPS/SSL support, the google map api stopped working. I checked online, and realised that google has a Premier account only that would allow me to use HTTPS supported maps api and it cost $10,000 per year. I do not this kind of money with me. So, can you give any other alternative to have a map api on my website. Anything that could give me driving directions would be fine. Regards Zeeshan

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  • What container type provides better (average) performance than std::map?

    - by Truncheon
    In the following example a std::map structure is filled with 26 values from A - Z (for key) and 0 - 26 for value. The time taken (on my system) to lookup the last entry (10000000 times) is roughly 250 ms for the vector, and 125 ms for the map. (I compiled using release mode, with O3 option turned on for g++ 4.4) But if for some odd reason I wanted better performance than the std::map, what data structures and functions would I need to consider using? I apologize if the answer seems obvious to you, but I haven't had much experience in the performance critical aspects of C++ programming. UPDATE: This example is rather trivial and hides the true complexity of what I'm trying to achieve. My real world project is a simple scripting language that uses a parser, data tree, and interpreter (instead of a VM stack system). I need to use some kind of data structure (perhaps map) to store the variables names created by script programmers. These are likely to be pretty randomly named, so I need a lookup method that can quickly find a particular key within a (probably) fairly large list of names. #include <ctime> #include <map> #include <vector> #include <iostream> struct mystruct { char key; int value; mystruct(char k = 0, int v = 0) : key(k), value(v) { } }; int find(const std::vector<mystruct>& ref, char key) { for (std::vector<mystruct>::const_iterator i = ref.begin(); i != ref.end(); ++i) if (i->key == key) return i->value; return -1; } int main() { std::map<char, int> mymap; std::vector<mystruct> myvec; for (int i = 'a'; i < 'a' + 26; ++i) { mymap[i] = i - 'a'; myvec.push_back(mystruct(i, i - 'a')); } int pre = clock(); for (int i = 0; i < 10000000; ++i) { find(myvec, 'z'); } std::cout << "linear scan: milli " << clock() - pre << "\n"; pre = clock(); for (int i = 0; i < 10000000; ++i) { mymap['z']; } std::cout << "map scan: milli " << clock() - pre << "\n"; return 0; }

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  • what use does the javascript forEach method have (that map can't do)?

    - by JohnMerlino
    Hey all, The only difference I see in map and foreach is that map is returning an array and foreach is not. However, I don't even understand the last line of the foreach method "func.call(scope, this[i], i, this);". For example, isn't "this" and "scope" referring to same object and isn't this[i] and i referring to the current value in the loop? I noticed on another post someone said "Use forEach when you want to do something on the basis of each element of the list. You might be adding things to the page, for example. Essentially, it's great for when you want "side effects". I don't know what is meant by side effects. Array.prototype.map = function(fnc) { var a = new Array(this.length); for (var i = 0; i < this.length; i++) { a[i] = fnc(this[i]); } return a; } Array.prototype.forEach = function(func, scope) { scope = scope || this; for (var i = 0, l = this.length; i < l; i++) func.call(scope, this[i], i, this); } Finally, are there any real uses for these methods in javascript (since we aren't updating a database) other than to manipulate numbers like this: alert([1,2,3,4].map(function(x){ return x + 1})); //this is the only example I ever see of map in javascript. Thanks for any reply.

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  • Is there a value in using map() vs for?

    - by roder
    Does map() iterate through the list like "for" would? Is there a value in using map vs for? If so, right now my code looks like this: for item in items: item.my_func() If it makes sense, I would like to make it map(). Is that possible? What is an example like?

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  • what use does the javascript for each method have (that map can't do)?

    - by JohnMerlino
    Hey all, The only difference I see in map and foreach is that map is returning an array and foreach is not. However, I don't even understand the last line of the foreach method "func.call(scope, this[i], i, this);". For example, isn't "this" and "scope" referring to same object and isn't this[i] and i referring to the current value in the loop? I noticed on another post someone said "Use forEach when you want to do something on the basis of each element of the list. You might be adding things to the page, for example. Essentially, it's great for when you want "side effects". I don't know what is meant by side effects. Array.prototype.map = function(fnc) { var a = new Array(this.length); for (var i = 0; i < this.length; i++) { a[i] = fnc(this[i]); } return a; } Array.prototype.forEach = function(func, scope) { scope = scope || this; for (var i = 0, l = this.length; i < l; i++) func.call(scope, this[i], i, this); } Finally, are there any real uses for these methods in javascript (since we aren't updating a database) other than to manipulate numbers like this: alert([1,2,3,4].map(function(x){ return x + 1})); //this is the only example I ever see of map in javascript. Thanks for any reply.

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  • What's the fastest lookup algorithm for a pair data structure (i.e, a map)?

    - by truncheon
    In the following example a std::map structure is filled with 26 values from A - Z (for key) and 0 – 26 for value. The time taken (on my system) to lookup the last entry (10000000 times) is roughly 250 ms for the vector, and 125 ms for the map. (I compiled using release mode, with O3 option turned on for g++ 4.4) But if for some odd reason I wanted better performance than the std::map, what data structures and functions would I need to consider using? I apologize if the answer seems obvious to you, but I haven't had much experience in the performance critical aspects of C++ programming. UPDATE: This example is rather trivial and hides the true complexity of what I'm trying to achieve. My real world project is a simple scripting language that uses a parser, data tree, and interpreter (instead of a VM stack system). I need to use some kind of data structure (perhaps map) to store the variables names created by script programmers. These are likely to be pretty randomly named, so I need a lookup method that can quickly find a particular key within a (probably) fairly large list of names. #include <ctime> #include <map> #include <vector> #include <iostream> struct mystruct { char key; int value; mystruct(char k = 0, int v = 0) : key(k), value(v) { } }; int find(const std::vector<mystruct>& ref, char key) { for (std::vector<mystruct>::const_iterator i = ref.begin(); i != ref.end(); ++i) if (i->key == key) return i->value; return -1; } int main() { std::map<char, int> mymap; std::vector<mystruct> myvec; for (int i = 'a'; i < 'a' + 26; ++i) { mymap[i] = i - 'a'; myvec.push_back(mystruct(i, i - 'a')); } int pre = clock(); for (int i = 0; i < 10000000; ++i) { find(myvec, 'z'); } std::cout << "linear scan: milli " << clock() - pre << "\n"; pre = clock(); for (int i = 0; i < 10000000; ++i) { mymap['z']; } std::cout << "map scan: milli " << clock() - pre << "\n"; return 0; }

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