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chiranjivi

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About chiranjivi

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  1. chiranjivi

    Applying alpha gradient to an image

      In theory I can use shaders, yes - in practise though I've shied away from them because they seem pretty complex, and I barely have a tenuous grasp on the basics at present.       This is the kind of thing I was hoping for - some functionality that would allow me to draw another texture over the top of what I currently have, but overwriting only the alpha channel and not touching the RGB. I'll have a look at the gl documentation about blending functions and see if anything looks particularly enlightening.
  2. chiranjivi

    Applying alpha gradient to an image

      Thank you for being reasonable about it. I didn't realise it was considered bad form to take the tooltip literally, I'll be less liberal about it in future if it upsets people (not you personally, just in the general sense).     Well, what I've actually done so far is draw a number of sprites onto a LibGDX framebuffer; having done that I'm trying to figure out how take that framebuffer and to 'fade out' its left and right edges, after which I was intending to render it onto the screen over the background. The framebuffer already contains an alpha channel, I'm just unsure how to manipulate it in order to achieve the desired effect.
  3. chiranjivi

    Applying alpha gradient to an image

      The tooltip for the downvote button says 'this response is not useful', which I didn't find it to be. It seems to me like I was using it appropriately, but whatever you say, I guess.
  4. chiranjivi

    Applying alpha gradient to an image

      I'd welcome suggestions as to how I can do that with LibGDX/OpenGL, if you have any. I understand in theory that that's what I need to do, the reason I'm asking the question is because I don't understand how to actually effect it
  5. I have an image that's dynamically generated. I need to apply an alpha gradient to this image so that it 'fades out' at the edges. How can I do this? To illustrate things a bit here are some pictures. Let's say I have an image and a background;     I need to fade in the edges of the image, and then draw it onto the background. If the background were, say, entirely white, then I could 'fake' this fading effect by drawing a pre-created white quad with a linear gradient over the image at each end, like this:   If the background is another image however then I obviously can't do this, because I end up with something like this:       What I'd like to be ending up with is this:     ...but I don't know how I can manage that. I'm using LibGDX if that matters, but I suppose this is a framework-agnostic question really?
  6. chiranjivi

    Boost serialization exception problems

      Thanks for the advice - I did this and apparently it was one of the booleans that was causing the problem (the exception code had me looking in all the wrong places!). My tile factory function creates a Tile object and then sets all its variables depending on what type of tile it is; due to an oversight I was apparently setting a bool to an uninitialised value, and though it wasn't causing any ingame problems, Boost didn't like trying to serialize it. I'm still a bit confused about why it was throwing that particular exception code but all's well that ends well.
  7. Hi all, I'm trying to implement serialization, using boost, into a new game. To start, I built a small tester app with a main object which contained a vector of pointers to sub-objects, and everything worked fine; I could save and load states of the main object and all containers and such, no problem. Moving on, I tried to implement something similar in my current project. The object I am trying to serialize is a Level; it contains a bunch of assorted variables, and an array of Tile objects representing the map. I added serialize functions to the class declarations as follows:   class Level {     public:     Level (int _y, int _x);     Tile tmap[256][256];     int AREA_W, AREA_H;     // ...functions removed for clarity     friend class boost::serialization::access;     template<class Archive>     void serialize(Archive & ar, const unsigned int version) {         ar & AREA_H;         ar & AREA_W;         ar & tmap;     } }; class Tile { public: Tile (); int ac, rot, lmap[4]; bool w, s, l, b, a, c; string tc, name; // ...functions removed for clarity friend class boost::serialization::access; template<class Archive> void serialize(Archive & ar, const unsigned int version) { ar & ac; ar & rot; ar & lmap; ar & w; ar & s; ar & l; ar & b; ar & a; ar & c; ar & tc; ar & name; } }; However, If I actually try to deserialize the Level object while the app is running (serializing works fine as far as I can tell from looking at the output file), I get this rather intimidating call stack:       I don't know what I've done wrong as serializing simple types like this seems pretty standard? If I catch the exception that Boost throws and examine it:     std::ifstream ifs("savegame1.sav");     boost::archive::text_iarchive ia(ifs);     try {         // blah     } catch (const boost::archive::archive_exception e) {         cout << "boost::archive exception code is "<< e.code << endl;     } ...I get the console output  boost::archive exception code is 8. This confuses me a bit, because according to the boost docs (http://www.boost.org/doc/libs/1_54_0/libs/serialization/doc/exceptions.html), exception code enum 8 is...         unregistered_cast,      // base - derived relationship not registered with                                 // void_cast_register ... and I'm not serializing or deserializing any derived objects. I would welcome any help as I am pretty lost. Thanks in advance.
  8. chiranjivi

    Segfault upon exiting application

      Ah, yeah that seems like it would be it. I recently made an abstract class from which the player and the enemies derive so that they can share common functions, and the player object is global for the sake of convenience. What issue with the destructors is this causing? (Despite now knowing where the problem lies I'm still not sure how I can fix it).   Thanks for your help.
  9. I'm working on a project at the moment in CodeBlocks using SDL2. At some point during development (I'm not exactly sure when ) the application began to segfault upon closing down.   If I set a breakpoint somewhere and step through the code line-by-line, the crash doesn't happen until after the app successfully executes return 0; at the end of int main, so I don't know where I should be looking for the error.   When the segfault occurs, the console output usually reads "Process returned 255 (0xFF)", although I infrequently get "Process returned -1073741819 (0xC0000005)" instead, seemingly at random. 0xC0000005 as far as I can tell means it is accessing memory it shouldn't?   Here's a screenshot of the call stack:     I would post some code, but I have no idea what code might actually be relevant and the project is very large. I would welcome any insight here as I have no idea what is going on! Thanks in advance for any replies.   edited to add: apologies if this question would be better suited for a different subforum, I didn't really know where to put it
  10. chiranjivi

    Management of game objects

    Thanks both for your replies.     How would I handle deletion of objects in this scenario? Say we update everything in the master list and determine that an enemy's life has reached zero, so we erase it from the vector. Isn't there now a pointer in the Enemies type container which points to an unused memory location? Apologies if there is a simple answer to this that I am not seeing.
  11. Hi all,   I'm trying to implement a sensible management system for all the objects in a basic platform game. There are various types of objects - projectiles, the player, enemies, powerups, moving platforms, that type of thing.   Initially I thought for the sake of simplicity I'd have all objects derive from a base class Entity, and then stick them all in a vector<Entity*>. Then when it's time for them to act or to be drawn to the screen, I can just make a single pass over the vector and call it->update() or it->display(). This saves a bunch of code duplication from having them all in separate vectors for each type and having to iterate over each vector separately to call display functions and so on.   Difficulties arise with this method when I need to do something like collision-test all Projectiles against all Enemies - I have to iterate over the vector, testing if each element is a Projectile, and if it is, iterate over the vector again testing to see if each element is an Enemy, and then testing for a collision if so. I have to do this a bunch of times for, say, enemies vs projectiles, player vs projectiles, player vs powerups, enemies vs player, and it turns into a huge tangled mess of code and nested iterations over the vector, and the vast majority of element comparisons don't need to be made as the entities are of the wrong type.   I'm looking for an elegant way to simplify this, so that Type A vs Type B checks are as simple as possible, and also so that mass updating and displaying of objects is equally simple.   Is there an accepted best practice for this kind of thing? Thanks in advance for any replies.
  12. chiranjivi

    C++ vector of boost::weak_ptr troubles

    edit: how the hell did I post this twice
  13. chiranjivi

    C++ vector of boost::weak_ptr troubles

    Thanks everyone for your responses. I am still struggling with this, unfortunately.     That's actually the exact code I was using to begin with; I just simplified it for the purpose of posting the thread! It doesn't work in the same way that the original code doesn't work.       It isn't, I stuck a call to cout in the if {} block that checks some properties of the object like its XY position (std::cout<<this_ship->x<<":"<<this_ship->y<<std::endl;) and it returned the correct values, so shared_ptr is functioning properly and is pointing at a valid object.       On the function call itself. I don't really know what to make of that.
  14. I have a game that has a number of ships in space. The ships exist in the gameworld as boost::shared_ptr<Ship>. These ships can attack one another. The Ship class has a boost::weak_ptr<Ship> called target, which holds a reference to whatever it's currently firing at, and it also has a vector of weak_ptr<Ship> called aggro_vector. The aggro vector records all ships that have attacked this Ship, so that when it kills its current target, it can consult its aggro vector to see which other ships it is currently in combat with, and pick a new target.   This is the Ship class, sanitised: class Ship { public: Ship (int x, int y); boost::weak_ptr<Ship> target; std::vector< boost::weak_ptr<Ship> > aggro_vector; void determine_next_target(); void set_as_target (boost::shared_ptr<Ship> next_target); }   What I'm having trouble with is getting the Ship to correctly look through its aggro_vector and choose a new target.   Here is the function that picks the next target from the aggro vector. It iterates through all the weak_ptrs, and if .lock() successfully returns a shared_ptr, it hands this shared_ptr off to the member function that registers the next target. Otherwise the weak_ptr refers to a ship that has since been destroyed and is removed from the aggro vector: void Ship::determine_next_target() { std::vector< boost::weak_ptr<Ship> >::iterator it = aggro_vector.begin(); while(it != aggro_vector.end()) { if (boost::shared_ptr<Ship> this_ship = (*it).lock()) { set_as_target(this_ship); ++it; } else { it = aggro_vector.erase(it); } } }   When this code is compiled and run, it crashes at the line set_as_target(this_ship). If this line is commented out, the remainder of the code works as it should (although obviously the determine_next_target() function now does nothing other than remove expired weak_ptrs).   To be clear, the set_as_target(boost::shared_ptr<Ship>) function works fine and is called from a bunch of other places in the code with no problem. It doesn't appear to be that function, but rather the fact that I'm attempting to call that function in this way.   Why am I having problems passing a shared_ptr to an outside function in this fashion? Is there something about iterating over a vector of weak_ptr that I'm missing, or am I just failing to grasp, in the broader sense, some aspect of how these pointers should be used?   Thanks in advance for any help.
  15. chiranjivi

    GLFW/GLUT glutBitmapString - high CPU usage?

    Martins, Thanks for your reply, I will look into the alternatives you recommended.
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