• Advertisement
Sign in to follow this  

OpenGL cross platform game dev questions

This topic is 4975 days old which is more than the 365 day threshold we allow for new replies. Please post a new topic.

If you intended to correct an error in the post then please contact us.

Recommended Posts

Greetings y'all. A close friend of mine and I have been kicking around the idea of developing a game together over the past nine months or so. While we've done a few things here and there (he's done some concept art, I've done some prototyping and what not), we haven't done a whole lot of core game functionality. Originally this was going to be a Windows only game, done pretty much all in DirectX, but over the past few weeks I got to thinking otherwise. You see, the two of us don't know if this game will even make any sort of money, but we keep optimistic. In fact, I was hoping it'd eventually become something like shareware. So with that in mind, I decided I'd begin the design over from scratch, but this time keeping in mind that I want this game to be able to run at least on Windows and Mac platforms, and hopefully can reach Linux gamers out there. The game is really a simple top down 2Dish game, very similar to GTA2 style graphics. Input is primarily (pretty much exclusively) keyboard driven. Now that I've taken quite a bit of time explaining the situation, allow me to dive into my questions. I must first say, though, that this is really my first full-fledged game that I'm programming. I know some of you may think that I'm biting off way more than I can chew, but believe me, I'm a very ambitious person. If I want to get something done, I'll stick to it until the end, and developing this game is something I have wanted to get done for a while now. ;) Anyways, on to the questions. Because I want this to be a cross platform project, I've pretty much committed to using OpenGL for my graphics API (I want the buildings to have that 3D feel to them like in GTA2). Now I've started reading up on how to use OpenGL and what not by reading the Red Book, and it's all fairly simple reading so far, nothing I can't handle. But the thing that's been racking my brain is the whole basic window creation step. I know how to create the window in Windows, but obviously that won't work on Mac or Linux platforms. So this leads me to investigating further by searching the forums and the Net. Now I've read a lot about SDL, and have seen that many people here have recommended using SDL, especially when it comes to the initial window set up. I've also read you can directly utilize OpenGL while using SDL. I guess it'd be a no-brainer to ask if SDL is an excellent choice for cross-platform development? Are there any snags or gotchas I should watch out for if I decide going the SDL+OpenGL route? Also, and I know I probably should need to worry about this, but for curiousity's sake, what sorts of limitations are there when you use OpenGL through SDL? Are some features inaccessible? Is there any reason to be looking for alternatives to SDL? As far as audio is concerned, I planned on using OpenAL for a cross platform library to handle playing my sound and music (which will most likely be in *.ogg format). Is there any reason why this library shouldn't work with OpenGL+SDL, or can I expect it to work fairly seemlessly with it? And I guess lastly, any tips or words of advice or 'gotchas' anyone can offer? Like, any endian issues or any platform specific issues I need to watch out for, or anything you've learned from experience that you can part on? I'm sorry, I realize this was a long and somewhat discombobulated post, but I do appreciate and thank you all taking the time to read it and giving help you can offer. :)

Share this post


Link to post
Share on other sites
Advertisement
There's really no reason to use anything other than SDL when using OpenGL as your primary graphics API.

SDL will take care of window creation, and give you a generic Event mechanism. SDL_img will take care of loading all kinds of image formats (and google must have something on converting SDL_Surfaces to GL textures by now). SDL_mixer or OpenAL will take care of sound. SDL_net will take care of doing network access.

Did I miss anything?

Share this post


Link to post
Share on other sites
SDL is teh r0x.
Seriously, we use SDL for Eternal Lands, and it works GREAT.
However, SDL is not very good with the sound, so I suggest using OpenAL and OGG/Vorbis (if you want music).
You can also use sdl_net for network (if you need network).

Share this post


Link to post
Share on other sites
well, porting opengl through sdl is an excellent choice. i'm starting to do it myself, more to avoid the travesty of using the winapi than crossplatform issues, but it is nice and simple. the only thing i've come across that you need to be aware of are several of the functions used in opengl that have been converted to sdl (such as SDL_GL_SwapBuffers()). however, they are few and far between, so there really should be no problem. however, since you asked, you can port opengl through several scripts (most notably, python), but you'd be porting opengl through a ported script (if you were writing in c++) which can be a pain. just fyi. anyway, good luck, and give word when you're done. sounds interesting.

Share this post


Link to post
Share on other sites
Sign in to follow this  

  • Advertisement
  • Advertisement
  • Popular Tags

  • Advertisement
  • Popular Now

  • Similar Content

    • By LifeArtist
      Good Evening,
      I want to make a 2D game which involves displaying some debug information. Especially for collision, enemy sights and so on ...
      First of I was thinking about all those shapes which I need will need for debugging purposes: circles, rectangles, lines, polygons.
      I am really stucked right now because of the fundamental question:
      Where do I store my vertices positions for each line (object)? Currently I am not using a model matrix because I am using orthographic projection and set the final position within the VBO. That means that if I add a new line I would have to expand the "points" array and re-upload (recall glBufferData) it every time. The other method would be to use a model matrix and a fixed vbo for a line but it would be also messy to exactly create a line from (0,0) to (100,20) calculating the rotation and scale to make it fit.
      If I proceed with option 1 "updating the array each frame" I was thinking of having 4 draw calls every frame for the lines vao, polygons vao and so on. 
      In addition to that I am planning to use some sort of ECS based architecture. So the other question would be:
      Should I treat those debug objects as entities/components?
      For me it would make sense to treat them as entities but that's creates a new issue with the previous array approach because it would have for example a transform and render component. A special render component for debug objects (no texture etc) ... For me the transform component is also just a matrix but how would I then define a line?
      Treating them as components would'nt be a good idea in my eyes because then I would always need an entity. Well entity is just an id !? So maybe its a component?
      Regards,
      LifeArtist
    • By QQemka
      Hello. I am coding a small thingy in my spare time. All i want to achieve is to load a heightmap (as the lowest possible walking terrain), some static meshes (elements of the environment) and a dynamic character (meaning i can move, collide with heightmap/static meshes and hold a varying item in a hand ). Got a bunch of questions, or rather problems i can't find solution to myself. Nearly all are deal with graphics/gpu, not the coding part. My c++ is on high enough level.
      Let's go:
      Heightmap - i obviously want it to be textured, size is hardcoded to 256x256 squares. I can't have one huge texture stretched over entire terrain cause every pixel would be enormous. Thats why i decided to use 2 specified textures. First will be a tileset consisting of 16 square tiles (u v range from 0 to 0.25 for first tile and so on) and second a 256x256 buffer with 0-15 value representing index of the tile from tileset for every heigtmap square. Problem is, how do i blend the edges nicely and make some computationally cheap changes so its not obvious there are only 16 tiles? Is it possible to generate such terrain with some existing program?
      Collisions - i want to use bounding sphere and aabb. But should i store them for a model or entity instance? Meaning i have 20 same trees spawned using the same tree model, but every entity got its own transformation (position, scale etc). Storing collision component per instance grats faster access + is precalculated and transformed (takes additional memory, but who cares?), so i stick with this, right? What should i do if object is dynamically rotated? The aabb is no longer aligned and calculating per vertex min/max everytime object rotates/scales is pretty expensive, right?
      Drawing aabb - problem similar to above (storing aabb data per instance or model). This time in my opinion per model is enough since every instance also does not have own vertex buffer but uses the shared one (so 20 trees share reference to one tree model). So rendering aabb is about taking the model's aabb, transforming with instance matrix and voila. What about aabb vertex buffer (this is more of a cosmetic question, just curious, bumped onto it in time of writing this). Is it better to make it as 8 points and index buffer (12 lines), or only 2 vertices with min/max x/y/z and having the shaders dynamically generate 6 other vertices and draw the box? Or maybe there should be just ONE 1x1x1 cube box template moved/scaled per entity?
      What if one model got a diffuse texture and a normal map, and other has only diffuse? Should i pass some bool flag to shader with that info, or just assume that my game supports only diffuse maps without fancy stuff?
      There were several more but i forgot/solved them at time of writing
      Thanks in advance
    • By RenanRR
      Hi All,
      I'm reading the tutorials from learnOpengl site (nice site) and I'm having a question on the camera (https://learnopengl.com/Getting-started/Camera).
      I always saw the camera being manipulated with the lookat, but in tutorial I saw the camera being changed through the MVP arrays, which do not seem to be camera, but rather the scene that changes:
      Vertex Shader:
      #version 330 core layout (location = 0) in vec3 aPos; layout (location = 1) in vec2 aTexCoord; out vec2 TexCoord; uniform mat4 model; uniform mat4 view; uniform mat4 projection; void main() { gl_Position = projection * view * model * vec4(aPos, 1.0f); TexCoord = vec2(aTexCoord.x, aTexCoord.y); } then, the matrix manipulated:
      ..... glm::mat4 projection = glm::perspective(glm::radians(fov), (float)SCR_WIDTH / (float)SCR_HEIGHT, 0.1f, 100.0f); ourShader.setMat4("projection", projection); .... glm::mat4 view = glm::lookAt(cameraPos, cameraPos + cameraFront, cameraUp); ourShader.setMat4("view", view); .... model = glm::rotate(model, glm::radians(angle), glm::vec3(1.0f, 0.3f, 0.5f)); ourShader.setMat4("model", model);  
      So, some doubts:
      - Why use it like that?
      - Is it okay to manipulate the camera that way?
      -in this way, are not the vertex's positions that changes instead of the camera?
      - I need to pass MVP to all shaders of object in my scenes ?
       
      What it seems, is that the camera stands still and the scenery that changes...
      it's right?
       
       
      Thank you
       
    • By dpadam450
      Sampling a floating point texture where the alpha channel holds 4-bytes of packed data into the float. I don't know how to cast the raw memory to treat it as an integer so I can perform bit-shifting operations.

      int rgbValue = int(textureSample.w);//4 bytes of data packed as color
      // algorithm might not be correct and endianness might need switching.
      vec3 extractedData = vec3(  rgbValue & 0xFF000000,  (rgbValue << 8) & 0xFF000000, (rgbValue << 16) & 0xFF000000);
      extractedData /= 255.0f;
    • By Devashish Khandelwal
      While writing a simple renderer using OpenGL, I faced an issue with the glGetUniformLocation function. For some reason, the location is coming to be -1.
      Anyone has any idea .. what should I do?
  • Advertisement