Archived

This topic is now archived and is closed to further replies.

RuneLancer

OpenGL How do I set up 2D in OpenGL? o.o

Recommended Posts

Sorry, that was too good to pass up. No, I''m not going to ask the stupid question that''s been asked so often a sticky ended up being made. I''m going to ask a question about 3D. You may all put the torches and pointy objects down now. What is the best way to store a series of triangles or quads in a file? I''m trying to keep track of the most things I can, but I don''t want to have 3-4 meg maps by the time I''m through. So far I''m storing the texture ID of the polygon, texture coordinates (to stretch and tile stuff), the XYZ coordinates of each point, and the RGBA color (so I can have, say, a blue house or a red house with the same texture, as well as having alpha transparency too; this is with glColor, btw). This is for every polygon. Surely, there''s a better way to do this? It also seems as though I''ll be chewing up a lot of overhead by switching textures and seeting new colors every polygon... Any suggestions on how to make it run as smooth as possible? (I''m rather new to this domaine, if you can''t tell. )

Share this post


Link to post
Share on other sites
quote:
Original post by RuneLancer
So far I''m storing the texture ID of the polygon, texture coordinates (to stretch and tile stuff), the XYZ coordinates of each point, and the RGBA color.

I hope you realise that the texture id you use to bind a texture is different each time your application runs. You''ll need to reference the actual texure filename and somehow associate that with your texture id.

quote:
I''ll be chewing up a lot of overhead by switching textures and seeting new colors every polygon... Any suggestions on how to make it run as smooth as possible? (I''m rather new to this domaine, if you can''t tell. )

Per-poly (or even per vertex) colours are not a problem - you can just bung them in an array running parallel with your vertex positions and it''ll work fine. Per-poly textures however is another matter. You should batch your triangles by surface properties (particularly textures and material settings) so you end up drawing all polys with a texture at once.

Whether you group your polys at load time or when you actually save them to disk is another matter. If you''ve got things like characters and objects odds are you''ll only have a single texture per object. For things like levels you''ll probably have textures spread all over the place and it might be easier to group them into batches just before rendering (after figuring out whats visible).

Share this post


Link to post
Share on other sites
By texture ID, I don''t mean OpenGL''s texture ID, but rather the in-game ID I use to refer to the various textures I''ll have loaded in memory.

So I should group stuff by property? That gives me a few ideas...

I could group by texture, and then in every texture group, group by color. Since I will probably be using the same color (1.0f 1.0f 1.0f) for most of the polygons, I''d have large chunks I could group together. Or an other option would be to have a flag stating wether I want to change the colors or not, and if this flag is on I''d have an extra set of data for the colors. Otherwise, I''d use 1.0f 1.0f 1.0f by default.

That would mean loading stuff sequentially instead of just memcpy''ing right into my array, but load-time is where the player expects a few seconds of delay anyways. And, really, loading a few hundred kilobytes of data sequentially takes, what, a few seconds at most?

I''ll try that. I''m still mostly thinking in 2D, where tiles have to be in the same order that they''ll be displayed since they''d be blitted in a for loop that covers the map''s X/Y area. With polygons, it doesn''t matter. So I guess proper organization of my vertices could help reduce redundant data in my map files...

Share this post


Link to post
Share on other sites
quote:
Original post by RuneLancer
Or an other option would be to have a flag stating wether I want to change the colors or not, and if this flag is on I''d have an extra set of data for the colors. Otherwise, I''d use 1.0f 1.0f 1.0f by default.

My gut feeling is that would be the better choice. You''ve effectivly got an optional set of vertex colours that way, and the case where you have a single non-white colour for a group of polys is unlikely.

quote:
That would mean loading stuff sequentially instead of just memcpy''ing right into my array, but load-time is where the player expects a few seconds of delay anyways. And, really, loading a few hundred kilobytes of data sequentially takes, what, a few seconds at most?

Load & save time is effectivly ''free'' (within reason) so if you can save runtime speed and/or memory by a slightly more complex load mechanism thats a good trade off.

quote:
I''ll try that. I''m still mostly thinking in 2D, where tiles have to be in the same order that they''ll be displayed since they''d be blitted in a for loop that covers the map''s X/Y area.

I find the easiest way of thinking about this is to have some sort of abstract renderer layer inbetween the drawing code and OpenGL. That way you can do something simple (like an x/y loop over visible tiles and draw each in order) which looks like regular blitting. But what your renderer is actually doing is not drawing them directly but putting them into groups ready for a final, optimally sorted, drawing bit just before you swap your display buffers.

Share this post


Link to post
Share on other sites

  • Announcements

  • Forum Statistics

    • Total Topics
      628342
    • Total Posts
      2982176
  • Similar Content

    • By test opty
      Hi all,
       
      I'm starting OpenGL using a tut on the Web. But at this point I would like to know the primitives needed for creating a window using OpenGL. So on Windows and using MS VS 2017, what is the simplest code required to render a window with the title of "First Rectangle", please?
       
       
    • By DejayHextrix
      Hi, New here. 
      I need some help. My fiance and I like to play this mobile game online that goes by real time. Her and I are always working but when we have free time we like to play this game. We don't always got time throughout the day to Queue Buildings, troops, Upgrades....etc.... 
      I was told to look into DLL Injection and OpenGL/DirectX Hooking. Is this true? Is this what I need to learn? 
      How do I read the Android files, or modify the files, or get the in-game tags/variables for the game I want? 
      Any assistance on this would be most appreciated. I been everywhere and seems no one knows or is to lazy to help me out. It would be nice to have assistance for once. I don't know what I need to learn. 
      So links of topics I need to learn within the comment section would be SOOOOO.....Helpful. Anything to just get me started. 
      Thanks, 
      Dejay Hextrix 
    • By mellinoe
      Hi all,
      First time poster here, although I've been reading posts here for quite a while. This place has been invaluable for learning graphics programming -- thanks for a great resource!
      Right now, I'm working on a graphics abstraction layer for .NET which supports D3D11, Vulkan, and OpenGL at the moment. I have implemented most of my planned features already, and things are working well. Some remaining features that I am planning are Compute Shaders, and some flavor of read-write shader resources. At the moment, my shaders can just get simple read-only access to a uniform (or constant) buffer, a texture, or a sampler. Unfortunately, I'm having a tough time grasping the distinctions between all of the different kinds of read-write resources that are available. In D3D alone, there seem to be 5 or 6 different kinds of resources with similar but different characteristics. On top of that, I get the impression that some of them are more or less "obsoleted" by the newer kinds, and don't have much of a place in modern code. There seem to be a few pivots:
      The data source/destination (buffer or texture) Read-write or read-only Structured or unstructured (?) Ordered vs unordered (?) These are just my observations based on a lot of MSDN and OpenGL doc reading. For my library, I'm not interested in exposing every possibility to the user -- just trying to find a good "middle-ground" that can be represented cleanly across API's which is good enough for common scenarios.
      Can anyone give a sort of "overview" of the different options, and perhaps compare/contrast the concepts between Direct3D, OpenGL, and Vulkan? I'd also be very interested in hearing how other folks have abstracted these concepts in their libraries.
    • By aejt
      I recently started getting into graphics programming (2nd try, first try was many years ago) and I'm working on a 3d rendering engine which I hope to be able to make a 3D game with sooner or later. I have plenty of C++ experience, but not a lot when it comes to graphics, and while it's definitely going much better this time, I'm having trouble figuring out how assets are usually handled by engines.
      I'm not having trouble with handling the GPU resources, but more so with how the resources should be defined and used in the system (materials, models, etc).
      This is my plan now, I've implemented most of it except for the XML parts and factories and those are the ones I'm not sure of at all:
      I have these classes:
      For GPU resources:
      Geometry: holds and manages everything needed to render a geometry: VAO, VBO, EBO. Texture: holds and manages a texture which is loaded into the GPU. Shader: holds and manages a shader which is loaded into the GPU. For assets relying on GPU resources:
      Material: holds a shader resource, multiple texture resources, as well as uniform settings. Mesh: holds a geometry and a material. Model: holds multiple meshes, possibly in a tree structure to more easily support skinning later on? For handling GPU resources:
      ResourceCache<T>: T can be any resource loaded into the GPU. It owns these resources and only hands out handles to them on request (currently string identifiers are used when requesting handles, but all resources are stored in a vector and each handle only contains resource's index in that vector) Resource<T>: The handles given out from ResourceCache. The handles are reference counted and to get the underlying resource you simply deference like with pointers (*handle).  
      And my plan is to define everything into these XML documents to abstract away files:
      Resources.xml for ref-counted GPU resources (geometry, shaders, textures) Resources are assigned names/ids and resource files, and possibly some attributes (what vertex attributes does this geometry have? what vertex attributes does this shader expect? what uniforms does this shader use? and so on) Are reference counted using ResourceCache<T> Assets.xml for assets using the GPU resources (materials, meshes, models) Assets are not reference counted, but they hold handles to ref-counted resources. References the resources defined in Resources.xml by names/ids. The XMLs are loaded into some structure in memory which is then used for loading the resources/assets using factory classes:
      Factory classes for resources:
      For example, a texture factory could contain the texture definitions from the XML containing data about textures in the game, as well as a cache containing all loaded textures. This means it has mappings from each name/id to a file and when asked to load a texture with a name/id, it can look up its path and use a "BinaryLoader" to either load the file and create the resource directly, or asynchronously load the file's data into a queue which then can be read from later to create the resources synchronously in the GL context. These factories only return handles.
      Factory classes for assets:
      Much like for resources, these classes contain the definitions for the assets they can load. For example, with the definition the MaterialFactory will know which shader, textures and possibly uniform a certain material has, and with the help of TextureFactory and ShaderFactory, it can retrieve handles to the resources it needs (Shader + Textures), setup itself from XML data (uniform values), and return a created instance of requested material. These factories return actual instances, not handles (but the instances contain handles).
       
       
      Is this a good or commonly used approach? Is this going to bite me in the ass later on? Are there other more preferable approaches? Is this outside of the scope of a 3d renderer and should be on the engine side? I'd love to receive and kind of advice or suggestions!
      Thanks!
    • By nedondev
      I 'm learning how to create game by using opengl with c/c++ coding, so here is my fist game. In video description also have game contain in Dropbox. May be I will make it better in future.
      Thanks.
  • Popular Now