Sign in to follow this  
Sibil

OpenGL not-power-of-two Textures in Opengl 2.0

Recommended Posts

Hey guys! I googled it not-power-of-two but I found more confused people asking about that that professional people doing tutorial :P From version 2.0 Opengl supports not-power-of-two texture but if just use glTexImage2D with a not-power-of-two image the program crashs. I have Win XP and so the native version of Opengl is 1.1... Do I have to use something like: PFNGLGENBUFFERSARBPROC glGenBuffersARB; glGenBuffersARB = (PFNGLGENBUFFERSARBPROC)wglGetProcAddress("glGenBuffersARB"); to use the TexImage2D of the glext.h...? Does exist a simple program to convert jpg in power-of-two size? I know probably somewhere there are 1000 million tutorials about this 2 questions... So just give me the link because I couldn't find it :P Thank u very much ;)

Share this post


Link to post
Share on other sites
NPOT textures work in the TEXTURE_2D target fine for me. If not for you, try the TEXTURE_RECTANGLE_ARB target if it is available to you, but remember a rectangle's tex coords range from [0-width][0-height] not [0-1][0-1] like normal.

Share this post


Link to post
Share on other sites
Quote:
Original post by Sibil
Hey guys!

I googled it not-power-of-two but I found more confused people asking about that that professional people doing tutorial :P

From version 2.0 Opengl supports not-power-of-two texture but if just use glTexImage2D with a not-power-of-two image the program crashs.
I have Win XP and so the native version of Opengl is 1.1...
Do I have to use something like:

PFNGLGENBUFFERSARBPROC glGenBuffersARB;
glGenBuffersARB = (PFNGLGENBUFFERSARBPROC)wglGetProcAddress("glGenBuffersARB");

to use the TexImage2D of the glext.h...?

Does exist a simple program to convert jpg in power-of-two size?

I know probably somewhere there are 1000 million tutorials about this 2 questions...
So just give me the link because I couldn't find it :P

Thank u very much ;)


If it crashes, there could be different reasons like data alignement is not correct. If you data alignment is 1, then call glPixelStorei(GL_UNPACK_ALIGNMENT, 1);

If your driver reports GL 2.0 and up, then you can use NPOT and mipmaps.
Also, check if GL_ARB_texture_non_power_of_two is present. If present, then it should be completly hw accelerated. If not present, and if you use mipmaps, or anisotropy, or something other than GL_CLAMP_TO_EDGE, it will fall on software path.

Quote:
Does exist a simple program to convert jpg in power-of-two size?


Gimp, it is open source and free.

Share this post


Link to post
Share on other sites
I don't know if it was clear but I can use texture and mipmap with P.O.T. textures the problem occured with NPOT

Quote:

Gimp, it is open source and free.


I'm looking for a program that automaticaly resize the image...
Does Gimp do that? I've something like 40 texture and resize them one by one would be very a waste of time :P

Quote:

Also, check if GL_ARB_texture_non_power_of_two is present. If present, then it should be completly hw accelerated

How Can I check if GL_ARB_texture_non_power_of_two is present?

Quote:

If not present, and if you use mipmaps, or anisotropy, or something other than GL_CLAMP_TO_EDGE, it will fall on software path.


What does fall on software path?

Share this post


Link to post
Share on other sites
Do you want to upload NPOT textures to OpenGL? And I am guessing you don't have a OpenGL2.0 card? If so just use gluBuild2DMipmaps it will resize them for you to the nearest POT. Don't forget to set the min/max filter to correct usage formats.

Oh and get glee or glew extension loader libs. Either one is fine. I use GLEE. This will make your life a lot easier when using newer features.

Share this post


Link to post
Share on other sites
Quote:
Original post by Sibil
I don't know if it was clear but I can use texture and mipmap with P.O.T. textures the problem occured with NPOT

Quote:

Gimp, it is open source and free.


I'm looking for a program that automaticaly resize the image...
Does Gimp do that? I've something like 40 texture and resize them one by one would be very a waste of time :P

Quote:

Also, check if GL_ARB_texture_non_power_of_two is present. If present, then it should be completly hw accelerated

How Can I check if GL_ARB_texture_non_power_of_two is present?

Quote:

If not present, and if you use mipmaps, or anisotropy, or something other than GL_CLAMP_TO_EDGE, it will fall on software path.


What does fall on software path?


Anyway, it sounds like POW2 textures would do it for you. I don't know of any tool that can resize a bunch of textures but I'm sure it is easy to write one.
You can use gluScaleImage to scale.

To check if GL_ARB_texture_non_power_of_two or any other extension is present, there is tons of code out there. I use glhIsGLExtensionSupported from my own glhlibrary

The rendering will fall on the software path.

Share this post


Link to post
Share on other sites
I've check the version with glGetString(GL_VERSION) and I've 2.0.1

However I discover that the program perfectly load NPOT texture!!!
except one of dimension 4050 x 3633 that was the first one that I've tried :P
There are restrictions on the size or on the memory?

Quote:

Also, check if GL_ARB_texture_non_power_of_two is present. If present, then it should be completly hw accelerated


I've also check glGetString(GL_EXTENSION) and in the list there's GL_ARB_texture_non_power_of_two .
That means that GL_ARB_texture_non_power_of_two is working or that I'm able to use that extension if I add some code...?

Share this post


Link to post
Share on other sites
A texture of that size is roughly 58 megabytes (assuming 8bpp RGBA), so it may very well be that you don't have enough (continguous) memory on the card. It depends on what you're allocating as render buffer and what you've uploaded already, of course.
For example, if you have window at 1280*1024, which is not really unreasonable today, that's already 5 MB just for the frame buffer (and up to 3 times as much if you do double/triple buffering). If you have antialiasing enabled, add to that the multisample buffers. Fragmentation may contribute a good bit to it too.

Another theoretical problem might be the maximum texture size, but I'm not aware of any card that's less than 5 years old that doesn't support at least 40962.

NPOT should generally work on OpenGL 1.1 cards too, with "should generally work" as in "should not crash".
The driver should silently allocate the next bigger POT size and simply leave some of it unused.

Share this post


Link to post
Share on other sites
Did you try as V-man said, and use glPixelStorei(GL_UNPACK_ALIGNMENT, 1); Because these dimensions 4050 x 3633 from a quick look don't fall on 4byte alignments. BTW what hardware are you on? Nvidia, ATI, integrated?

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now

Sign in to follow this  

  • Announcements

  • Forum Statistics

    • Total Topics
      628333
    • Total Posts
      2982127
  • Similar Content

    • 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.
    • By Abecederia
      So I've recently started learning some GLSL and now I'm toying with a POM shader. I'm trying to optimize it and notice that it starts having issues at high texture sizes, especially with self-shadowing.
      Now I know POM is expensive either way, but would pulling the heightmap out of the normalmap alpha channel and in it's own 8bit texture make doing all those dozens of texture fetches more cheap? Or is everything in the cache aligned to 32bit anyway? I haven't implemented texture compression yet, I think that would help? But regardless, should there be a performance boost from decoupling the heightmap? I could also keep it in a lower resolution than the normalmap if that would improve performance.
      Any help is much appreciated, please keep in mind I'm somewhat of a newbie. Thanks!
  • Popular Now