Sign in to follow this  
Followers 0
lanhaiou

OpenGL
is glBindTexture() not efficency ?

1 post in this topic

Hello,

I am trying to write a tile based 2D game using openGL, and I'm new to openGL..
I heard that glBindTexture() is not efficency and we'd better to bind texture only one time and drawing all the staff using this texture(this texture

constains all the tiles we need).
so I have 2 questions, could anybody help? thanks very much!
1\ Is this description above right ?
2\ Is the following Game logic the right way to rendering a game with good efficency?
if not, could I have some indication? thanks?

/* this render() is called every 30 millisecond to render the game.
there may be about 2000 tiles need to be rendered one time. */

render()
{
glEnable2D;
/*this texture contains all the tiles needed in the game*/
glBindTexture(GL_TEXTURE_2D, mTexture);

glClear();
for(...)// the drawing loop to draw all the staff
{
/* draw the needed tiles from the same texture */
glBegin();
//drawing...
glEnd();
}
SwapBuffers();
glDisable2D;
}

Thanks!
0

Share this post


Link to post
Share on other sites
glBindTexture will likely cause a pipeline stall at the next draw call. Insofar, glBindTexture is not inefficient itself, but using it too often is. I say "likely" because it is possible that it does not cause a stall, depending on the hardware (but you have to assume the worst case, not the best case).

On the other hand, glBegin/glEnd is not efficient for drawing thousands of tiles (i.e. single quads) either.

What you want to do ideally is bind a texture once, bind a vertex buffer, and draw your 2000 quads with one call to [url="http://www.opengl.org/sdk/docs/man3/xhtml/glDrawElements.xml"]glDrawElements[/url]. Even using a plain old vertex array (i.e. not a buffer object) would be much preferrable, because it's much more efficient for the GL to upload that block of data.
1

Share this post


Link to post
Share on other sites
Thank you very much ![img]http://public.gamedev.net//public/style_emoticons/default/smile.png[/img]

[quote name='samoth' timestamp='1332156865' post='4923258']
glBindTexture will likely cause a pipeline stall at the next draw call. Insofar, glBindTexture is not inefficient itself, but using it too often is. I say "likely" because it is possible that it does not cause a stall, depending on the hardware (but you have to assume the worst case, not the best case).

On the other hand, glBegin/glEnd is not efficient for drawing thousands of tiles (i.e. single quads) either.

What you want to do ideally is bind a texture once, bind a vertex buffer, and draw your 2000 quads with one call to [url="http://www.opengl.org/sdk/docs/man3/xhtml/glDrawElements.xml"]glDrawElements[/url]. Even using a plain old vertex array (i.e. not a buffer object) would be much preferrable, because it's much more efficient for the GL to upload that block of data.
[/quote]
0

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  
Followers 0

  • Similar Content

    • By Jon Alma
      Some time ago I implemented a particle system using billboarding techniques to ensure that the particles are always facing the viewer.  These billboards are always centered on one 3d coordinate.
      I would like to build on this and use billboarding as the basis for things like laser bolts and gunshots.  Here the difference is that instead of a single point particle I now have to draw a billboard between two points - the start and end of the laser bolt for example.  I appreciate that having two end points places limits on how much the billboard can be rotated to face the viewer, but I'm looking to code a best effort solution.  For the moment I am struggling to work out how to do this or find any tutorials / code examples that explain how to draw a billboard between two points ... can anyone help?
      Thanks.
    • By Sagaceil
      It's always better to fight with a bro.
    • By recp
      Hi,
      I'm working on new asset importer (https://github.com/recp/assetkit) based on COLLADA specs, the question is not about COLLADA directly
      also I'm working on a new renderer to render (https://github.com/recp/libgk) imported document.
      In the future I'll spend more time on this renderer of course, currently rendering imported (implemented parts) is enough for me
      assetkit imports COLLADA document (it will support glTF too),
      importing scene, geometries, effects/materials, 2d textures and rendering them seems working
      My actual confusion is about shaders. COLLADA has COMMON profile and GLSL... profiles,
      GLSL profile provides shaders for effects so I don't need to wory about them just compile, link, group them before render

      The problem occours in COMMON profile because I need to write shaders,
      Actually I wrote them for basic matrials and another version for 2d texture
      I would like to create multiple program but I am not sure how to split this this shader into smaller ones,

      Basic material version (only colors):
      https://github.com/recp/libgk/blob/master/src/default/shader/gk_default.frag
      Texture version:
      https://gist.github.com/recp/b0368c74c35d9d6912f524624bfbf5a3
      I used subroutines to bind materials, actually I liked it,
      In scene graph every node can have different program, and it switches between them if parentNode->program != node->program
      (I'll do scene graph optimizations e.g.  view frustum culling, grouping shaders... later)

      I'm going to implement transparency but I'm considering to create separate shaders,
      because default shader is going to be branching hell
      I can't generate shader for every node because I don't know how many node can be exist, there is no limit.
      I don't know how to write a good uber-shader for different cases:

      Here material struct:
      struct Material { ColorOrTexture emission; ColorOrTexture ambient; ColorOrTexture specular; ColorOrTexture reflective; ColorOrTexture transparent; ColorOrTexture diffuse; float shininess; float reflectivEyety; float transparency; float indexOfRefraction; }; ColorOrTexture could be color or 2d texture, if there would be single colorOrTex then I could split into two programs,
      Also I'm going to implement transparency, I am not sure how many program that I needed

      I'm considering to maintain a few default shaders for COMMON profile,
      1-no-texture, 2-one of colorOrTexture contains texture, 3-........

      Any advices in general or about how to optimize/split (if I need) these shaders which I provied as link?
      What do you think the shaders I wrote, I would like to write them without branching if posible,
      I hope I don't need to write 50+ or 100+ shaders, and 100+ default programs

      PS: These default shaders should render any document, they are not specific, they are general purpose...
             I'm compiling and linking default shaders when app launched

      Thanks
    • By CircleOfLight97
      Hi guys,
      I would like to contribute to a game project as a developer (open source possibly). I have some experiences in C/C++ in game development (perso projects). I don't know either unreal or unity but I have some knowledges in opengl, glsl and shading theory as I had some courses at university regarding to that. I have some knowledges in maths and basic in physics. I know a little how to use blender to do modelling, texturing and simple game assets (no characters, no animation no skinning/rigging). I have no game preferences but I like aventure game, dungeon crawler, platformers, randomly generated things. I know these kind of projects involve a lot of time and I'd be really to work on it but if there are no cleary defined specific design goals/stories/gameplay mechanics I would like to not be part of it x) and I would rather prefer a smaller but well defined project to work on that a huge and not 'finishable' one.
      CircleOfLight97
    • By gamesthatcouldbeworse
      Hi, I finally released KILL COMMANDO on gamejolt for free. It is a retro-funsplatter-shooter with C64 style. Give it a try.
  • Popular Now