Sign in to follow this  
Blasteroids

OpenGL Rendering Order Advice Please

Recommended Posts

Blasteroids    122
Hello all, This is my first attempt at OpenGL programming and engine programming. Its not brilliant but its giving me lots of experience. I have implemented a type of scene graph with automatic bounds calculation and use this for culling and rendering. Currently I am rendering objects as I encouter then in the scene graph, unless they are culled. I should be able to easily extract these into a culling bin for sorting but what order should the objects be rendered in OpenGL? What would be the fastest/correct way of drawing the objects with alpha, etc ? I hope that makes sense :) Here are a couple of images of a very basic engine test; Exe of test http://exoload.net/uploads/806/1155975677.zip Keys Arrows : up/down/left/right camera move C : Culling B : Culling Bounds show M : Mouse look (Limited) If anyone tried test, please post FPSc result at stock load before movement that would be great! Slightly offtopic from OpenGL now, I noticed on one machine that in mouselook its very "jerky" but on others it was not. I am using just window messaging. Has anyone else found this ? Perhaps I would be better off using DirectInput ? Thanks in advance!

Share this post


Link to post
Share on other sites
reiko    290
If the objects use alpha blending, you will generally need to render in back-to-front (furthest-to-nearest) order for it to look correct.

Without alpha blending rendering order becomes less important, but you may find you get better hardware depth culling by rendering in front-to-back order.

If the scene has objects with and without blending, then try to render all the non-blended objects first, front-to-back, then the blended ones, back-to-front.

Can't help with the jittery mouse problem though, sorry!

Share this post


Link to post
Share on other sites
Blasteroids    122
reiko,
Thanks for the info, I think I am starting to understand a little.

So I would do this;
1) Enable depth buffer testing.
2) Sort all objects by Z.
3) Render all non-alpha objects from near to far.
4) Render all alpha objects from far to near.

I will try and give that a go when I get some time.

Thanks again for the info.

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  

  • Similar Content

    • By povilaslt2
      Hello. I'm Programmer who is in search of 2D game project who preferably uses OpenGL and C++. You can see my projects in GitHub. Project genre doesn't matter (except MMO's :D).
    • By ZeldaFan555
      Hello, My name is Matt. I am a programmer. I mostly use Java, but can use C++ and various other languages. I'm looking for someone to partner up with for random projects, preferably using OpenGL, though I'd be open to just about anything. If you're interested you can contact me on Skype or on here, thank you!
      Skype: Mangodoor408
    • By tyhender
      Hello, my name is Mark. I'm hobby programmer. 
      So recently,I thought that it's good idea to find people to create a full 3D engine. I'm looking for people experienced in scripting 3D shaders and implementing physics into engine(game)(we are going to use the React physics engine). 
      And,ye,no money =D I'm just looking for hobbyists that will be proud of their work. If engine(or game) will have financial succes,well,then maybe =D
      Sorry for late replies.
      I mostly give more information when people PM me,but this post is REALLY short,even for me =D
      So here's few more points:
      Engine will use openGL and SDL for graphics. It will use React3D physics library for physics simulation. Engine(most probably,atleast for the first part) won't have graphical fron-end,it will be a framework . I think final engine should be enough to set up an FPS in a couple of minutes. A bit about my self:
      I've been programming for 7 years total. I learned very slowly it as "secondary interesting thing" for like 3 years, but then began to script more seriously.  My primary language is C++,which we are going to use for the engine. Yes,I did 3D graphics with physics simulation before. No, my portfolio isn't very impressive. I'm working on that No,I wasn't employed officially. If anybody need to know more PM me. 
       
    • By Zaphyk
      I am developing my engine using the OpenGL 3.3 compatibility profile. It runs as expected on my NVIDIA card and on my Intel Card however when I tried it on an AMD setup it ran 3 times worse than on the other setups. Could this be a AMD driver thing or is this probably a problem with my OGL code? Could a different code standard create such bad performance?
    • By Kjell Andersson
      I'm trying to get some legacy OpenGL code to run with a shader pipeline,
      The legacy code uses glVertexPointer(), glColorPointer(), glNormalPointer() and glTexCoordPointer() to supply the vertex information.
      I know that it should be using setVertexAttribPointer() etc to clearly define the layout but that is not an option right now since the legacy code can't be modified to that extent.
      I've got a version 330 vertex shader to somewhat work:
      #version 330 uniform mat4 osg_ModelViewProjectionMatrix; uniform mat4 osg_ModelViewMatrix; layout(location = 0) in vec4 Vertex; layout(location = 2) in vec4 Normal; // Velocity layout(location = 3) in vec3 TexCoord; // TODO: is this the right layout location? out VertexData { vec4 color; vec3 velocity; float size; } VertexOut; void main(void) { vec4 p0 = Vertex; vec4 p1 = Vertex + vec4(Normal.x, Normal.y, Normal.z, 0.0f); vec3 velocity = (osg_ModelViewProjectionMatrix * p1 - osg_ModelViewProjectionMatrix * p0).xyz; VertexOut.velocity = velocity; VertexOut.size = TexCoord.y; gl_Position = osg_ModelViewMatrix * Vertex; } What works is the Vertex and Normal information that the legacy C++ OpenGL code seem to provide in layout location 0 and 2. This is fine.
      What I'm not getting to work is the TexCoord information that is supplied by a glTexCoordPointer() call in C++.
      Question:
      What layout location is the old standard pipeline using for glTexCoordPointer()? Or is this undefined?
       
      Side note: I'm trying to get an OpenSceneGraph 3.4.0 particle system to use custom vertex, geometry and fragment shaders for rendering the particles.
  • Popular Now