• Announcements

    • khawk

      Download the Game Design and Indie Game Marketing Freebook   07/19/17

      GameDev.net and CRC Press have teamed up to bring a free ebook of content curated from top titles published by CRC Press. The freebook, Practices of Game Design & Indie Game Marketing, includes chapters from The Art of Game Design: A Book of Lenses, A Practical Guide to Indie Game Marketing, and An Architectural Approach to Level Design. The GameDev.net FreeBook is relevant to game designers, developers, and those interested in learning more about the challenges in game development. We know game development can be a tough discipline and business, so we picked several chapters from CRC Press titles that we thought would be of interest to you, the GameDev.net audience, in your journey to design, develop, and market your next game. The free ebook is available through CRC Press by clicking here. The Curated Books The Art of Game Design: A Book of Lenses, Second Edition, by Jesse Schell Presents 100+ sets of questions, or different lenses, for viewing a game’s design, encompassing diverse fields such as psychology, architecture, music, film, software engineering, theme park design, mathematics, anthropology, and more. Written by one of the world's top game designers, this book describes the deepest and most fundamental principles of game design, demonstrating how tactics used in board, card, and athletic games also work in video games. It provides practical instruction on creating world-class games that will be played again and again. View it here. A Practical Guide to Indie Game Marketing, by Joel Dreskin Marketing is an essential but too frequently overlooked or minimized component of the release plan for indie games. A Practical Guide to Indie Game Marketing provides you with the tools needed to build visibility and sell your indie games. With special focus on those developers with small budgets and limited staff and resources, this book is packed with tangible recommendations and techniques that you can put to use immediately. As a seasoned professional of the indie game arena, author Joel Dreskin gives you insight into practical, real-world experiences of marketing numerous successful games and also provides stories of the failures. View it here. An Architectural Approach to Level Design This is one of the first books to integrate architectural and spatial design theory with the field of level design. The book presents architectural techniques and theories for level designers to use in their own work. It connects architecture and level design in different ways that address the practical elements of how designers construct space and the experiential elements of how and why humans interact with this space. Throughout the text, readers learn skills for spatial layout, evoking emotion through gamespaces, and creating better levels through architectural theory. View it here. Learn more and download the ebook by clicking here. Did you know? GameDev.net and CRC Press also recently teamed up to bring GDNet+ Members up to a 20% discount on all CRC Press books. Learn more about this and other benefits here.
Sign in to follow this  
Followers 0
aregee

OpenGL
Handling multiple objects (models) with VAOs and VBOs

6 posts in this topic

Having scrapped everything I know about OpenGL, I think I finally have got the grasp on a few of the deal breaking difficulties of "modern" OpenGL.  I can now make a shader from scratch, compile, and connect inputs and outputs and make uniforms to scale, rotate or transform an object.  I have also struggled a bit understand VAOs and VBOs, and how they are connected, but I think I am starting to grasp the concept now.

 

My project is to make a very simple 3D editor.  That sort of makes the data dynamic, although the data in a different setting most likely will be static.  That makes me philosophise a bit about how to organise the objects (models) that you can make in the editor.  I want an as efficient way to handle objects as possible.

 

I have been thinking about three methods:

 

1. One oversized buffer object to handle incoming vertex (color, etc...) data.

2. One VAO, then one VBO for each object.

3. One VAO for each object.

 

I don't like option 1.  I don't like to guesstimate, or the complications that will arise when you fail on your estimate, then need to rebuild buffers or handle removal of objects, etc.  I like to allocate just the right amount of buffer that I need to hold my data, and I want a structure that makes it easy to organise a list of objects.  Besides, I am picturing a tree structure in my head.  That is what I desire.  (Or just a linked list to begin with.)

 

Option 2 is the one I actually prototyped.  That didn't work.  All I got to screen was the last object, no matter what I did.

 

Option 3 is the one that I have come to understand is the way to go.  I don't oppose to this option.  It is much better than 1, but it will incur state changes that I don't need.

 

I actually want to go for option 2.  Is that possible?  Can anyone tell me the exact steps needed for this to work, if it works at all?  If not, I will just implement option 3.  I have already tested that scenario, and it works.

0

Share this post


Link to post
Share on other sites


Option 3 is the one that I have come to understand is the way to go. I don't oppose to this option. It is much better than 1, but it will incur state changes that I don't need.

 

Can you elaborate on what unneeded state changes this will incur? You bind the VAO and then the VBOs for each object once when they are loaded, and from then on all you need to do is set the correct VAO and the object can be drawn. One VAO is not possible since when you bind another VBO to the same attribute location it will overwrite the previous one, so one VAO per Object is the way to go. Batching (as in your option 1) is a viable option though, its mostly used to increase performance.

2

Share this post


Link to post
Share on other sites

I think you answered my question.  Regarding state changes, I am thinking about the overhead by switching between VAOs.  Maybe most of that cost is incurred when you initially set it up, so it is negligible when you do the actual rendering?  Thank you for the answer.  That gives me a little bit more to go on understanding how everything is connected.

0

Share this post


Link to post
Share on other sites


Regarding state changes, I am thinking about the overhead by switching between VAOs. Maybe most of that cost is incurred when you initially set it up, so it is negligible when you do the actual rendering?

 

Yes, most of the "overhead" happens on setup, and thats where arguably you don't have to worry about it for rendering speed. Actually, without VAOs you'd have to do all that setup once per frame, and thats why they are very handy. I don't know the implementation details, but I quess they are a lot faster then doing VBO-binds and vertex attrbiute definitions for each object, so don't worry.

1

Share this post


Link to post
Share on other sites
Ironically, I've seen some other benchmarks that showed that reusing a single VAO (continually reinitializing it) was actually faster than pre-initializing many of them and then just switching between them... This of course depends on the driver, and GL drivers can be weird.

You can mix 2/3 with 1 to get a hybrid. Say you're loading 3 models at once that you know are required for the duration of the level -- they could potentially all put their different attribute streams into different offsets within the same VBO allocation.
2

Share this post


Link to post
Share on other sites

Ironically, I've seen some other benchmarks that showed that reusing a single VAO (continually reinitializing it) was actually faster than pre-initializing many of them and then just switching between them... This of course depends on the driver, and GL drivers can be weird.

 

That makes me even more curious about the inner workings of the implementation.  It strongly hints at fundamentally different approaches to implement GL drivers at different vendors to achieve the same result.  I wonder if anyone has done benchmarking of drivers on comparable hardware, if that is at all feasible.  Not that it has any practical value, as the overall performance is what really matters.

0

Share this post


Link to post
Share on other sites

Made it!  Rendering 10000 "VAOs" that really is just one random triangle each, with ok performance on my slow computer:

 

opengl0001.png

 

Now to load some real models instead of random data.  Thanks for help! :)

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 mapra99
      Hello

      I am working on a recent project and I have been learning how to code in C# using OpenGL libraries for some graphics. I have achieved some quite interesting things using TAO Framework writing in Console Applications, creating a GLUT Window. But my problem now is that I need to incorporate the Graphics in a Windows Form so I can relate the objects that I render with some .NET Controls.

      To deal with this problem, I have seen in some forums that it's better to use OpenTK instead of TAO Framework, so I can use the glControl that OpenTK libraries offer. However, I haven't found complete articles, tutorials or source codes that help using the glControl or that may insert me into de OpenTK functions. Would somebody please share in this forum some links or files where I can find good documentation about this topic? Or may I use another library different of OpenTK?

      Thanks!
    • By Solid_Spy
      Hello, I have been working on SH Irradiance map rendering, and I have been using a GLSL pixel shader to render SH irradiance to 2D irradiance maps for my static objects. I already have it working with 9 3D textures so far for the first 9 SH functions.
      In my GLSL shader, I have to send in 9 SH Coefficient 3D Texures that use RGBA8 as a pixel format. RGB being used for the coefficients for red, green, and blue, and the A for checking if the voxel is in use (for the 3D texture solidification shader to prevent bleeding).
      My problem is, I want to knock this number of textures down to something like 4 or 5. Getting even lower would be a godsend. This is because I eventually plan on adding more SH Coefficient 3D Textures for other parts of the game map (such as inside rooms, as opposed to the outside), to circumvent irradiance probe bleeding between rooms separated by walls. I don't want to reach the 32 texture limit too soon. Also, I figure that it would be a LOT faster.
      Is there a way I could, say, store 2 sets of SH Coefficients for 2 SH functions inside a texture with RGBA16 pixels? If so, how would I extract them from inside GLSL? Let me know if you have any suggestions ^^.
    • By KarimIO
      EDIT: I thought this was restricted to Attribute-Created GL contexts, but it isn't, so I rewrote the post.
      Hey guys, whenever I call SwapBuffers(hDC), I get a crash, and I get a "Too many posts were made to a semaphore." from Windows as I call SwapBuffers. What could be the cause of this?
      Update: No crash occurs if I don't draw, just clear and swap.
      static PIXELFORMATDESCRIPTOR pfd = // pfd Tells Windows How We Want Things To Be { sizeof(PIXELFORMATDESCRIPTOR), // Size Of This Pixel Format Descriptor 1, // Version Number PFD_DRAW_TO_WINDOW | // Format Must Support Window PFD_SUPPORT_OPENGL | // Format Must Support OpenGL PFD_DOUBLEBUFFER, // Must Support Double Buffering PFD_TYPE_RGBA, // Request An RGBA Format 32, // Select Our Color Depth 0, 0, 0, 0, 0, 0, // Color Bits Ignored 0, // No Alpha Buffer 0, // Shift Bit Ignored 0, // No Accumulation Buffer 0, 0, 0, 0, // Accumulation Bits Ignored 24, // 24Bit Z-Buffer (Depth Buffer) 0, // No Stencil Buffer 0, // No Auxiliary Buffer PFD_MAIN_PLANE, // Main Drawing Layer 0, // Reserved 0, 0, 0 // Layer Masks Ignored }; if (!(hDC = GetDC(windowHandle))) return false; unsigned int PixelFormat; if (!(PixelFormat = ChoosePixelFormat(hDC, &pfd))) return false; if (!SetPixelFormat(hDC, PixelFormat, &pfd)) return false; hRC = wglCreateContext(hDC); if (!hRC) { std::cout << "wglCreateContext Failed!\n"; return false; } if (wglMakeCurrent(hDC, hRC) == NULL) { std::cout << "Make Context Current Second Failed!\n"; return false; } ... // OGL Buffer Initialization glClear(GL_DEPTH_BUFFER_BIT | GL_COLOR_BUFFER_BIT); glBindVertexArray(vao); glUseProgram(myprogram); glDrawElements(GL_TRIANGLES, indexCount, GL_UNSIGNED_SHORT, (void *)indexStart); SwapBuffers(GetDC(window_handle));  
    • By Tchom
      Hey devs!
       
      I've been working on a OpenGL ES 2.0 android engine and I have begun implementing some simple (point) lighting. I had something fairly simple working, so I tried to get fancy and added color-tinting light. And it works great... with only one or two lights. Any more than that, the application drops about 15 frames per light added (my ideal is at least 4 or 5). I know implementing lighting is expensive, I just didn't think it was that expensive. I'm fairly new to the world of OpenGL and GLSL, so there is a good chance I've written some crappy shader code. If anyone had any feedback or tips on how I can optimize this code, please let me know.
       
      Vertex Shader
      uniform mat4 u_MVPMatrix; uniform mat4 u_MVMatrix; attribute vec4 a_Position; attribute vec3 a_Normal; attribute vec2 a_TexCoordinate; varying vec3 v_Position; varying vec3 v_Normal; varying vec2 v_TexCoordinate; void main() { v_Position = vec3(u_MVMatrix * a_Position); v_TexCoordinate = a_TexCoordinate; v_Normal = vec3(u_MVMatrix * vec4(a_Normal, 0.0)); gl_Position = u_MVPMatrix * a_Position; } Fragment Shader
      precision mediump float; uniform vec4 u_LightPos["+numLights+"]; uniform vec4 u_LightColours["+numLights+"]; uniform float u_LightPower["+numLights+"]; uniform sampler2D u_Texture; varying vec3 v_Position; varying vec3 v_Normal; varying vec2 v_TexCoordinate; void main() { gl_FragColor = (texture2D(u_Texture, v_TexCoordinate)); float diffuse = 0.0; vec4 colourSum = vec4(1.0); for (int i = 0; i < "+numLights+"; i++) { vec3 toPointLight = vec3(u_LightPos[i]); float distance = length(toPointLight - v_Position); vec3 lightVector = normalize(toPointLight - v_Position); float diffuseDiff = 0.0; // The diffuse difference contributed from current light diffuseDiff = max(dot(v_Normal, lightVector), 0.0); diffuseDiff = diffuseDiff * (1.0 / (1.0 + ((1.0-u_LightPower[i])* distance * distance))); //Determine attenuatio diffuse += diffuseDiff; gl_FragColor.rgb *= vec3(1.0) / ((vec3(1.0) + ((vec3(1.0) - vec3(u_LightColours[i]))*diffuseDiff))); //The expensive part } diffuse += 0.1; //Add ambient light gl_FragColor.rgb *= diffuse; } Am I making any rookie mistakes? Or am I just being unrealistic about what I can do? Thanks in advance
    • By yahiko00
      Hi,
      Not sure to post at the right place, if not, please forgive me...
      For a game project I am working on, I would like to implement a 2D starfield as a background.
      I do not want to deal with static tiles, since I plan to slowly animate the starfield. So, I am trying to figure out how to generate a random starfield for the entire map.
      I feel that using a uniform distribution for the stars will not do the trick. Instead I would like something similar to the screenshot below, taken from the game Star Wars: Empire At War (all credits to Lucasfilm, Disney, and so on...).

      Is there someone who could have an idea of a distribution which could result in such a starfield?
      Any insight would be appreciated
  • Popular Now