• 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

One Buffer Vs. Multiple Buffers...

10 posts in this topic



Consider this a consultation of opinion question:


Is it better to use one interleaved buffer for multiple buffers for vertex/normal/UV data?


Was reading this question and response here: http://stackoverflow.com/questions/12245687/does-using-one-buffer-for-vertices-uvs-and-normals-in-opengl-perform-better-tha


Just seeing what is better; I have implemented both but my framerate was high enough in both cases where I didn't notice a big difference.


Thank you for your time.


Share this post

Link to post
Share on other sites

making separate buffers for attributes can find itself wise in case it allows you to exchange X vertex buffer changes of batched inteleved buffers per frame for a one multiple buffers binding over frame group, (or aplication entirely). Yet, in my eyes, driver ,or, does a sad cache coherency unfriendly delivery of vertex attributes , or, interleves the separate buffers to interleved one in the end, resulting in the same logic as rebinding 6 batched interleved vertex buffers per frame. Who knows


Share this post

Link to post
Share on other sites

making separate buffers for attributes can find itself wise in case it allows you to exchange X vertex buffer changes of batched inteleved buffers per frame for a one multiple buffers binding over frame group

In this situation, it's better to build all the interleaved variations manually before uploading them to the driver, then just pick the most appropriate vertex buffer. I have seen engines that know what shaders are used for what mesh and create the correct custom buffer for that situation.


Always seemed like a hassle to me though.


Share this post

Link to post
Share on other sites

This is very interesting, because i've got very different results (gtx 670 and 480).

My use case is a compute shader tree traversal, and the nodes have vec4 data for position, color, direction and integer data packed in uvec4 (tree indices etc.)

First i've used a single shader storage buffer the AoS way. That was too slow, so i tried to put each vec in its own texture, so SoA.

Can't remember exactly but the speed up was 10-30 times i think.


Does this make sense? I assumed using SoA is faster because multiple texture units can be used to grab the data.

The other fact is that i do not need to read all the data for any node i visit, which is a difference to the fixed vertex pipeline example from above.

I do not need to read node direction if position is already too far away etc., and in AoS method i did read the full struct in any case before any test.

But i doupt this alone explains the huge speed up.


Please let me know what you think, i'm new to gpu and it's still hard to predict performance.

And there are crazy things happening, f. ex. sometimes it's faster to reserve shared memory without using it.

Sounds stupid, but it's true, especially for simple shaders. Someone discovered this before and posted on NV forum, but no official responce.

I assume the reason is reserving shared memory prevents the thread sheduler from doing too much task switching.

I don't know if this happens on other languages too (Cuda, CL, DX).


Other crazy things are:

It's faster to do a blur on the tree with all 4 children, 4 neighbours and parent, than to do a simple color averaging from children to parent on the same tree. ???

It's >2x faster to do a stackless but very divergent tree traversal one thread per node, than to do a perfect data / code / runtime coherent parallel traversal using a satck (stack is too big for shared memory).


I really have the feeling that drivers are not well polished for compute shader performance, but it's a little too much work to port to cuda to see the difference...

Any thoughts welcome :)


Share this post

Link to post
Share on other sites

Stop asking, just try, profile, and share the results.

I agree; in this case I did try both and the results for me were initially the same BUT I keep reading everywhere that interleaved is better so for now I will work with interleaved buffers.

Share this post

Link to post
Share on other sites

And there are crazy things happening, f. ex. sometimes it's faster to reserve shared memory without using it.

This is actually not that uncommon. The problem is that the cores only have a limited amount of register space (64k per SMx core) which gets divided up by however many threads are running in parallel. So if you are running 1024 threads per SMx, every thread can use up to 64 registers. If you are running the maximum of 2048 threads, every thread only gets to use 32 registers. If more local variables are needed than registers are available, some registers are spilled onto the stack similarly to how it's done on the CPU. But contrary to the CPU, the GPU memory latencies are incredibly high so spilling stuff that is often needed onto the stack can increase the runtime.

Now shared memory is also a restricted resource (64KB on kepler per SMx) but one that can't be spilled. So, if every block only needs less than 2KB, you can get the maximum of 32 resident blocks per SMx. But if you increase the amount of reserved shared memory, lets say to just below 4KB, then you can only have 16 resident blocks. Now, halving the amount of resident blocks also halves the total amount of resident threads, so each thread has twice the amount of registers at its disposal.

So, increasing the amount of reserved shared memory can decrease the number of resident blocks/threads, which increases the number of registers each thread can use, which can reduce register spilling and costly loads from the stack. I don't know about compute shaders, but for cuda I believe the profiler can check for this.

Share this post

Link to post
Share on other sites

This helps a lot (i copied this post to my source to read again later).

It explains also why performance is a matter of number of threads vs. needed memory, which is what i've recoginezed the last months.


There is one thing that i've got very wrong all the time: I thought a single SMX can only run 32 threads, and if you want more they would be spread across multiple SMX units.

I really understand much better now :)


Many thanks!


Share this post

Link to post
Share on other sites

Experts can't predict performance either. We're just driven by common guidelines AND THEN WE TRY OUR OPTIONS AND PROFILE.

But let's be fair - most of us can't afford test labs with multiple generations of GPUs, multiple versions of drivers, and so forth. Nevermind the time consumed in testing the different permutations. A different driver (or version) has the potential to randomly upheave the whole thing, and it's not like NV or AMD are about to help us out with real application profiles. So most of us are stuck with the handful of hardware/software configurations that are at hand, making educated guesses about the rest. I'm probably better off than most here - for my part I have access to a 6770, 7970, a GTX 480, a GTX 670, a Titan, and a couple Macbooks' worth of mobile GPUs. If this were strictly hobby work, I'd probably be lucky to even have one sample of NV and AMD available.


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 Toastmastern
      So it's been a while since I took a break from my whole creating a planet in DX11. Last time around I got stuck on fixing a nice LOD.
      A week back or so I got help to find this:
      In general this is what I'm trying to recreate in DX11, he that made that planet LOD uses OpenGL but that is a minor issue and something I can solve. But I have a question regarding the code
      He gets the position using this row
      vec4d pos = b.var.vec4d["position"]; Which is then used further down when he sends the variable "center" into the drawing function:
      if (pos.len() < 1) pos.norm(); world::draw(vec3d(pos.x, pos.y, pos.z));  
      Inside the draw function this happens:
      draw_recursive(p3[0], p3[1], p3[2], center); Basically the 3 vertices of the triangle and the center of details that he sent as a parameter earlier: vec3d(pos.x, pos.y, pos.z)
      Now onto my real question, he does vec3d edge_center[3] = { (p1 + p2) / 2, (p2 + p3) / 2, (p3 + p1) / 2 }; to get the edge center of each edge, nothing weird there.
      But this is used later on with:
      vec3d d = center + edge_center[i]; edge_test[i] = d.len() > ratio_size; edge_test is then used to evaluate if there should be a triangle drawn or if it should be split up into 3 new triangles instead. Why is it working for him? shouldn't it be like center - edge_center or something like that? Why adding them togheter? I asume here that the center is the center of details for the LOD. the position of the camera if stood on the ground of the planet and not up int he air like it is now.

      Full code can be seen here:
      If anyone would like to take a look and try to help me understand this code I would love this person. I'm running out of ideas on how to solve this in my own head, most likely twisted it one time to many up in my head
      Thanks in advance
    • By fllwr0491
      I googled around but are unable to find source code or details of implementation.
      What keywords should I search for this topic?
      Things I would like to know:
      A. How to ensure that partially covered pixels are rasterized?
         Apparently by expanding each triangle by 1 pixel or so, rasterization problem is almost solved.
         But it will result in an unindexable triangle list without tons of overlaps. Will it incur a large performance penalty?
      B. A-buffer like bitmask needs a read-modiry-write operation.
         How to ensure proper synchronizations in GLSL?
         GLSL seems to only allow int32 atomics on image.
      C. Is there some simple ways to estimate coverage on-the-fly?
         In case I am to draw 2D shapes onto an exisitng target:
         1. A multi-pass whatever-buffer seems overkill.
         2. Multisampling could cost a lot memory though all I need is better coverage.
            Besides, I have to blit twice, if draw target is not multisampled.
    • By mapra99

      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?

    • 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));  
  • Popular Now