• 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
sth

OpenGL
High performance texture splatting?

7 posts in this topic

Is there a way to improve the performance of texture reads in OpenGL (ES)?
I'd like to do texture splatting but I'm running into severe performance problems when using multiple texture reads in my fragment shader. With a single texture, I get a constant 60fps (vsync limited, with room to spare). Adding a second texture read, my performance drops down to 40fps and with the shader provided below, performance is down to 15fps.

Any ideas?

[source lang="plain"]# Simplified fragment shader for demonstration purposes

varying lowp vec2 v_texcoord;
varying lowp vec4 v_color;

uniform sampler2D texture0;
uniform sampler2D texture1;
uniform sampler2D texture2;
uniform sampler2D texture3;
uniform sampler2D texture4;


void main()
{
lowp vec4 alpha = texture2D(texture4, v_texcoord);

lowp vec4 color = texture2D(texture0, v_texcoord);
color = mix(color, texture2D(texture1, v_texcoord), alpha[0]);
color = mix(color, texture2D(texture2, v_texcoord), alpha[1]);
color = mix(color, texture2D(texture3, v_texcoord), alpha[2]);

gl_FragColor = v_color * color;
}[/source] Edited by sth
0

Share this post


Link to post
Share on other sites
If you throw out the vsync sample, your frame times are 40Hz/25ms for 2 samples, and 15Hz/66.6..ms for 5 samples. Divide the frame times by the number of samples and you get 12.5ms and 13.3..ms, which are pretty similar.
From that, it looks like you're just using more texture bandwidth than your GPU can cope with... draw less pixels using these shaders -- use distance material-LOD maybe?

You can also reduce data in many ways, such as packing 4 different monochrome textures together along with 4 uniform colours.
1

Share this post


Link to post
Share on other sites
Perhaps try avoiding the mix and optimize the code manually:

[code]
void main()
{
lowp vec4 alpha = texture2D(texture4, v_texcoord);

lowp vec4 color0 = texture2D(texture0, v_texcoord);
lowp vec4 color1 = texture2D(texture1, v_texcoord);
lowp vec4 color2 = texture2D(texture2, v_texcoord);
lowp vec4 color3 = texture2D(texture3, v_texcoord);

gl_FragColor = v_color * (alpha[0] * color0 + alpha[1] * color1 + alpha[2] * color2 + alpha[3] * color3);
}[/code]

(I reindexed the way how the indices of the alpha vector affect the read color texture for straightforwardness). The idea is that alpha[0] is already precomputed to be 1.0f - alpha[1] - alpha[2] - alpha[3] in the texture, so one doesn't need to compute that in the shader. I feel this would be faster than using mix(), but can't be sure without profiling. Let me know how it compares.

Something that's potentially optimizable is to drop one or two texture channels to splat, and subdivide your mesh down by which splat textures it is using at each triangle. Also, if the splat texture is low-frequency, try storing the splat weights as vertex attributes and pass them through to pixel shader, which will avoid you one texture read.

Finally, if the splat texture is very low frequency, you can try just decaling the contents, i.e. manually generate geometry planes that you alphablend on top of the terrain.
1

Share this post


Link to post
Share on other sites
Also, Why not try just 3 splat channels instead of 4. 3 should be sufficient especially if it is for a small screen embedded device.
1

Share this post


Link to post
Share on other sites
[quote name='Hodgman' timestamp='1340028032' post='4950245']
If you throw out the vsync sample, your frame times are 40Hz/25ms for 2 samples, and 15Hz/66.6..ms for 5 samples. Divide the frame times by the number of samples and you get 12.5ms and 13.3..ms, which are pretty similar.
From that, it looks like you're just using more texture bandwidth than your GPU can cope with...[/quote]
I think you're right, it looks pretty much bandwidth-limited right now.
Today I realized that I still had trilinear filtering enabled. Disabling it cut the frame times [i]in half[/i]. I can't recall trilinear filtering ever having such a profound effect in any of my projects, but I guess that's just what happens when you're running at the limit.

Anyway, at least I'm now back to playable framerates.

[quote name='clb' timestamp='1340028652' post='4950252']
Perhaps try avoiding the mix and optimize the code manually:
[/quote]
Thanks for the suggestion. I tried it but it didn't have any effect on the performance.

[quote name='dpadam450' timestamp='1340044660' post='4950331']
Also, Why not try just 3 splat channels instead of 4. 3 should be sufficient especially if it is for a small screen embedded device.
[/quote]
I'm considering it, but I'm still not sure if I really want it.
The thing is that these days it's not just phone screens, it's also tablet screens and (wireless) TV output.
0

Share this post


Link to post
Share on other sites
[quote]The thing is that these days it's not just phone screens, it's also tablet screens and (wireless) TV output.[/quote]
Well the thing really is, you don't have enough power currently on GLES. If you want 20 different types of splats, you could do that as well, just divide your terrain into sections and only allow 1 section 3 splats (rgb). Each section can have any 3 of the 20 splats.
0

Share this post


Link to post
Share on other sites
[quote name='sth' timestamp='1340061761' post='4950422']I think you're right, it looks pretty much bandwidth-limited right now.Today I realized that I still had trilinear filtering enabled. Disabling it cut the frame times in half. I can't recall trilinear filtering ever having such a profound effect in any of my projects, but I guess that's just what happens when you're running at the limit.[/quote]Yeah, trilinear filtering will double the amount of data that each pixel has to pull into the texture cache, so if you're already texture-bound, it going to make things a lot worse.[quote name='dpadam450' timestamp='1340064858' post='4950429']
Well the thing really is, you don't have enough power currently on GLES. If you want 20 different types of splats, you could do that as well, just divide your terrain into sections and only allow 1 section 3 splats (rgb). Each section can have any 3 of the 20 splats.[/quote]Yep, I've worked on a few games where each triangle could only have 2 layers on it, but the entire terrain could have many, many layers. We'd use a tool to split the terrain up into sections, where each section only had 2 texture layers. As long as you never needed 3 or more materials present at a single vertex, it worked ok.
0

Share this post


Link to post
Share on other sites
[quote name='dpadam450' timestamp='1340064858' post='4950429']
[quote]The thing is that these days it's not just phone screens, it's also tablet screens and (wireless) TV output.[/quote]
Well the thing really is, you don't have enough power currently on GLES. If you want 20 different types of splats, you could do that as well, just divide your terrain into sections and only allow 1 section 3 splats (rgb). Each section can have any 3 of the 20 splats.
[/quote]
I'll have to see. My current implementation already allows every chunk of the terrain to have its own set of textures, although it would be nicer not to be bound to the fixed chunk structure.
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 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:
      https://github.com/sp4cerat/Planet-LOD
      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:
      https://github.com/sp4cerat/Planet-LOD/blob/master/src.simple/Main.cpp
      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
      Toastmastern
       
       
    • 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
      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));  
  • Popular Now