• 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
spek

OpenGL
Texture compression DDS / S3TC

14 posts in this topic

Hey,

About texture compression... Never used it so far, but I just made an (OpenGL) program that loads a DDS file. So far so good, but before really implementing it in my engine, I need some good reasons. Well, what I can think of:
- No time wasted generating mip-maps
- Smaller disk size
- Smaller > Faster loading from disk
- Extra features such as cubeMap / 3D textures
- Allows to use bigger resolutions

Then on the other hand...
- Lower quality
- Slower rendering?? Or is it actually faster (less bandwidth)??

The lower quality probably depends on the compression settings I guess, and images that really need detail still can use uncompressed formats. But, how bad is the loss really? I can't really see a difference usually. But I didn't have a lot of examples.

About the performance. I've been tought, 100 years ago, that decompressing takes time. Not sure how the video-card does things, but does the decompression hit the performance? The only thing I read is that is can actually boost the performance because less bandwidth is used. In my case I have quite a lot surface textures (512 x 512, 1024 x 1024, resolutions like that).


A last question. How to calculate the video memory usage of a compressed texture? Is it equal to the amount of bytes pixeldata you read? Or does OpenGL / GPU convert the data?
0

Share this post


Link to post
Share on other sites
In general compression is going to be a win. It can significantly ease the burden on your memory usage, and it helps with bandwidth as well. The GPU can decode them on the fly (since S3TC is designed to be very simple to decode a 4x4 block) so you don't need to worry about any added cost for the decode. You do have to be careful though with quality, for certain cases it's very easy to end up with a really crappy-looking texture once you've compressed them.

Here are some general tips. I'm going to use the D3D10/D3D11 terminology for the different compression formats, since I don't know the corresponding OpenGL names (sorry!):

1. Use a good compressor! This is key. Some are much better than others. For offline compression, I recommend using the ATI_Compress library. It's dead simple, it's multithreaded, and has great quality. We used to Nvidia texture tools at work since it's open source, but the quality was worse and it was significantly slower.

2. Have the option to opt out of compression for certain textures. You're bound to find a few cases where the hit in quality just isn't worth it...for instance anything with a really smooth gradient usually ends up being paletized pretty badly.

3. Use the right format! BC1 has the lowest memory footprint for an RGB texture, but also doesn't have an alpha channel. BC2 and BC3 do have alpha channels, with different means of encoding them (most people just stick to BC3). For monochrome textures, you'll want BC4. It has 1 hi-quality channel (basically the alpha channel from BC3). For normal maps, you'll want to use BC5 which has 2 hi-quality channels (store XY and reconstruct Z in the shader). If BC4 and BC5 aren't available on your target spec, then you can use BC3 for normal maps and put the X in the alpha channel and Y in the green channel and then reconstruct Z in the shader (those are the two channels with the most precision).

4. For color maps you can get a bit better quality by determining the min and max values in the texture, and then rescaling that range to [0, 1]. Then in the shader you use the min and max to scale it back to the normal.

5. BC6 and BC7 are really awesome (HDR, and hi-quality LDR respectively), but only available on DX11-class hardware. There's also not really any tools support for it yet. The D3DX library can encode to it, but it's super slow. There's also a sample in the SDK that does the encoding on the GPU using a compute shader, but it's pretty bare bones and doesn't support cube maps or mipmaps.
1

Share this post


Link to post
Share on other sites
Hey Vilem! It's been a while. Sorry for forgetting to mail you a year ago. It suddenly got so busy with people offering help on T22 :)

Thanks for the info MJP & Vilem. These arguments are good enough to put DDS support in the engine. I thought decoding would give a small hit, but having the hardware doing it for "free" is awesome.

Images with compressing quality issues can still keep using uncompressed formats. About that... asides from smooth gradients are there particular cases that have quality problems?
- Textures using the alpha channel for transparency (foliages, metal fences, ...)
- NormalMaps with small details
- Images with a lot of small details, but not varying colors (a sand texture for example)
Most of the images we're using are indoor material textures such as a concrete wall or wood floor btw.

Not sure where BC1..7 stands for. While coding a bit I came across DXT1, DXT3 and DXT5. Are those the same?
0

Share this post


Link to post
Share on other sites
[quote]Sorry for forgetting to mail you a year ago. It suddenly got so busy with people offering help on T22[/quote]

No problem, I watch your T22 blog from time to time and your project looks very very promising!

[quote]Not sure where BC1..7 stands for. While coding a bit I came across DXT1, DXT3 and DXT5. Are those the same?[/quote]

AFAIR BC* is naming system of Direct3D, while DXT* are names used in OpenGL:

DXT1 is actually BC1
DXT3 is actually BC3
DXT5 is actually BC5

Actually I think there are also DXT2 and DXT4 (but these aren't used commonly and I'm also not sure if GL implements them), BC6 and BC7 are new things, I think that BPTC is whats standing in OpenGL instead of BC7 in Direct3D.

0

Share this post


Link to post
Share on other sites
Yeah DX9 used to call them DXT* and the old OpenGL extensions also called them DXT, but in DX10 onwards they started calling them BC* (where BC stands for "block compression"). I have no idea if the names have changed with the newer (3.x - 4.x) version of OpenGL, which is why I just used the DX10 names. For quick reference:

BC1 - 5:6:5 RGB + 1bit alpha. DXT1 in DX9/GL extensions. 1:6 compression ratio
BC2 - 5:6:5 RGB + 4bit explicit alpha (better for non-coherent alpha values). DXT3 in DX9/GL extensions. 1:4 compression
BC3 - 5:6:5 RGB + 8bit interpreted alpha (better for coherent alpha values). DXT5 in DX9/GL extensions. 1:4 compression
BC4 - 8bit interpreted R, similar to the alpha from BC3. Was previously known as ATI1N in DX9, I think it was called LATC1 in GL extensions. 1:2 compression
BC5 - 8bit interpreted RG, basically just double BC4 channels. Was previously known as ATI2N in DX9, LATC2 in GL extensions. Referred to as "3Dc" in ATI marketing. 1:2 compression
BC6H - 16:16:16 floating point RGB. No idea what this is called in OpenGL.1:6 compression ratio
BC7 - 4-7bit RGB + 0-8bit alpha. Actually a combination of different encoding modes, where the best mode is chosen for each 4x4 block to best represent the data. 1:4 compression ratio
0

Share this post


Link to post
Share on other sites
BC4 = RED_RGTC1 in OpenGL
BC5 = RG_RGTC2 in OpenGL
from http://www.opengl.org/registry/specs/ARB/texture_compression_rgtc.txt (in Core from 3.0)

BC6H = BPTC_UNORM / SRGB_ALPHA_BPTC_UNORM
BC7 = BPTC_SIGNED_FLOAT / BPTC_UNSIGNED_FLOAT
from http://www.opengl.org/registry/specs/ARB/texture_compression_bptc.txt (in Core from 4.2)

Both extensions especially mentions compatibility with DirectX.
0

Share this post


Link to post
Share on other sites
[quote name='Martins Mozeiko' timestamp='1316122987' post='4862230']
BC6H = BPTC_UNORM / SRGB_ALPHA_BPTC_UNORM
BC7 = BPTC_SIGNED_FLOAT / BPTC_UNSIGNED_FLOAT
from [url="http://www.opengl.org/registry/specs/ARB/texture_compression_bptc.txt"]http://www.opengl.or...ession_bptc.txt[/url] (in Core from 4.2)
[/quote]

I think these are backwards
0

Share this post


Link to post
Share on other sites
[quote name='MJP' timestamp='1316128777' post='4862260']
[quote name='Martins Mozeiko' timestamp='1316122987' post='4862230']
BC6H = BPTC_UNORM / SRGB_ALPHA_BPTC_UNORM
BC7 = BPTC_SIGNED_FLOAT / BPTC_UNSIGNED_FLOAT
from [url="http://www.opengl.org/registry/specs/ARB/texture_compression_bptc.txt"]http://www.opengl.or...ession_bptc.txt[/url] (in Core from 4.2)
[/quote]

I think these are backwards
[/quote]
Oops! Yes, you are right. BC7 = BPTC_xyz_FLOAT, BC6H = xyz_BPTC_UNORM.
0

Share this post


Link to post
Share on other sites
One more question. I managed to create a DDS file now with the ATI_Compress tool. Works like a charm, but... does anyone know how to make multiple Mip-Map levels? The DDS writer in ATI_Compress_Helper only makes 1 level by default. Now I could try to make my own writer, but maybe it can be done with some easy adjustments.

Thanks
Rick


0

Share this post


Link to post
Share on other sites
Compress won't generate mips, you have to generate them first and then compress each mip level individually. In our texture pipeline we generate the mips ourselves, but you could use another library to do it if you want.
0

Share this post


Link to post
Share on other sites
Definitely faster rendering; I've benchmarked it up to 20% faster. Quality can drop off quite badly depending on the texture you're using though; for something like lower resolution 2D GUI textures it can be unacceptable.

Make sure that you load the DDS natively and that you're not going through any software decompression/recompression stages too.
0

Share this post


Link to post
Share on other sites
[quote name='MJP' timestamp='1316110690' post='4862152']
BC6 and BC7 are really awesome (HDR, and hi-quality LDR respectively), but only available on DX11-class hardware. There's also not really any tools support for it yet. The D3DX library can encode to it, but it's super slow. There's also a sample in the SDK that does the encoding on the GPU using a compute shader, but it's pretty bare bones and doesn't support cube maps or mipmaps
[/quote]

MJP, this post wasn't all that long ago, but wondering whether you've since come across a decent compression tool that supports BC6/7.
0

Share this post


Link to post
Share on other sites
[quote name='360GAMZ' timestamp='1326100237' post='4900890']
[quote name='MJP' timestamp='1316110690' post='4862152']
BC6 and BC7 are really awesome (HDR, and hi-quality LDR respectively), but only available on DX11-class hardware. There's also not really any tools support for it yet. The D3DX library can encode to it, but it's super slow. There's also a sample in the SDK that does the encoding on the GPU using a compute shader, but it's pretty bare bones and doesn't support cube maps or mipmaps
[/quote]

MJP, this post wasn't all that long ago, but wondering whether you've since come across a decent compression tool that supports BC6/7.
[/quote]

Unfortunately not. I've been meaning to look into it more, but haven't gotten around to it yet. I do have a hacked-up version of the DX GPU compressor that will do BC6H for cube maps and mip levels that's sitting on my PC at home, but that's about it.
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