• 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
Chris_F

OpenGL
Texture Compression in OpenGL

9 posts in this topic

I'm trying to get a firm grasp on the texture compression formats available with OpenGL. Am I getting warm?

 

S3TC: Equivalent to BC1, BC2 and BC3. As far as I know no version of OpenGL has any guarantees as to whether this is supported, but it is probably available on just about every modern desktop GPU. Safe to assume it is supported?

 

RGTC: Equivalent to BC4 and BC5. Not sure what the spec says, but I'm guessing that like S3TC it is probably not mandatory but likely supported on any DirectX 10 or 11 hardware. RGTC appears in the OpenGL 4.3 core spec, it may have been added earlier. Safe to assume it is supported?

 

BPTC: Equivalent to BC6H and BC7. Mandatory since OpenGL 4.2. Being core doesn't necessarily guarantee actual hardware support, but I think it is safe to assume that any DirectX 11 hardware will support it natively.

 

ETC2, EAC: New texture compression format, no DirectX equivalent. Mandatory since OpenGL 4.3, but as far as I know, no GPU currently has hardware support, which means that current implementations of OpenGL 4.3+ are going to be implementing it inside the driver, negating any benefit from it.

 

ASTC: New texture compression format, no DirectX equivalent. Not mandatory in any version of OpenGL (as of 4.4) and not supported by modern desktop GPUs yet.

Edited by Chris_F
1

Share this post


Link to post
Share on other sites

PVRTC is common on iOS devices; I guess that if you're porting from (or porting to) (or want to be compatible with) these you're going to need to prepare for coming across it at some point in time.  I don't see any GL extension for supporting it in the registry through, so you'd probably be stuck with doing some software transcoding.

0

Share this post


Link to post
Share on other sites

ETC1/ETC2/EAC is very common in mobile (originally developed at Ericsson research, after all).

 

ETC1 is guaranteed to be supported by Android 2.2 and above. ETC2 and EAC are guaranteed to be included by all conforming OpenGL ES 3.0 implementations, and is part of the WebGL specification.

1

Share this post


Link to post
Share on other sites

wrt to OpenGL, nothing should be assumed. Any feature support required can be and should be check at runtime before using. As for compressed texture formats, support differs widely, especially in the mobile space so again, check for the supported feature and use if its available, never assume. While DX driver writers have to follow the letter of the law based on the specification, OpenGL is not so lucky. From my personal experience, vendors seem to interpret the specs in different ways. I've have 3 different mobille GPU and give 3 different behavior when compiling simple shaders ( ARM Mali-400, PowerVR SGX ( dont't remember the version, but its the GPU in the TI EVM 335x ) and a Adreno 205 ).

0

Share this post


Link to post
Share on other sites

Is there a way to see if there is actual hardware support for a compression format? For example, if you ship a OpenGL 4.3+ game, here is no point in compressing a texture as ETC2 or EAC if the driver is just going to uncompress it before uploading it to graphics memory.

1

Share this post


Link to post
Share on other sites

Without actually doing a runtime query there is no way to know whether or not a particular compressed format is supported in general. You could build a known device list for a particular supported feature, in this case compressed texture formats. Compressed textures have several benefits and are usually highly recommended to be used.

1. Compressed textures takes up less space both on secondary storage, and RAM, to include VRAM. So for platforms like mobile devices, where storage space is a premium or network bandwidth is not free, this is a plus.

2. Compressed formats that are supported by the GPU stays compressed and the GPU have specialized HW to access these textures. There is no decompression for upload, the actual compressed data is uploaded. This ties in to #1, uploading compressed data requires less transfer bandwith..another plus.

 

0

Share this post


Link to post
Share on other sites

The problem with a known device list is that it gets out of date very fast.

 

In general I reckon you can safely assume that the S3TC formats are ubiquitously supported; D3D supports them and in D3D10+ support is mandatory.  For any other compression format you can assume nothing, unless you're talking about something that the vendor explicitly supports and recommends, such as PVRTC on iOS.

0

Share this post


Link to post
Share on other sites

It's not hard to build the base table, at least on the mobile side of things:

 

- Any mobile chip from NVidia supports ST3C.

- Any mobile chip from Qualcom supports ATITC.

- Any mobile chip from PowerVR supports PVRTC.

- All iOS devices support PVRTC.

- All android devices support ETC1.

- All OpenGL ES 3.0-capable devices support EAC and ETC2.

 
I'm less familiar with desktop, but given that there are only 3 major chipset vendors (AMD, NVidia and Intel), and that Direct3D versions draw hard lines in the sand with respect to feature support, it can't be much worse.
1

Share this post


Link to post
Share on other sites

i think you cant even assume that any kind of texture compression is supported at all. your code must be able to deal with any such situations.

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 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));  
    • 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
  • Popular Now