• 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

SSAO acting as depth filter (help needed)

2 posts in this topic

I've recently been working on a shaderpack for the Minecraft Shader Mod. I'm currently trying to write an SSAO function, but I'm getting some really strange results. I'm going to try to explain this clearly, but I'm so befuddled that who knows what will happen.


I'm using a rather simple SSAO algorithm:

  1. Grab the depth of the current fragment
  2. Compare that depth to the depths of 8 fragments in a circle around the current fragment
  3. For each of those depths that is less than the depth from step 1, subtract a small amount from a variable that starts at 1
  4. Multiply the lighting strength by the variable that was subtracted from

You'll notice that I don't account for the fragment's normal. I don't intend to. I just want a simple algorithm that I can get working, then I'll make it more accurate.


My code is as follows:

void calcSSAO( inout Pixel pixel ) {
    //not that it works...
    float ssaoFac = SSAO_STRENGTH;
    float compareDepth = getDepthLinear( coord );
    float radiusx = SSAO_RADIUS / viewWidth;
    float radiusy = SSAO_RADIUS / viewHeight;
    vec2 sampleScale = vec2( radiusx, radiusy );

    float occlusionPerSample = ssaoFac / float( SSAO_SAMPLES ); 

    vec2 sampleCoord;
    for( int i = 0; i < SSAO_SAMPLES; i++ ) {
        sampleCoord = poisson( i ) * sampleScale;
        if( getDepthLinear( sampleCoord ) < compareDepth ) {
            ssaoFac -= occlusionPerSample;

    pixel.directLighting = *= ssaoFac;
    pixel.torchLighting *= ssaoFac;
  • Pixel is a struct I've defined to hold a fragment's color, normal, world position, lighting, and whatever other per-pixel data I happen to need
  • getDepthLinear is a function which samples the depth texture at a specified UV coordinate and returns the world-space depth
  • coord is a varying which holds the UV position of the current fragment
  • viewWidth and viewHeight are the width and height of the screen (in pixels)
  • poisson is a function (because GLSL 120 arrays are poorly supported) which returns one of 32 poisson disk samples

If you want to see the whole shader, you can find it at http://pastebin.com/Eg7PEDCx


The result of this shader is http://i.imgur.com/5yqhLY3.png. Drawing just the SSAO term, I get http://i.imgur.com/3RXMwMv.png.


As you can see, fragments that are close to the camera have an SSAO term of 1, which extends until about 1.5 units from the camera. Then there is a small fade region, then the SSAO term is 0. I have absolutely no idea why I'm getting this result, and more importantly, I have no idea how to fix it. Do any of you have any ideas?


Share this post

Link to post
Share on other sites

Any chance line 357 should be sampleCoord = coord + poisson( i ) * sampleScale; ?

Yes. probably. Let me see if that helps...


Yes, that fixes it. Thank you very much!


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