• 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
Prune

const & uniform question revisited

9 posts in this topic

I came across this thread from 4.5 years ago: http://www.gamedev.net/topic/461399-const--uniform-question-in-glsl/

 

However, I wonder whether things have changed. This does not give me any errors, though the hold thread suggests it should:

 

layout(location = VIEW_SZ) uniform vec2 viewSz;
const vec2 scale = 1.0f / viewSz;

 

But it's still not clear to me whether scale is computed at each invocation of the shader for every fragment (and whether it makes a difference that scale is global vs making it local, in terms of evaluation time--I've read already that making it local may help the compiler with register allocation).

 

If it's computed, then of course it makes sense to precalculate the inverse and pass it in as a uniform.

0

Share this post


Link to post
Share on other sites

I did something similar, and whereas it worked on my ATI cards, the driver refused to compile it on nVidia.

 

I would avoid anyhting not specifically const in a const declaration.

0

Share this post


Link to post
Share on other sites

But it's still not clear to me whether scale is computed at each invocation of the shader for every fragment

It is; all you have told the compiler is that the value will not change after initialization.


The correct solution is to precompute it as suggested by Hodgman.

That aside, never use const in a declaration whose right side is not a const expression; it fails to compile on some hardware/drivers, especially for example in OpenGL ES 2.0 and above or those that adhere to the standard strictly (your code should error).

https://www.opengl.org/wiki/Type_Qualifier_(GLSL)


L. Spiro

1

Share this post


Link to post
Share on other sites

So the following should be a const expr because all arguments are literals:

 

const vec3 light = normalize(vec3(1.0f, 1.0f, 1.0f));

0

Share this post


Link to post
Share on other sites

So the following should be a const expr because all arguments are literals:

 

const vec3 light = normalize(vec3(1.0f, 1.0f, 1.0f));

 

vec3(1.0f, 1.0f, 1.0f) is a const expression because it is a type constructor that contains only const expressions, and normalize is a built-in function that is given a const expression, so light is also a valid const expression.

0

Share this post


Link to post
Share on other sites


But why wouldn't this apply to user functions passed const expressions as arguments?

 

Because it's not in the standard. C++11 has constexpr which allows this kind of thing. Since it is all compile time there is no technical reason why GLSL couldn't do this, it simply doesn't yet.

0

Share this post


Link to post
Share on other sites

What about textureSize()? It's a built-in function, and it takes no arguments (which _is_ a const expr); on the other hand, it depends on the bound texture. So is it const expr or not?

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