• 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
skytiger

float2 dx = ddx(uv.xy * size.x); // does this make sense?

3 posts in this topic

(given that uv is float2)

shouldn't it be:

[source lang="cpp"]float dx = ddx(uv.x * size.x);

float dy = ddy(uv.y * size.y);

[/source]

and why is there an ddx() and a ddy() ? why not just a dd() ?
0

Share this post


Link to post
Share on other sites
ddx is the partial derivative of the value with respect to screen-space X, ddy is the partial derivative of the value with respect to screen-space Y. In other words ddx tells you how much the value changes if you were to move to right a pixel, while ddy tells you how much the value changes if you were to move down a pixel. That is why there are two different functions.

I can't tell you whether your code makes sense without knowing what you're actually trying to accomplish, and also knowing what "size" is.
2

Share this post


Link to post
Share on other sites
Yeah, what mjp said.

If you intend to use the derivatives for manual tex2d lookup because you're having issues with branch code, you'll probably want to do:
[code]float2 dx = ddx(uv.xy * size.xy);
float2 dy = ddy(uv.xy * size.xy);[/code]
2

Share this post


Link to post
Share on other sites
I see now!

float2 dx = ddx(uv.xy);

ddx() is returning a vector in texture space

The original code was calculating a lod level manually to allow for sampling neighbouring pixels (in DX9)
[source lang="cpp"]float MipMapLevel(in float2 uv, in float2 textureSize) {

float2 dx = ddx(uv * textureSize.x);
float2 dy = ddy(uv * textureSize.y);

float d = max(dot(dx, dx), dot(dy, dy));

return log2(sqrt(d));

}//function

// then I can use tex2Dlod() with correct pixel offsets for manual interpolation
[/source]
also, from my testing on an ATI3870, fractional LOD levels seem to cause blending between mip levels
so I need to round or truncate my lod level before calculating the pixel offsets

thanks MJP (edit: and Matias, good point) Edited by skytiger
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