• 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
PhillipHamlyn

GeoClipMap and Point Sampling with Linear Interpolation

1 post in this topic

Hi,

 

I just want to check an assumption before I go diving off into code; the standard Vertex Texture Fetch (text2dlod) with "manual" linear interpolation as shown here http://www.catalinzima.com/tutorials/4-uses-of-vtf/terrain-rendering-using-heightmaps/ wont work with a GeoClipMap style of heightmap rendering will it ?

 

I have an initial version which gives very weird results, and I'm attributing it to the fact that the point sampler used in text2dlod is a nearest point sampler, but linear interpolation examples that I've seen for VTF show a simple frac() of the initial texture coords to get the weighting for the neighbour texture pixels.  I think this wont be accurate will it ?; becuase the frac() is carried out on the initial texture coordinates, but the point sampler isn't working on a trunc() basis but a round() basis - if the geometry is fixed to that texture coord then you'd never notice it, but with a GeoClipMap the texture coord is calculated from world space dynamically and constantly changes - which means I get weird jumping artefacts as the camera moves and the vertexes texture coord slides from one pixel to another - suddenly jumping pixels when the rounding point is hit (I presume also that its Bankers Rounding so actually behaves differently for each pixel offset).

 

Can anyone with a geoclipmap implementation tell me if this is the right direction I'm going it, or am I chasing shadows ?

 

Phillip H

0

Share this post


Link to post
Share on other sites

Hi,

 

Just to keep the trail clean, and to answer my own question.

 

Since Point sampling is the only one allowed for a vertex texture fetch (VTF) and it works on nearest point (i.e. round()) not trunc() most examples of manual linear interpolation will not work if the Vertex position moves between frames (such as when you are doing a geoclipmap or other camera-anchored vertexes which then use world oriented data for height lookups or other stuff).

 

Most examples dont really care if the Lerp operation is offset agains the "wrong" pixel in the texture. When you are presenting a camera-anchored vertex buffer then the user will see all sorts of popping and flipping if you dont change the manual linear filter implementation.

 

I haven't tested this thoroughly, but I need to check the actual pixel that is sampled by calculating my texture offset using a trunc() of my initial texture UV * textureSize. I can then safely Lerp() the Frac() of the initial texture UV * textureSize since I know that I have definitely sampled the correct pixel, and not been rounded to the next one (in which case frac() would be useless).

 

I'll post my outcome once I've tested this.

1

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