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      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.
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mr_sad

Semi-fixed timestep with horizontal accel/deceleration

1 post in this topic

I would like to implement the code as featured at the end of the Fix Your Timestep article (found here: [url="http://gafferongames.com/game-physics/fix-your-timestep/"]http://gafferongames...-your-timestep/[/url]).

I would like to apply that implementation to a sprite which can move left or right, and which accelerates from a standing position to its maximum speed when the right arrow or left arrow is held down (in the corresponding direction) and decelerates when no arrow key is held down.

Could someone please provide the XNA code that would enable me to do this? I don't ordinarily ask for things like this, but I've been banging away at it for days and I'm just going in circles.

The semi-fixed timestep code from the article is displayed here for your convenience:

double t = 0.0;
const double dt = 0.01;

double currentTime = hires_time_in_seconds();
double accumulator = 0.0;

State previous;
State current;

while ( !quit )
{
double newTime = time();
double frameTime = newTime - currentTime;
if ( frameTime > 0.25 )
frameTime = 0.25; // note: max frame time to avoid spiral of death
currentTime = newTime;

accumulator += frameTime;

while ( accumulator >= dt )
{
previousState = currentState;
integrate( currentState, t, dt );
t += dt;
accumulator -= dt;
}

const double alpha = accumulator / dt;

State state = currentState*alpha + previousState * ( 1.0 - alpha );

render( state );
}
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Try this and see if this works.

In Main, delete the "using (Game game1...) { ... }" block, create your own GraphicsDevice (you have to use WinForms), and copy and paste the code from the article.

[CODE]
static void Main(string[] args)
{
GraphicsDevice device = new GraphicsDevice();

<code from the article>
}
[/CODE]

Then make sure you call GraphicsDevice.Present() in your render() function

[CODE]
void render(state, GraphicsDevice)
{
GraphicsDevice.Clear();

<render using state>

GraphicsDevice.Present();
}
[/CODE]

Hopefully that should work. If you want your gameloop to integrate better with the Windows message loop you can read this ([url="http://blogs.msdn.com/b/tmiller/archive/2005/05/05/415008.aspx"]link[/url]).

Let me know how it works out.
Victor
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