• 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.

Archived

This topic is now archived and is closed to further replies.

hfoucher

Soccer ball motion approximation

3 posts in this topic

A year ago, I started developing a soccer game called OpenKickOff (www.openkickoff.org) based on the famous KickOff2 game. Okay my trouble is... ball motion ! What I found a long time ago are those 2 equations providing x(t) and z(t): x(t) = M/K*v*cos(angle))*(1-exp(-K/M*t)) z(t) = M/K*(v*sin(angle)+M*G/K)*(1-exp(-t*K/M))-M*G/K*t+h0 Where: M is the ball mass v the initial velocity at ball kick angle the initial vertical angle at ball kick (0 = horizontal) K air resistance constant G = 9.81 m.s-2 This works fine but require high calculation along the game. Are there other equations to approximate ball motion during a soccer game that are frequently used in game design ? herve@openkickoff.org
0

Share this post


Link to post
Share on other sites
There are two obvious optimisations:

First you need to only calculate cos(angle) and sin(angle) once per kick. You may be able to calculate them together, e.g. some APIs provide a SinCos function which works them both out at once.

Second you do not need to use exp to do drag. Exp arises when you try to write down a precise formula for the position at all times, as it''s the solution to an equation of motion of a particle with linear drag.

But you can intead use numerical techniques. The first equation can be derived from the equation of motion

dv
-- = -Kv/M
dt

where v is the velocity. This can be used to update the horizontal velocity u with the approximation formula

u = u - (K * u / M) * t

where t is the time step between updates.

Then use

x = x + u * t

to update x.

Similarly for the vertical motion use

v = v - (K * v / M + G) * t

and

z = z + v * t

Because u, v, x and z are calculated from previous values they need to be initialised, and for your situation this would be

u = V * cos(angle)
v = V * sin(angle)
x = 0
z = h0

where ''V'' is the launch speed.

It''s important to note that these numerical methods are approximations: over even a short time step u and v are changing, so calculations done with them are incorrect by the end of the time step.

It is therefore important that the time step is as small as possible, and so that updates are done as often as possible. This is usually one of the key decisaions in designing a simulation, and it''s difficult to give precise recommendations, but it''s often best to use an fixed update rate different from the frame rate if it can vary.
0

Share this post


Link to post
Share on other sites
Other things to note:
Velocity in the non-vertical directions (the directions not effected by gravity) is virtually constant while the ball is in the air. Air resistance will have some effect, but if you need to speed it up more, compute the horizontal velocity once.

Air resistance will be almost negligable.

Also, mass of an object does not effect an object once it is in the air.

While these will cause your code to be inaccurate, the inaccuracies will be inconsequential for a soccer game. They will speed it up a little bit though, which is more important than being 100% accurate.
0

Share this post


Link to post
Share on other sites