• 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
icuit

How to draw a earth

5 posts in this topic

Hi, guys!

I want to draw a earth as to overlay some interest on it .
but you know that the earth is [font=Arial][size=4]spheroid and[/size][/font][font=Arial][size=2] [/size][/font][font=Arial][size=2][b][b]semi-major axis is longer than the other.[/b][/b][/size][/font]
[font=Arial][size=2][b][b] [/b][/b][/size][/font]
[font=Arial][size=2][b] [/b]anybody who give some ideas? 3ks here.[/size][/font]
0

Share this post


Link to post
Share on other sites
So kinda like this?
[url="http://learningwebgl.com/blog/?p=1778"]http://learningwebgl.com/blog/?p=1778[/url]

basically a sphere with a texture of earth sphere-mapped to it.

Your post is hard to decipher.
0

Share this post


Link to post
Share on other sites
The Earth is a planet, not a spheroid. Its precise mathematical model is rather complex.
For the most precise approximation of the mean sea level you should use geoid. The geoid is changing. It depends on the magnetic field of the Earth, but also depends on the Sun and the Moon. You can download some pretty precise geoid models of the Earth.

Less precise, but more common is the approximation that uses ellipsoid. WGS84 ellipsoid is used for GPS navigation and is very common these days.

The least accurate approximation of Earth curvature is a sphere. I have no idea what your visualization would serve for, but in 99.99% you will not see the difference between the shpere and WGS84 ellipsoid. You have noticed that there are differences between axis, but that difference is only 0.3%!!! The difference can be noticeable only when placing satellites high above the Earth, since calculated geographic position of the point beneath would significantly depend on the chosen approximation.

Also you would need same DEM data. For precise modeling you need several terabytes of data (both textures and DEM).

If the overlay is in a specific projection, you'll also need assistance of some GIS tool, or reprojecting library.
1

Share this post


Link to post
Share on other sites
@Aks9: Kudos for pointing out WGS84.

Though I really believe that it's entirely impossible for any of us to see a difference between a sphere and WGS84 in this situation. At 26'' screen resolution, a fullscreen earth would have a difference of 4 pixels between horizontal and vertical diameters. I'm pretty sure that even if shown both images side by side, I would be unable to tell one from the other. And in a "placebo controlled" experiment, I would probably be wrong 50% of the time :-)
0

Share this post


Link to post
Share on other sites
[quote name='Aks9' timestamp='1310550501' post='4834734']
The Earth is a planet, not a spheroid. Its precise mathematical model is rather complex.
For the most precise approximation of the mean sea level you should use geoid. The geoid is changing. It depends on the magnetic field of the Earth, but also depends on the Sun and the Moon. You can download some pretty precise geoid models of the Earth.

Less precise, but more common is the approximation that uses ellipsoid. WGS84 ellipsoid is used for GPS navigation and is very common these days.

The least accurate approximation of Earth curvature is a sphere. I have no idea what your visualization would serve for, but in 99.99% you will not see the difference between the shpere and WGS84 ellipsoid. You have noticed that there are differences between axis, but that difference is only 0.3%!!! The difference can be noticeable only when placing satellites high above the Earth, since calculated geographic position of the point beneath would significantly depend on the chosen approximation.

Also you would need same DEM data. For precise modeling you need several terabytes of data (both textures and DEM).

If the overlay is in a specific projection, you'll also need assistance of some GIS tool, or reprojecting library.
[/quote]

thanks for reply.
I think I need a precise mathematical model to the earth, because I am a gis programmer. I can expertly use professional gis tool, but lack of 3d knowledge.
At first I want to model the earth reference to google earth or worldwind earth.
the most precise approximation of the mean sea level is changing at any time, that's exactly rather complex for me.
I preliminary plan to use ellipsoid and refer to WGS84, as it is commonly and widely used in the world. we can cplit the earth by longitude and latitude.
In WGS84,the parameters described as the semi-major axis is 6378137.0,and the slope is 298.257223563.

I bought the ?opengl super bible?forth editon.In the book,it uses the glut libs. but i do not find a api to draw a ellipsoid.
could you give more advices? thanks.
0

Share this post


Link to post
Share on other sites
You can only draw triangles. So take your math model and turn it into triangles - probably thousands of them
0

Share this post


Link to post
Share on other sites
in the physics section on my website you will find a video tutorial that shows how you can render a planet
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