• 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

worldtoscreen / screentoworld

4 posts in this topic

Can someone please please show me how to do a world to screen and screen to world function for a 3d game. Ive spent days searching for how to do it but havent find any good tutorials..


This is the data I have to work with


World X,Y,Z pos to convert / screen X,Y to convert

Angle - Field of View = 27.7996

Angle - Roll = 0.0

Depth of Field - Amount = 0.0

Depth of Field - Depth = 8.0

Depth of Field - End = 8.0

Depth of Field - Start = 0.0003

Distance = 34.0

Distance - Far Clip = 600.0

Distance - Near Clip = 0.0999

Distance - Shadow Clip = 75.0

Target - Pitch = 56.0

Target - X

Target - Y

Target - Yaw = 180.0

Target - Z Offset = 0.0

Edited by seasick

Share this post

Link to post
Share on other sites

To transform a point in world to screen space you need to run it through the camera projections, much like you do with any graphics that you render. Let's say you start with a position in world space, you do WORLD -> VIEW -> PROJECTION. After that you have the position in clip space. If you then divide xyz by w (remember that clip space has 4 coordinates) you get NDC or normalized device coordinates. You can then map these to whatever you want, eg. pixels. This is how I do it in my engine:


bool Camera::worldToScreen(const Vec3& worldPos, int& x, int& y)
    Vec4 posHomogeneous(worldPos, 1.0f);
    Vec4 posInClipSpace = posHomogeneous * getViewMatrix() * mProjectionMatrix;
    Vec3 posInNDC(posInClipSpace.x / posInClipSpace.w, posInClipSpace.y / posInClipSpace.w, posInClipSpace.z / posInClipSpace.w);

    // Check if the point is in the camera's view.
    if(posInClipSpace.w > 0.0f && 
        posInNDC.x >= -1.0f && posInNDC.x <= 1.0f && 
        posInNDC.y >= -1.0f && posInNDC.y <= 1.0f && 
        posInNDC.z >= 0.0f && posInNDC.z <= 1.0f)
        x = (int)Math::remapFloat(posInNDC.x, -1.0f, 1.0f, 0.0f, (float)mGraphicsEngine->getScreenWidth());
        y = (int)Math::remapFloat(posInNDC.y, -1.0f, 1.0f, (float)mGraphicsEngine->getScreenHeight(), 0.0f);
        return true;

    return false;

That would give you the screen coordinates in pixels.


To go the other way, it is a little more involved. The usual thing to do is do a ray cast from the camera and see what it hits. This is how I construct the ray (again in the camera class):

Vec3 rayOrigin;
Vec3 rayDirection;

float vx = (((2.0f * screenX) / (float)mGraphicsEngine->getScreenWidth()) - 1.0f ) / mProjectionMatrix._11;
float vy = (((-2.0f * screenY) / (float)mGraphicsEngine->getScreenHeight()) + 1.0f ) / mProjectionMatrix._22;

rayOrigin.set(0.0f, 0.0f, 0.0f);
rayDirection.set(vx, vy, 1.0f);

That gives you a ray in camera space (view space). You can then transform this into world space and do ray casting against objects using that ray. How you do the ray casting is up to you (and how the scene is organized), but I first do a ray-AABB test against all objects and then a ray-triangle test once I hit an AABB, to optimize a bit. This might not be the most efficient way.


Hope it helps!



Share this post

Link to post
Share on other sites

The same way you generate them when you draw stuff. For example, in XNA there's Matrix.CreateLookAt() which you can use for view matrices, and something like Matrix.CreatePerspectiveFieldOfView() to create a projection matrix. The view matrix describes your cameras positioning and the projection matrix describes your camera 'lens'. Somewhat simplified.


Edit: If you don't know these already, chances are you are trying to learn picking etc before trying to learn rendering. You should probably go the other way around, check some tutorials on 3d rendering instead and make sure you understand the concepts of vertices, matrices, transformations, pipelines etc. Working with 3D is very different from working with 2D, so you shouldn't try to solve your problems the same ways.

Edited by DvDmanDT

Share this post

Link to post
Share on other sites

Best article I have found on the topic of OpenGL matrices. I think you should get familiar with the algebra behind the geometric pipeline if you are serious about developing a 3d game! -> http://solarianprogrammer.com/2013/05/22/opengl-101-matrices-projection-view-model/


PS: The coordinate system of Direct3D is different, but if you understand the maths its not too difficult to convert from one to the other.


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