• 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
redneon

Calculating aribtrary point position in rectangle

7 posts in this topic

I have four points in 2D space that make up a rectangle, top left, top right, bottom left and bottom right. Given the x and y of an arbitrary point I want to know where that lies in the rectangle. eg, if the point happens to lie on the top left corner it'd be (0,0) and if it happens to lie an the bottom right corner it'd be (width,height). I don't have a rotation matrix for said rectangle but I could make one from the points. I just thought there should be a much simpler way but my mind is having a blank.

 

0

Share this post


Link to post
Share on other sites

I have four points in 2D space that make up a rectangle, top left, top right, bottom left and bottom right. Given the x and y of an arbitrary point I want to know where that lies in the rectangle. eg, if the point happens to lie on the top left corner it'd be (0,0) and if it happens to lie an the bottom right corner it'd be (width,height). I don't have a rotation matrix for said rectangle but I could make one from the points. I just thought there should be a much simpler way but my mind is having a blank.

I guess it'll be better if you just make the translation and rotation of the rectangle and the point, and then a simple substraction will give you the result.

 

If you really want to avoid that you can define two lines in space, one from top-left to top-right and the other from top-left to bottom left. Then, compute the distance of the arbitrary point to each of those lines. Those distances will be the result you want: http://en.wikipedia.org/wiki/Distance_from_a_point_to_a_line

 

Anyway, the second method looks more complex than the first one with those squared roots and power of 2, and the need of compute the lines of the rectangle.

 

Hmm. Actually, it could be a trapezoid based on the position of the camera.

What are you trying to do? Is it a 2D or 3D game? If the camera position makes a rectangle look like a trapezoid then I guess it's 3D, in which case translation and rotation matrices will make everything easier for future stuffs.

Edited by DiegoSLTS
0

Share this post


Link to post
Share on other sites

It's a 3D game but the problem is 2D. To cut a long story short, I'm having to pass four uniforms into a pixel shader for the 2D screen space positions of the four corners of a shape. This will end up being a rectangle if the camera is head on, otherwise it'll be a trapezoid. For each pixel in the shader I have the screen space position and I want to know 1) if the pixel is within those four coordinates and if so 2) calculate the amount across and up the shape for texture lookup.

0

Share this post


Link to post
Share on other sites

Actually, I might be in luck. It looks like the camera will always be head on, which will make the shape always a rectangle. I imagine that makes things easier?

0

Share this post


Link to post
Share on other sites

It's a 3D game but the problem is 2D. To cut a long story short, I'm having to pass four uniforms into a pixel shader for the 2D screen space positions of the four corners of a shape. This will end up being a rectangle if the camera is head on, otherwise it'll be a trapezoid. For each pixel in the shader I have the screen space position and I want to know 1) if the pixel is within those four coordinates and if so 2) calculate the amount across and up the shape for texture lookup.

 

 

It sounds a lot like you're just trying to draw a quad? How about instead of sending 4 points as uniforms, send 4 points as vertices with texture coordinates, which will get transformed in the vertex shader and rasterized in the pixel shader. The texture coordinates will be interpolated by the hardware so you won't have to do any math to determine them. And all the pixels that get rasterized will, by definition, be within the rectangle, so you won't have to perform any tests for that, either.

0

Share this post


Link to post
Share on other sites

Yeah, that was part of the long story short. In this particular example, because of the way the pipeline works doing that would require some refactoring that I didn't want to do. You're right, though. That is the proper way to do it. I should just bite the bullet and do the refactoring instead of being lazy :)

1

Share this post


Link to post
Share on other sites

Yeah, that was part of the long story short. In this particular example, because of the way the pipeline works doing that would require some refactoring that I didn't want to do. You're right, though. That is the proper way to do it. I should just bite the bullet and do the refactoring instead of being lazy smile.png

 

Haaa --  I know that one!  It is so easy to be lazy in that way that you end up spending so much more time to get things done than if you had just done the right thing right the first time!  biggrin.png

 

I know, because I have been there soooo many times.  ;) 

 

Edit: And it feels so much better when you do end up doing things the way you really want to - the proper way - and you know that your code is another small notch better than it was earlier.

Edited by aregee
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