• 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.

IronFist

Finding an angle for a line to point at.

2 posts in this topic

What I am trying to do is draw a line from a central point out to the x and y coordinates of the mouse, and the line has to be a certain length. In other words, I want the line to be pointing at the mouse all the time from a central point, but it cannot be longer than a set length (So I can't just have it draw a line from the central point to the mouse coords).
Ex)
----------------------
          C
         /
        /
       /
      E
     .
    .
   .
  M
------------------
KEY:
C - Central pivot point (beginning of the line)
E - end of line 
/ - line (the length of the line is the distance between # and @)
. - imaginary line
M - Mouse location
  
So far, to draw a line that is a certain length, I would do something like this:
xfinalpos = xbeginposition + sin(20*(PI/180))*linelength;
yfinalpos = ybeginposition + cos(20*(PI/180))*linelength;
  
That works because I already know the angle -> 20. But when I move the mouse around the central point, I don't know the angle. I think I need to use arcsin, arccos, or arctan, but I am not sure which one, or how to use them. Can anyone help me do this? Edited by - IronFist on July 28, 2001 2:25:42 AM
0

Share this post


Link to post
Share on other sites
Note that this sample code is C++ and certainly not the best setup, nor functionally complete, but should suffice to show how to get things done without need for cos/sin/tan/arc-whatever. It does involve a square root (the length of a vector is the square root of the dot product of the vector with itself), but otherwise it''s pretty simple.

Also note that this doesn''t check to see if the mouse is closer to the center point than the specified distance. It shouldn''t be difficult to add that, though.

  
struct Point {
float x, y;
float len() const { return fsqrt(x*x + y*y); }
void normalize() {
float oo_len = 1.0f / len(); //one over length

x *= oo_len;
y *= oo_len;
}
Point& operator-=(const Point& rhs) {
x -= rhs.x;
y -= rhs.y;
return *this;
}
friend Point operator-(const Point& a, const Point& b) {
Point r = a;
r -= b;
return r;
}
Point& operator*=(float k) {
x *= k;
y *= k;
return *this;
}
};

Point get_radial_point(const Point& source, const Point& target, float dist)
{
//get the direction

Point aim = target - source;

//normalize it (ie, make its length == 1)

aim.normalize();

//scale it by the desired distance

aim *= dist;

return aim;
}

//somewhere in your code

Point mouse = read_mouse();
Point center = calculate_center();
Point endpoint = get_radial_point(center, mouse, distance);
draw_line(center, endpoint);




---- --- -- -
Blue programmer needs food badly. Blue programmer is about to die!
0

Share this post


Link to post
Share on other sites