Just wondering if this has been attempted before.
I'm making a game where by 2D objects fall from the top and I use my nose to 'catch' those objects.
Currently I have it set up in such a way that if the X and Y values for the nose and 2D object are the same, it increases the counter.
However I've noticed that the position for 3D and 2D objects both reflect very different values.
I've tried using null objects to contain the 2D canvas, but it didn't work either.
Messing around with tolerance values didn't achieve the desired effect.
Equals Patch
First number is taken from the null object, second number is taken from the nose's position.
From nullobject: -0.09079
From nose: 0.00108
Is this something to do with limitations or am I doing something wrongly here? Thanks for taking your time to read this :(
Here is a project that translates 3D nose position to 2D screen space. I made a video on how to do it: video and here is a link to free download.
It requires a few lines of script and the Scene Module to project the 3D position to 2D screen space.
const Scene = require('Scene');
const Patches = require('Patches');
Promise.all([
// The 3D Object or 3D Point we want to track
Scene.root.findFirst('Nose3D'),
]).then(function (results) {
// Define variable names for items we found
const nose3D = results[0];
// This transforms the world coordinate of the 3D Object to a screen coordinate.
var nose2D = Scene.projectToScreen(nose3D.worldTransform.position)
// Get the Nose3D Position, then set the projectToScreen point Nose2D
Patches.outputs.getPoint("Nose3D").then(pointSignal => {
Patches.inputs.setPoint2D('Nose2D', nose2D);
});
});
I try to use 2 ellipses to detect a collision if they overlap. I have to rotate the ellipses but I can't figure out how this works. I'm working with the "com.badlogic.gdx.math.Ellipse" class but it seems to have no method for rotating. Any ideas? Thx in advance!!
Unfortunately, LibGDX doesn't have in-built rotating functions for ellipses.
Instead, I'd either be resorting to a circle in which rotation does not matter, or use polygons to check intersection.
Polygons are formed through an array of float values (vertices), where, every even element of the array is the horizontal component (x) and the odd, the vertical component (y).
Polygon polygon1 = new Polygon(vertexSet1);
Polygon polygon2 = new Polygon(vertexSet2);
Then, by using an Intersector, you can then check whether these polygons have intersected. The more vertices, the more accurate your shape will be. Just remember to have 6 or more elements in your vertex array, as the 6 floats will give 3 (x, y) points which is the minimum required for a polygon.
if (intersector.overlapConvexPolygons(polygon1, polygon2) {
//do your intersection code
}
The polygons themselves have commands to translate, scale and rotate, allowing for the rotations you mentioned above.
This may be an issue that I simply do no know the proper terminology to research the answer to this, I am pretty sure the solution is a function of trig.
I have a method which accepts an X/Y position coordinate and an angle in degrees. It should return an updated X/Y based on the rotation angle provided.
For example, A point is usually located at x=0,y=2 (top middle). Now I need to rotate it to it's side by 90 degrees. In my mind I know it's location is now x=2,y=0 (middle right) but I do not know the equation to produce this.
I think I need to first determine the quadrant of the starting point, and then perform the proper trig function from there. This is for a game I am developing using libgdx which is where the Vector2 object comes from.
I have come this far:
public Vector2 getPointsRotated(Vector2 startPoint, float angle){
Vector2 newPoint = new Vector2(0,0);
// determine the starting quadrant
int quad=0;
if((startPoint.x>=0)&&(startPoint.y>=0)){quad=0;}
if((startPoint.x<0)&&(startPoint.y>=0)){quad=1;}
if((startPoint.x<0)&&(startPoint.y<0)){quad=2;}
if((startPoint.x>=0)&&(startPoint.y<0)){quad=3;}
if(quad==0){
// doesn't work
newPoint.x = (float) ((newPoint.x)* (Math.sin(angle)));
newPoint.y = (float) ((newPoint.y)* (Math.cos(angle)));
}
// ...
// other quadrants also don't work
// ...
return newPoint;
}
Thanks for any help.
Update:
I have been avoiding and returning to this problem for a few days. Now after finally posting the question here I figure it out within minutes (for ppl using libgdx anyway).
Libgdx provides a rotate function for Vector2s
so something like:
Vector2 position = new Vector2(0,2);
position.rotate(angle);
works perfectly.
I find rotation matrices are very helpful for this sort of problem.
https://gamedev.stackexchange.com/questions/54299/tetris-rotations-using-linear-algebra-rotation-matrices
I'm currently struggling on a problem that seems far beyond my maths capacities (been a long time since I've made some proper maths...) and I would appreciate some help on that.
Here's my setting :
I got some simple shapes (rectangles), and I "project" their bottom points on a line, coming from an Origin point.
Up to this point everything is fine.
But now I'd like to draw the original shape distorted as if it was projected with some perspective on a plane.
Please consider that I have nothing related to any rotation, isometric or any 3D or fake 2D perspective in my code, I'm only trying to draw some shapes using the graphics library to only have a feeling of something real.
Here's a quick drawing of what I'm trying to do :
What I know :
Origin point coordinates
the rect position & sizes
the red line position
the A & B points coordinates
What I want to determine is the coordinates of the C & D points, thing that could be easy if I wasn't struggling to find the "Origin bis" coordinates.
What I'm trying to do is to fake the projection of my rectangle on something that can be considered as a "floor" (related to the plane where my original rectangle is that can be seen as a wall).
Maybe I'm over-complicating the problem or maybe I fail to see any other easier way to do it, but I'm really not good anymore in any geometry or maths thing... :-(
Thanks a lot for your answers !
hmm i don't know if I undestood it correctly but I think you have too few input parameters:
you said the following information is given:
Origin point coordinates
the rect position & sizes
the red line position
the A & B points coordinates
I don't think it is possible to get your projected rectangle with this information alone.
Additionally, I think your green lines and the 'origin Bis' aren't helpful as well.
Perhaps, try this:
Supose, a blue line going through the points C & D is given as well.
Then you could find your projected rectangle by projecting the top of the rectangle onto that blue line.
So in summary:
You define an origin + two parallel lines, a red and a blue one.
Then you can project the top of the rect onto the blue line and the bottom of the rect onto the red line, yielding the points A,B,C,D
I hope this helps.
If I'm right, this code will show what you wanted to see.
First of all, I've ignored your initial setup of objects and information, and focused on the example situation itself; fake-projecting shadow for a "monolith" (any object is possible with the example below, even textured)
My reason was that it's really quite easy with the Matrix class of ActionScript, a handy tool worth learning.
Solution:
You can use the built-in Matrix class to do skew transform on DisplayObjects.
Try this example:
(The "useful" part lies in the _EF EnterFrame handler ;) )
import flash.display.MovieClip;
import flash.geom.Matrix;
import flash.events.Event;
import flash.display.BitmapData;
const PIP180:Number = Math.PI / 180;
const MAX_SHADOW_HEIGHT_MULTIPLIER:Number = 0.25; // you can also calculate this from an angle, like ... = Math.sin(angle * PIP180);
const ANIM_DEG_PER_FRAME:Number = 1.0 * PIP180; // the shadow creeps at a +1 degree per frame rate
var tx:BitmapData = new MonolithTexture(); // define this BitmapData in the library
var skew:Number = -10 * PIP180; // initial
var mono:MovieClip = new MovieClip();
mono.graphics.beginBitmapFill(tx);
// drawn that way the registration point is 0,0, so it's standing on the ground
mono.graphics.drawRect(0, -tx.height, tx.width, tx.height);
mono.graphics.endFill();
// align monolith to the "ground"
mono.x = stage.stageWidth / 2;
mono.y = stage.stageHeight - 100;
// make it be 100x300 pixel
mono.width = 100;
mono.height = 300;
var shad:MovieClip = new MovieClip();
// colored:
shad.graphics.beginFill(0x000000);
// or textured:
//shad.graphics.beginBitmapFill(tx);
shad.graphics.drawRect(0, -tx.height, tx.width, tx.height);
shad.graphics.endFill();
addChild(shad); // shadow first
addChild(mono); // then the caster object
addEventListener(Event.ENTER_FRAME, _EF);
function _EF(e:Event):void {
// animate skew on the positive half circle
skew = (skew + ANIM_DEG_PER_FRAME) % Math.PI;
// Matrix takes 6 parameters: a, b, c, d, x, y
// for this shadow trick, use them as follows:
// a = width scaling (as mono and shad are drawn in the same way, copy mono.scaleX for a perfect fit
// b = 0, because we don't want to project the vertical axis of transformation to the horizontal
// c = horizontal skew
// d = height scaling * skew * making it a bit flat using the constant
// x = mono.x, ...
// y = mono.y since originally mono and shad look alike, only the Matrix makes shad render differently
var mtx:Matrix = new Matrix(mono.scaleX, 0, Math.cos(skew), mono.scaleY * Math.sin(skew) * MAX_SHADOW_HEIGHT_MULTIPLIER, mono.x, mono.y);
shad.transform.matrix = mtx;
}
Now all you got to know to utilize this in your case, is the following N factors:
Q1: from what angle you want to project the shadow?
A1: horizontal factor is the skew variable itself, while vertical angle is stored as constant here, called MAX_SHADOW_HEIGHT_MULTIPLIER
Q2: do you want to project shadow only "upwards", or freely?
A2: if "upwards" is fine, keep skew in the positive range, otherwise let it take negative values as well for a "downward" shadow
P.S.: if you render the internals of the objects that they don't snap to 0 y as a base point, you can make them seem float/sink, or offset both objects vertically with a predefined value, with the opposite sign.
You face 1 very simple problem, as you said:
'What I want to determine is the coordinates of the C & D points, thing that could be easy if I wasn't struggling to find the "Origin bis" coordinates.'
But these co-ordinates relate to each other, so without one (or another value such as an angle) you cannot have the other. If you are to try this in 3D you are simply allowing the 3D engine to define 'Origin bis' and do your calculating for C and D itself.
So regardless you will need an 'Original bis', another value relating to the redline or your Rect for which to calculate the placement of C and D.
I remember making stuff like this and sometimes it's better to just stick with simple, you either make an 'Original bis' defines by yourself (it can be either stationary or move with the player/background) and get C and D the way you got A and B only that you use a lower line than the red line, or as I would of done, once you have A and B, simple skew/rotate your projection from those points down a bit further, and you get something the same as an 'Original bis' that follows the player. This works fine at simulating 'feeling of something real' but sadly as has been said, it looking real depends on what you are portraying. We do not know what the areas above or below the red line are (sky/ground, ground/water) and whether 'Origin' and 'Origin bis' is your light source, vanishing point, etc.
I'm answering my own question (hopefully for your benefit), but this is the issue:
I've created a world map with polylines (in Google maps API v3). Some of these lines span the IDL (international date line). I want to place directional arrows on some of my lines, one arrow in the center of each line. On lines that span the IDL, the arrow center calculated by averaging the 2 end points together:
(latlng1.lat()+latlng2.lat()/2), (latlng1.lng()+latlng2.lng()/2)
draws the line the opposite way around the world leaving a floating arrow on my map instead of in the center of the actual line.
I initially sought a formula for getting the reverse of the line and somehow determining which was used. But it's too dependent on the map display. I even went so far as to see if I could get the center from the end points of the line if I first converted them to pixels, but the data conversion had no effect on the outcome.
So I then thought to look for an intersect method on the polyline, passing a point to check - and if it wasn't, find the center point from the reverse line (which I believe would 180-center.lng()) but there is no intersection method on polylines. So I started looking into the bounds object, because there are some intersection/contains methods on bounds.
So here is a very simple solution for a relatively undocumented problem:
(credit for function to retrieve bounds goes to Ben Appleton, ty):
function getBoundsForPoly(poly) {
var bounds = new google.maps.LatLngBounds;
poly.getPath().forEach(function(latLng) {
bounds.extend(latLng);
});
return bounds;
}
var poly_bounds = MapAbstraction.get_poly_bounds(line);
var center_point =poly_bounds.getCenter();
and then I can pass my center_point to my marker creation tool to generate the arrow in the actual center of the line without worrying about which way it was drawn.