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augustlate/Rect.hx

Last active June 7, 2016 11:18
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Bounding Rectangle helper class for kha
Raw
Rect.hx
//Copyright 2016 August Late. Licensed under zlib.
//Tiny utility class for working with bounding rectangles
import kha.math.Vector2;
import kha.math.FastMatrix4;
class Rect {
//Computes the smallest axis aligned rect that will contain the transformed rect.
public static function transform(rect : Rect,m : FastMatrix4) : Rect {
var r = new Rect();
r.center.x = m._00 * rect.center.x + m._10 * rect.center.y + m._30;
r.center.y = m._01 * rect.center.x + m._11 * rect.center.y + m._31;
r.halfExtents.x = Math.abs(m._00)*rect.halfExtents.x + Math.abs(m._10)*rect.halfExtents.y;
r.halfExtents.y = Math.abs(m._01)*rect.halfExtents.x + Math.abs(m._11)*rect.halfExtents.y;
return r;
}
static public function MinMax(min_x : Float, min_y : Float, max_x : Float, max_y : Float) : Rect{
return Rect.create(min_x,min_y,Math.abs(max_x-min_x),Math.abs(max_y-min_y));
}
static public function create(x : Float,y : Float, width:Float, height:Float) : Rect{
var rect = new Rect();
rect.halfExtents = new Vector2(0.5*width,0.5*height);
rect.center = new Vector2(x+rect.halfExtents.x,y+rect.halfExtents.y);
return rect;
}
public function new(){
center = new Vector2();
halfExtents = new Vector2();
}
public var min(get,never) : Vector2;
public var max(get,never) : Vector2;
public var x(get,never) : Float;
public var y(get,never) : Float;
public var width(get,never) : Float;
public var height(get,never) : Float;
@:embed public var center : Vector2;
@:embed public var halfExtents : Vector2;
function get_min() : Vector2 {
return center.sub(halfExtents);
}
function get_max() : Vector2 {
return center.add(halfExtents);
}
function get_x() : Float { return center.x-halfExtents.x; }
function get_y() : Float { return center.y-halfExtents.y; }
function get_width() : Float { return halfExtents.x*2; }
function get_height() : Float { return halfExtents.y*2; }
}
Raw
Transform.hx
//Copyright 2016 August Late. Licensed as zlib.
//This code lets us generate a complete 2d transform in a single step.
function computeTransform(rotation : Float, origin : Vector2, position : Vector2, scale : Vector2){
var cos = Math.cos(rotation);
var sin = Math.sin(rotation);
var scaled_origin = new FastVector2(
origin.x*scale.x,
origin.y*scale.y
);
var transformed_origin = new FastVector2(
scaled_origin.x * cos - scaled_origin.y * sin,
scaled_origin.x * sin + scaled_origin.y * cos
);
return new FastMatrix4(
scale.x*cos, scale.y*-sin,0, position.x-transformed_origin.x,
scale.x*sin, scale.y*cos, 0, position.y-transformed_origin.y,
0, 0, 1, 0,
0, 0, 0, 1
);
}
Raw
UsingRect.hx
//Copyright 2016 August Late. Licensed under zlib.
//This code makes using transforms to compute scissor rects extremely painless.
var rect = Rect.MinMax(0,0,1,1);
var scissor = Rect.transform(rect,viewMatrix.multmat(object.localToWorld));
g.scissor(Std.int(scissor.x),Std.int(scissor.y),Std.int(scissor.width),Std.int(scissor.height));
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