collider 0.3.1

A library for continuous 2D collision detection for game developement
Documentation 
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// Copyright 2016-2018 Matthew D. Michelotti
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//   http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

use geom::*;
use geom::shape::{PlacedBounds, Sector};
use float::n64;

// This module contains methods to solve for the normal vector
// between two PlacedShapes.

pub fn rect_rect_normal(dst: &PlacedShape, src: &PlacedShape) -> DirVec2 {
    let (card, overlap) = Card::values().iter().cloned()
        .map(|card| (card, dst.card_overlap(src, card)))
        .min_by_key(|&(_, overlap)| n64(overlap))
        .unwrap();
    DirVec2::new(card.into(), overlap)
}

pub fn circle_circle_normal(dst: &PlacedShape, src: &PlacedShape) -> DirVec2 {
    let mut dir = dst.pos - src.pos;
    let dist = dir.len();
    if dist == 0.0 { dir = v2(1.0, 0.0); }
    DirVec2::new(dir, (src.dims().x + dst.dims().x) * 0.5 - dist)
}

pub fn rect_circle_normal(dst: &PlacedShape, src: &PlacedShape) -> DirVec2 {
    let sector = dst.sector(src.pos);
    if sector.is_corner() {
        circle_circle_normal(&PlacedShape::new(dst.corner(sector), Shape::circle(0.0)), src)
    } else {
        rect_rect_normal(dst, src)
    }
}

pub fn masked_rect_rect_normal(dst: &PlacedShape, src: &PlacedShape, mask: CardMask) -> DirVec2 {
    let (card, overlap) = Card::values().iter().cloned()
        .filter(|&card| mask[card])
        .map(|card| (card, dst.card_overlap(src, card)))
        .min_by_key(|&(_, overlap)| n64(overlap))
        .unwrap_or_else(|| panic!("CardMask must be non-empty"));
    DirVec2::new(card.into(), overlap)
}

pub fn masked_circle_circle_normal(dst: &PlacedShape, src: &PlacedShape, mask: CardMask) -> DirVec2 {
    assert!(mask == CardMask::full(), "CardMask for circle-circle normal must be full");
    circle_circle_normal(dst, src)
}

pub fn masked_rect_circle_normal(dst: &PlacedShape, src: &PlacedShape, mask: CardMask) -> DirVec2 {
    let sector = dst.sector(src.pos);
    if mask_has_corner_sector(sector, mask.flip()) {
        circle_circle_normal(&PlacedShape::new(dst.corner(sector), Shape::circle(0.0)), src)
    } else {
        masked_rect_rect_normal(dst, src, mask)
    }
}

fn mask_has_corner_sector(sector: Sector, mask: CardMask) -> bool {
    if let Some((h_card, v_card)) = sector.corner_cards() {
        mask[h_card] && mask[v_card]
    } else {
        false
    }
}

pub fn circle_any_contact(a: &PlacedShape, b: &PlacedShape) -> Vec2 {
    let normal = a.normal_from(b);
    a.pos + normal.dir() * (normal.len() - a.shape.dims().x) * 0.5
}

pub fn rect_rect_contact(a: &PlacedShape, b: &PlacedShape) -> Vec2 {
    v2(
        rect_rect_contact_1d(a.min_x(), a.max_x(), b.min_x(), b.max_x()),
        rect_rect_contact_1d(a.min_y(), a.max_y(), b.min_y(), b.max_y()),
    )
}

fn rect_rect_contact_1d(a_min: f64, a_max: f64, b_min: f64, b_max: f64) -> f64 {
    0.5 * (a_min.max(b_min) + b_max.min(a_max))
}