veloren/world/src/site2/gen.rs

use common::{
    terrain::Block,
    store::{Id, Store},
};
use vek::*;

pub enum Primitive {
    Empty, // Placeholder

    // Shapes
    Aabb(Aabb<i32>),
    Pyramid { aabb: Aabb<i32>, inset: i32 },

    // Combinators
    And(Id<Primitive>, Id<Primitive>),
    Or(Id<Primitive>, Id<Primitive>),
    Xor(Id<Primitive>, Id<Primitive>),
}

pub struct Fill {
    pub prim: Id<Primitive>,
    pub block: Block,
}

impl Fill {
    fn contains_at(&self, tree: &Store<Primitive>, prim: Id<Primitive>, pos: Vec3<i32>) -> bool {
        // Custom closure because vek's impl of `contains_point` is inclusive :(
        let aabb_contains = |aabb: Aabb<i32>, pos: Vec3<i32>| (aabb.min.x..aabb.max.x).contains(&pos.x)
            && (aabb.min.y..aabb.max.y).contains(&pos.y);

        match &tree[prim] {
            Primitive::Empty => false,

            Primitive::Aabb(aabb) => aabb_contains(*aabb, pos),
            Primitive::Pyramid { aabb, inset } => {
                let inner = Aabr { min: aabb.min.xy() + *inset, max: aabb.max.xy() - *inset };
                aabb_contains(*aabb, pos) && (inner.projected_point(pos.xy()) - pos.xy())
                    .map(|e| e.abs())
                    .reduce_max() as f32 / (*inset as f32) < 1.0 - (pos.z - aabb.min.z) as f32 / (aabb.max.z - aabb.min.z) as f32
            },

            Primitive::And(a, b) => self.contains_at(tree, *a, pos) & self.contains_at(tree, *b, pos),
            Primitive::Or(a, b) => self.contains_at(tree, *a, pos) | self.contains_at(tree, *b, pos),
            Primitive::Xor(a, b) => self.contains_at(tree, *a, pos) ^ self.contains_at(tree, *b, pos),
        }
    }

    pub fn sample_at(&self, tree: &Store<Primitive>, pos: Vec3<i32>) -> Option<Block> {
        Some(self.block).filter(|_| self.contains_at(tree, self.prim, pos))
    }

    fn get_bounds_inner(&self, tree: &Store<Primitive>, prim: Id<Primitive>) -> Aabb<i32> {
        match &tree[prim] {
            Primitive::Empty => Aabb::new_empty(Vec3::zero()),
            Primitive::Aabb(aabb) => *aabb,
            Primitive::Pyramid { aabb, .. } => *aabb,
            Primitive::And(a, b) => self.get_bounds_inner(tree, *a).intersection(self.get_bounds_inner(tree, *b)),
            Primitive::Or(a, b) | Primitive::Xor(a, b) => self.get_bounds_inner(tree, *a).union(self.get_bounds_inner(tree, *b)),
        }
    }

    pub fn get_bounds(&self, tree: &Store<Primitive>) -> Aabb<i32> {
        self.get_bounds_inner(tree, self.prim)
    }
}

pub trait Structure {
    fn render<F: FnMut(Primitive) -> Id<Primitive>, G: FnMut(Fill)>(
        &self,
        emit_prim: F,
        emit_fill: G,
    ) {}

    // Generate a primitive tree and fills for this structure
    fn render_collect(&self) -> (Store<Primitive>, Vec<Fill>) {
        let mut tree = Store::default();
        let mut fills = Vec::new();
        let root = self.render(|p| tree.insert(p), |f| fills.push(f));
        (tree, fills)
    }
}