From e90f330a5eea9d381c27ce3c5740c3e36e191e12 Mon Sep 17 00:00:00 2001
From: Don Garrett <dgarrett@acm.org>
Date: Thu, 13 Jun 2024 11:15:22 -0500
Subject: [PATCH] Add support for CapStyle::Dome.

---
 src/layers.rs | 36 ++++++++++++++++++++++++++++++++++--
 1 file changed, 34 insertions(+), 2 deletions(-)

diff --git a/src/layers.rs b/src/layers.rs
index a15fbf0..67a12c5 100644
--- a/src/layers.rs
+++ b/src/layers.rs
@@ -1,6 +1,6 @@
 use stl_io::{self, Vertex};
 
-use crate::mushroom::Mushroom;
+use crate::mushroom::{CapStyle, Mushroom};
 
 #[derive(Debug, PartialEq, Clone)]
 pub struct Layer {
@@ -53,7 +53,7 @@ fn stalk_layers(mushroom: &Mushroom, base: &Vertex, _resolution: f32) -> Vec<Lay
     .to_vec();
 }
 
-fn cap_layers(mushroom: &Mushroom, base: &Vertex, _resolution: f32) -> Vec<Layer> {
+fn cap_layers_cylinder(mushroom: &Mushroom, base: &Vertex) -> Vec<Layer> {
     let top = Vertex::new([base[0], base[1], base[2] + mushroom.cap_h]);
 
     return [
@@ -69,6 +69,38 @@ fn cap_layers(mushroom: &Mushroom, base: &Vertex, _resolution: f32) -> Vec<Layer
     .to_vec();
 }
 
+fn cap_layers_dome(mushroom: &Mushroom, base: &Vertex, resolution: f32) -> Vec<Layer> {
+    let mut result: Vec<Layer> = Vec::with_capacity((mushroom.cap_h / resolution) as usize);
+
+    let mut height = 0.0;
+    loop {
+        // A = mushroom.cap_h
+        // B = mushroom.cap_r
+        // x=B/π * arccos(y/A)
+        let radius = (mushroom.cap_r / std::f32::consts::PI) * (height / mushroom.cap_h).acos();
+
+        result.push(Layer {
+            center: Vertex::new([base[0], base[1], base[2] + height]),
+            radius: radius,
+        });
+
+        height += resolution;
+        if height >= mushroom.cap_h {
+            break;
+        }
+    }
+
+    return result;
+}
+
+fn cap_layers(mushroom: &Mushroom, base: &Vertex, resolution: f32) -> Vec<Layer> {
+    match mushroom.cap_style {
+        CapStyle::Cylinder => cap_layers_cylinder(mushroom, base),
+        CapStyle::Dome => cap_layers_dome(mushroom, base, resolution),
+        CapStyle::Pointed => cap_layers_dome(mushroom, base, resolution),
+    }
+}
+
 pub fn mushroom(mushroom: &Mushroom, resolution: f32) -> Layers {
     let _vertical_steps = (mushroom.height() / resolution) as u32;