diff --git a/BUILD.md b/BUILD.md
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+# Building OrcaSlicer with ZAA on macOS
+
+A step-by-step guide to building OrcaSlicer from source on macOS. No prior experience with building software required.
+
+## What You'll Need
+
+- A Mac running macOS 11.3 (Big Sur) or later
+- About 15 GB of free disk space
+- An internet connection
+- About 1-2 hours for the first build (mostly waiting)
+
+## Step 1: Open Terminal
+
+Press **Cmd + Space**, type **Terminal**, and press Enter. A window with a command prompt will appear. All commands below are typed into this window.
+
+## Step 2: Install Xcode Command Line Tools
+
+This installs the compiler and basic development tools.
+
+```bash
+xcode-select --install
+```
+
+A dialog will pop up. Click **Install** and wait for it to finish (a few minutes).
+
+To verify it worked:
+
+```bash
+xcode-select -p
+```
+
+You should see something like `/Library/Developer/CommandLineTools` or `/Applications/Xcode.app/Contents/Developer`.
+
+## Step 3: Install Homebrew
+
+[Homebrew](https://brew.sh) is a package manager that makes it easy to install developer tools on macOS.
+
+```bash
+/bin/bash -c "$(curl -fsSL https://raw.githubusercontent.com/Homebrew/install/HEAD/install.sh)"
+```
+
+Follow the prompts. When it finishes, it will tell you to run one or two commands to add Homebrew to your PATH. **Run those commands** — they look something like:
+
+```bash
+echo 'eval "$(/opt/homebrew/bin/brew shellenv)"' >> ~/.zprofile
+eval "$(/opt/homebrew/bin/brew shellenv)"
+```
+
+To verify:
+
+```bash
+brew --version
+```
+
+## Step 4: Install CMake
+
+CMake is the build system OrcaSlicer uses.
+
+```bash
+brew install cmake
+```
+
+To verify:
+
+```bash
+cmake --version
+```
+
+You need version 3.13 or later (anything recent from Homebrew will work).
+
+## Step 5: Install Git (if needed)
+
+Git usually comes with the Xcode Command Line Tools. Check:
+
+```bash
+git --version
+```
+
+If it's not found:
+
+```bash
+brew install git
+```
+
+## Step 6: Clone the Repository
+
+Choose where you want the source code. For example, in your home directory:
+
+```bash
+cd ~
+git clone https://github.com/mnott/OrcaSlicer.git
+cd OrcaSlicer
+```
+
+If you want the ZAA feature branch:
+
+```bash
+git checkout feature/zaa-contouring
+```
+
+## Step 7: Build
+
+The `build.sh` script handles everything. For a first-time build:
+
+```bash
+chmod +x build.sh
+./build.sh --full
+```
+
+This does three things:
+1. **Builds dependencies** (Boost, wxWidgets, OpenSSL, etc.) — takes 30-60 minutes the first time
+2. **Configures CMake** — sets up the build system
+3. **Builds OrcaSlicer** — compiles the application
+
+Go get a coffee. The dependency step only needs to run once.
+
+### After the first build
+
+For subsequent builds (after making code changes), just run:
+
+```bash
+./build.sh
+```
+
+This does an incremental build — only recompiles what changed. Usually takes 1-5 minutes.
+
+### Other build options
+
+```bash
+./build.sh --help       # Show all options
+./build.sh --clean      # Clean rebuild (if something is broken)
+./build.sh --deps       # Rebuild dependencies only
+./build.sh --configure  # Reconfigure CMake only
+```
+
+## Step 8: Run OrcaSlicer
+
+After a successful build, the script prints the app location. You can run it with:
+
+```bash
+open build/arm64/src/RelWithDebInfo/OrcaSlicer.app
+```
+
+Or find `OrcaSlicer.app` in Finder and double-click it.
+
+## Troubleshooting
+
+### "CMake not found"
+
+Make sure Homebrew is in your PATH (see Step 3), then `brew install cmake`.
+
+### "No rule to make target" or CMake generator errors
+
+Your build directory may have been configured with a different generator. Clean and reconfigure:
+
+```bash
+./build.sh --clean --full
+```
+
+### Build fails during dependencies
+
+Some deps need a lot of memory. Close other applications and try again. If a specific dependency fails, check if you have the latest Xcode Command Line Tools:
+
+```bash
+softwareupdate --list
+```
+
+### wxWidgets "hardcoded path" errors
+
+wxWidgets bakes the installation path into its config files. If you move the source directory after building deps, you need to rebuild them:
+
+```bash
+./build.sh --deps
+./build.sh --clean
+```
+
+### "Permission denied" on build.sh
+
+```bash
+chmod +x build.sh
+```
+
+### Apple Silicon (M1/M2/M3/M4) vs Intel
+
+The build script auto-detects your architecture. If you need to specify it explicitly:
+
+```bash
+./build.sh --full --arch arm64    # Apple Silicon
+./build.sh --full --arch x86_64   # Intel
+```
+
+## Project Structure
+
+```
+OrcaSlicer/
+├── src/
+│   ├── libslic3r/        # Core slicing engine
+│   │   ├── ContourZ.cpp  # ZAA raycasting algorithm
+│   │   └── ...
+│   └── slic3r/GUI/       # User interface
+├── deps/                  # External dependencies
+├── build/                 # Build output (created by build.sh)
+│   └── arm64/
+│       └── src/RelWithDebInfo/
+│           └── OrcaSlicer.app
+├── docs/
+│   └── ZAA.md            # ZAA feature documentation
+├── build.sh              # Build script (this guide uses it)
+├── BUILD.md              # This file
+└── build_release_macos.sh  # Official release build script
+```
+
+## ZAA (Z Anti-Aliasing)
+
+See [docs/ZAA.md](docs/ZAA.md) for details on the Z Anti-Aliasing feature. In short: enable **Z contouring** in Print Settings > Quality to get smoother curved surfaces.
diff --git a/build.sh b/build.sh
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+#!/usr/bin/env bash
+# OrcaSlicer Build Script (macOS)
+# Handles the full build lifecycle: deps, configure, build
+#
+# Usage:
+#   ./build.sh              # Incremental build (after initial setup)
+#   ./build.sh --full       # Full build from scratch (deps + configure + build)
+#   ./build.sh --deps       # Build dependencies only
+#   ./build.sh --configure  # Run CMake configure only
+#   ./build.sh --clean      # Remove build dir and rebuild
+#   ./build.sh --help       # Show all options
+
+set -e
+set -o pipefail
+
+# ── Configuration ──────────────────────────────────────────────
+
+SCRIPT_DIR="$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)"
+ARCH="${ARCH:-$(uname -m)}"
+BUILD_CONFIG="${BUILD_CONFIG:-RelWithDebInfo}"
+OSX_DEPLOYMENT_TARGET="${OSX_DEPLOYMENT_TARGET:-11.3}"
+NCPU=$(sysctl -n hw.ncpu 2>/dev/null || echo 4)
+
+BUILD_DIR="${SCRIPT_DIR}/build/${ARCH}"
+DEPS_DIR="${SCRIPT_DIR}/deps"
+DEPS_BUILD_DIR="${DEPS_DIR}/build/${ARCH}"
+DEPS_INSTALL_DIR="${DEPS_BUILD_DIR}/OrcaSlicer_dep"
+
+# CMake 4.x compatibility
+CMAKE_VERSION=$(cmake --version 2>/dev/null | head -1 | sed 's/[^0-9]*\([0-9]*\).*/\1/')
+CMAKE_COMPAT=""
+if [ "${CMAKE_VERSION:-3}" -ge 4 ] 2>/dev/null; then
+    CMAKE_COMPAT="-DCMAKE_POLICY_VERSION_MINIMUM=3.5"
+fi
+
+# ── Colors ─────────────────────────────────────────────────────
+
+GREEN='\033[0;32m'
+YELLOW='\033[1;33m'
+RED='\033[0;31m'
+BLUE='\033[0;34m'
+BOLD='\033[1m'
+NC='\033[0m'
+
+info()  { echo -e "${BLUE}▸${NC} $*"; }
+ok()    { echo -e "${GREEN}✓${NC} $*"; }
+warn()  { echo -e "${YELLOW}⚠${NC} $*"; }
+err()   { echo -e "${RED}✗${NC} $*"; }
+
+# ── Parse Arguments ────────────────────────────────────────────
+
+DO_DEPS=false
+DO_CONFIGURE=false
+DO_BUILD=true
+DO_CLEAN=false
+DO_FULL=false
+
+while [[ $# -gt 0 ]]; do
+    case $1 in
+        --full)       DO_FULL=true; shift ;;
+        --deps)       DO_DEPS=true; DO_BUILD=false; shift ;;
+        --configure)  DO_CONFIGURE=true; DO_BUILD=false; shift ;;
+        --clean)      DO_CLEAN=true; shift ;;
+        --arch)       ARCH="$2"; shift 2 ;;
+        --config)     BUILD_CONFIG="$2"; shift 2 ;;
+        --help|-h)
+            echo "OrcaSlicer Build Script (macOS)"
+            echo ""
+            echo "Usage: $0 [OPTIONS]"
+            echo ""
+            echo "Build modes:"
+            echo "  (no flags)     Incremental build (fastest, use after initial setup)"
+            echo "  --full         Full build from scratch: deps → configure → build"
+            echo "  --deps         Build dependencies only (takes 30-60 min first time)"
+            echo "  --configure    Run CMake configure only"
+            echo "  --clean        Remove build directory, then rebuild"
+            echo ""
+            echo "Options:"
+            echo "  --arch ARCH    Architecture: arm64, x86_64 (default: $(uname -m))"
+            echo "  --config CFG   Build config: Release, RelWithDebInfo, Debug"
+            echo "                 (default: RelWithDebInfo)"
+            echo ""
+            echo "Examples:"
+            echo "  $0 --full            # First-time build (do this first!)"
+            echo "  $0                   # Quick rebuild after code changes"
+            echo "  $0 --clean           # Clean rebuild if something is broken"
+            echo ""
+            echo "Prerequisites: Xcode Command Line Tools, CMake 3.13+"
+            echo "  xcode-select --install"
+            echo "  brew install cmake"
+            exit 0
+            ;;
+        *)
+            err "Unknown option: $1 (use --help)"
+            exit 1
+            ;;
+    esac
+done
+
+# --full implies all steps
+if [ "$DO_FULL" = true ]; then
+    DO_DEPS=true
+    DO_CONFIGURE=true
+    DO_BUILD=true
+fi
+
+# ── Preflight Checks ──────────────────────────────────────────
+
+echo ""
+echo -e "${BOLD}OrcaSlicer Build${NC}"
+echo "━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━"
+echo "  Architecture:  ${ARCH}"
+echo "  Config:        ${BUILD_CONFIG}"
+echo "  CPU cores:     ${NCPU}"
+echo "  CMake:         $(cmake --version 2>/dev/null | head -1 || echo 'NOT FOUND')"
+[ -n "$CMAKE_COMPAT" ] && echo "  CMake compat:  4.x → policy 3.5"
+echo ""
+
+# Check prerequisites
+if ! command -v cmake &>/dev/null; then
+    err "CMake not found. Install it with: brew install cmake"
+    exit 1
+fi
+
+if ! command -v git &>/dev/null; then
+    err "Git not found. Install Xcode Command Line Tools: xcode-select --install"
+    exit 1
+fi
+
+if ! xcode-select -p &>/dev/null; then
+    err "Xcode Command Line Tools not found. Install: xcode-select --install"
+    exit 1
+fi
+
+# ── Clean ──────────────────────────────────────────────────────
+
+if [ "$DO_CLEAN" = true ]; then
+    warn "Removing build directory: ${BUILD_DIR}"
+    rm -rf "${BUILD_DIR}"
+    ok "Clean complete"
+    echo ""
+fi
+
+# ── Build Dependencies ─────────────────────────────────────────
+
+if [ "$DO_DEPS" = true ]; then
+    info "Building dependencies (this takes a while the first time)..."
+    mkdir -p "${DEPS_INSTALL_DIR}"
+    cd "${DEPS_BUILD_DIR}"
+
+    cmake "${DEPS_DIR}" \
+        -G "Unix Makefiles" \
+        -DCMAKE_BUILD_TYPE="${BUILD_CONFIG}" \
+        -DCMAKE_OSX_ARCHITECTURES:STRING="${ARCH}" \
+        -DCMAKE_OSX_DEPLOYMENT_TARGET="${OSX_DEPLOYMENT_TARGET}" \
+        ${CMAKE_COMPAT}
+
+    cmake --build . --config "${BUILD_CONFIG}" --target deps -j"${NCPU}"
+
+    ok "Dependencies built"
+    echo ""
+fi
+
+# ── Configure ──────────────────────────────────────────────────
+
+if [ "$DO_CONFIGURE" = true ] || { [ "$DO_BUILD" = true ] && [ ! -f "${BUILD_DIR}/Makefile" ] && [ ! -f "${BUILD_DIR}/build.ninja" ]; }; then
+    info "Configuring CMake..."
+    mkdir -p "${BUILD_DIR}"
+    cd "${BUILD_DIR}"
+
+    cmake "${SCRIPT_DIR}" \
+        -G "Unix Makefiles" \
+        -DCMAKE_BUILD_TYPE="${BUILD_CONFIG}" \
+        -DCMAKE_OSX_ARCHITECTURES="${ARCH}" \
+        -DCMAKE_OSX_DEPLOYMENT_TARGET="${OSX_DEPLOYMENT_TARGET}" \
+        ${CMAKE_COMPAT}
+
+    ok "CMake configured"
+    echo ""
+fi
+
+# ── Build ──────────────────────────────────────────────────────
+
+if [ "$DO_BUILD" = true ]; then
+    if [ ! -d "${BUILD_DIR}" ]; then
+        err "Build directory not found: ${BUILD_DIR}"
+        err "Run '$0 --full' for a first-time build"
+        exit 1
+    fi
+
+    info "Building OrcaSlicer..."
+    cd "${SCRIPT_DIR}"
+
+    cmake --build "${BUILD_DIR}" \
+        --config "${BUILD_CONFIG}" \
+        --target OrcaSlicer \
+        -j"${NCPU}"
+
+    echo ""
+    echo -e "${GREEN}━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━${NC}"
+    ok "Build complete!"
+    echo ""
+    echo "  App: ${BUILD_DIR}/src/${BUILD_CONFIG}/OrcaSlicer.app"
+    echo ""
+    echo "  Run: open \"${BUILD_DIR}/src/${BUILD_CONFIG}/OrcaSlicer.app\""
+    echo -e "${GREEN}━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━${NC}"
+fi