Organize projects into folders with READMEs and preview renders.

Move the Ring solar siding adapter into its own directory, add repo and
project documentation, and introduce a preview script (OpenSCAD+xvfb or
PyVista fallback) for catalog images.

ring-solar-siding-adapter/README.md

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+# Ring Solar Siding Adapter
+
+![Preview](preview.png)
+
+Parametric adapter plate that sits between a **Ring Solar Charger** (integrated battery-doorbell solar unit) and horizontal beaded vinyl lap siding.
+
+| | |
+|---|---|
+| **Source** | [`ring-solar-siding-adapter.scad`](ring-solar-siding-adapter.scad) |
+| **Footprint** | ~93 × 171 mm (matches the Ring back) |
+| **Units** | Millimeters throughout |
+
+## What it is
+
+- **Front face:** flat — the Ring unit mounts here.
+- **Rear face:** shaped to match siding — bead groove at the top, flat shelf in the middle, curved taper at the bottom.
+
+## What it's for
+
+The Ring's back is flat; siding is not. Without an adapter, you get gaps, uneven pressure, and a poor mount.
+
+This plate:
+
+- Conforms to the siding profile so the rear sits flush against the wall.
+- Receives the siding bead in a semicircular groove near the top.
+- Provides two through-holes aligned with the Ring's house-mount screws — screws pass through Ring → adapter → siding → sheathing.
+
+Typical stack:
+
+```
+Ring Solar Charger
+       ↓ screws
+  Adapter plate  ← this part
+       ↓
+  Vinyl siding
+       ↓
+  Sheathing
+```
+
+## Rear profile (side view, bottom → top)
+
+```
+plate top ─────────────  bead coping groove (receives siding bead)
+            flat rear shelf
+taper start ─────────────  flat_upper_ratio sets this boundary
+            curved taper
+plate bottom ────────────  deepest projection toward front
+```
+
+**Depth convention:** lower depth = toward the wall; higher depth = toward the front (Ring).
+
+## Parameters
+
+### Plate
+
+| Parameter | Meaning |
+|-----------|---------|
+| `plate_width` | Width of the adapter (Ring back width). |
+| `plate_height` | Height of the adapter (Ring back height). |
+| `min_wall_thickness` | Minimum solid depth at the thinnest point (bead groove pinch). Also scales bottom taper reach. |
+| `edge_round` | Rounds front edges via minkowski. Keep `0` while tuning; set ~1 for final print (slower render). |
+
+### Siding profile
+
+| Parameter | Meaning |
+|-----------|---------|
+| `siding_projection` | Nominal max siding depth from wall. Feeds `face_inset_z` via clearance and inset. |
+| `face_inset_depth` | How far the flat upper rear sits in from max projection. |
+| `bead_coping_radius` | Radius of the semicircular bead groove (measured on your siding). |
+| `bead_coping_offset_top` | Distance from plate top to center of the bead groove. |
+| `flat_upper_ratio` | Fraction of plate height (from top down) with a flat rear. Lower = taper starts higher. |
+| `bottom_taper_depth_ratio` | How far the bottom rear reaches toward the front beyond the flat shelf: `min_wall_thickness × this`. Higher = more projection at bottom. |
+| `rear_extension` | Pushes flat rear and taper toward the wall without moving the front face or bead groove vs front/top. Adds overall depth. |
+| `course_pitch` | Bead-to-bead spacing on your siding (~6.5"). Reference for tuning. |
+| `profile_segments` | Curve sampling resolution. Higher = smoother, slower. |
+| `profile_mode` | `curved` = smooth taper; `stepped` = debug fallback with sharp transitions. |
+| `rear_clearance` | Small gap so the part doesn't bind on siding. |
+
+**Common tuning relationships:**
+
+| Goal | Parameter |
+|------|-----------|
+| Move taper start up/down | `flat_upper_ratio` |
+| Bottom taper more/less toward front | `bottom_taper_depth_ratio` |
+| Whole plate deeper front-to-back (bead stays put) | `rear_extension` |
+| Bead groove up/down | `bead_coping_offset_top` |
+| Groove size | `bead_coping_radius` |
+
+### Mounting holes
+
+| Parameter | Meaning |
+|-----------|---------|
+| `mount_hole_offset_top` | Upper hole center distance from plate top. |
+| `mount_hole_offset_bottom` | Lower hole center distance from plate bottom. |
+| `mount_hole_dia` | Hole diameter (4.5 mm for 4 mm Ring screws). |
+| `mount_hole_x` | Horizontal offset from center (`0` = centered). |
+
+### Export
+
+| Parameter | Meaning |
+|-----------|---------|
+| `part_mode` | What to generate (see below). |
+| `profile_strip_width` | Width of the narrow siding fit-test strip. |
+| `front_slice_depth` | Thickness of the front-face test cap (mm). |
+
+**Export modes:**
+
+| Mode | Purpose |
+|------|---------|
+| `full` | Complete adapter with holes — final part. |
+| `profile_strip` | Narrow strip through the rear profile — cheap siding fit test. |
+| `front_slice` | Thin front cap with holes — check width, height, hole placement vs Ring. |
+
+## Suggested workflow
+
+1. **`profile_strip`** — tune siding profile (`flat_upper_ratio`, `bottom_taper_depth_ratio`, `rear_extension`, bead params).
+2. **`front_slice`** — verify Ring hole alignment.
+3. **`full`** — print final plate (PETG/ASA recommended outdoors; PLA OK for tests).
+
+**Print orientation:** front face (Ring side) on the bed, rear profile vertical.
+
+## Related files
+
+| File | Purpose |
+|------|---------|
+| [`ring-solar-siding-adapter.backup.scad`](ring-solar-siding-adapter.backup.scad) | Earlier geometry — flat upper rear + lower taper only, no bead coping groove |
+| `*.stl` | Exported meshes (gitignored; export locally) |
+
+## Regenerate preview
+
+From the repo root:
+
+```bash
+pip install pyvista                    # headless fallback (WSL without display)
+sudo apt install xvfb                  # optional — native OpenSCAD PNG export
+python3 scripts/render-preview.py ring-solar-siding-adapter
+```
+
+Or export a PNG directly from OpenSCAD when a display (or `xvfb-run`) is available:
+
+```bash
+xvfb-run -a openscad --render --viewall --imgsize=1200,900 \
+  -o ring-solar-siding-adapter/preview.png \
+  ring-solar-siding-adapter/ring-solar-siding-adapter.scad
+```

ring-solar-siding-adapter/ring-solar-siding-adapter.backup.scad

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+// Ring Solar Charger — Vinyl Siding Adapter Plate
+// BACKUP: flat upper rear + slow lower taper, no bead coping groove yet.
+// Units: millimeters. Vanilla OpenSCAD only.
+
+/* [Plate] */
+plate_width = 93.1;
+plate_height = 171.45;
+min_wall_thickness = 3.0;
+edge_round = 0;
+
+/* [Siding Profile] */
+siding_projection = 27.0;
+face_inset_depth = 8.0;
+flat_upper_ratio = 0.55;
+course_pitch = 165.1;
+profile_segments = 8;
+profile_mode = "curved";
+rear_clearance = 0.2;
+
+/* [Mounting Holes] */
+mount_hole_offset_top = 50.0;
+mount_hole_offset_bottom = 44.7;
+mount_hole_dia = 4.5;
+mount_hole_x = 0;
+
+/* [Export] */
+part_mode = "full";
+profile_strip_width = 20;
+
+/* [Hidden] */
+$fn = 64;
+epsilon = 0.01;
+
+function projection_z() = siding_projection - rear_clearance;
+
+function face_inset_z() = projection_z() - face_inset_depth;
+
+function face_y_flat_end() = plate_height * (1 - flat_upper_ratio);
+
+function lower_curve_z(y) =
+    let(
+        y1 = face_y_flat_end(),
+        t = y / max(y1, epsilon),
+        ease = pow(sin(t * 90), 1.4),
+        z_bottom = projection_z(),
+        z_top = face_inset_z()
+    )
+    z_top + (z_bottom - z_top) * (1 - ease);
+
+function stepped_rear_z(y) =
+    y >= face_y_flat_end() ? face_inset_z() : projection_z();
+
+function rear_z_at(y) =
+    y >= face_y_flat_end() ? face_inset_z()
+    : profile_mode == "stepped" ? stepped_rear_z(y)
+    : lower_curve_z(y);
+
+function rear_profile_points() =
+    let(step = plate_height / max(profile_segments * 12, 24))
+    [for (y = [0 : step : plate_height])
+        [y, rear_z_at(y)]];
+
+function max_rear_z() =
+    let(pts = rear_profile_points())
+    max([for (p = pts) p[1]]);
+
+function front_z() = max_rear_z() + min_wall_thickness;
+
+function rear_y_min() =
+    min([for (p = rear_profile_points()) p[1]]);
+
+function minkowski_active() =
+    edge_round > 0 && min_wall_thickness >= 2 * edge_round + 1;
+
+function hole_y_min() =
+    rear_y_min() - (minkowski_active() ? edge_round : 0) - epsilon;
+
+function hole_y_max() =
+    front_z() + (minkowski_active() ? edge_round : 0) + epsilon;
+
+function cross_section_polygon() =
+    let(
+        rear_pts = rear_profile_points(),
+        fz = front_z()
+    )
+    [
+        for (p = rear_pts) p,
+        [plate_height, fz],
+        [0, fz]
+    ];
+
+module cross_section_2d() {
+    polygon(cross_section_polygon());
+}
+
+module adapter_body(width) {
+    linear_extrude(width, center = true)
+        cross_section_2d();
+}
+
+module mount_holes() {
+    y_min = hole_y_min();
+    y_max = hole_y_max();
+    hole_depth = y_max - y_min;
+    center_y = (y_min + y_max) / 2;
+    for (y_pos = [plate_height - mount_hole_offset_top, mount_hole_offset_bottom]) {
+        translate([y_pos, center_y, mount_hole_x])
+            rotate([90, 0, 0])
+                cylinder(h = hole_depth, d = mount_hole_dia, center = true);
+    }
+}
+
+module rounded_body(width) {
+    if (minkowski_active()) {
+        minkowski() {
+            adapter_body(max(width - 2 * edge_round, 1));
+            sphere(r = edge_round);
+        }
+    } else {
+        adapter_body(width);
+    }
+}
+
+module adapter_plate() {
+    width = part_mode == "profile_strip" ? profile_strip_width : plate_width;
+    if (part_mode == "full") {
+        difference() {
+            rounded_body(width);
+            mount_holes();
+        }
+    } else {
+        rounded_body(width);
+    }
+}
+
+adapter_plate();

ring-solar-siding-adapter/ring-solar-siding-adapter.scad

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+// Ring Solar Charger — Vinyl Siding Adapter Plate
+// Mounts the integrated Ring Solar Charger on horizontal beaded vinyl lap siding.
+// Units: millimeters. Vanilla OpenSCAD only.
+//
+// Rear profile (y=0 bottom, y=plate_height top):
+//   TOP    — bead coping cavity scooped into rear face (concave semicircle)
+//   MID    — flat rear shelf continues downward
+//   BOTTOM — slow taper outward toward siding projection
+//
+// Backup (flat + taper only): ring-solar-siding-adapter.backup.scad
+
+/* [Plate] */
+plate_width = 93.1;
+plate_height = 171.45;
+min_wall_thickness = 5.0;
+edge_round = 0;
+
+/* [Siding Profile] */
+siding_projection = 27.0;
+face_inset_depth = 8.0;
+bead_coping_radius = 10.00;      // Semicircle radius for bead groove (measured on siding)
+bead_coping_offset_top = 11.00;  // Distance from plate top to groove center (tune on wall)
+flat_upper_ratio = 0.55;         // Fraction of plate height that stays flat at the top
+bottom_taper_depth_ratio = 1.6;  // Rear depth at plate bottom = min_wall_thickness * this (outward from flat shelf)
+rear_extension = 7.5;            // Extra depth toward wall; front face + bead groove stay fixed vs front/top
+course_pitch = 165.1;
+profile_segments = 8;
+profile_mode = "curved"; // [curved, stepped]
+rear_clearance = 0.2;
+
+/* [Mounting Holes] */
+mount_hole_offset_top = 50.0;
+mount_hole_offset_bottom = 44.7;
+mount_hole_dia = 4.5;
+mount_hole_x = 0;
+
+/* [Export] */
+part_mode = "full"; // [full, profile_strip, front_slice]
+profile_strip_width = 20;
+front_slice_depth = 3.5; // [2:0.5:8]
+
+/* [Hidden] */
+$fn = 64;
+epsilon = 0.01;
+
+// ---------------------------------------------------------------------------
+// Siding rear-profile geometry
+// OpenSCAD 2D polygon uses [plate_Y, plate_Z]; linear_extrude() goes along +Z (width).
+// OpenSCAD 3D: X = plate height (y), Y = depth (z), Z = plate width.
+// Lower depth Y = toward wall (back). Higher depth Y = toward Ring (front).
+// ---------------------------------------------------------------------------
+
+function projection_z() = siding_projection - rear_clearance;
+
+function face_inset_z() = projection_z() - face_inset_depth;
+
+// Flat rear shelf shifted toward the wall; bead groove keeps absolute depth at face_inset_z.
+function flat_rear_z() = face_inset_z() - rear_extension;
+
+function bead_coping_y_center() = plate_height - bead_coping_offset_top;
+
+// Bottom of flat rear shelf (flat_upper_ratio measured from plate top downward).
+function face_y_flat_end() = plate_height * (1 - flat_upper_ratio);
+
+// Rear depth where the bottom taper ends (outward from flat shelf, in wall-thickness units).
+function bottom_rear_z() =
+    flat_rear_z() + min_wall_thickness * bottom_taper_depth_ratio;
+
+// Slow taper from bottom_rear_z at the plate bottom up to the flat rear shelf.
+function lower_curve_z(y) =
+    let(
+        y1 = face_y_flat_end(),
+        t = y / max(y1, epsilon),
+        ease = pow(sin(t * 90), 1.4),
+        z_bottom = bottom_rear_z(),
+        z_top = flat_rear_z()
+    )
+    z_top + (z_bottom - z_top) * (1 - ease);
+
+function stepped_rear_z(y) =
+    y >= face_y_flat_end() ? flat_rear_z() : bottom_rear_z();
+
+// Bead coping: fixed depth vs front/top. Flat chord at face_inset_z; arc scoops into plate.
+function bead_coping_rear_z(y) =
+    let(
+        r = bead_coping_radius,
+        shelf = face_inset_z(),
+        dy = y - bead_coping_y_center(),
+        disc = r * r - dy * dy
+    )
+    disc >= 0 ? shelf + sqrt(disc) : flat_rear_z();
+
+// Flat top shelf + bead cavity + lower taper.
+function rear_z_at(y) =
+    y >= face_y_flat_end() ? bead_coping_rear_z(y)
+    : profile_mode == "stepped" ? stepped_rear_z(y)
+    : lower_curve_z(y);
+
+function rear_profile_points() =
+    let(
+        step = plate_height / max(profile_segments * 12, 24),
+        yc = bead_coping_y_center(),
+        r = bead_coping_radius,
+        arc_step = r / 16
+    )
+    concat(
+        [for (y = [0 : step : max(yc - r - epsilon, 0)]) [y, rear_z_at(y)]],
+        [for (y = [yc - r : arc_step : yc + r]) [y, rear_z_at(y)]],
+        [for (y = [min(yc + r + step, plate_height) : step : plate_height]) [y, rear_z_at(y)]]
+    );
+
+function max_rear_z() =
+    let(pts = rear_profile_points())
+    max([for (p = pts) p[1]]);
+
+// Front face anchored to bead groove + min wall (independent of rear_extension).
+function front_z() =
+    face_inset_z() + bead_coping_radius + min_wall_thickness;
+
+function rear_y_min() =
+    min([for (p = rear_profile_points()) p[1]]);
+
+function minkowski_active() =
+    edge_round > 0 && min_wall_thickness >= 2 * edge_round + 1;
+
+function hole_y_min() =
+    rear_y_min() - (minkowski_active() ? edge_round : 0) - epsilon;
+
+function hole_y_max() =
+    front_z() + (minkowski_active() ? edge_round : 0) + epsilon;
+
+function cross_section_polygon() =
+    let(
+        rear_pts = rear_profile_points(),
+        fz = front_z()
+    )
+    [
+        for (p = rear_pts) p,
+        [plate_height, fz],
+        [0, fz]
+    ];
+
+// ---------------------------------------------------------------------------
+// Modules
+// ---------------------------------------------------------------------------
+
+module cross_section_2d() {
+    polygon(cross_section_polygon());
+}
+
+module adapter_body(width) {
+    linear_extrude(width, center = true)
+        cross_section_2d();
+}
+
+module mount_holes() {
+    y_min = hole_y_min();
+    y_max = hole_y_max();
+    hole_depth = y_max - y_min;
+    center_y = (y_min + y_max) / 2;
+    for (y_pos = [plate_height - mount_hole_offset_top, mount_hole_offset_bottom]) {
+        translate([y_pos, center_y, mount_hole_x])
+            rotate([90, 0, 0])
+                cylinder(h = hole_depth, d = mount_hole_dia, center = true);
+    }
+}
+
+module rounded_body(width) {
+    if (minkowski_active()) {
+        minkowski() {
+            adapter_body(max(width - 2 * edge_round, 1));
+            sphere(r = edge_round);
+        }
+    } else {
+        adapter_body(width);
+    }
+}
+
+// Keep only the front face cap for fit-checking width, height, and hole placement.
+module front_slice_mask(width) {
+    fz = front_z();
+    translate([plate_height / 2, fz - front_slice_depth / 2, 0])
+        cube(
+            [plate_height + 2 * epsilon, front_slice_depth + 2 * epsilon, width + 2 * epsilon],
+            center = true
+        );
+}
+
+module adapter_plate() {
+    width = part_mode == "profile_strip" ? profile_strip_width : plate_width;
+    if (part_mode == "full") {
+        difference() {
+            rounded_body(width);
+            mount_holes();
+        }
+    } else if (part_mode == "front_slice") {
+        intersection() {
+            difference() {
+                rounded_body(width);
+                mount_holes();
+            }
+            front_slice_mask(width);
+        }
+    } else {
+        rounded_body(width);
+    }
+}
+
+adapter_plate();