EXT_implicit_cylinder_region Proposal

extensions/2.0/Vendor/EXT_implicit_cylinder_region/README.md

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+# EXT_implicit_cylinder_region
+
+## Contributors
+
+- Janine Liu, Cesium
+- Sean Lilley, Cesium
+
+## Status
+
+Draft
+
+## Dependencies
+
+Written against the glTF 2.0 specification. Depends on the [`KHR_implicit_shapes`](https://github.com/eoineoineoin/glTF/tree/refs/heads/collisionShapeMerge/extensions/2.0/Khronos/KHR_implicit_shapes) extension.
+
+## Overview
+
+This extension defines a cylinder-conforming region as an additional shape type for the `KHR_implicit_shapes` extension. These regions are useful for visualizing real-world data that has been captured by cylindrical sensors.
+
+`EXT_implicit_cylinder_region` extends the `shape` object in `KHR_implicit_shapes`. The `shape.type` should be set to `"cylinder region"`. The properties define a region following the surface of a cylinder between two different radius values.
+
+The cylinder does not need to be completely represented by the volume—for instance, the region may be hollow inside like a tube. However, an inner radius of `0` results in a completely solid cylinder.
+
+### Details
+
+The cylinder is centered at the origin, where the radius is measured along the `x` and `z` axes. The `height` of the cylinder is aligned with the `y` axis.
+
+<table>
+  <tr>
+    <th>
+    Example
+    </th>
+  </tr>
+  <tr>
+    <td>
+
+```json
+"extensions": [
+  {
+    "KHR_implicit_shapes": {
+      "shapes": [
+        {
+          "type": "cylinder region",
+          "extensions": {
+            "EXT_implicit_cylinder_region": {
+              "minRadius": 0.5,
+              "maxRadius": 1,
+              "height": 2
+            }
+          }
+        }
+      ]
+    }
+  }
+]
+```
+
+  </td>
+    <td>
+    <img src="figures/hollow-cylinder.png">
+    </td>
+  </tr>
+</table>
+
+A cylinder region may also be confined to a certain angular range. The `minAngle` and `maxAngle` properties define the angles at which the region starts and stops on the cylinder.
+
+Angles are given in radians within the range `[-pi, pi]` and open counter-clockwise around the cylinder. The bounds are aligned such that an angle of `0` aligns with the glTF right axis, i.e., the `-x` axis (see figure below.)
+
+![](figures/cylinder-angle.png)
+
+<table>
+  <tr>
+    <th>
+    Example
+    </th>
+  </tr>
+  <tr>
+    <td>
+
+```json
+"extensions": [
+  {
+    "KHR_implicit_shapes": {
+      "shapes": [
+        {
+          "type": "cylinder region",
+          "extensions": {
+            "EXT_implicit_cylinder_region": {
+              "minRadius": 0.5,
+              "maxRadius": 1,
+              "height": 2,
+              "minAngle": -1.570796,
+              "maxAngle": 1.570796
+            }
+          }
+        }
+      ]
+    }
+  }
+]
+```
+</td>
+    <td>
+    <img src="figures/half-cylinder.png">
+    </td>
+  </tr>
+</table>
+
+## Optional vs. Required
+This extension is required, meaning it should be placed in both the `extensionsUsed` list and `extensionsRequired` list.

extensions/2.0/Vendor/EXT_implicit_cylinder_region/schema/glTF.KHR_implicit_shapes.shape.EXT_implicit_cylinder_region.schema.json

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+{
+    "$schema": "https://json-schema.org/draft/2020-12/schema",
+    "$id": "glTF.KHR_implicit_shapes.shape.EXT_implicit_cylinder_region.schema.json",
+    "title": "EXT_implicit_cylinder_region extension on KHR_implicit_shapes.shape",
+    "type": "object",
+    "description": "Extension of `KHR_implicit_shapes.shape` to represent an implicit cylinder region in a glTF model.",
+    "allOf": [
+        {
+            "$ref": "glTFProperty.schema.json"
+        }
+    ],
+    "properties": {
+        "minRadius": {
+            "type": "number",
+            "description": "The inner radius of the cylinder region along the X and Z axes, in meters.",
+            "minimum": 0
+        },
+        "maxRadius": {
+            "type": "number",
+            "description": "The outer radius of the cylinder region along the X and Z axes, in meters.",
+            "minimum": 0
+        },
+        "height": {
+            "type": "number",
+            "description": "The height of the cylinder in meters along the Y-axis, in meters.",
+            "minimum": 0
+        },
+        "minAngle": {
+            "type": "number",
+            "description": "The minimum angle of the cylinder region in radians. In other words, this is the angle where the cylinder region starts. Must be in the range [-pi, pi].",
+            "minimum": -3.14159265359,
+            "maximum": 3.14159265359,
+            "default": -3.14159265359
+        },
+        "maxAngle": {
+            "type": "number",
+            "description": "The maximum angle of the cylinder region in radians. In other words, this is the angle where the cylinder region ends. Must be in the range [-pi, pi].",
+            "minimum": -3.14159265359,
+            "maximum": 3.14159265359,
+            "default": 3.14159265359
+        }
+    },
+    "required": [
+        "minRadius",
+        "maxRadius",
+        "height"
+    ]
+}