Fixed and Relative Positions
- Ryan Chapman
- Catherine Hillier (Unlicensed)
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Overview
Some Resources (like Move Object Resource and Move User Resource ) take a “Position” parameter. Position can either be Relative or Fixed. This document describes the difference between these two position types.
Fixed Position
The main difference between Fixed and Relative Positions is that Fixed Position uses the World’s coordinate system to compute offsets and rotation. A Fixed Position takes an optional anchor.
Fixed Position Without an Anchor
Field Name | Description |
|---|---|
Position (required) | Object is positioned at the World X,Y,Z coordinates. |
Rotation (optional) | If set, Object is rotated to the given rotation based on World coordinates (e.g. a rotation of Y=90 will look “East”). If not set, the Object’s rotation will not change. |
Fixed Position With an Anchor
Field Name | Description |
|---|---|
Position (required) | Object is offset from the anchor’s position using world X,Y,Z coordinates. For example, Z=3 will offset the Object 3m to the “north” of the anchor regardless of the rotation of the anchor. |
Rotation (optional) | If set, Object is rotated to the given rotation based on World coordinates (e.g. a rotation of Y=90 will look “East”). If not set, the Object’s rotation will not change. Note that the object’s Rotation is not impacted by the rotation of the anchor for Fixed Position. |
Relative Position
Relative position uses Cylindrical Coordinates (distance, angle, elevation) instead of X, Y, Z. If there is no anchor set, Relative Position uses the user’s current position as the anchor.
Relative Position Without an Anchor
Field Name | Description |
|---|---|
Position (required) | Object is positioned relative to the user. An angle=0 positions the Object directly in front of the user. Angle=180 would position the object directly behind. For immersive environments (e.g. VR) the elevation is relative to the “ground”. |
Rotation (optional) | If set, Rotation is applied relative to the user’s current heading. If not set, the Rotation is configured to match the user’s current heading. Note that because the object will be rotated to match the user’s “forward” axis, the user will be looking at the back of the object by default. |
Relative Position With an Anchor
Field Name | Description |
|---|---|
Position (required) | Object is positioned relative to the anchor. An angle=0 positions the Object directly in front of the object. Note that “in front” means “along the Z axis”. Angle=180 would position the object directly behind. Elevation is applied relative to the Y position of the object. |
Rotation (optional) | If set, Rotation is applied relative to the anchor’s rotation. If not set, Rotation of the Object is set to match the rotation of the anchor. |
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