pxmlw6n2f/sdformat_for_tcp/sdf/Migration.md

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# Migration Guide for SDF Protocol
This document contains information about migrating
between different versions of the SDF protocol.
The SDF protocol version number is specified in the `version` attribute
of the `sdf` element (1.4, 1.5, 1.6, etc.)
and is distinct from sdformat library version
(2.3, 3.0, 4.0, etc.).
# Note on backward compatibility
There are `*.convert` files that allow old sdf files to be migrated
forward programmatically.
This document aims to contain similar information to those files
but with improved human-readability.
## SDF protocol 1.5 to 1.6
### Additions
1. **heightmap_shape.sdf** `sampling` element
+ description: Samples per heightmap datum.
For rasterized heightmaps, this indicates the number of samples to take per pixel.
Using a lower value, e.g. 1, will generally improve the performance
of the heightmap but lower the heightmap quality.
+ type: unsigned int
+ default: 2
+ required: 0
+ [pull request 293](https://bitbucket.org/osrf/sdformat/pull-requests/293)
1. **link.sdf** `enable_wind` element
+ description: If true, the link is affected by the wind
+ type: bool
+ default: false
+ required: 0
+ [pull request 240](https://bitbucket.org/osrf/sdformat/pull-requests/240)
1. **model.sdf** `enable_wind` element
+ description: If set to true, all links in the model
will be affected by the wind.
Can be overriden by the link wind property.
+ type: bool
+ default: false
+ required: 0
+ [pull request 240](https://bitbucket.org/osrf/sdformat/pull-requests/240)
1. **model_state.sdf** `scale` element
+ description: Scale for the 3 dimensions of the model.
+ type: vector3
+ default: "1 1 1"
+ required: 0
+ [pull request 246](https://bitbucket.org/osrf/sdformat/pull-requests/246)
1. **physics.sdf** `friction_model` element
+ description: Name of ODE friction model to use. Valid values include:
+ pyramid_model: (default) friction forces limited in two directions
in proportion to normal force.
+ box_model: friction forces limited to constant in two directions.
+ cone_model: friction force magnitude limited in proportion to normal force.
See [gazebo pull request 1522](https://bitbucket.org/osrf/gazebo/pull-request/1522)
(merged in [gazebo 8c05ad64967c](https://bitbucket.org/osrf/gazebo/commits/8c05ad64967c))
for the implementation of this feature.
+ type: string
+ default: "pyramid_model"
+ required: 0
+ [pull request 294](https://bitbucket.org/osrf/sdformat/pull-requests/294)
1. **world.sdf** `wind` element
+ description: The wind tag specifies the type and properties of the wind.
+ required: 0
+ [pull request 240](https://bitbucket.org/osrf/sdformat/pull-requests/240)
1. **world.sdf** `wind::linear_velocity` element
+ description: Linear velocity of the wind.
+ type: vector3
+ default: "0 0 0"
+ required: 0
+ [pull request 240](https://bitbucket.org/osrf/sdformat/pull-requests/240)
### Modifications
1. `gravity` and `magnetic_field` elements are moved
from `physics` to `world`
+ [pull request 247](https://bitbucket.org/osrf/sdformat/pull-requests/247)
+ [gazebo pull request 2090](https://bitbucket.org/osrf/gazebo/pull-requests/2090)
1. A new style for representing the noise properties of an `imu` was implemented
in [pull request 199](https://bitbucket.org/osrf/sdformat/pull-requests/199)
for sdf 1.5 and the old style was declared as deprecated.
The old style has been removed from sdf 1.6 with the conversion script
updating to the new style.
+ [pull request 199](https://bitbucket.org/osrf/sdformat/pull-requests/199)
+ [pull request 243](https://bitbucket.org/osrf/sdformat/pull-requests/243)
+ [pull request 244](https://bitbucket.org/osrf/sdformat/pull-requests/244)