Clutter.Actor.get_relative_transformation_matrix

### Method

# Clutter Actorget_relative_transformation_matrix

#### Declaration [src]

    void
    clutter_actor_get_relative_transformation_matrix (
      ClutterActor* self,
      ClutterActor* ancestor,
      graphene_matrix_t* matrix
    )

#### Description [src]

This gets a transformation `matrix` that will transform coordinates from the coordinate space of `self` into the coordinate space of `ancestor`.

For example if you need a matrix that can transform the local actor coordinates of `self` into stage coordinates you would pass the actor’s stage pointer as the `ancestor`.

If you pass `NULL` then the transformation will take you all the way through to eye coordinates. This can be useful if you want to extract the entire modelview transform that Clutter applies before applying the projection transformation. If you want to explicitly set a modelview on a CoglFramebuffer using `cogl_set_modelview_matrix()` for example then you would want a matrix that transforms into eye coordinates.

Note: This function explicitly initializes the given `matrix`. If you just want clutter to multiply a relative transformation with an existing matrix you can use `clutter_actor_apply_relative_transformation_matrix()` instead.

#### Parameters

`ancestor`

  Type: `ClutterActor`

  The ancestor actor whose coordinate space you want to transform to or `NULL` if you want to transform all the way to eye coordinates.

  The argument can be `NULL`.
  The data is owned by the caller of the method.

`matrix`

  Type: `graphene_matrix_t`

  A #graphene_matrix_t to store the transformation.

  The argument will be set by the function.
  The returned data is owned by the instance.