Update particle builtins description in Spatial shader

tutorials/shaders/shader_reference/particle_shader.rst

@@ -10,7 +10,7 @@ or Spatial, depending on whether they are 2D or 3D.
 
 Particle shaders are unique because they are not used to draw the object itself;
 they are used to calculate particle properties, which are then used by a
-:ref:`CanvasItem<doc_canvas_item_shader>` or :ref:`Spatial<doc_spatial_shader>` 
+:ref:`CanvasItem<doc_canvas_item_shader>` or :ref:`Spatial<doc_spatial_shader>`
 shader. They contain two processor functions: ``start()`` and ``process()``.
 
 Unlike other shader types, particle shaders keep the data that was output the
@@ -80,6 +80,11 @@ Start and Process built-ins
 
 These properties can be accessed from both the ``start()`` and ``process()`` functions.
 
+When using the built-in :ref:`class_ParticleProcessMaterial`, ``USERDATA1`` is defined
+with the following value in the built-in:
+
+* **w**: Accumulated angle from angular velocity in radians, as applied by the angular velocity texture.
+
 +------------------------------------+-----------------------------------------------------------------------------------------------------------------------------------------+
 | Function                           | Description                                                                                                                             |
 +====================================+=========================================================================================================================================+

tutorials/shaders/shader_reference/spatial_shader.rst

@@ -234,9 +234,9 @@ However, the value passed to the fragment shader still comes from ``VERTEX``.
 For instancing, the ``INSTANCE_CUSTOM`` variable contains the instance custom data. When using particles, this information
 is usually:
 
-* **x**: Rotation angle in radians.
-* **y**: Phase during lifetime (``0.0`` to ``1.0``).
-* **z**: Animation frame.
+* **x**: Current rotation angle in radians.
+* **z**: Current animation frame.
+* **y / w** (division): Lifetime fraction from 0.0 to 1.0.
 
 This allows you to easily adjust the shader to a particle system using default particle material. When writing a custom particle
 shader, this value can be used as desired.