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Clarify COLOR and TEXTURE in CanvasItem shaders

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tetrapod00
2024-10-17 23:00:16 -07:00
parent c2d020610b
commit 4fd1d2377f
1 changed files with 50 additions and 9 deletions
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59
tutorials/shaders/shader_reference/canvas_item_shader.rst
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@@ -142,15 +142,56 @@ is usually:
Fragment built-ins
^^^^^^^^^^^^^^^^^^
Certain Nodes (for example, :ref:`Sprite2Ds <class_Sprite2D>`) display a texture
by default. However, when a custom fragment function is attached to these nodes,
the texture lookup needs to be done manually. Godot provides the texture color
in the ``COLOR`` built-in variable multiplied by the node's color. To read the
texture color by itself, you can use:
COLOR and TEXTURE
~~~~~~~~~~~~~~~~~
The built-in variable ``COLOR`` is used for a few things:
- In the ``vertex()`` function, ``COLOR`` contains the color from the vertex
primitive multiplied by the CanvasItem's
:ref:`modulate<class_CanvasItem_property_modulate>` multiplied by the
CanvasItem's :ref:`self_modulate<class_CanvasItem_property_self_modulate>`.
- In the ``fragment()`` function, the input value ``COLOR`` is that same value
multiplied by the color from the default ``TEXTURE`` (if present).
- In the ``fragment()`` function, ``COLOR`` is also the final output.
Certain nodes (for example, :ref:`Sprite2D <class_Sprite2D>`) display a texture
by default, for example :ref:`texture <class_Sprite2D_property_texture>`. When
using a custom ``fragment()`` function, you have a few options on how to sample
this texture.
To read only the contents of the default texture, ignoring the vertex ``COLOR``:
.. code-block:: glsl
COLOR = texture(TEXTURE, UV);
void fragment() {
COLOR = texture(TEXTURE, UV);
}
To read the contents of the default texture multiplied by vertex ``COLOR``:
.. code-block:: glsl
void fragment() {
// Equivalent to an empty fragment() function, since COLOR is also the output variable.
COLOR = COLOR;
}
To read only the vertex ``COLOR`` in ``fragment()``, ignoring the main texture,
you must pass ``COLOR`` as a varying, then read it in ``fragment()``:
.. code-block:: glsl
varying vec4 vertex_color;
void vertex() {
vertex_color = COLOR;
}
void fragment() {
COLOR = vertex_color;
}
NORMAL
~~~~~~
Similarly, if a normal map is used in the :ref:`CanvasTexture <class_CanvasTexture>`, Godot uses
it by default and assigns its value to the built-in ``NORMAL`` variable. If you are using a normal
@@ -175,7 +216,7 @@ it to the ``NORMALMAP`` property. Godot will handle converting it for use in 2D
+---------------------------------------------+---------------------------------------------------------------+
| in vec2 **TEXTURE_PIXEL_SIZE** | Normalized pixel size of default 2D texture. |
| | For a Sprite2D with a texture of size 64x32px, |
| | **TEXTURE_PIXEL_SIZE** = ``vec2(1/64, 1/32)`` |
| | ``TEXTURE_PIXEL_SIZE`` = ``vec2(1/64, 1/32)`` |
+---------------------------------------------+---------------------------------------------------------------+
| in bool **AT_LIGHT_PASS** | Always ``false``. |
+---------------------------------------------+---------------------------------------------------------------+
@@ -206,8 +247,8 @@ it to the ``NORMALMAP`` property. Godot will handle converting it for use in 2D
| inout vec3 **LIGHT_VERTEX** | Same as ``VERTEX`` but can be written to alter lighting. |
| | Z component represents height. |
+---------------------------------------------+---------------------------------------------------------------+
| inout vec4 **COLOR** | Color from vertex function multiplied by the **TEXTURE** |
| | color. Also output color value. |
| inout vec4 **COLOR** | ``COLOR`` from the ``vertex()`` function multiplied by the |
| | ``TEXTURE`` color. Also output color value. |
+---------------------------------------------+---------------------------------------------------------------+
Light built-ins