CanvasItem shaders
CanvasItem shaders contain less built-in variables and functionality than Spatial shaders, but they maintain the same basic structure with vertex, fragment, and light processor functions.
Built-ins
Values marked as “in” are read-only. Values marked as “out” are for optional writing and will not necessarily contain sensible values. Values marked as “inout” provide a sensible default value, and can optionally be written to. Samplers are not subjects of writing and they are not marked.
Global built-ins are available everywhere, including custom functions.
Vertex built-ins
Vertex data (VERTEX
) is presented in local space (pixel coordinates, relative to the camera). If not written to, these values will not be modified and be passed through as they came.
Note
WORLD_MATRIX
is actually a modelview matrix. It takes input in local space and transforms it into view space.
In order to get the world space coordinates of a vertex, you have to pass in a custom uniform like so:
Then, in your vertex shader:
Other built-ins, such as UV and COLOR, are also passed through to the fragment function if not modified.
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 to 1).
Certain Nodes (for example, ) 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 does not provide the texture color in the built-in variable; to read the texture color for such nodes, use:
This differs from the behavior of the built-in normal map. If a normal map is attached, Godot uses it by default and assigns its value to the built-in NORMAL
variable. If you are using a normal map meant for use in 3D, it will appear inverted. In order to use it in your shader, you must assign it to the NORMALMAP
property. Godot will handle converting it for use in 2D and overwriting NORMAL
.
Light built-ins
When the shader is on a light pass, the AT_LIGHT_PASS
variable will be true
.