godot-docs/tutorials/shading/shading_reference/spatial_shader.rst

.. _doc_spatial_shader:

Spatial shaders
===============

Spatial shaders are used for shading 3D objects. They are the most complex type of shader Godot offers. 
Spatial shaders are highly configurable with different render modes and different rendering options
(e.g. Subsurface Scattering, Transmission, Ambient Occlusion, Rim lighting etc). Users can optionally
write vertex, fragment, and light processor functions to affect how objects are drawn.

Render modes
^^^^^^^^^^^^

+---------------------------------+-----------------------------------------------------------------------+
| Render mode                     | Description                                                           |
+=================================+=======================================================================+
| **blend_mix**                   | Mix blend mode (alpha is transparency), default.                      |
+---------------------------------+-----------------------------------------------------------------------+
| **blend_add**                   | Additive blend mode.                                                  |
+---------------------------------+-----------------------------------------------------------------------+
| **blend_sub**                   | Subtractive blend mode.                                               |
+---------------------------------+-----------------------------------------------------------------------+
| **blend_mul**                   | Multiplicative blend mode.                                            |
+---------------------------------+-----------------------------------------------------------------------+
| **depth_draw_opaque**           | Only draw depth for opaque geometry (not transparent).                |
+---------------------------------+-----------------------------------------------------------------------+
| **depth_draw_always**           | Always draw depth (opaque and transparent).                           |
+---------------------------------+-----------------------------------------------------------------------+
| **depth_draw_never**            | Never draw depth.                                                     |
+---------------------------------+-----------------------------------------------------------------------+
| **depth_draw_alpha_prepass**    | Do opaque depth pre-pass for transparent geometry.                    |
+---------------------------------+-----------------------------------------------------------------------+
| **depth_test_disable**          | Disable depth testing.                                                |
+---------------------------------+-----------------------------------------------------------------------+
| **cull_front**                  | Cull front-faces.                                                     |
+---------------------------------+-----------------------------------------------------------------------+
| **cull_back**                   | Cull back-faces (default).                                            |
+---------------------------------+-----------------------------------------------------------------------+
| **cull_disabled**               | Culling disabled (double sided).                                      |
+---------------------------------+-----------------------------------------------------------------------+
| **unshaded**                    | Result is just albedo. No lighting/shading happens in material.       |
+---------------------------------+-----------------------------------------------------------------------+
| **diffuse_lambert**             | Lambert shading for diffuse (default).                                |
+---------------------------------+-----------------------------------------------------------------------+
| **diffuse_lambert_wrap**        | Lambert wrapping (roughness dependent) for diffuse.                   |
+---------------------------------+-----------------------------------------------------------------------+
| **diffuse_oren_nayar**          | Oren Nayar for diffuse.                                               |
+---------------------------------+-----------------------------------------------------------------------+
| **diffuse_burley**              | Burley (Disney PBS) for diffuse.                                      |
+---------------------------------+-----------------------------------------------------------------------+
| **diffuse_toon**                | Toon shading for diffuse.                                             |
+---------------------------------+-----------------------------------------------------------------------+
| **specular_schlick_ggx**        | Schlick-GGX for specular (default).                                   |
+---------------------------------+-----------------------------------------------------------------------+
| **specular_blinn**              | Blinn for specular (compatibility).                                   |
+---------------------------------+-----------------------------------------------------------------------+
| **specular_phong**              | Phong for specular (compatibility).                                   |
+---------------------------------+-----------------------------------------------------------------------+
| **specular_toon**               | Toon for specular.                                                    |
+---------------------------------+-----------------------------------------------------------------------+
| **specular_disabled**           | Disable specular.                                                     |
+---------------------------------+-----------------------------------------------------------------------+
| **skip_vertex_transform**       | VERTEX/NORMAL/etc. need to be transformed manually in vertex function.|
+---------------------------------+-----------------------------------------------------------------------+
| **world_vertex_coords**         | VERTEX/NORMAL/etc. are modified in world coordinates instead of local.|
+---------------------------------+-----------------------------------------------------------------------+
| **ensure_correct_normals**      | Use when non-uniform scale is applied to mesh.                        |
+---------------------------------+-----------------------------------------------------------------------+
| **vertex_lighting**             | Use vertex-based lighting.                                            |
+---------------------------------+-----------------------------------------------------------------------+
| **shadows_disabled**            | Disable computing shadows in shader.                                  |
+---------------------------------+-----------------------------------------------------------------------+
| **ambient_light_disabled**      | Disable contribution from ambient light and radiance map.             |
+---------------------------------+-----------------------------------------------------------------------+

Vertex 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.

Vertex data (``VERTEX``, ``NORMAL``, ``TANGENT``, ``BITANGENT``) are presented in local 
model space. If not written to, these values will not be modified and be passed through 
as they came.

They can optionally be presented in world space by using the *world_vertex_coords* render mode.

Users can disable the built-in modelview transform (projection will still happen later) and do 
it manually with the following code:

.. code-block:: glsl

    shader_type spatial;
    render_mode skip_vertex_transform;

    void vertex() {
        VERTEX = (MODELVIEW_MATRIX * vec4(VERTEX, 1.0)).xyz;
        NORMAL = (MODELVIEW_MATRIX * vec4(NORMAL, 0.0)).xyz;
        // same as above for binormal and tangent, if normal mapping is used
    }

Other built-ins, such as UV, UV2 and COLOR, are also passed through to the fragment function if not modified.

Users can override the modelview and projection transforms using the ``POSITION`` built-in. When ``POSITION`` is used,
the value from ``VERTEX`` is ignored and projection does not happen. 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 to 1).
* **z**: Animation frame.

This allows you to easily adjust the shader to a particle system using default particles material. When writing a custom particles
shader, this value can be used as desired.

+--------------------------------------+-------------------------------------------------------+
| Built-in                             | Description                                           |
+======================================+=======================================================+
| inout mat4 **WORLD_MATRIX**          | Model space to world space transform.                 |
+--------------------------------------+-------------------------------------------------------+
| in mat4 **INV_CAMERA_MATRIX**        | World space to view space transform.                  |
+--------------------------------------+-------------------------------------------------------+
| inout mat4 **PROJECTION_MATRIX**     | View space to clip space transform.                   |
+--------------------------------------+-------------------------------------------------------+
| in mat4 **CAMERA_MATRIX**            | View space to world space transform.                  |
+--------------------------------------+-------------------------------------------------------+
| inout mat4 **MODELVIEW_MATRIX**      | Model space to view space transform (use if possible).|
+--------------------------------------+-------------------------------------------------------+
| inout mat4 **INV_PROJECTION_MATRIX** | Clip space to view space transform.                   |
+--------------------------------------+-------------------------------------------------------+
| in float **TIME**                    | Elapsed total time in seconds.                        |
+--------------------------------------+-------------------------------------------------------+
| in vec2 **VIEWPORT_SIZE**            | Size of viewport (in pixels).                         |
+--------------------------------------+-------------------------------------------------------+
| inout vec3 **VERTEX**                | Vertex in local coordinates.                          |
+--------------------------------------+-------------------------------------------------------+
| inout vec3 **NORMAL**                | Normal in local coordinates.                          |
+--------------------------------------+-------------------------------------------------------+
| inout vec3 **TANGENT**               | Tangent in local coordinates.                         |
+--------------------------------------+-------------------------------------------------------+
| inout vec3 **BINORMAL**              | Binormal in local coordinates.                        |
+--------------------------------------+-------------------------------------------------------+
| inout vec2 **UV**                    | UV main channel.                                      |
+--------------------------------------+-------------------------------------------------------+
| inout vec2 **UV2**                   | UV secondary channel.                                 |
+--------------------------------------+-------------------------------------------------------+
| inout vec4 **COLOR**                 | Color from vertices.                                  |
+--------------------------------------+-------------------------------------------------------+
| inout float **POINT_SIZE**           | Point size for point rendering.                       |
+--------------------------------------+-------------------------------------------------------+
| out vec4  **POSITION**               | If written to, overrides final vertex position.       |
+--------------------------------------+-------------------------------------------------------+
| in int **INSTANCE_ID**               | Instance ID for instancing.                           |
+--------------------------------------+-------------------------------------------------------+
| in vec4 **INSTANCE_CUSTOM**          | Instance custom data (for particles, mostly).         |
+--------------------------------------+-------------------------------------------------------+
| out float **ROUGHNESS**              | Roughness for vertex lighting.                        |
+--------------------------------------+-------------------------------------------------------+
| in bool **OUTPUT_IS_SRGB**           | True when calculations happen in sRGB color space     |
|                                      | (true in GLES2, false in GLES3).                      |
+--------------------------------------+-------------------------------------------------------+

Fragment built-ins
^^^^^^^^^^^^^^^^^^

The default use of a Godot fragment processor function is to set up the material properties of your object
and to let the built-in renderer handle the final shading. However, you are not required to use all 
these properties, and if you don't write to them, Godot will optimize away the corresponding functionality. 

+-----------------------------------+--------------------------------------------------------------------------------------------------+
| Built-in                          | Description                                                                                      |
+===================================+==================================================================================================+
| in vec4 **FRAGCOORD**             | Coordinate of pixel center. In screen space. ``xy`` specifies  position in window, ``z``         |
|                                   | specifies fragment depth if ``DEPTH`` is not used. Origin is lower-left.                         |
+-----------------------------------+--------------------------------------------------------------------------------------------------+
| in mat4 **WORLD_MATRIX**          | Model space to world space transform.                                                            |
+-----------------------------------+--------------------------------------------------------------------------------------------------+
| in mat4 **INV_CAMERA_MATRIX**     | World space to view space transform.                                                             |
+-----------------------------------+--------------------------------------------------------------------------------------------------+
| in mat4 **CAMERA_MATRIX**         | View space to world space transform.                                                             |
+-----------------------------------+--------------------------------------------------------------------------------------------------+
| in mat4 **PROJECTION_MATRIX**     | View space to clip space transform.                                                              |
+-----------------------------------+--------------------------------------------------------------------------------------------------+
| in mat4 **INV_PROJECTION_MATRIX** | Clip space to view space transform.                                                              |
+-----------------------------------+--------------------------------------------------------------------------------------------------+
| in float **TIME**                 | Elapsed total time in seconds.                                                                   |
+-----------------------------------+--------------------------------------------------------------------------------------------------+
| in vec2 **VIEWPORT_SIZE**         | Size of viewport (in pixels).                                                                    |
+-----------------------------------+--------------------------------------------------------------------------------------------------+
| in vec3 **VERTEX**                | Vertex that comes from vertex function (default, in view space).                                 |
+-----------------------------------+--------------------------------------------------------------------------------------------------+
| in vec3 **VIEW**                  | Vector from camera to fragment position (in view space).                                         |
+-----------------------------------+--------------------------------------------------------------------------------------------------+
| in bool **FRONT_FACING**          | True if current face is front face.                                                              |
+-----------------------------------+--------------------------------------------------------------------------------------------------+
| inout vec3 **NORMAL**             | Normal that comes from vertex function (default, in view space).                                 |
+-----------------------------------+--------------------------------------------------------------------------------------------------+
| inout vec3 **TANGENT**            | Tangent that comes from vertex function.                                                         |
+-----------------------------------+--------------------------------------------------------------------------------------------------+
| inout vec3 **BINORMAL**           | Binormal that comes from vertex function.                                                        |
+-----------------------------------+--------------------------------------------------------------------------------------------------+
| out vec3 **NORMALMAP**            | Set normal here if reading normal from a texture instead of NORMAL.                              |
+-----------------------------------+--------------------------------------------------------------------------------------------------+
| out float **NORMALMAP_DEPTH**     | Depth from variable above. Defaults to 1.0.                                                      |
+-----------------------------------+--------------------------------------------------------------------------------------------------+
| in vec2 **UV**                    | UV that comes from vertex function.                                                              |
+-----------------------------------+--------------------------------------------------------------------------------------------------+
| in vec2 **UV2**                   | UV2 that comes from vertex function.                                                             |
+-----------------------------------+--------------------------------------------------------------------------------------------------+
| in vec4 **COLOR**                 | COLOR that comes from vertex function.                                                           |
+-----------------------------------+--------------------------------------------------------------------------------------------------+
| out vec3 **ALBEDO**               | Albedo (default white).                                                                          |
+-----------------------------------+--------------------------------------------------------------------------------------------------+
| out float **ALPHA**               | Alpha (0..1); if written to, the material will go to the transparent pipeline.                   |
+-----------------------------------+--------------------------------------------------------------------------------------------------+
| out float **METALLIC**            | Metallic (0..1).                                                                                 |
+-----------------------------------+--------------------------------------------------------------------------------------------------+
| out float **SPECULAR**            | Specular. Defaults to 0.5, best not to modify unless you want to change IOR.                     |
+-----------------------------------+--------------------------------------------------------------------------------------------------+
| out float **ROUGHNESS**           | Roughness (0..1).                                                                                |
+-----------------------------------+--------------------------------------------------------------------------------------------------+
| out float **RIM**                 | Rim (0..1). If used, Godot calculates rim lighting.                                              |
+-----------------------------------+--------------------------------------------------------------------------------------------------+
| out float **RIM_TINT**            | Rim Tint, goes from 0 (white) to 1 (albedo). If used, Godot calculates rim lighting.             |
+-----------------------------------+--------------------------------------------------------------------------------------------------+
| out float **CLEARCOAT**           | Small added specular blob. If used, Godot calculates Clearcoat.                                  |
+-----------------------------------+--------------------------------------------------------------------------------------------------+
| out float **CLEARCOAT_GLOSS**     | Gloss of Clearcoat. If used, Godot calculates Clearcoat.                                         |
+-----------------------------------+--------------------------------------------------------------------------------------------------+
| out float **ANISOTROPY**          | For distorting the specular blob according to tangent space.                                     |
+-----------------------------------+--------------------------------------------------------------------------------------------------+
| out vec2 **ANISOTROPY_FLOW**      | Distortion direction, use with flowmaps.                                                         |
+-----------------------------------+--------------------------------------------------------------------------------------------------+
| out float **SSS_STRENGTH**        | Strength of Subsurface Scattering. If used, Subsurface Scattering will be applied to object.     |
+-----------------------------------+--------------------------------------------------------------------------------------------------+
| out vec3 **TRANSMISSION**         | Transmission mask (default 0,0,0). Allows light to pass through object. Only applied if used.    |
+-----------------------------------+--------------------------------------------------------------------------------------------------+
| out float **AO**                  | Strength of Ambient Occlusion. For use with pre-baked AO.                                        |
+-----------------------------------+--------------------------------------------------------------------------------------------------+
| out float **AO_LIGHT_AFFECT**     | How much AO affects lights (0..1; default 0).                                                    |
+-----------------------------------+--------------------------------------------------------------------------------------------------+
| out vec3 **EMISSION**             | Emission color (can go over 1,1,1 for HDR).                                                      |
+-----------------------------------+--------------------------------------------------------------------------------------------------+
| sampler2D **SCREEN_TEXTURE**      | Built-in Texture for reading from the screen. Mipmaps contain increasingly blurred copies.       |
+-----------------------------------+--------------------------------------------------------------------------------------------------+
| sampler2D **DEPTH_TEXTURE**       | Built-in Texture for reading depth from the screen. Must convert to linear using INV_PROJECTION. |
+-----------------------------------+--------------------------------------------------------------------------------------------------+
| out float **DEPTH**               | Custom depth value (0..1).                                                                       |
+-----------------------------------+--------------------------------------------------------------------------------------------------+
| in vec2 **SCREEN_UV**             | Screen UV coordinate for current pixel.                                                          |
+-----------------------------------+--------------------------------------------------------------------------------------------------+
| in vec2 **POINT_COORD**           | Point Coordinate for drawing points with POINT_SIZE.                                             |
+-----------------------------------+--------------------------------------------------------------------------------------------------+
| out float **ALPHA_SCISSOR**       | If written to, values below a certain amount of alpha are discarded.                             |
+-----------------------------------+--------------------------------------------------------------------------------------------------+
| in bool **OUTPUT_IS_SRGB**        | True when calculations happen in sRGB color space (true in GLES2, false in GLES3).               |
+-----------------------------------+--------------------------------------------------------------------------------------------------+


Light built-ins
^^^^^^^^^^^^^^^

Writing light processor functions is completely optional. You can skip the light function by setting
render_mode to ``unshaded``. If no light function is written, Godot will use the material
properties written to in the fragment function to calculate the lighting for you (subject to
the render_mode).

To write a light function, assign something to ``DIFFUSE_LIGHT`` or ``SPECULAR_LIGHT``. Assigning nothing 
means no light is processed.

The light function is called for every light in every pixel. It is called within a loop for
each light type.

Below is an example of a custom light function using a Lambertian lighting model:

.. code-block:: glsl

    void light() {
        DIFFUSE_LIGHT += dot(NORMAL, LIGHT) * ATTENUATION * ALBEDO;
    }

If you want the lights to add together, add the light contribution to ``DIFFUSE_LIGHT`` using ``+=``, rather than overwriting it.

+-----------------------------------+---------------------------------------------+
| Built-in                          | Description                                 |
+===================================+=============================================+
| in vec4 **FRAGCOORD**             | Coordinate of pixel center. In screen space.|
|                                   | ``xy`` specifies  position in window, ``z`` |
|                                   | specifies fragment depth if ``DEPTH`` is    |
|                                   | not used. Origin is lower-left.             |
+-----------------------------------+---------------------------------------------+
| in mat4 **WORLD_MATRIX**          | Model space to world space transform.       |
+-----------------------------------+---------------------------------------------+
| in mat4 **INV_CAMERA_MATRIX**     | World space to view space transform.        |
+-----------------------------------+---------------------------------------------+
| in mat4 **CAMERA_MATRIX**         | View space to world space transform.        |
+-----------------------------------+---------------------------------------------+
| in mat4 **PROJECTION_MATRIX**     | View space to clip space transform.         |
+-----------------------------------+---------------------------------------------+
| in mat4 **INV_PROJECTION_MATRIX** | Clip space to view space transform.         |
+-----------------------------------+---------------------------------------------+
| in float **TIME**                 | Elapsed total time in seconds.              |
+-----------------------------------+---------------------------------------------+
| in vec2 **VIEWPORT_SIZE**         | Size of viewport (in pixels).               |
+-----------------------------------+---------------------------------------------+
| in vec3 **NORMAL**                | Normal vector, in view space.               |
+-----------------------------------+---------------------------------------------+
| in vec3 **VIEW**                  | View vector, in view space.                 |
+-----------------------------------+---------------------------------------------+
| in vec3 **LIGHT**                 | Light Vector, in view space.                |
+-----------------------------------+---------------------------------------------+
| in vec3 **LIGHT_COLOR**           | Color of light multiplied by energy.        |
+-----------------------------------+---------------------------------------------+
| in vec3 **ATTENUATION**           | Attenuation based on distance or shadow.    |
+-----------------------------------+---------------------------------------------+
| in vec3 **ALBEDO**                | Base albedo.                                |
+-----------------------------------+---------------------------------------------+
| in vec3 **TRANSMISSION**          | Transmission mask.                          |
+-----------------------------------+---------------------------------------------+
| in float **ROUGHNESS**            | Roughness.                                  |
+-----------------------------------+---------------------------------------------+
| out vec3 **DIFFUSE_LIGHT**        | Diffuse light result.                       |
+-----------------------------------+---------------------------------------------+
| out vec3 **SPECULAR_LIGHT**       | Specular light result.                      |
+-----------------------------------+---------------------------------------------+
| in bool **OUTPUT_IS_SRGB**        | True when calculations happen in sRGB       |
|                                   | color space (true in GLES2, false in GLES3).|
+-----------------------------------+---------------------------------------------+