Spatial shaders¶

Spatial shaders are used for shading 3D objects. They are the most complex type of shader Redot 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.
shadow_to_opacity	Lighting modifies the alpha so shadowed areas are opaque and non-shadowed areas are transparent. Useful for overlaying shadows onto a camera feed in AR.

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¶

Global built-ins are available everywhere, including custom functions.

Built-in	Description
in float TIME	Global time, in seconds.

Vertex built-ins¶

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:

shader_type spatial;
render_mode skip_vertex_transform;

void vertex() {
    VERTEX = (MODELVIEW_MATRIX * vec4(VERTEX, 1.0)).xyz;
    NORMAL = normalize((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 particle shader, this value can be used as desired.

Built-in	Description
in vec2 VIEWPORT_SIZE	Size of viewport (in pixels).
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 vec3 NODE_POSITION_WORLD	Node position, in world space.
in vec3 NODE_POSITION_VIEW	Node position, in view space.
in vec3 CAMERA_POSITION_WORLD	Camera position, in world space.
in vec3 CAMERA_DIRECTION_WORLD	Camera direction, in world space.
inout vec3 VERTEX	Vertex in local coordinates.
in int VERTEX_ID	The index of the current vertex in the vertex buffer. Not supported in GLES2 (returns 0).
out vec4 POSITION	If written to, overrides final vertex position.
inout vec3 NORMAL	Normal in local coordinates.
inout vec3 TANGENT	Tangent in local coordinates.
inout vec3 BINORMAL	Binormal in local coordinates.
out float ROUGHNESS	Roughness for vertex lighting.
inout vec2 UV	UV main channel.
inout vec2 UV2	UV secondary channel.
in bool OUTPUT_IS_SRGB	`true` when calculations happen in sRGB color space (`true` in GLES2, `false` in GLES3).
inout vec4 COLOR	Color from vertices.
inout float POINT_SIZE	Point size for point rendering.
in int INSTANCE_ID	Instance ID for instancing. Not supported in GLES2 (returns 0).
in vec4 INSTANCE_CUSTOM	Instance custom data (for particles, mostly).

Note

MODELVIEW_MATRIX combines both the WORLD_MATRIX and INV_CAMERA_MATRIX and is better suited when floating point issues may arise. For example, if the object is very far away from the world origin, you may run into floating point issues when using the seperated WORLD_MATRIX and INV_CAMERA_MATRIX.

Fragment built-ins¶

The default use of a Redot 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, Redot will optimize away the corresponding functionality.

Built-in	Description
in vec2 VIEWPORT_SIZE	Size of viewport (in pixels).
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 vec3 NODE_POSITION_WORLD	Node world space position.
in vec3 NODE_POSITION_VIEW	Node view space position.
in vec3 CAMERA_POSITION_WORLD	Camera world space position.
in vec3 CAMERA_DIRECTION_WORLD	Camera world space direction.
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 bool OUTPUT_IS_SRGB	`true` when calculations happen in sRGB color space (`true` in GLES2, `false` in GLES3).
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 ALPHA_SCISSOR	If written to, values below a certain amount of alpha are discarded.
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, Redot calculates rim lighting.
out float RIM_TINT	Rim Tint, goes from 0 (white) to 1 (albedo). If used, Redot calculates rim lighting.
out float CLEARCOAT	Small added specular blob. If used, Redot calculates Clearcoat.
out float CLEARCOAT_GLOSS	Gloss of Clearcoat. If used, Redot 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 vec3 EMISSION	Emission color (can go over 1,1,1 for HDR).
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).
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). If `DEPTH` is being written to in any shader branch, then you are responsible for setting the `DEPTH` for all other branches. Otherwise, the graphics API will leave them uninitialized.
in vec2 SCREEN_UV	Screen UV coordinate for current pixel.
in vec2 POINT_COORD	Point Coordinate for drawing points with POINT_SIZE.

Note

Shaders going through the transparent pipeline when ALPHA is written to may exhibit transparency sorting issues. Read the transparency sorting section in the 3D rendering limitations page for more information and ways to avoid issues.

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, Redot 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:

void light() {
    DIFFUSE_LIGHT += clamp(dot(NORMAL, LIGHT), 0.0, 1.0) * ATTENUATION * ALBEDO;
}

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

Warning

In GLES2, lights will always be added together even if you override DIFFUSE_LIGHT using =. This is due to lighting being computed in multiple passes (one for each light), unlike GLES3.

Warning

The light() function won't be run if the vertex_lighting render mode is enabled, or if Rendering > Quality > Shading > Force Vertex Shading is enabled in the Project Settings. (It's enabled by default on mobile platforms.)

Built-in	Description
in float TIME	Elapsed total time in seconds.
in vec2 VIEWPORT_SIZE	Size of viewport (in pixels).
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 vec3 NORMAL	Normal vector, in view space.
in vec2 UV	UV that comes from vertex function.
in vec2 UV2	UV2 that comes from vertex function.
in vec3 VIEW	View vector, in view space.
in vec3 LIGHT	Light Vector, in view space.
in vec3 ATTENUATION	Attenuation based on distance or shadow.
in bool OUTPUT_IS_SRGB	`true` when calculations happen in sRGB color space (`true` in GLES2, `false` in GLES3).
in vec3 ALBEDO	Base albedo.
in vec3 LIGHT_COLOR	Color of light multiplied by `energy * PI`. The `PI` multiplication is present because physically-based lighting models include a division by `PI`.
out float ALPHA	Alpha (0..1); if written to, the material will go to the transparent pipeline.
in float ROUGHNESS	Roughness.
in vec3 TRANSMISSION	Transmission mask from fragment function.
out vec3 DIFFUSE_LIGHT	Diffuse light result.
out vec3 SPECULAR_LIGHT	Specular light result.

Note

Shaders going through the transparent pipeline when ALPHA is written to may exhibit transparency sorting issues. Read the transparency sorting section in the 3D rendering limitations page for more information and ways to avoid issues.