Spatial Material

Introduction

SpatialMaterial is a default 3D material that aims to provide most of the features artists look for in a material, without the need for writing shader code. However, it can be converted to shader code if additional functionality is needed.

This tutorial explains most parameters present in SpatialMaterial.

You can add a SpatialMaterial to an object by choosing “New SpatialMaterial” in the Material property of the Inspector.

Flags

Spatial materials have many flags determining the general usage of a material.

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Transparent

In Godot, materials are not transparent unless specifically configured to be. The main reason behind this is that transparent materials are rendered using a different technique (sorted from back to front and rendered in order).

This technique is less efficient (many state changes happen) and makes the materials unusable with many mid- and post-processing effects (such as SSAO, SSR, etc.) that require perfectly opaque geometry.

For this reason, materials in Godot are assumed opaque unless specified otherwise. The main settings that enable transparency are:

  • Transparent flag (this one)
  • Blend mode set to other than “Mix”
  • Enabling distance or proximity fade

Unshaded

In most cases it is common for materials to be affected by lighting (shaded).

However, in some cases you might want to show just the albedo (color) and ignore the rest. Toggling this flag on will remove all shading and display pure, unlit color.

../../_images/spatial_material26.png

Vertex Lighting

Godot has a more or less uniform cost per pixel thanks to depth pre-pass. All lighting calculations are made by running the lighting shader on every pixel.

As these calculations are costly, performance can be brought down considerably in some corner cases such as drawing several layers of transparency (which is common in particle systems). Switching to per-vertex lighting may help in these cases.

Additionally, on low-end or mobile devices, switching to vertex lighting can considerably increase rendering performance.

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Keep in mind that when vertex lighting is enabled, only directional lighting can produce shadows (for performance reasons).

No Depth Test

In order for close objects to appear over far away objects, depth testing is performed. Disabling it has the result of objects appearing over (or under) everything else.

Disabling this makes the most sense for drawing indicators in world space, and works very well with the Render Priority property of Material (see the bottom of this page).

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Use Point Size

This option is only effective when the geometry rendered is made of points (generally it’s made of triangles when imported from 3D DCCs). If so, then those points can be resized (see below).

World Triplanar

When using triplanar mapping (see below, in the UV1 and UV2 settings), triplanar is computed in object local space. This option makes triplanar work in world space.

Fixed Size

This causes the object to be rendered at the same size no matter the distance. This is useful mostly for indicators (no depth test and high render priority) and some types of billboards.

Do Not Receive Shadows

Makes the object not receive any kind of shadow that would otherwise be cast onto it.

Disable Ambient Light

Makes the object not receive any kind of ambient lighting that would otherwise light it.

Vertex Color

This setting allows choosing what is done by default to vertex colors that come from your 3D modelling application. By default they are ignored.

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Use as Albedo

Choosing this option means vertex color is used as albedo color.

Is SRGB

Most 3D DCCs will likely export vertex colors as sRGB, so toggling this option on will help them look correct.

Parameters

SpatialMaterial also has several configurable parameters to tweak many aspects of the rendering:

../../_images/spatial_material5.png

Diffuse Mode

Specifies the algorithm used by diffuse scattering of light when hitting the object. The default is Burley. Other modes are also available:

  • Burley: Default mode, the original Disney Principled PBS diffuse algorithm.
  • Lambert: Is not affected by roughness.
  • Lambert Wrap: Extends Lambert to cover more than 90 degrees when roughness increases. Works great for hair and simulating cheap subsurface scattering. This implementation is energy conserving.
  • Oren Nayar: This implementation aims to take microsurfacing into account (via roughness). Works well for clay-like materials and some types of cloth.
  • Toon: Provides a hard cut for lighting, with smoothing affected by roughness. It is recommended you disable sky contribution from your environment’s ambient light settings or disable ambient light in the spatial material to achieve a better effect.
../../_images/spatial_material6.png

Specular Mode

Specifies how the specular blob will be rendered. The specular blob represents the shape of a light source reflected in the object.

  • ShlickGGX: The most common blob used by PBR 3D engines nowadays.
  • Blinn: Common in previous-generation engines. Not worth using nowadays, but left here for the sake of compatibility.
  • Phong: Same as above.
  • Toon: Creates a toon blob, which changes size depending on roughness.
  • Disabled: Sometimes the blob gets in the way. Begone!
../../_images/spatial_material7.png

Blend Mode

Controls the blend mode for the material. Keep in mind that any mode other than Mix forces the object to go through the transparent pipeline.

  • Mix: Default blend mode, alpha controls how much the object is visible.
  • Add: Object is blended additively, nice for flares or some fire-like effects.
  • Sub: Object is subtracted.
  • Mul: Object is multiplied.
../../_images/spatial_material8.png

Cull Mode

Determines which side of the object is not drawn when backfaces are rendered:

  • Back: The back of the object is culled when not visible (default).
  • Front: The front of the object is culled when not visible.
  • Disabled: Used for objects that are double-sided (no culling is performed).

Depth Draw Mode

Specifies when depth rendering must take place.

  • Opaque Only (default): Depth is only drawn for opaque objects.
  • Always: Depth draw is drawn for both opaque and transparent objects.
  • Never: No depth draw takes place (do not confuse this with the No Depth Test option above).
  • Depth Pre-Pass: For transparent objects, an opaque pass is made first with the opaque parts, then transparency is drawn above. Use this option with transparent grass or tree foliage.
../../_images/material_depth_draw.png

Line Width

When drawing lines, specify the width of the lines being drawn. This option is not available on most modern hardware.

Point Size

When drawing points, specify the point size in pixels.

Billboard Mode

Enables billboard mode for drawing materials. This controls how the object faces the camera:

  • Disabled: Billboard mode is disabled.
  • Enabled: Billboard mode is enabled, the object’s -Z axis will always face the camera.
  • Y-Billboard: The object’s X axis will always be aligned with the camera.
  • Particles: Most suited for particle systems, because it allows specifying animation options.
../../_images/spatial_material9.png

The above options are only enabled for Particle Billboard.

Grow

Grows the object vertices in the direction pointed by their normals:

../../_images/spatial_material10.png

This is commonly used to create cheap outlines. Add a second material pass, make it black and unshaded, reverse culling (Cull Front), and add some grow:

../../_images/spatial_material11.png

Use Alpha Scissor

When transparency other than 0 or 1 is not needed, it’s possible to set a threshold to prevent the object from rendering semi-transparent pixels.

../../_images/spatial_material12.png

This renders the object via the opaque pipeline, which is faster and allows it to use mid- and post-process effects such as SSAO, SSR, etc.

Material colors, maps and channels

Besides the parameters, what defines materials themselves are the colors, textures, and channels. Godot supports a extensive list of them. They are described in detail below:

Albedo

Albedo is the base color for the material, on which all the other settings operate. When set to Unshaded, this is the only color that is visible. In previous versions of Godot, this channel was named Diffuse. The change of name mainly happened because, in PBR rendering, this color affects many more calculations than just the diffuse lighting path.

Albedo color and texture can be used together as they are multiplied.

Alpha channel in albedo color and texture is also used for the object transparency. If you use a color or texture with alpha channel, make sure to either enable transparency or alpha scissoring for it to work.

Metallic

Godot uses a metallic model over competing models due to its simplicity. This parameter defines how reflective the material is. The more reflective, the less diffuse/ambient light affects the material and the more light is reflected. This model is called “energy-conserving”.

The Specular parameter is a general amount for the reflectivity (unlike Metallic, this is not energy-conserving, so leave it at 0.5 and don’t touch it unless you need to).

The minimum internal reflectivity is 0.04, so it’s impossible to make a material completely unreflective, just like in real life.

../../_images/spatial_material13.png

Roughness

Roughness affects the way reflection happens. A value of 0 makes it a perfect mirror while a value of 1 completely blurs the reflection (simulating natural microsurfacing). Most common types of materials can be achieved with the right combination of Metallic and Roughness.

../../_images/spatial_material14.png

Emission

Emission specifies how much light is emitted by the material (keep in mind this does not include light surrounding geometry unless GI Probes are used). This value is added to the resulting final image and is not affected by other lighting in the scene.

../../_images/spatial_material15.png

Normalmap

Normal mapping allows you to set a texture that represents finer shape detail. This does not modify geometry, only the incident angle for light. In Godot, only the red and green channels of normal maps are used for wider compatibility.

../../_images/spatial_material16.png

Rim

Some fabrics have small micro-fur that causes light to scatter around it. Godot emulates this with the Rim parameter. Unlike other rim lighting implementations which just use the emission channel, this one actually takes light into account (no light means no rim). This makes the effect considerably more believable.

../../_images/spatial_material17.png

Rim size depends on roughness, and there is a special parameter to specify how it must be colored. If Tint is 0, the color of the light is used for the rim. If Tint is 1, then the albedo of the material is used. Using intermediate values generally works best.

Clearcoat

The Clearcoat parameter is used to add a secondary pass of transparent coat to the material. This is common in car paint and toys. In practice, it’s a smaller specular blob added on top of the existing material.

Anisotropy

This changes the shape of the specular blob and aligns it to tangent space. Anisotropy is commonly used with hair, or to make materials such as brushed aluminum more realistic. It works especially well when combined with flowmaps.

../../_images/spatial_material18.png

Ambient Occlusion

It is possible to specify a baked ambient occlusion map. This map affects how much ambient light reaches each surface of the object (it does not affect direct light by default). While it is possible to use Screen-Space Ambient Occlusion (SSAO) to generate ambient occlusion, nothing beats the quality of a well-baked AO map. It is recommended to bake ambient occlusion whenever possible.

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Depth

Setting a depth map on a material produces a ray-marched search to emulate the proper displacement of cavities along the view direction. This is not real added geometry, but an illusion of depth. It may not work for complex objects, but it produces a realistic depth effect for textures. For best results, Depth should be used together with normal mapping.

../../_images/spatial_material20.png

Subsurface Scattering

This effect emulates light that penetrates an object’s surface, is scattered, and then comes out. It is useful to create realistic skin, marble, colored liquids, etc.

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Transmission

This controls how much light from the lit side (visible to light) is transferred to the dark side (opposite from the light). This works well for thin objects such as plant leaves, grass, human ears, etc.

../../_images/spatial_material22.png

Refraction

When refraction is enabled, it supersedes alpha blending, and Godot attempts to fetch information from behind the object being rendered instead. This allows distorting the transparency in a way similar to refraction in real life.

../../_images/spatial_material23.png

Detail

Godot allows using secondary albedo and normal maps to generate a detail texture, which can be blended in many ways. By combining this with secondary UV or triplanar modes, many interesting textures can be achieved.

../../_images/spatial_material24.png

UV1 and UV2

Godot supports two UV channels per material. Secondary UV is often useful for ambient occlusion or emission (baked light). UVs can be scaled and offset which is useful when using repeating textures.

Triplanar Mapping

Triplanar mapping is supported for both UV1 and UV2. This is an alternative way to obtain texture coordinates, sometimes called “Autotexture”. Textures are sampled in X, Y and Z and blended by the normal. Triplanar mapping can be performed in either world space or object space.

In the image below, you can see how all primitives share the same material with world triplanar, so the brick texture continues smoothly between them.

../../_images/spatial_material25.png

Proximity and distance fade

Godot allows materials to fade by proximity to each other as well as depending on the distance from the viewer. Proximity fade is useful for effects such as soft particles or a mass of water with a smooth blending to the shores. Distance fade is useful for light shafts or indicators that are only present after a given distance.

Keep in mind enabling these enables alpha blending, so abusing them for an entire scene is usually not a good idea.

../../_images/spatial_material_proxfade.gif

Render priority

The rendering order of objects can be changed, although this is mostly useful for transparent objects (or opaque objects that perform depth draw but no color draw, such as cracks on the floor).