Light3D is the [i]abstract[/i] base class for light nodes. As it can't be instantiated, it shouldn't be used directly. Other types of light nodes inherit from it. Light3D contains the common variables and parameters used for lighting.
If [code]true[/code], the light will smoothly fade away when far from the active [Camera3D] starting at [member distance_fade_begin]. This acts as a form of level of detail (LOD). The light will fade out over [member distance_fade_begin] + [member distance_fade_length], after which it will be culled and not sent to the shader at all. Use this to reduce the number of active lights in a scene and thus improve performance.
[b]Note:[/b] Only effective for [OmniLight3D] and [SpotLight3D].
The distance from the camera at which the light's shadow cuts off (in 3D units). Set this to a value lower than [member distance_fade_begin] + [member distance_fade_length] to further improve performance, as shadow rendering is often more expensive than light rendering itself.
[b]Note:[/b] Only effective for [OmniLight3D] and [SpotLight3D], and only when [member shadow_enabled] is [code]true[/code].
[b]Note:[/b] Due to a rendering engine limitation, shadows will be disabled instantly instead of fading smoothly according to [member distance_fade_length]. This may result in visible pop-in depending on the scene topography.
The light's angular size in degrees. Increasing this will make shadows softer at greater distances. Only available for [DirectionalLight3D]s. For reference, the Sun from the Earth is approximately [code]0.5[/code].
The light's strength multiplier (this is not a physical unit). For [OmniLight3D] and [SpotLight3D], changing this value will only change the light color's intensity, not the light's radius.
[Texture2D] projected by light. [member shadow_enabled] must be on for the projector to work. Light projectors make the light appear as if it is shining through a colored but transparent object, almost like light shining through stained-glass.
The size of the light in Godot units. Only available for [OmniLight3D]s and [SpotLight3D]s. Increasing this value will make the light fade out slower and shadows appear blurrier. This can be used to simulate area lights to an extent.
The intensity of the specular blob in objects affected by the light. At [code]0[/code], the light becomes a pure diffuse light. When not baking emission, this can be used to avoid unrealistic reflections when placing lights above an emissive surface.
Used to adjust shadow appearance. Too small a value results in self-shadowing ("shadow acne"), while too large a value causes shadows to separate from casters ("peter-panning"). Adjust as needed.
Blurs the edges of the shadow. Can be used to hide pixel artifacts in low-resolution shadow maps. A high value can impact performance, make shadows appear grainy and can cause other unwanted artifacts. Try to keep as near default as possible.
If [code]true[/code], the light will cast real-time shadows. This has a significant performance cost. Only enable shadow rendering when it makes a noticeable difference in the scene's appearance, and consider using [member distance_fade_enabled] to hide the light when far away from the [Camera3D].
Offsets the lookup into the shadow map by the object's normal. This can be used to reduce self-shadowing artifacts without using [member shadow_bias]. In practice, this value should be tweaked along with [member shadow_bias] to reduce artifacts as much as possible.
If [code]true[/code], reverses the backface culling of the mesh. This can be useful when you have a flat mesh that has a light behind it. If you need to cast a shadow on both sides of the mesh, set the mesh to use double-sided shadows with [constant GeometryInstance3D.SHADOW_CASTING_SETTING_DOUBLE_SIDED].
Light is ignored when baking. This is the fastest mode, but the light will be taken into account when baking global illumination. This mode should generally be used for dynamic lights that change quickly, as the effect of global illumination is less noticeable on those lights.
[b]Note:[/b] Hiding a light does [i]not[/i] affect baking [LightmapGI]. Hiding a light will still affect baking [VoxelGI] and SDFGI (see [member Environment.sdfgi_enabled).
Light is taken into account in static baking ([VoxelGI], [LightmapGI], SDFGI ([member Environment.sdfgi_enabled])). The light can be moved around or modified, but its global illumination will not update in real-time. This is suitable for subtle changes (such as flickering torches), but generally not large changes such as toggling a light on and off.
Light is taken into account in dynamic baking ([VoxelGI] and SDFGI ([member Environment.sdfgi_enabled]) only). The light can be moved around or modified with global illumination updating in real-time. The light's global illumination appearance will be slightly different compared to [constant BAKE_STATIC]. This has a greater performance cost compared to [constant BAKE_STATIC].
