manual/render/eevee/limitations.rst

@@ -66,6 +66,7 @@ Depth of Field
   but will be correctly handled by the sample-based method. For this, you need to
   disable the post-process depth of field by setting the *Max Size* to 0.
 
+.. _eevee-limitations-screenspace:
 
 Screen Space Effects
 ====================
@@ -82,6 +83,7 @@ These limitations creates a few problems:
   This can be partially fixed by using the *overscan* feature.
 - Screen space effects lack deep information (or the thickness of objects).
   This is why most effects have a thickness parameter to control how to consider potential intersected pixels.
+- Objects behind other objects (occluded) are not considered by these effects.
 - Blended surfaces are not considered by these effects.
   They are not part of the depth prepass and do not appear in the depth buffer.
 - Objects that a part of :ref:`Holdout Collections <bpy.ops.outliner.collection_holdout_set>`

manual/render/eevee/render_settings/clamping.rst

@@ -0,0 +1,45 @@
+
+********
+Clamping
+********
+
+.. reference::
+
+   :Panel:     :menuselection:`Render --> Clamping`
+
+
+.. _bpy.types.SceneEEVEE.clamp_surface_direct:
+.. _bpy.types.SceneEEVEE.clamp_surface_indirect:
+
+Surface
+_______
+
+Direct Light
+   This option limits the maximum light intensity a surface can reflect.
+   It reduces :term:`Aliasing` noise and :term:`Fireflies` at the cost of accuracy.
+   Setting this option to 0.0 disables clamping altogether.
+   Lower values have a greater effect on the resulting image than higher values.
+
+
+Indirect Light
+   Similar to **Direct Light* but limits the maximum light intensity reflected using ray-tracing and light-probes.
+
+.. note::
+
+    These options provides a way to limit :term:`Fireflies` and :term:`Aliasing` of highly reflective surfaces and dense volumes.
+    However, note that as you clamp out such values, other bright lights will be dimmed as well.
+
+    Care must be taken when using this setting to find a balance between mitigating fireflies and
+    losing intentionally bright parts.
+
+.. _bpy.types.SceneEEVEE.clamp_volume_direct:
+.. _bpy.types.SceneEEVEE.clamp_volume_indirect:
+
+Volume
+______
+
+Direct Light
+   The same as *Surface Direct Light* but for volume direct lighting.
+
+Indirect Light
+   The same as *Surface Direct Light* but for volume indirect lighting.

manual/render/eevee/render_settings/horizon_scan.rst

@@ -1,18 +0,0 @@
-************
-Horizon Scan
-************
-
-.. reference::
-
-   :Panel:     :menuselection:`Render --> Horizon Scan`
-
-Precision
-   Precision of the horizon scan.
-
-Thickness
-   Constant thickness of the surfaces considered when doing horizon scan and by extension ambient
-   occlusion.
-
-Bias
-   Bias the horozon angles to reduce self intersection artifacts.
-    

manual/render/eevee/render_settings/index.rst

@@ -8,15 +8,15 @@
    :maxdepth: 2
 
    sampling.rst
-   depth_of_field.rst
-   horizon_scan.rst
+   clamping.rst
    raytracing.rst
+   shadows.rst
    volumes.rst
    performance.rst
    curves.rst
    lights.rst
-   shadows.rst
    light_probes.rst
    film.rst
+   depth_of_field.rst
    motion_blur.rst
    grease_pencil.rst

manual/render/eevee/render_settings/raytracing.rst

@@ -8,73 +8,119 @@ Raytracing
 
    :Panel:     :menuselection:`Render --> Raytracing`
 
+The ray-tracing pipeline goal is to increase the accuracy of surface indirect lighting.
+This is done by generating ray from each :abbr:`BSDF (Bidirectional Scattering Distribution Function)`
+and finding their intersection with the scene individually.
+
+When disabled, it is replaced by a faster pipeline that uses pre-filtered light-probes.
+This fallback mode offers a more visually stable and optimized alternative when visual fidelity is not the primary goal.
+
+.. seealso:: :ref:`Limitations <eevee-limitations-raytracing>`.
+
 Method
-   Select the tracing method used to find scene-ray intersecions
+   Determine the tracing method used to find scene-ray intersections and indirect lighting.
+
+   :Light Probe:
+      Use light-probe spheres and planes to find scene intersection.
+      This option is has the lowest tracing cost but rely on manually placed light-probes.
 
    :Screen-Trace:
-      Raytrace against the depth buffer
-
-   :None:
-      No intersection with scene geometry
-
-Settings
-   Split the settings per ray type (Reflection/Refraction/Diffuse)
-
-   :Unified:
-      All the ray types use the same settings
-   
-   :Split:
-      Settings are individual to each ray type
-
-Ray Type
-========
-
-When the settings are split per ray type this section will be repeated for reflection, refraction
-and diffuse rays.
+      Trace ray against the screen depth buffer. Fallback to light-probes if ray exits the view.
 
 Resolution
-   Number of rays per pixel. Choice out of 1, 1/4 and 1/16 rays per pixel.
+   Resolution at which the ray-tracing is performed.
+   Lower options will be faster and use less memory but will produce blurrier results.
 
-Clamp
-   Clamp ray intensity to reduce noise. Use 0 to disable.
-
-Denoising
-   Denoising can be enabled to reduce noise in raytraced effects.
-
-   Spatial Reuse
-      Reuse the rays from neighbor pixels.
-
-   Temporal Accumulation
-      Accumulate samples by reprojectiong last ray tracing results.
-
-   Bilateral Filter
-      Blur the resolved radiance using a bilateral filter.
+Max Roughness
+   Maximum roughness a :abbr:`BSDF (Bidirectional Scattering Distribution Function)` can have to use ray-tracing.
+   BSDFs with higher roughness will progressively use the *Fast GI Approximation*.
+   A value of 1 will raytrace every surfaces and disable the Fast GI.
 
 
-Refractions
-   Screen space refractions work the same way as screen space reflections and use the same parameters.
-   But they are not enabled by default on all surfaces.
-   Enabling it will have a small performance cost.
-   You need to enable them in :menuselection:`Material Properties --> Settings`.
-   Materials using screen space refractions will not cast screen space reflections.
+Screen Tracing
+______________
 
-Half Resolution Trace
-   Use half resolution ray tracing. Only cast a ray for every fourth pixel.
-   Enabling this option drastically reduces video memory usage and increases performance at the cost of quality.
+These settings control the behavior of the screen space ray-tracing.
+They are only visible if *Screen-Trace* is the chosen tracing *Method*.
 
-Trace Precision
-   Increases precision of the ray tracing but introduces more noise and lowers the maximum trace distance.
+Precision
+   Higher values increase precision of the screen space ray-tracing but lowers the maximum trace distance.
    Increased precision also increases performance cost.
 
 Thickness
    How thick to consider the pixels of the depth buffer during the tracing.
    Higher values will stretch the reflections and add flickering. Lower values may make the ray miss surfaces.
 
-Edge Fading
-   Smoothly fade out the reflected and refracted pixels if they are close to a screen edge.
-   The unit is in screen percentage.
 
-Clamp
-   Clamp the reflected color intensity to remove noise and :term:`Fireflies`.
+Denoising
+_________
 
-.. seealso:: :ref:`Limitations <eevee-limitations-raytracing>`.
+Denoising can be enabled to reduce the noise amount from the raw ray-traced output.
+This can help image stability but will also over blur the final ray-traced output.
+
+Spatial Reuse
+   Reuse the rays from neighbor pixels.
+   Can introduce some light leaks across surfaces.
+
+Temporal Accumulation
+   Accumulate samples by re-projecting last ray tracing results.
+   This removes :term:`Fireflies` but also introduce a lot of color bias.
+   Useful for viewport temporal stability or making render converge faster.
+
+Bilateral Filter
+   Blur the resolved ray-traced output using a bilateral filter.
+
+
+Fast GI Approximation
+_____________________
+
+This Fast GI Approximation is a fallback to the ray-tracing pipeline for
+:abbr:`BSDF (Bidirectional Scattering Distribution Function)` with high roughness.
+It produces less noisy output and capture bounce lighting more efficiently than individually traced rays.
+
+This is currently implemented as a screen space effect and will inherit.
+
+.. seealso:: :ref:`Limitations <eevee-limitations-screenspace>`.
+
+Method
+   Determine the methods used to compute the fast GI approximation.
+
+   :Ambient Occlusion:
+      Use scene intersections to shadow the distant lighting from light-probes.
+      This is the fastest option.
+
+   :Global Illumination:
+      Compute global illumination taking into account light bouncing off surrounding objects.
+
+Resolution
+   Resolution at which the fast GI is computed.
+   Lower options will be faster and use less memory but will produce blurrier results.
+
+Ray Count
+   Amount of GI ray per pixels at the specified *Resolution*.
+   Higher values will reduce noise.
+
+Step Count
+   Amount of screen sample per GI ray.
+   Higher values will reduce the noise amount and increase the quality.
+
+   .. note::
+
+      With higher step count, there is less chance to miss other surfaces that could reflect of block the light.
+      This means that the Fast GI *Thickness* parameter can be tweaked to lower values without loosing too much light bounce energy.
+
+Precision
+   Higher values increase the precision of the scene intersections with the GI rays.
+   Increased precision also increases performance cost.
+
+
+Distance
+   If non-zero, the maximum distance at which other surfaces will contribute to the fast GI approximation.
+
+Thickness Near
+   Geometric thickness of the surfaces when computing fast GI and ambient occlusion.
+   Reduces light leaking and missing contact occlusion.
+
+Thickness Far
+   Angular thickness of the surfaces when computing fast GI and ambient occlusion.
+   Reduces energy loss and missing occlusion of far geometry.