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Cycles: reduce shadow terminator artifacts

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Offset rays from the flat surface to match where they would be for a smooth
surface as specified by the normals. In the shading panel there is now a
Shading Offset (existing option) and Geometry Offset (new).

The Geometry Offset works as follows:
* 0: disabled
* 0.001: only terminated triangles (normal points to the light, geometry
  doesn't) are affected
* 0.1 (default): triangles at grazing angles are affected, and the effect
  fades out
* 1: all triangles are affected

Limitations:
* The artifact is still visible in some cases, it could be that some quads
  require to be treated specifically as quads.
* Inconsistent normals cause artifacts.
* If small objects cast shadows to a big low poly surface, the shadows can
  appear to be in a wrong place - because the surface moved slightly above
  the geometry. This can be noticed only at grazing angles to light.
* Approximated surfaces of two non-intersecting low-poly objects can overlap
  that causes off-the-wall shadows.

Generally, using one or a few levels of subdivision can get rid of artifacts
faster than before.

Differential Revision: https://developer.blender.org/D11065
This commit is contained in:
Mikhail Matrosov
2021-06-28 13:54:18 +02:00
committed by Brecht Van Lommel
parent ce25b5812b
commit 9c6a382f95
10 changed files with 138 additions and 22 deletions
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7
intern/cycles/render/object.cpp
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@@ -93,7 +93,8 @@ NODE_DEFINE(Object)
SOCKET_POINT(dupli_generated, "Dupli Generated", zero_float3());
SOCKET_POINT2(dupli_uv, "Dupli UV", zero_float2());
SOCKET_TRANSFORM_ARRAY(motion, "Motion", array<Transform>());
SOCKET_FLOAT(shadow_terminator_offset, "Terminator Offset", 0.0f);
SOCKET_FLOAT(shadow_terminator_shading_offset, "Shadow Terminator Shading Offset", 0.0f);
SOCKET_FLOAT(shadow_terminator_geometry_offset, "Shadow Terminator Geometry Offset", 0.1f);
SOCKET_STRING(asset_name, "Asset Name", ustring());
SOCKET_BOOLEAN(is_shadow_catcher, "Shadow Catcher", false);
@@ -507,7 +508,9 @@ void ObjectManager::device_update_object_transform(UpdateObjectTransformState *s
kobject.cryptomatte_asset = util_hash_to_float(hash_asset);
}
kobject.shadow_terminator_offset = 1.0f / (1.0f - 0.5f * ob->shadow_terminator_offset);
kobject.shadow_terminator_shading_offset = 1.0f /
(1.0f - 0.5f * ob->shadow_terminator_shading_offset);
kobject.shadow_terminator_geometry_offset = ob->shadow_terminator_geometry_offset;
/* Object flag. */
if (ob->use_holdout) {