scripts/startup/bl_ui/properties_data_lightprobe.py

@@ -111,6 +111,12 @@ class DATA_PT_lightprobe_eevee_next(DataButtonsPanel, Panel):
             col.prop(probe, "grid_bake_samples")
             col.prop(probe, "surfel_density")
 
+            col.separator()
+
+            col.prop(probe, "grid_normal_bias")
+            col.prop(probe, "grid_view_bias")
+            col.prop(probe, "grid_irradiance_smoothing")
+
         elif probe.type == 'CUBEMAP':
             col = layout.column()
             col.prop(probe, "resolution")

source/blender/blenloader/intern/versioning_400.cc

@@ -378,10 +378,13 @@ void blo_do_versions_400(FileData *fd, Library * /*lib*/, Main *bmain)
 
     /* Keep this block, even when empty. */
 
-    if (!DNA_struct_elem_find(fd->filesdna, "LightProbe", "int", "grid_bake_sample_count")) {
+    if (!DNA_struct_elem_find(fd->filesdna, "LightProbe", "int", "grid_bake_samples")) {
       LISTBASE_FOREACH (LightProbe *, lightprobe, &bmain->lightprobes) {
         lightprobe->grid_bake_samples = 2048;
         lightprobe->surfel_density = 1.0f;
+        lightprobe->grid_normal_bias = 0.3f;
+        lightprobe->grid_view_bias = 0.0f;
+        lightprobe->grid_facing_bias = 0.5f;
       }
     }
 

source/blender/draw/engines/eevee_next/eevee_lightprobe.cc

@@ -30,6 +30,8 @@ void LightProbeModule::sync_grid(const Object *ob, ObjectHandle &handle)
   IrradianceGrid &grid = grid_map_.lookup_or_add_default(handle.object_key);
   grid.used = true;
   if (handle.recalc != 0 || grid.initialized == false) {
+    const ::LightProbe *lightprobe = static_cast<const ::LightProbe *>(ob->data);
+
     grid.initialized = true;
     grid.updated = true;
     grid.object_to_world = float4x4(ob->object_to_world);
@@ -37,6 +39,9 @@ void LightProbeModule::sync_grid(const Object *ob, ObjectHandle &handle)
         math::normalize(math::transpose(float3x3(grid.object_to_world))));
 
     grid.cache = ob->lightprobe_cache;
+    grid.normal_bias = lightprobe->grid_normal_bias;
+    grid.view_bias = lightprobe->grid_view_bias;
+    grid.facing_bias = lightprobe->grid_facing_bias;
     /* Force reupload. */
     inst_.irradiance_cache.bricks_free(grid.bricks);
   }

source/blender/draw/engines/eevee_next/eevee_shader_shared.hh

@@ -922,6 +922,11 @@ struct IrradianceGridData {
   packed_int3 grid_size;
   /** Index in brick descriptor list of the first brick of this grid. */
   int brick_offset;
+  /** Biases to apply to the shading point in order to sample a valid probe. */
+  float normal_bias;
+  float view_bias;
+  float facing_bias;
+  int _pad1;
 };
 BLI_STATIC_ASSERT_ALIGN(IrradianceGridData, 16)
 

source/blender/draw/engines/eevee_next/shaders/eevee_lightprobe_eval_lib.glsl

@@ -12,8 +12,15 @@
 /**
  * Return sample coordinates of the first SH coef in unormalized texture space.
  */
-vec3 lightprobe_irradiance_grid_atlas_coord(IrradianceGridData grid_data, vec3 lP)
+vec3 lightprobe_irradiance_grid_atlas_coord(IrradianceGridData grid_data,
+                                            vec3 lP,
+                                            vec3 lV,
+                                            vec3 lNg)
 {
+  /* Shading point bias. */
+  lP += lNg * grid_data.normal_bias;
+  lP += lV * grid_data.view_bias;
+
   ivec3 brick_coord = ivec3((lP - 0.5) / float(IRRADIANCE_GRID_BRICK_SIZE - 1));
   /* Avoid sampling adjacent bricks. */
   brick_coord = max(brick_coord, ivec3(0));
@@ -23,8 +30,58 @@ vec3 lightprobe_irradiance_grid_atlas_coord(IrradianceGridData grid_data, vec3 l
   vec3 brick_lP = lP - vec3(brick_coord) * float(IRRADIANCE_GRID_BRICK_SIZE - 1);
 
   int brick_index = lightprobe_irradiance_grid_brick_index_get(grid_data, brick_coord);
-
   IrradianceBrick brick = irradiance_brick_unpack(bricks_infos_buf[brick_index]);
+
+  /* A cell is the interpolation region between 8 texels. */
+  vec3 cell_lP = brick_lP - 0.5;
+  vec3 cell_start = floor(cell_lP);
+  vec3 cell_fract = cell_lP - cell_start;
+  /**
+   * References:
+   *
+   * "Probe-based lighting, strand-based hair system, and physical hair shading in Unity’s Enemies"
+   * by Francesco Cifariello Ciardi, Lasse Jon Fuglsang Pedersen and John Parsaie.
+   *
+   * "Multi-Scale Global Illumination in Quantum Break"
+   * by Ari Silvennoinen and Ville Timonen.
+   *
+   * “Dynamic Diffuse Global Illumination with Ray-Traced Irradiance Fields”
+   * by Morgan McGuire.
+   */
+  float trilinear_weights[8];
+  float total_weight = 0.0;
+  for (int i = 0; i < 8; i++) {
+    ivec3 sample_position = (ivec3(i) >> ivec3(0, 1, 2)) & 1;
+
+    vec3 trilinear = select(1.0 - cell_fract, cell_fract, bvec3(sample_position));
+    float positional_weight = trilinear.x * trilinear.y * trilinear.z;
+
+    float len;
+    vec3 corner_vec = vec3(sample_position) - cell_fract;
+    vec3 corner_dir = normalize_and_get_length(corner_vec, len);
+    float cos_theta = (len > 1e-8) ? dot(lNg, corner_dir) : 1.0;
+    float geometry_weight = saturate(cos_theta * 0.5 + 0.5);
+
+    /* TODO(fclem): Need to bake validity. */
+    float validity_weight = 1.0;
+
+    /* Biases. See McGuire's presentation. */
+    positional_weight += 0.001;
+    geometry_weight = sqr(geometry_weight) + 0.2 + grid_data.facing_bias;
+
+    trilinear_weights[i] = saturate(positional_weight * geometry_weight * validity_weight);
+    total_weight += trilinear_weights[i];
+  }
+  float total_weight_inv = safe_rcp(total_weight);
+
+  vec3 trilinear_coord = vec3(0.0);
+  for (int i = 0; i < 8; i++) {
+    vec3 sample_position = vec3((ivec3(i) >> ivec3(0, 1, 2)) & 1);
+    trilinear_coord += sample_position * trilinear_weights[i] * total_weight_inv;
+  }
+  /* Replace sampling coordinates with manually weighted trilinear coordinates. */
+  brick_lP = 0.5 + cell_start + trilinear_coord;
+
   vec3 output_coord = vec3(vec2(brick.atlas_coord), 0.0) + brick_lP;
 
   return output_coord;
@@ -35,7 +92,7 @@ vec4 textureUnormalizedCoord(sampler3D tx, vec3 co)
   return texture(tx, co / vec3(textureSize(tx, 0)));
 }
 
-SphericalHarmonicL1 lightprobe_irradiance_sample(sampler3D atlas_tx, vec3 P)
+SphericalHarmonicL1 lightprobe_irradiance_sample(sampler3D atlas_tx, vec3 P, vec3 V, vec3 Ng)
 {
   vec3 lP;
   int grid_index;
@@ -52,16 +109,24 @@ SphericalHarmonicL1 lightprobe_irradiance_sample(sampler3D atlas_tx, vec3 P)
     }
   }
 
-  vec3 atlas_coord = lightprobe_irradiance_grid_atlas_coord(grids_infos_buf[grid_index], lP);
+  /* TODO(fclem): Make sure this is working as expected. */
+  mat3x3 world_to_grid_transposed = mat3x3(grids_infos_buf[grid_index].world_to_grid_transposed);
+  vec3 lNg = safe_normalize(world_to_grid_transposed * Ng);
+  vec3 lV = safe_normalize(V * world_to_grid_transposed);
 
+  vec3 atlas_coord = lightprobe_irradiance_grid_atlas_coord(
+      grids_infos_buf[grid_index], lP, lV, lNg);
+
+  vec4 texture_coord = vec4(atlas_coord, float(IRRADIANCE_GRID_BRICK_SIZE)) /
+                       vec3(textureSize(atlas_tx, 0)).xyzz;
   SphericalHarmonicL1 sh;
-  sh.L0.M0 = textureUnormalizedCoord(atlas_tx, atlas_coord);
-  atlas_coord.z += float(IRRADIANCE_GRID_BRICK_SIZE);
-  sh.L1.Mn1 = textureUnormalizedCoord(atlas_tx, atlas_coord);
-  atlas_coord.z += float(IRRADIANCE_GRID_BRICK_SIZE);
-  sh.L1.M0 = textureUnormalizedCoord(atlas_tx, atlas_coord);
-  atlas_coord.z += float(IRRADIANCE_GRID_BRICK_SIZE);
-  sh.L1.Mp1 = textureUnormalizedCoord(atlas_tx, atlas_coord);
+  sh.L0.M0 = textureLod(atlas_tx, texture_coord.xyz, 0.0);
+  texture_coord.z += texture_coord.w;
+  sh.L1.Mn1 = textureLod(atlas_tx, texture_coord.xyz, 0.0);
+  texture_coord.z += texture_coord.w;
+  sh.L1.M0 = textureLod(atlas_tx, texture_coord.xyz, 0.0);
+  texture_coord.z += texture_coord.w;
+  sh.L1.Mp1 = textureLod(atlas_tx, texture_coord.xyz, 0.0);
   return sh;
 }
 
@@ -73,7 +138,10 @@ void lightprobe_eval(ClosureDiffuse diffuse,
                      inout vec3 out_diffuse,
                      inout vec3 out_specular)
 {
-  SphericalHarmonicL1 irradiance = lightprobe_irradiance_sample(irradiance_atlas_tx, P);
+  /* NOTE: Use the diffuse normal for biasing the probe sampling location since it is smoother than
+   * geometric normal. Could also try to use interp.N. */
+  SphericalHarmonicL1 irradiance = lightprobe_irradiance_sample(
+      irradiance_atlas_tx, P, V, diffuse.N);
 
   out_diffuse += spherical_harmonics_evaluate_lambert(diffuse.N, irradiance);
 }

source/blender/draw/engines/overlay/shaders/overlay_extra_lightprobe_grid_vert.glsl

@@ -54,7 +54,7 @@ void main()
   if (z_delta > 0.0) {
     float fac = 1.0 - z_delta * 10000.0;
     /* Smooth blend to avoid flickering. */
-    finalColor = mix(colorBackground, finalColor, clamp(fac, 0.5, 1.0));
+    finalColor = mix(colorBackground, finalColor, clamp(fac, 0.2, 1.0));
   }
 
   view_clipping_distances(ws_cell_location);

source/blender/makesdna/DNA_lightprobe_defaults.h

@@ -21,6 +21,9 @@
     .grid_resolution_y = 4, \
     .grid_resolution_z = 4, \
     .grid_bake_samples = 2048, \
+    .grid_normal_bias = 0.3f, \
+    .grid_view_bias = 0.0f, \
+    .grid_facing_bias = 0.5f, \
     .surfel_density = 1.0f, \
     .distinf = 2.5f, \
     .distpar = 2.5f, \

source/blender/makesdna/DNA_lightprobe_types.h

@@ -57,6 +57,11 @@ typedef struct LightProbe {
   int grid_resolution_z;
   /** Irradiance grid: number of directions to evaluate light transfer in. */
   int grid_bake_samples;
+  /** Irradiance grid: Sampling biases. */
+  float grid_normal_bias;
+  float grid_view_bias;
+  float grid_facing_bias;
+  float _pad0;
 
   /** Surface element density for scene surface cache. In surfel per unit distance. */
   float surfel_density;

source/blender/makesrna/intern/rna_lightprobe.cc

@@ -166,6 +166,32 @@ static void rna_def_lightprobe(BlenderRNA *brna)
       prop, "Resolution Z", "Number of samples along the z axis of the volume");
   RNA_def_property_update(prop, NC_MATERIAL | ND_SHADING, "rna_LightProbe_recalc");
 
+  prop = RNA_def_property(srna, "grid_normal_bias", PROP_FLOAT, PROP_FACTOR);
+  RNA_def_property_ui_text(prop,
+                           "Normal Bias",
+                           "Offset sampling of the irradiance grid in "
+                           "the surface normal direction to reduce light bleeding");
+  RNA_def_property_range(prop, 0.0f, FLT_MAX);
+  RNA_def_property_ui_range(prop, 0.0f, 1.0f, 1, 3);
+  RNA_def_property_update(prop, NC_MATERIAL | ND_SHADING, "rna_LightProbe_recalc");
+
+  prop = RNA_def_property(srna, "grid_view_bias", PROP_FLOAT, PROP_FACTOR);
+  RNA_def_property_ui_text(prop,
+                           "View Bias",
+                           "Offset sampling of the irradiance grid in "
+                           "the viewing direction to reduce light bleeding");
+  RNA_def_property_range(prop, 0.0f, FLT_MAX);
+  RNA_def_property_ui_range(prop, 0.0f, 1.0f, 1, 3);
+  RNA_def_property_update(prop, NC_MATERIAL | ND_SHADING, "rna_LightProbe_recalc");
+
+  prop = RNA_def_property(srna, "grid_irradiance_smoothing", PROP_FLOAT, PROP_FACTOR);
+  RNA_def_property_float_sdna(prop, nullptr, "grid_facing_bias");
+  RNA_def_property_ui_text(
+      prop, "Facing Bias", "Smoother irradiance interpolation but introduce light bleeding");
+  RNA_def_property_range(prop, 0.0f, FLT_MAX);
+  RNA_def_property_ui_range(prop, 0.0f, 1.0f, 1, 3);
+  RNA_def_property_update(prop, NC_MATERIAL | ND_SHADING, "rna_LightProbe_recalc");
+
   prop = RNA_def_property(srna, "grid_bake_samples", PROP_INT, PROP_NONE);
   RNA_def_property_ui_text(
       prop, "Bake Samples", "Number of ray directions to evaluate when baking");