GPencil: Do not hide fading options when uncheked.

# Conflicts:
#	release/scripts/addons
#	release/scripts/addons_contrib

source/blender/gpencil_modifiers/intern/MOD_gpencil_ui_common.c

@@ -206,6 +206,21 @@ void gpencil_modifier_curve_panel_draw(const bContext *UNUSED(C), Panel *panel)
   uiTemplateCurveMapping(layout, ptr, "curve", 0, false, false, false, false);
 }
 
+void gpencil_modifier_fading_draw(const bContext *UNUSED(C), Panel *panel)
+{
+  PointerRNA *ptr = gpencil_modifier_panel_get_property_pointers(panel, NULL);
+
+  uiLayout *layout = panel->layout;
+  uiLayoutSetPropSep(layout, true);
+
+  bool fading_enabled = RNA_boolean_get(ptr, "use_fading");
+  uiItemR(layout, ptr, "object", 0, NULL, ICON_CUBE);
+  uiLayout *sub = uiLayoutColumn(layout, true);
+  uiItemR(sub, ptr, "fading_start", 0, NULL, ICON_NONE);
+  uiItemR(sub, ptr, "fading_end", 0, IFACE_("End"), ICON_NONE);
+  uiItemR(layout, ptr, "fading_end_factor", 0, NULL, ICON_NONE);
+}
+
 /**
  * Draw modifier error message.
  */

source/blender/gpencil_modifiers/intern/MOD_gpencil_ui_common.h

@@ -37,6 +37,8 @@ void gpencil_modifier_masking_panel_draw(Panel *panel, bool use_material, bool u
 void gpencil_modifier_curve_header_draw(const bContext *UNUSED(C), Panel *panel);
 void gpencil_modifier_curve_panel_draw(const bContext *UNUSED(C), Panel *panel);
 
+void gpencil_modifier_fading_draw(const bContext *UNUSED(C), Panel *panel);
+
 void gpencil_modifier_panel_end(struct uiLayout *layout, PointerRNA *ptr);
 
 struct PointerRNA *gpencil_modifier_panel_get_property_pointers(struct Panel *panel,

source/blender/gpencil_modifiers/intern/MOD_gpencilopacity.c

@@ -50,6 +50,8 @@
 #include "BKE_screen.h"
 
 #include "DEG_depsgraph.h"
+#include "DEG_depsgraph_build.h"
+#include "DEG_depsgraph_query.h"
 
 #include "UI_interface.h"
 #include "UI_resources.h"
@@ -87,6 +89,39 @@ static void copyData(const GpencilModifierData *md, GpencilModifierData *target)
   tgmd->curve_intensity = BKE_curvemapping_copy(gmd->curve_intensity);
 }
 
+static float give_opacity_fading_factor(OpacityGpencilModifierData *mmd,
+                                        Object *ob_this,
+                                        float *pos,
+                                        bool apply_obmat)
+{
+  float factor_depth = 1;
+
+  if (((mmd->flag & GP_OPACITY_FADING) == 0) || ((mmd->object) == NULL)) {
+    return factor_depth;
+  }
+
+  float gvert[3];
+  if (apply_obmat) {
+    mul_v3_m4v3(gvert, ob_this->obmat, pos);
+  }
+  float dist = len_v3v3(mmd->object->obmat[3], gvert);
+  float fading_max = MAX2(mmd->fading_start, mmd->fading_end);
+  float fading_min = MIN2(mmd->fading_start, mmd->fading_end);
+
+  /* Better with ratiof() function from line art. */
+  if (dist > fading_max) {
+    factor_depth = 0;
+  }
+  else if (dist <= fading_max && dist > fading_min) {
+    factor_depth = (fading_max - dist) / (fading_max - fading_min);
+  }
+  else {
+    factor_depth = 1;
+  }
+
+  return factor_depth;
+}
+
 /* opacity strokes */
 static void deformStroke(GpencilModifierData *md,
                          Depsgraph *UNUSED(depsgraph),
@@ -125,7 +160,6 @@ static void deformStroke(GpencilModifierData *md,
   for (int i = 0; i < gps->totpoints; i++) {
     bGPDspoint *pt = &gps->points[i];
     MDeformVert *dvert = gps->dvert != NULL ? &gps->dvert[i] : NULL;
-
     /* Stroke using strength. */
     if (mmd->modify_color != GP_MODIFY_COLOR_FILL) {
       /* verify vertex group */
@@ -141,6 +175,9 @@ static void deformStroke(GpencilModifierData *md,
         factor_curve *= BKE_curvemapping_evaluateF(mmd->curve_intensity, 0, value);
       }
 
+      float factor_depth = give_opacity_fading_factor(mmd, ob, &pt->x, true);
+      factor_curve = interpf(mmd->factor, mmd->fading_end_factor, factor_depth);
+
       if (def_nr < 0) {
         if (mmd->flag & GP_OPACITY_NORMALIZE) {
           pt->strength = factor_curve;
@@ -169,7 +206,12 @@ static void deformStroke(GpencilModifierData *md,
 
   /* Fill using opacity factor. */
   if (mmd->modify_color != GP_MODIFY_COLOR_STROKE) {
+
     gps->fill_opacity_fac = mmd->factor;
+
+    float factor_depth = give_opacity_fading_factor(mmd, ob, ob->obmat[3], true);
+    gps->fill_opacity_fac = interpf(mmd->factor, mmd->fading_end_factor, factor_depth);
+
     CLAMP(gps->fill_opacity_fac, 0.0f, 1.0f);
   }
 }
@@ -204,6 +246,16 @@ static void foreachIDLink(GpencilModifierData *md, Object *ob, IDWalkFunc walk,
   OpacityGpencilModifierData *mmd = (OpacityGpencilModifierData *)md;
 
   walk(userData, ob, (ID **)&mmd->material, IDWALK_CB_USER);
+  walk(userData, ob, (ID **)&mmd->object, IDWALK_CB_NOP);
+}
+
+static void updateDepsgraph(GpencilModifierData *md, const ModifierUpdateDepsgraphContext *ctx)
+{
+  OpacityGpencilModifierData *mmd = (OpacityGpencilModifierData *)md;
+  if (mmd->object != NULL) {
+    DEG_add_object_relation(ctx->node, mmd->object, DEG_OB_COMP_TRANSFORM, "Opacity Modifier");
+  }
+  DEG_add_object_relation(ctx->node, ctx->object, DEG_OB_COMP_TRANSFORM, "Opacity Modifier");
 }
 
 static void panel_draw(const bContext *UNUSED(C), Panel *panel)
@@ -231,6 +283,20 @@ static void panel_draw(const bContext *UNUSED(C), Panel *panel)
   gpencil_modifier_panel_end(layout, ptr);
 }
 
+static void fading_header_draw(const bContext *UNUSED(C), Panel *panel)
+{
+  uiLayout *layout = panel->layout;
+
+  PointerRNA *ptr = gpencil_modifier_panel_get_property_pointers(panel, NULL);
+
+  uiItemR(layout, ptr, "use_fading", 0, NULL, ICON_NONE);
+}
+
+static void fading_panel_draw(const bContext *C, Panel *panel)
+{
+  gpencil_modifier_fading_draw(C, panel);
+}
+
 static void mask_panel_draw(const bContext *UNUSED(C), Panel *panel)
 {
   PointerRNA *ptr = gpencil_modifier_panel_get_property_pointers(panel, NULL);
@@ -269,6 +335,8 @@ static void panelRegister(ARegionType *region_type)
 {
   PanelType *panel_type = gpencil_modifier_panel_register(
       region_type, eGpencilModifierType_Opacity, panel_draw);
+  PanelType *fading_panel_type = gpencil_modifier_subpanel_register(
+      region_type, "fading", "", fading_header_draw, fading_panel_draw, panel_type);
   PanelType *mask_panel_type = gpencil_modifier_subpanel_register(
       region_type, "mask", "Influence", NULL, mask_panel_draw, panel_type);
   gpencil_modifier_subpanel_register(
@@ -292,7 +360,7 @@ GpencilModifierTypeInfo modifierType_Gpencil_Opacity = {
     /* initData */ initData,
     /* freeData */ freeData,
     /* isDisabled */ NULL,
-    /* updateDepsgraph */ NULL,
+    /* updateDepsgraph */ updateDepsgraph,
     /* dependsOnTime */ NULL,
     /* foreachIDLink */ foreachIDLink,
     /* foreachTexLink */ NULL,

source/blender/gpencil_modifiers/intern/MOD_gpencilthick.c

@@ -47,6 +47,8 @@
 #include "BKE_screen.h"
 
 #include "DEG_depsgraph.h"
+#include "DEG_depsgraph_build.h"
+#include "DEG_depsgraph_query.h"
 
 #include "UI_interface.h"
 #include "UI_resources.h"
@@ -132,6 +134,29 @@ static void deformStroke(GpencilModifierData *md,
     }
 
     float curvef = 1.0f;
+
+    float factor_depth = 1;
+    if (mmd->flag & GP_THICK_FADING) {
+      if (mmd->object) {
+        float gvert[3];
+        mul_v3_m4v3(gvert, ob->obmat, &pt->x);
+        float dist = len_v3v3(mmd->object->obmat[3], gvert);
+        float fading_max = MAX2(mmd->fading_start, mmd->fading_end);
+        float fading_min = MIN2(mmd->fading_start, mmd->fading_end);
+
+        /* Better with ratiof() function from line art. */
+        if (dist > fading_max) {
+          factor_depth = 0;
+        }
+        else if (dist <= fading_max && dist > fading_min) {
+          factor_depth = (fading_max - dist) / (fading_max - fading_min);
+        }
+        else {
+          factor_depth = 1;
+        }
+      }
+    }
+
     if ((mmd->flag & GP_THICK_CUSTOM_CURVE) && (mmd->curve_thickness)) {
       /* Normalize value to evaluate curve. */
       float value = (float)i / (gps->totpoints - 1);
@@ -148,6 +173,9 @@ static void deformStroke(GpencilModifierData *md,
       weight *= curvef;
     }
 
+    float fac_begin = mmd->flag & GP_THICK_NORMALIZE ? 1 : mmd->thickness_fac;
+    target *= interpf(fac_begin, mmd->fading_end_factor, factor_depth);
+
     pt->pressure = interpf(target, pt->pressure, weight);
 
     CLAMP_MIN(pt->pressure, 0.0f);
@@ -175,6 +203,16 @@ static void foreachIDLink(GpencilModifierData *md, Object *ob, IDWalkFunc walk,
   ThickGpencilModifierData *mmd = (ThickGpencilModifierData *)md;
 
   walk(userData, ob, (ID **)&mmd->material, IDWALK_CB_USER);
+  walk(userData, ob, (ID **)&mmd->object, IDWALK_CB_NOP);
+}
+
+static void updateDepsgraph(GpencilModifierData *md, const ModifierUpdateDepsgraphContext *ctx)
+{
+  ThickGpencilModifierData *mmd = (ThickGpencilModifierData *)md;
+  if (mmd->object != NULL) {
+    DEG_add_object_relation(ctx->node, mmd->object, DEG_OB_COMP_TRANSFORM, "Thickness Modifier");
+  }
+  DEG_add_object_relation(ctx->node, ctx->object, DEG_OB_COMP_TRANSFORM, "Thickness Modifier");
 }
 
 static void panel_draw(const bContext *UNUSED(C), Panel *panel)
@@ -197,6 +235,20 @@ static void panel_draw(const bContext *UNUSED(C), Panel *panel)
   gpencil_modifier_panel_end(layout, ptr);
 }
 
+static void fading_header_draw(const bContext *UNUSED(C), Panel *panel)
+{
+  uiLayout *layout = panel->layout;
+
+  PointerRNA *ptr = gpencil_modifier_panel_get_property_pointers(panel, NULL);
+
+  uiItemR(layout, ptr, "use_fading", 0, NULL, ICON_NONE);
+}
+
+static void fading_panel_draw(const bContext *C, Panel *panel)
+{
+  gpencil_modifier_fading_draw(C, panel);
+}
+
 static void mask_panel_draw(const bContext *UNUSED(C), Panel *panel)
 {
   gpencil_modifier_masking_panel_draw(panel, true, true);
@@ -206,6 +258,8 @@ static void panelRegister(ARegionType *region_type)
 {
   PanelType *panel_type = gpencil_modifier_panel_register(
       region_type, eGpencilModifierType_Thick, panel_draw);
+  PanelType *fading_panel_type = gpencil_modifier_subpanel_register(
+      region_type, "fading", "", fading_header_draw, fading_panel_draw, panel_type);
   PanelType *mask_panel_type = gpencil_modifier_subpanel_register(
       region_type, "mask", "Influence", NULL, mask_panel_draw, panel_type);
   gpencil_modifier_subpanel_register(region_type,
@@ -233,7 +287,7 @@ GpencilModifierTypeInfo modifierType_Gpencil_Thick = {
     /* initData */ initData,
     /* freeData */ freeData,
     /* isDisabled */ NULL,
-    /* updateDepsgraph */ NULL,
+    /* updateDepsgraph */ updateDepsgraph,
     /* dependsOnTime */ NULL,
     /* foreachIDLink */ foreachIDLink,
     /* foreachTexLink */ NULL,

source/blender/makesdna/DNA_gpencil_modifier_defaults.h

@@ -184,6 +184,8 @@
     .layer_pass = 0, \
     .hardeness = 1.0f, \
     .curve_intensity = NULL, \
+    .fading_end = 10.0f, \
+    .fading_end_factor = 0.2f, \
   }
 
 #define _DNA_DEFAULT_SimplifyGpencilModifierData \
@@ -251,6 +253,8 @@
     .thickness_fac = 1.0f, \
     .thickness = 30, \
     .layer_pass = 0, \
+    .fading_end = 10.0f, \
+    .fading_end_factor = 0.2f, \
   }
 
 #define _DNA_DEFAULT_TimeGpencilModifierData \

source/blender/makesdna/DNA_gpencil_modifier_types.h

@@ -177,9 +177,14 @@ typedef struct ThickGpencilModifierData {
   float thickness_fac;
   /** Absolute thickness overide. */
   int thickness;
+  /** Fading reference object */
+  struct Object *object;
+  /** Start/end distances of the fading effect. */
+  float fading_start;
+  float fading_end;
+  float fading_end_factor;
   /** Custom index for passes. */
   int layer_pass;
-  char _pad[4];
   struct CurveMapping *curve_thickness;
 } ThickGpencilModifierData;
 
@@ -191,6 +196,7 @@ typedef enum eThickGpencil_Flag {
   GP_THICK_NORMALIZE = (1 << 4),
   GP_THICK_INVERT_LAYERPASS = (1 << 5),
   GP_THICK_INVERT_MATERIAL = (1 << 6),
+  GP_THICK_FADING = (1 << 7),
 } eThickGpencil_Flag;
 
 typedef struct TimeGpencilModifierData {
@@ -283,9 +289,16 @@ typedef struct OpacityGpencilModifierData {
   int flag;
   /** Main Opacity factor. */
   float factor;
+  /** Fading controlling object */
+  int _pad0;
+  struct Object *object;
+  /** Start/end distances of the fading effect. */
+  float fading_start;
+  float fading_end;
+  float fading_end_factor;
   /** Modify stroke, fill or both. */
   char modify_color;
-  char _pad[3];
+  char _pad1[3];
   /** Custom index for passes. */
   int layer_pass;
 
@@ -301,6 +314,7 @@ typedef enum eOpacityGpencil_Flag {
   GP_OPACITY_INVERT_MATERIAL = (1 << 5),
   GP_OPACITY_CUSTOM_CURVE = (1 << 6),
   GP_OPACITY_NORMALIZE = (1 << 7),
+  GP_OPACITY_FADING = (1 << 8),
 } eOpacityGpencil_Flag;
 
 typedef struct ArrayGpencilModifierData {

source/blender/makesrna/intern/rna_gpencil_modifier.c

@@ -342,6 +342,8 @@ static void greasepencil_modifier_object_set(Object *self,
 RNA_GP_MOD_OBJECT_SET(Armature, object, OB_ARMATURE);
 RNA_GP_MOD_OBJECT_SET(Lattice, object, OB_LATTICE);
 RNA_GP_MOD_OBJECT_SET(Mirror, object, OB_EMPTY);
+RNA_GP_MOD_OBJECT_SET(Opacity, object, OB_EMPTY);
+RNA_GP_MOD_OBJECT_SET(Thick, object, OB_EMPTY);
 
 #  undef RNA_GP_MOD_OBJECT_SET
 
@@ -886,6 +888,38 @@ static void rna_def_modifier_gpencilthick(BlenderRNA *brna)
   RNA_def_property_ui_text(prop, "Thickness Factor", "Factor to multiply the thickness with");
   RNA_def_property_update(prop, 0, "rna_GpencilModifier_update");
 
+  prop = RNA_def_property(srna, "use_fading", PROP_BOOLEAN, PROP_NONE);
+  RNA_def_property_boolean_sdna(prop, NULL, "flag", GP_THICK_FADING);
+  RNA_def_property_ui_text(prop, "Fading", "Fading effect");
+  RNA_def_property_update(prop, 0, "rna_GpencilModifier_update");
+
+  /* Distance reference object */
+  prop = RNA_def_property(srna, "object", PROP_POINTER, PROP_NONE);
+  RNA_def_property_ui_text(prop, "Object", "Object used as distance reference");
+  RNA_def_property_pointer_funcs(prop, NULL, "rna_ThickGpencilModifier_object_set", NULL, NULL);
+  RNA_def_property_flag(prop, PROP_EDITABLE | PROP_ID_SELF_CHECK);
+  RNA_def_property_override_flag(prop, PROPOVERRIDE_OVERRIDABLE_LIBRARY);
+  RNA_def_property_update(prop, 0, "rna_GpencilModifier_dependency_update");
+
+  prop = RNA_def_property(srna, "fading_start", PROP_FLOAT, PROP_NONE);
+  RNA_def_property_float_sdna(prop, NULL, "fading_start");
+  RNA_def_property_ui_range(prop, 0, 1000.0, 1.0, 2);
+  RNA_def_property_ui_text(prop, "Fading Start", "Start distance of fading effect");
+  RNA_def_property_update(prop, 0, "rna_GpencilModifier_update");
+
+  prop = RNA_def_property(srna, "fading_end", PROP_FLOAT, PROP_NONE);
+  RNA_def_property_float_sdna(prop, NULL, "fading_end");
+  RNA_def_property_ui_range(prop, 0, 1000.0, 1.0, 2);
+  RNA_def_property_ui_text(prop, "Fading End", "End distance of fading effect");
+  RNA_def_property_update(prop, 0, "rna_GpencilModifier_update");
+
+  prop = RNA_def_property(srna, "fading_end_factor", PROP_FLOAT, PROP_NONE);
+  RNA_def_property_float_sdna(prop, NULL, "fading_end_factor");
+  RNA_def_property_range(prop, 0.0, FLT_MAX);
+  RNA_def_property_ui_range(prop, 0.0, 10.0, 0.1, 3);
+  RNA_def_property_ui_text(prop, "End Factor", "Fading end thickness factor");
+  RNA_def_property_update(prop, 0, "rna_GpencilModifier_update");
+
   prop = RNA_def_property(srna, "pass_index", PROP_INT, PROP_NONE);
   RNA_def_property_int_sdna(prop, NULL, "pass_index");
   RNA_def_property_range(prop, 0, 100);
@@ -1375,6 +1409,38 @@ static void rna_def_modifier_gpencilopacity(BlenderRNA *brna)
   RNA_def_property_ui_text(prop, "Hardness", "Factor of stroke hardness");
   RNA_def_property_update(prop, 0, "rna_GpencilModifier_update");
 
+  prop = RNA_def_property(srna, "use_fading", PROP_BOOLEAN, PROP_NONE);
+  RNA_def_property_boolean_sdna(prop, NULL, "flag", GP_OPACITY_FADING);
+  RNA_def_property_ui_text(prop, "Fading", "Fading effect");
+  RNA_def_property_update(prop, 0, "rna_GpencilModifier_update");
+
+  /* Distance reference object */
+  prop = RNA_def_property(srna, "object", PROP_POINTER, PROP_NONE);
+  RNA_def_property_ui_text(prop, "Object", "Object used as distance reference");
+  RNA_def_property_pointer_funcs(prop, NULL, "rna_OpacityGpencilModifier_object_set", NULL, NULL);
+  RNA_def_property_flag(prop, PROP_EDITABLE | PROP_ID_SELF_CHECK);
+  RNA_def_property_override_flag(prop, PROPOVERRIDE_OVERRIDABLE_LIBRARY);
+  RNA_def_property_update(prop, 0, "rna_GpencilModifier_dependency_update");
+
+  prop = RNA_def_property(srna, "fading_start", PROP_FLOAT, PROP_NONE);
+  RNA_def_property_float_sdna(prop, NULL, "fading_start");
+  RNA_def_property_ui_range(prop, 0, 1000.0, 1.0, 2);
+  RNA_def_property_ui_text(prop, "Fading Start", "Start distance of fading effect");
+  RNA_def_property_update(prop, 0, "rna_GpencilModifier_update");
+
+  prop = RNA_def_property(srna, "fading_end", PROP_FLOAT, PROP_NONE);
+  RNA_def_property_float_sdna(prop, NULL, "fading_end");
+  RNA_def_property_ui_range(prop, 0, 1000.0, 1.0, 2);
+  RNA_def_property_ui_text(prop, "Fading End", "End distance of fading effect");
+  RNA_def_property_update(prop, 0, "rna_GpencilModifier_update");
+
+  prop = RNA_def_property(srna, "fading_end_factor", PROP_FLOAT, PROP_NONE);
+  RNA_def_property_float_sdna(prop, NULL, "fading_end_factor");
+  RNA_def_property_range(prop, 0.0, FLT_MAX);
+  RNA_def_property_ui_range(prop, 0.0, 10.0, 0.1, 3);
+  RNA_def_property_ui_text(prop, "End Factor", "Fading end thickness factor");
+  RNA_def_property_update(prop, 0, "rna_GpencilModifier_update");
+
   prop = RNA_def_property(srna, "pass_index", PROP_INT, PROP_NONE);
   RNA_def_property_int_sdna(prop, NULL, "pass_index");
   RNA_def_property_range(prop, 0, 100);