GPencil: Add randomize options to Length modifier

This patch adds a randomize factor for the start/end lengths in the Length modifier.

Reviewed By: #grease_pencil, antoniov, pepeland, HooglyBoogly

Differential Revision: https://developer.blender.org/D12928

4 files changed, 153 insertions, 5 deletions

diff --git a/source/blender/gpencil_modifiers/intern/MOD_gpencillength.c b/source/blender/gpencil_modifiers/intern/MOD_gpencillength.c
index 80b60547e92..af0067e06aa 100644
--- a/source/blender/gpencil_modifiers/intern/MOD_gpencillength.c
+++ b/source/blender/gpencil_modifiers/intern/MOD_gpencillength.c
@@ -23,8 +23,10 @@
 
 #include <stdio.h>
 
+#include "BLI_hash.h"
 #include "BLI_listbase.h"
 #include "BLI_math.h"
+#include "BLI_rand.h"
 #include "BLI_utildefines.h"
 
 #include "BLT_translation.h"
@@ -56,6 +58,7 @@
 #include "MOD_gpencil_util.h"
 
 #include "DEG_depsgraph.h"
+#include "DEG_depsgraph_query.h"
 
 static void initData(GpencilModifierData *md)
 {
@@ -71,6 +74,20 @@ static void copyData(const GpencilModifierData *md, GpencilModifierData *target)
   BKE_gpencil_modifier_copydata_generic(md, target);
 }
 
+static float *noise_table(int len, int offset, int seed)
+{
+  float *table = MEM_callocN(sizeof(float) * len, __func__);
+  for (int i = 0; i < len; i++) {
+    table[i] = BLI_hash_int_01(BLI_hash_int_2d(seed, i + offset + 1));
+  }
+  return table;
+}
+
+BLI_INLINE float table_sample(float *table, float x)
+{
+  return interpf(table[(int)ceilf(x)], table[(int)floor(x)], fractf(x));
+}
+
 static bool gpencil_modify_stroke(bGPDstroke *gps,
                                   const float length,
                                   const float overshoot_fac,
@@ -104,9 +121,15 @@ static bool gpencil_modify_stroke(bGPDstroke *gps,
   return changed;
 }
 
-static void applyLength(LengthGpencilModifierData *lmd, bGPdata *gpd, bGPDstroke *gps)
+static void applyLength(GpencilModifierData *md,
+                        Depsgraph *depsgraph,
+                        bGPdata *gpd,
+                        bGPDframe *gpf,
+                        bGPDstroke *gps,
+                        Object *ob)
 {
   bool changed = false;
+  LengthGpencilModifierData *lmd = (LengthGpencilModifierData *)md;
   const float len = (lmd->mode == GP_LENGTH_ABSOLUTE) ? 1.0f :
                                                         BKE_gpencil_stroke_length(gps, true);
   const int totpoints = gps->totpoints;
@@ -120,11 +143,48 @@ static void applyLength(LengthGpencilModifierData *lmd, bGPdata *gpd, bGPDstroke
   int first_mode = 1;
   float second_fac = lmd->end_fac;
   int second_mode = 2;
+
+  float rand[2] = {0.0f, 0.0f};
+  if (lmd->rand_start_fac != 0.0 || lmd->rand_end_fac != 0.0) {
+    int seed = lmd->seed;
+
+    /* Make sure different modifiers get different seeds. */
+    seed += BLI_hash_string(ob->id.name + 2);
+    seed += BLI_hash_string(md->name);
+
+    if (lmd->flag & GP_LENGTH_USE_RANDOM) {
+      seed += ((int)DEG_get_ctime(depsgraph)) / lmd->step;
+    }
+
+    float rand_offset = BLI_hash_int_01(seed);
+
+    /* Get stroke index for random offset. */
+    int rnd_index = BLI_findindex(&gpf->strokes, gps);
+    const uint primes[2] = {2, 3};
+    double offset[2] = {0.0f, 0.0f};
+    double r[2];
+
+    float *noise_table_length = noise_table(4, (int)floor(lmd->rand_offset), seed + 2);
+
+    /* To ensure a nice distribution, we use halton sequence and offset using the seed. */
+    BLI_halton_2d(primes, offset, rnd_index, r);
+    for (int j = 0; j < 2; j++) {
+      float noise = table_sample(noise_table_length, j * 2 + fractf(lmd->rand_offset));
+
+      rand[j] = fmodf(r[j] + rand_offset, 1.0f);
+      rand[j] = fabs(fmodf(sin(rand[j] * 12.9898f + j * 78.233f) * 43758.5453f, 1.0f) + noise);
+    }
+
+    MEM_SAFE_FREE(noise_table_length);
+
+    first_fac = first_fac + rand[0] * lmd->rand_start_fac;
+    second_fac = second_fac + rand[1] * lmd->rand_end_fac;
+  }
+
   if (first_fac < 0) {
     SWAP(float, first_fac, second_fac);
     SWAP(int, first_mode, second_mode);
   }
-
   const int first_extra_point_count = ceil(first_fac * lmd->point_density);
   const int second_extra_point_count = ceil(second_fac * lmd->point_density);
 
@@ -161,10 +221,10 @@ static void applyLength(LengthGpencilModifierData *lmd, bGPdata *gpd, bGPDstroke
 }
 
 static void deformStroke(GpencilModifierData *md,
-                         Depsgraph *UNUSED(depsgraph),
+                         Depsgraph *depsgraph,
                          Object *ob,
                          bGPDlayer *gpl,
-                         bGPDframe *UNUSED(gpf),
+                         bGPDframe *gpf,
                          bGPDstroke *gps)
 {
   bGPdata *gpd = ob->data;
@@ -187,7 +247,7 @@ static void deformStroke(GpencilModifierData *md,
     /* Don't affect cyclic strokes as they have no start/end. */
     return;
   }
-  applyLength(lmd, gpd, gps);
+  applyLength(md, depsgraph, gpd, gpf, gps, ob);
 }
 
 static void bakeModifier(Main *UNUSED(bmain),
@@ -214,6 +274,39 @@ static void foreachIDLink(GpencilModifierData *md, Object *ob, IDWalkFunc walk,
   walk(userData, ob, (ID **)&mmd->material, IDWALK_CB_USER);
 }
 
+static void random_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_random", 0, IFACE_("Randomize"), ICON_NONE);
+}
+
+static void random_panel_draw(const bContext *UNUSED(C), Panel *panel)
+{
+  uiLayout *layout = panel->layout;
+
+  PointerRNA *ptr = gpencil_modifier_panel_get_property_pointers(panel, NULL);
+
+  uiLayoutSetPropSep(layout, true);
+
+  uiLayoutSetActive(layout, RNA_boolean_get(ptr, "use_random"));
+
+  uiItemR(layout, ptr, "step", 0, NULL, ICON_NONE);
+}
+
+static void offset_panel_draw(const bContext *UNUSED(C), Panel *panel)
+{
+  uiLayout *layout = panel->layout;
+  PointerRNA *ptr = gpencil_modifier_panel_get_property_pointers(panel, NULL);
+  uiLayoutSetPropSep(layout, true);
+  uiItemR(layout, ptr, "random_start_factor", 0, IFACE_("Random Offset Start"), ICON_NONE);
+  uiItemR(layout, ptr, "random_end_factor", 0, IFACE_("Random Offset End"), ICON_NONE);
+  uiItemR(layout, ptr, "random_offset", 0, NULL, ICON_NONE);
+  uiItemR(layout, ptr, "seed", 0, NULL, ICON_NONE);
+}
+
 static void panel_draw(const bContext *UNUSED(C), Panel *panel)
 {
   uiLayout *layout = panel->layout;
@@ -277,6 +370,10 @@ static void panelRegister(ARegionType *region_type)
       region_type, eGpencilModifierType_Length, panel_draw);
   gpencil_modifier_subpanel_register(
       region_type, "curvature", "", curvature_header_draw, curvature_panel_draw, panel_type);
+  PanelType *offset_panel = gpencil_modifier_subpanel_register(
+      region_type, "offset", "Random Offsets", NULL, offset_panel_draw, panel_type);
+  gpencil_modifier_subpanel_register(
+      region_type, "randomize", "", random_header_draw, random_panel_draw, offset_panel);
   gpencil_modifier_subpanel_register(
       region_type, "mask", "Influence", NULL, mask_panel_draw, panel_type);
 }
diff --git a/source/blender/makesdna/DNA_gpencil_modifier_defaults.h b/source/blender/makesdna/DNA_gpencil_modifier_defaults.h
index e0947085694..88eb164c2b4 100644
--- a/source/blender/makesdna/DNA_gpencil_modifier_defaults.h
+++ b/source/blender/makesdna/DNA_gpencil_modifier_defaults.h
@@ -333,6 +333,11 @@
     .point_density = 30.0f,\
     .segment_influence = 0.0f,\
     .max_angle = DEG2RAD(170.0f),\
+    .rand_start_fac = 0.0f,\
+    .rand_end_fac = 0.0f,\
+    .rand_offset = 0.0f,\
+    .seed = 0,\
+    .step = 4,\
   }
 
 #define _DNA_DEFAULT_DashGpencilModifierData \
diff --git a/source/blender/makesdna/DNA_gpencil_modifier_types.h b/source/blender/makesdna/DNA_gpencil_modifier_types.h
index f7964e1f2fa..0f69a256f56 100644
--- a/source/blender/makesdna/DNA_gpencil_modifier_types.h
+++ b/source/blender/makesdna/DNA_gpencil_modifier_types.h
@@ -492,10 +492,17 @@ typedef struct LengthGpencilModifierData {
   int layer_pass;
   /** Length. */
   float start_fac, end_fac;
+  /** Random length factors. */
+  float rand_start_fac, rand_end_fac, rand_offset;
   /** Overshoot trajectory factor. */
   float overshoot_fac;
+  /** (first element is the index) random values. */
+  int seed;
+  /** How many frames before recalculate randoms. */
+  int step;
   /** Modifier mode. */
   int mode;
+  char _pad[4];
   /* Curvature parameters. */
   float point_density;
   float segment_influence;
@@ -509,6 +516,7 @@ typedef enum eLengthGpencil_Flag {
   GP_LENGTH_INVERT_MATERIAL = (1 << 3),
   GP_LENGTH_USE_CURVATURE = (1 << 4),
   GP_LENGTH_INVERT_CURVATURE = (1 << 5),
+  GP_LENGTH_USE_RANDOM = (1 << 6),
 } eLengthGpencil_Flag;
 
 typedef enum eLengthGpencil_Type {
diff --git a/source/blender/makesrna/intern/rna_gpencil_modifier.c b/source/blender/makesrna/intern/rna_gpencil_modifier.c
index 72401b460be..7ca77e1c290 100644
--- a/source/blender/makesrna/intern/rna_gpencil_modifier.c
+++ b/source/blender/makesrna/intern/rna_gpencil_modifier.c
@@ -3488,6 +3488,44 @@ static void rna_def_modifier_gpencillength(BlenderRNA *brna)
   RNA_def_property_ui_text(prop, "End Factor", "Absolute added length to the end of each stroke");
   RNA_def_property_update(prop, 0, "rna_GpencilModifier_update");
 
+  prop = RNA_def_property(srna, "random_start_factor", PROP_FLOAT, PROP_NONE);
+  RNA_def_property_float_sdna(prop, NULL, "rand_start_fac");
+  RNA_def_property_ui_range(prop, -10.0f, 10.0f, 0.1, 1);
+  RNA_def_property_ui_text(prop,
+                           "Random Start Factor",
+                           "Size of random length added to the start of each stroke");
+  RNA_def_property_update(prop, 0, "rna_GpencilModifier_update");
+
+  prop = RNA_def_property(srna, "random_end_factor", PROP_FLOAT, PROP_NONE);
+  RNA_def_property_float_sdna(prop, NULL, "rand_end_fac");
+  RNA_def_property_ui_range(prop, -10.0f, 10.0f, 0.1, 1);
+  RNA_def_property_ui_text(
+      prop, "Random End Factor", "Size of random length added to the end of each stroke");
+  RNA_def_property_update(prop, 0, "rna_GpencilModifier_update");
+
+  prop = RNA_def_property(srna, "random_offset", PROP_FLOAT, PROP_NONE);
+  RNA_def_property_float_sdna(prop, NULL, "rand_offset");
+  RNA_def_property_ui_range(prop, 0.0f, 100.0f, 0.1, 3);
+  RNA_def_property_ui_text(
+      prop, "Random Noise Offset", "Smoothly offset each stroke's random value");
+  RNA_def_property_update(prop, 0, "rna_GpencilModifier_update");
+
+  prop = RNA_def_property(srna, "use_random", PROP_BOOLEAN, PROP_NONE);
+  RNA_def_property_boolean_sdna(prop, NULL, "flag", GP_LENGTH_USE_RANDOM);
+  RNA_def_property_ui_text(prop, "Random", "Use random values over time");
+  RNA_def_property_update(prop, 0, "rna_GpencilModifier_update");
+
+  prop = RNA_def_property(srna, "seed", PROP_INT, PROP_UNSIGNED);
+  RNA_def_property_ui_text(prop, "Seed", "Random seed");
+  RNA_def_property_update(prop, 0, "rna_GpencilModifier_update");
+
+  prop = RNA_def_property(srna, "step", PROP_INT, PROP_NONE);
+  RNA_def_property_int_sdna(prop, NULL, "step");
+  RNA_def_property_range(prop, 1, 100);
+  RNA_def_property_ui_text(
+      prop, "Step", "Number of frames before recalculate random values again");
+  RNA_def_property_update(prop, 0, "rna_GpencilModifier_update");
+
   prop = RNA_def_property(srna, "overshoot_factor", PROP_FLOAT, PROP_FACTOR);
   RNA_def_property_float_sdna(prop, NULL, "overshoot_fac");
   RNA_def_property_range(prop, 0.0f, 1.0f);