Gpencil Noise - Add noise offset parameter

This patch adds a noise offset option to the grease pencil noise modifier.
It allows the user to animate the noise along the length of the stroke to create movement that is currently not possible.

It works by adding an offset to the noise table and adding the remaining floating point value to the noise table sampling.

Reviewed By: #grease_pencil

Differential Revision: https://developer.blender.org/D10021

4 files changed, 33 insertions, 11 deletions

diff --git a/source/blender/gpencil_modifiers/intern/MOD_gpencilnoise.c b/source/blender/gpencil_modifiers/intern/MOD_gpencilnoise.c
index a65f1bf6d26..f80ad60eb07 100644
--- a/source/blender/gpencil_modifiers/intern/MOD_gpencilnoise.c
+++ b/source/blender/gpencil_modifiers/intern/MOD_gpencilnoise.c
@@ -110,11 +110,11 @@ static bool dependsOnTime(GpencilModifierData *md)
   return (mmd->flag & GP_NOISE_USE_RANDOM) != 0;
 }
 
-static float *noise_table(int len, int seed)
+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 + 1));
+    table[i] = BLI_hash_int_01(BLI_hash_int_2d(seed, i + offset + 1));
   }
   return table;
 }
@@ -172,11 +172,19 @@ static void deformStroke(GpencilModifierData *md,
   /* Sanitize as it can create out of bound reads. */
   float noise_scale = clamp_f(mmd->noise_scale, 0.0f, 1.0f);
 
-  int len = ceilf(gps->totpoints * noise_scale) + 1;
-  float *noise_table_position = (mmd->factor > 0.0f) ? noise_table(len, seed + 2) : NULL;
-  float *noise_table_strength = (mmd->factor_strength > 0.0f) ? noise_table(len, seed + 3) : NULL;
-  float *noise_table_thickness = (mmd->factor_thickness > 0.0f) ? noise_table(len, seed) : NULL;
-  float *noise_table_uvs = (mmd->factor_uvs > 0.0f) ? noise_table(len, seed + 4) : NULL;
+  int len = ceilf(gps->totpoints * noise_scale) + 2;
+  float *noise_table_position = (mmd->factor > 0.0f) ?
+                                    noise_table(len, (int)floor(mmd->noise_offset), seed + 2) :
+                                    NULL;
+  float *noise_table_strength = (mmd->factor_strength > 0.0f) ?
+                                    noise_table(len, (int)floor(mmd->noise_offset), seed + 3) :
+                                    NULL;
+  float *noise_table_thickness = (mmd->factor_thickness > 0.0f) ?
+                                     noise_table(len, (int)floor(mmd->noise_offset), seed) :
+                                     NULL;
+  float *noise_table_uvs = (mmd->factor_uvs > 0.0f) ?
+                               noise_table(len, (int)floor(mmd->noise_offset), seed + 4) :
+                               NULL;
 
   /* Calculate stroke normal. */
   if (gps->totpoints > 2) {
@@ -225,24 +233,27 @@ static void deformStroke(GpencilModifierData *md,
       cross_v3_v3v3(vec2, vec1, normal);
       normalize_v3(vec2);
 
-      float noise = table_sample(noise_table_position, i * noise_scale);
+      float noise = table_sample(noise_table_position,
+                                 i * noise_scale + fractf(mmd->noise_offset));
       madd_v3_v3fl(&pt->x, vec2, (noise * 2.0f - 1.0f) * weight * mmd->factor * 0.1f);
     }
 
     if (mmd->factor_thickness > 0.0f) {
-      float noise = table_sample(noise_table_thickness, i * noise_scale);
+      float noise = table_sample(noise_table_thickness,
+                                 i * noise_scale + fractf(mmd->noise_offset));
       pt->pressure *= max_ff(1.0f + (noise * 2.0f - 1.0f) * weight * mmd->factor_thickness, 0.0f);
       CLAMP_MIN(pt->pressure, GPENCIL_STRENGTH_MIN);
     }
 
     if (mmd->factor_strength > 0.0f) {
-      float noise = table_sample(noise_table_strength, i * noise_scale);
+      float noise = table_sample(noise_table_strength,
+                                 i * noise_scale + fractf(mmd->noise_offset));
       pt->strength *= max_ff(1.0f - noise * weight * mmd->factor_strength, 0.0f);
       CLAMP(pt->strength, GPENCIL_STRENGTH_MIN, 1.0f);
     }
 
     if (mmd->factor_uvs > 0.0f) {
-      float noise = table_sample(noise_table_uvs, i * noise_scale);
+      float noise = table_sample(noise_table_uvs, i * noise_scale + fractf(mmd->noise_offset));
       pt->uv_rot += (noise * 2.0f - 1.0f) * weight * mmd->factor_uvs * M_PI_2;
       CLAMP(pt->uv_rot, -M_PI_2, M_PI_2);
     }
@@ -292,6 +303,7 @@ static void panel_draw(const bContext *UNUSED(C), Panel *panel)
   uiItemR(col, ptr, "factor_thickness", 0, IFACE_("Thickness"), ICON_NONE);
   uiItemR(col, ptr, "factor_uvs", 0, IFACE_("UV"), ICON_NONE);
   uiItemR(col, ptr, "noise_scale", 0, NULL, ICON_NONE);
+  uiItemR(col, ptr, "noise_offset", 0, NULL, ICON_NONE);
   uiItemR(col, ptr, "seed", 0, NULL, ICON_NONE);
 
   gpencil_modifier_panel_end(layout, ptr);
diff --git a/source/blender/makesdna/DNA_gpencil_modifier_defaults.h b/source/blender/makesdna/DNA_gpencil_modifier_defaults.h
index fdb77bfd196..399bf6f0a6d 100644
--- a/source/blender/makesdna/DNA_gpencil_modifier_defaults.h
+++ b/source/blender/makesdna/DNA_gpencil_modifier_defaults.h
@@ -152,6 +152,7 @@
     .factor_thickness = 0.0f, \
     .factor_uvs = 0.0f, \
     .noise_scale = 0.0f, \
+    .noise_offset = 0.0f, \
     .step = 4, \
     .layer_pass = 0, \
     .seed = 1, \
diff --git a/source/blender/makesdna/DNA_gpencil_modifier_types.h b/source/blender/makesdna/DNA_gpencil_modifier_types.h
index 9ac40495887..1f7283a1c70 100644
--- a/source/blender/makesdna/DNA_gpencil_modifier_types.h
+++ b/source/blender/makesdna/DNA_gpencil_modifier_types.h
@@ -107,6 +107,8 @@ typedef struct NoiseGpencilModifierData {
   float factor_uvs;
   /** Noise Frequency scaling */
   float noise_scale;
+  float noise_offset;
+  char _pad[4];
   /** How many frames before recalculate randoms. */
   int step;
   /** Custom index for passes. */
diff --git a/source/blender/makesrna/intern/rna_gpencil_modifier.c b/source/blender/makesrna/intern/rna_gpencil_modifier.c
index fb505d9a1fa..71d5a53adb2 100644
--- a/source/blender/makesrna/intern/rna_gpencil_modifier.c
+++ b/source/blender/makesrna/intern/rna_gpencil_modifier.c
@@ -498,6 +498,13 @@ static void rna_def_modifier_gpencilnoise(BlenderRNA *brna)
   RNA_def_property_ui_text(prop, "Noise Scale", "Scale the noise frequency");
   RNA_def_property_update(prop, 0, "rna_GpencilModifier_update");
 
+  prop = RNA_def_property(srna, "noise_offset", PROP_FLOAT, PROP_FACTOR);
+  RNA_def_property_float_sdna(prop, NULL, "noise_offset");
+  RNA_def_property_range(prop, 0.0, FLT_MAX);
+  RNA_def_property_ui_range(prop, 0.0, 100.0, 0.1, 3);
+  RNA_def_property_ui_text(prop, "Noise Offset", "Offset the noise along the strokes");
+  RNA_def_property_update(prop, 0, "rna_GpencilModifier_update");
+
   prop = RNA_def_property(srna, "use_custom_curve", PROP_BOOLEAN, PROP_NONE);
   RNA_def_property_boolean_sdna(prop, NULL, "flag", GP_NOISE_CUSTOM_CURVE);
   RNA_def_property_ui_text(