GP: New Armature modifier and tools to handle weights

This commit adds a new armature modifier for grease pencil. The deformations are done reusing the mesh deform routines.

There is also a new operator in weight paint mode to help the artist to generate weights base on armatures. This operator is required because 2D animation workflow is not equal to meshes when parent an object to armatures.

In the drawing engine has been added the option to handle the Fade object parameter used in armatures to see the strokes while move the bones.

When rename bones, all related data of grease pencil is renamed too. This not only affect new armature code, but also layers parented and hook modifiers.

Thanks @aligorith for his review and help.

1 files changed, 4 insertions, 3 deletions

diff --git a/source/blender/blenkernel/intern/gpencil_modifier.c b/source/blender/blenkernel/intern/gpencil_modifier.c
index 1cfbaed37fe..af82d8fa200 100644
--- a/source/blender/blenkernel/intern/gpencil_modifier.c
+++ b/source/blender/blenkernel/intern/gpencil_modifier.c
@@ -423,9 +423,10 @@ void BKE_gpencil_stroke_modifiers(Depsgraph *depsgraph, Object *ob, bGPDlayer *g
 				/* some modifiers could require a recalc of fill triangulation data */
 				if (gpd->flag & GP_DATA_STROKE_FORCE_RECALC) {
 					if (ELEM(md->type,
-						eGpencilModifierType_Hook,
-						eGpencilModifierType_Lattice,
-						eGpencilModifierType_Offset))
+							eGpencilModifierType_Armature,
+							eGpencilModifierType_Hook,
+							eGpencilModifierType_Lattice,
+							eGpencilModifierType_Offset))
 					{
 
 						gps->flag |= GP_STROKE_RECALC_CACHES;