GPencil: Per-layer option to always show onion skinning

Sometimes it can be useful to be able to keep onion skins visible in the
OpenGL renders and/or when doing animation playback. In particular, there
are two use cases where this is quite useful:
 1) For creating a cheap motion-blur effect, especially when the before/after
    values are also animated.
 2) If you've animated a shot with onion skinning enabled, the poses may end
    up looking odd if the ghosts are not shown (as you may have been accounting
    for the ghosts when making the compositions).

This option can be found as the small "camera" toggle between the "Use Onion Skinning"
and "Use Custom Colors" options.

1 files changed, 7 insertions, 0 deletions

diff --git a/source/blender/makesrna/intern/rna_gpencil.c b/source/blender/makesrna/intern/rna_gpencil.c
index 41a73cfc528..14da990278c 100644
--- a/source/blender/makesrna/intern/rna_gpencil.c
+++ b/source/blender/makesrna/intern/rna_gpencil.c
@@ -1242,6 +1242,13 @@ static void rna_def_gpencil_layer(BlenderRNA *brna)
 	RNA_def_property_ui_text(prop, "After Color", "Base color for ghosts after the active frame");
 	RNA_def_property_update(prop, NC_GPENCIL | ND_DATA, "rna_GPencil_update");
 	
+	prop = RNA_def_property(srna, "use_ghosts_always", PROP_BOOLEAN, PROP_NONE);
+	RNA_def_property_boolean_sdna(prop, NULL, "flag", GP_LAYER_GHOST_ALWAYS);
+	RNA_def_property_ui_text(prop, "Always Show Ghosts",
+	                         "Ghosts are shown in renders and animation playback. Useful for special effects (e.g. motion blur)");
+	RNA_def_property_update(prop, NC_GPENCIL | ND_DATA, "rna_GPencil_update");
+	
+	
 	/* Flags */
 	prop = RNA_def_property(srna, "hide", PROP_BOOLEAN, PROP_NONE);
 	RNA_def_property_boolean_sdna(prop, NULL, "flag", GP_LAYER_HIDE);