Fix for [#26133] Explode modifier doesn't care about UVs (Option "split edges")

* This is basically a total rewrite of the edge split algorithm. The old one didn't handle tris at all and quads were cut wrong in some cases too with the addition of not handling uv coordinates at all.
* This new algorithm uses a flag system to categorize different splits and the identical but rotated cases in a similar way to how marching cubes indexes different cases.
* It cuts quads and tris and creates proper uv's for the new faces too.
* I also renamed the option to "edge cut" to differentiate if from the edge split modifier and added an option to override a uv-channel in the exploded mesh with particle age as x-coordinate so that the shrapnel can be faded out nicely etc.

1 files changed, 9 insertions, 3 deletions

diff --git a/source/blender/makesrna/intern/rna_modifier.c b/source/blender/makesrna/intern/rna_modifier.c
index 07db55ecba3..3c77ab63821 100644
--- a/source/blender/makesrna/intern/rna_modifier.c
+++ b/source/blender/makesrna/intern/rna_modifier.c
@@ -1720,9 +1720,9 @@ static void rna_def_modifier_explode(BlenderRNA *brna)
 	RNA_def_property_ui_text(prop, "Protect", "Clean vertex group edges");
 	RNA_def_property_update(prop, 0, "rna_Modifier_update");
 
-	prop= RNA_def_property(srna, "use_edge_split", PROP_BOOLEAN, PROP_NONE);
-	RNA_def_property_boolean_sdna(prop, NULL, "flag", eExplodeFlag_EdgeSplit);
-	RNA_def_property_ui_text(prop, "Split Edges", "Split face edges for nicer shrapnel");
+	prop= RNA_def_property(srna, "use_edge_cut", PROP_BOOLEAN, PROP_NONE);
+	RNA_def_property_boolean_sdna(prop, NULL, "flag", eExplodeFlag_EdgeCut);
+	RNA_def_property_ui_text(prop, "Cut Edges", "Cut face edges for nicer shrapnel");
 	RNA_def_property_update(prop, 0, "rna_Modifier_update");
 
 	prop= RNA_def_property(srna, "show_unborn", PROP_BOOLEAN, PROP_NONE);
@@ -1744,6 +1744,12 @@ static void rna_def_modifier_explode(BlenderRNA *brna)
 	RNA_def_property_boolean_sdna(prop, NULL, "flag", eExplodeFlag_PaSize);
 	RNA_def_property_ui_text(prop, "Size", "Use particle size for the shrapnel");
 	RNA_def_property_update(prop, 0, "rna_Modifier_update");
+
+	prop= RNA_def_property(srna, "particle_uv", PROP_STRING, PROP_NONE);
+	RNA_def_property_string_sdna(prop, NULL, "uvname");
+	RNA_def_property_string_maxlength(prop, 32);
+	RNA_def_property_ui_text(prop, "Particle UV", "UV Layer to change with particle age");
+	RNA_def_property_update(prop, 0, "rna_Modifier_update");
 }
 
 static void rna_def_modifier_cloth(BlenderRNA *brna)