Add an option to mesh.calc_tessface() to get rid of polygons and loops

The purpose of this change is to add extra possibility to render engines and
export scripts to reduce peak memory footprint during their operation.

This new argument should be used with care since it'll leave mesh in not really
compatible with blender format, but it's ok to be used on temp meshes.

Unfortunately, it's hard to get scene where it'll show huge benefit because
in my tests with cycles peak memory is reached in MEM_printmemlist_stats().

However, in the file with sintel dragon it gives around 1gig of memory benefit
after removing the polys which would allow other heavy to compute stuff such as
hair (or even pointiness calculation) to not be a peak memory usage.

In any case, this change is nice to have IMO, and only means more parts of
scene export code should be optimized memory-wise.

Reviewers: campbellbarton

Differential Revision: https://developer.blender.org/D1125

1 files changed, 10 insertions, 1 deletions

diff --git a/source/blender/makesrna/intern/rna_mesh_api.c b/source/blender/makesrna/intern/rna_mesh_api.c
index 3f487698420..a994bf5e9d1 100644
--- a/source/blender/makesrna/intern/rna_mesh_api.c
+++ b/source/blender/makesrna/intern/rna_mesh_api.c
@@ -141,6 +141,11 @@ static void rna_Mesh_free_tangents(Mesh *mesh)
 	CustomData_free_layers(&mesh->ldata, CD_MLOOPTANGENT, mesh->totloop);
 }
 
+static void rna_Mesh_calc_tessface(Mesh *mesh, int free_mpoly)
+{
+	ED_mesh_calc_tessface(mesh, free_mpoly != 0);
+}
+
 static void rna_Mesh_calc_smooth_groups(Mesh *mesh, int use_bitflags, int *r_poly_group_len,
                                         int **r_poly_group, int *r_group_total)
 {
@@ -269,8 +274,12 @@ void RNA_api_mesh(StructRNA *srna)
 	func = RNA_def_function(srna, "free_tangents", "rna_Mesh_free_tangents");
 	RNA_def_function_ui_description(func, "Free tangents");
 
-	func = RNA_def_function(srna, "calc_tessface", "ED_mesh_calc_tessface");
+	func = RNA_def_function(srna, "calc_tessface", "rna_Mesh_calc_tessface");
 	RNA_def_function_ui_description(func, "Calculate face tessellation (supports editmode too)");
+	RNA_def_boolean(func, "free_mpoly", 0, "Free MPoly", "Free data used by polygons and loops. "
+	                "WARNING: This destructive operation removes regular faces, "
+	                "only used on temporary mesh data-blocks to reduce memory footprint of render "
+	                "engines and export scripts.");
 
 	func = RNA_def_function(srna, "calc_smooth_groups", "rna_Mesh_calc_smooth_groups");
 	RNA_def_function_ui_description(func, "Calculate smooth groups from sharp edges");