Multires: Initial work to get sculpting to work with OpenSubdiv

Allows to go to sculpt mode, do brush strokes, get out of sculpt mode
and have deformation preserved.

The issues currently is that the current implementation of CCG
storage is created from the limit surface, without displacement
taken into account. It is trivial to get displaced coordinates,
but it is more tricky to get displaced normals. This is something
to be solved next.

Another limitation is that this only works for sculpting at a maximal
multires level. There is code to be done to support propagation
of displacement onto a higher levels.

1 files changed, 6 insertions, 1 deletions

diff --git a/source/blender/modifiers/intern/MOD_multires.c b/source/blender/modifiers/intern/MOD_multires.c
index ca62560caa8..813ce830b04 100644
--- a/source/blender/modifiers/intern/MOD_multires.c
+++ b/source/blender/modifiers/intern/MOD_multires.c
@@ -200,6 +200,7 @@ static Mesh *multires_as_ccg(MultiresModifierData *mmd,
 	if (ccg_settings.resolution < 3) {
 		return result;
 	}
+	BKE_subdiv_displacement_attach_from_multires(subdiv, mesh, mmd);
 	result = BKE_subdiv_to_ccg_mesh(subdiv, &ccg_settings, mesh);
 	return result;
 }
@@ -226,7 +227,11 @@ static Mesh *applyModifier_subdiv(ModifierData *md,
 	 * a wrong impression that things do work, even though crucial areas are
 	 * still missing in implementation.
 	 */
-	if ((ctx->object->mode & OB_MODE_SCULPT) && G.debug_value == 128) {
+	const bool for_orco = (ctx->flag & MOD_APPLY_ORCO) != 0;
+	if ((ctx->object->mode & OB_MODE_SCULPT) &&
+	    G.debug_value == 128 &&
+	    !for_orco)
+	{
 		/* NOTE: CCG takes ownership over Subdiv. */
 		result = multires_as_ccg(mmd, ctx, mesh, subdiv);
 		// BKE_subdiv_stats_print(&subdiv->stats);