[Bf-codereview] Skip subsurf normal allocation/calculation when not needed (issue 5555058)

[NicholasBishop at gmail.com]

Reviewers: bf-codereview_blender.org,

Description:
CCGSubsurf has already a function to disable calculation of normals, but
seems it wasn't used. This patch changes subsurf UV and
subsurf_calculate_limit_positions() to not calculate normals, and also
not allocate space for them.

Should be no functional changes, just a small speedup/less memory use
during subdivision for these cases.

Please review this at http://codereview.appspot.com/5555058/

Affected files:
   source/blender/blenkernel/intern/subsurf_ccg.c


Index: source/blender/blenkernel/intern/subsurf_ccg.c
===================================================================
--- source/blender/blenkernel/intern/subsurf_ccg.c        (revision 43549)
+++ source/blender/blenkernel/intern/subsurf_ccg.c     (working copy)
@@ -95,6 +95,7 @@ static void arena_release(CCGAllocatorHDL a) {
  typedef enum {
  	CCG_USE_AGING = 1,
  	CCG_USE_ARENA = 2,
+	CCG_CALC_NORMALS = 4,
  } CCGFlags;

  static CCGSubSurf *_getSubSurf(CCGSubSurf *prevSS, int subdivLevels,  
CCGFlags flags) {
@@ -125,7 +126,7 @@ static CCGSubSurf *_getSubSurf(CCGSubSurf *prevSS, int  
subdivLevels, CCGFlags fl
  	} else {
  		ifc.vertUserSize = ifc.edgeUserSize = ifc.faceUserSize = 8;
  	}
-	ifc.vertDataSize = sizeof(DMGridData);
+	ifc.vertDataSize = sizeof(float) * (flags & CCG_CALC_NORMALS ? 6 : 3);

  	if (useArena) {
  		CCGAllocatorIFC allocatorIFC;
@@ -145,7 +146,10 @@ static CCGSubSurf *_getSubSurf(CCGSubSurf *prevSS, int  
subdivLevels, CCGFlags fl
  		ccgSubSurf_setUseAgeCounts(ccgSS, 1, 8, 8, 8);
  	}

-	ccgSubSurf_setCalcVertexNormals(ccgSS, 1, offsetof(DMGridData, no));
+	if (flags & CCG_CALC_NORMALS)
+		ccgSubSurf_setCalcVertexNormals(ccgSS, 1, offsetof(DMGridData, no));
+	else
+		ccgSubSurf_setCalcVertexNormals(ccgSS, 0, 0);

  	return ccgSS;
  }
@@ -359,14 +363,14 @@ static void set_subsurf_uv(CCGSubSurf *ss,  
DerivedMesh *dm, DerivedMesh *result,
  		int numVerts = ccgSubSurf_getFaceNumVerts(f);

  		for (S=0; S<numVerts; S++) {
-			DMGridData *faceGridData= ccgSubSurf_getFaceGridDataArray(uvss, f, S);
+			float (*faceGridData)[3]= ccgSubSurf_getFaceGridDataArray(uvss, f, S);

  			for(y = 0; y < gridFaces; y++) {
  				for(x = 0; x < gridFaces; x++) {
-					copy_v2_v2(tf->uv[0], faceGridData[(y + 0)*gridSize + x + 0].co);
-					copy_v2_v2(tf->uv[1], faceGridData[(y + 1)*gridSize + x + 0].co);
-					copy_v2_v2(tf->uv[2], faceGridData[(y + 1)*gridSize + x + 1].co);
-					copy_v2_v2(tf->uv[3], faceGridData[(y + 0)*gridSize + x + 1].co);
+					copy_v2_v2(tf->uv[0], faceGridData[(y + 0)*gridSize + x + 0]);
+					copy_v2_v2(tf->uv[1], faceGridData[(y + 1)*gridSize + x + 0]);
+					copy_v2_v2(tf->uv[2], faceGridData[(y + 1)*gridSize + x + 1]);
+					copy_v2_v2(tf->uv[3], faceGridData[(y + 0)*gridSize + x + 1]);

  					tf++;
  				}
@@ -2787,7 +2791,7 @@ struct DerivedMesh *subsurf_make_derived_from_derived(
  	if(forEditMode) {
  		int levels= (smd->modifier.scene)?  
get_render_subsurf_level(&smd->modifier.scene->r, smd->levels): smd->levels;

-		smd->emCache = _getSubSurf(smd->emCache, levels, useAging);
+		smd->emCache = _getSubSurf(smd->emCache, levels, useAging| 
CCG_CALC_NORMALS);
  		ss_sync_from_derivedmesh(smd->emCache, dm, vertCos, useSimple);

  		result = getCCGDerivedMesh(smd->emCache,
@@ -2801,7 +2805,7 @@ struct DerivedMesh *subsurf_make_derived_from_derived(
  		if(levels == 0)
  			return dm;
  		
-		ss = _getSubSurf(NULL, levels, CCG_USE_ARENA);
+		ss = _getSubSurf(NULL, levels, CCG_USE_ARENA|CCG_CALC_NORMALS);

  		ss_sync_from_derivedmesh(ss, dm, vertCos, useSimple);

@@ -2831,7 +2835,7 @@ struct DerivedMesh *subsurf_make_derived_from_derived(
  		}

  		if(useIncremental && isFinalCalc) {
-			smd->mCache = ss = _getSubSurf(smd->mCache, levels, useAging);
+			smd->mCache = ss = _getSubSurf(smd->mCache, levels, useAging| 
CCG_CALC_NORMALS);

  			ss_sync_from_derivedmesh(ss, dm, vertCos, useSimple);

@@ -2844,7 +2848,7 @@ struct DerivedMesh *subsurf_make_derived_from_derived(
  				smd->mCache = NULL;
  			}

-			ss = _getSubSurf(NULL, levels, CCG_USE_ARENA);
+			ss = _getSubSurf(NULL, levels, CCG_USE_ARENA|CCG_CALC_NORMALS);
  			ss_sync_from_derivedmesh(ss, dm, vertCos, useSimple);

  			result = getCCGDerivedMesh(ss, drawInteriorEdges, useSubsurfUv, dm);