Current situation

A mesh can consist out of multiple material. Take a character with clothing's. the skin can be a different material as the different clothing's. During compositing it is a common use-case to only do a part of the composit on only a specific material. Currently this can not be done.

In blender movies this feature is known to be implemented, but until now it never got integrated into trunk.
Proposal

With material index the Blender internal renderer will be capable of creating a buffer containing the material indexes of the first pixel-hit. This will be implemented in the same manner as the object index.

In the compositor the ID Mask node can be used to extract the information out of the Render pass.
Impact
User interface

On the properties-space the next changes will be done

    Scene⇒Render layer⇒Passes⇒Material index will be added
    Material⇒Options⇒Pass index will be added

DNA

    Material struct will get an new field called “index”. this will be a short-type.
    Material struct the field pad will be removed.
    A new Render-layer pass will be added (bit 1«18)

RNA

    Material RNA is updated (based on “pass index” from object)
    Render layer RNA is updated (based on IndexOB)

Blender internal renderer

The Blender internal renderer will process the render pass as a copy of the Object index.
Blender compositor

The render layer input will get a new output socket called “IndexMA”
Usage

An example on how to use material index can be found at:

https://svn.blender.org/svnroot/bf-blender/trunk/lib/tests/compositing/composite_materialindex.blend

This is also example of a commit message longer than the commit itself :)

13 files changed, 68 insertions, 19 deletions

diff --git a/source/blender/blenkernel/BKE_node.h b/source/blender/blenkernel/BKE_node.h
index a126f405d09..c86080aa21f 100644
--- a/source/blender/blenkernel/BKE_node.h
+++ b/source/blender/blenkernel/BKE_node.h
@@ -319,9 +319,10 @@ void			ntreeGPUMaterialNodes(struct bNodeTree *ntree, struct GPUMaterial *mat);
 #define RRES_OUT_REFRACT	12
 #define RRES_OUT_INDIRECT	13
 #define RRES_OUT_INDEXOB	14
-#define RRES_OUT_MIST		15
-#define RRES_OUT_EMIT		16
-#define RRES_OUT_ENV		17
+#define RRES_OUT_INDEXMA	15
+#define RRES_OUT_MIST		16
+#define RRES_OUT_EMIT		17
+#define RRES_OUT_ENV		18
 
 /* note: types are needed to restore callbacks, don't change values */
 #define CMP_NODE_VIEWER		201
diff --git a/source/blender/blenkernel/intern/node.c b/source/blender/blenkernel/intern/node.c
index 64e374fe4c0..4e76ab0727d 100644
--- a/source/blender/blenkernel/intern/node.c
+++ b/source/blender/blenkernel/intern/node.c
@@ -3156,7 +3156,9 @@ static void force_hidden_passes(bNode *node, int passflag)
 	if(!(passflag & SCE_PASS_INDIRECT)) sock->flag |= SOCK_UNAVAIL;
 	sock= BLI_findlink(&node->outputs, RRES_OUT_INDEXOB);
 	if(!(passflag & SCE_PASS_INDEXOB)) sock->flag |= SOCK_UNAVAIL;
-	sock= BLI_findlink(&node->outputs, RRES_OUT_MIST);
+        sock= BLI_findlink(&node->outputs, RRES_OUT_INDEXMA);
+        if(!(passflag & SCE_PASS_INDEXMA)) sock->flag |= SOCK_UNAVAIL;
+        sock= BLI_findlink(&node->outputs, RRES_OUT_MIST);
 	if(!(passflag & SCE_PASS_MIST)) sock->flag |= SOCK_UNAVAIL;
 	sock= BLI_findlink(&node->outputs, RRES_OUT_EMIT);
 	if(!(passflag & SCE_PASS_EMIT)) sock->flag |= SOCK_UNAVAIL;
diff --git a/source/blender/editors/space_outliner/outliner.c b/source/blender/editors/space_outliner/outliner.c
index 0ce6b5d2ce2..c3699e4b704 100644
--- a/source/blender/editors/space_outliner/outliner.c
+++ b/source/blender/editors/space_outliner/outliner.c
@@ -480,7 +480,11 @@ static void outliner_add_passes(SpaceOops *soops, TreeElement *tenla, ID *id, Sc
 	te->name= "Index Object";
 	te->directdata= &srl->passflag;
 	
-	te= outliner_add_element(soops, &tenla->subtree, id, tenla, TSE_R_PASS, LOG2I(SCE_PASS_RGBA));
+        te= outliner_add_element(soops, &tenla->subtree, id, tenla, TSE_R_PASS, LOG2I(SCE_PASS_INDEXMA));
+        te->name= "Index Material";
+        te->directdata= &srl->passflag;
+
+        te= outliner_add_element(soops, &tenla->subtree, id, tenla, TSE_R_PASS, LOG2I(SCE_PASS_RGBA));
 	te->name= "Color";
 	te->directdata= &srl->passflag;
 	
diff --git a/source/blender/makesdna/DNA_material_types.h b/source/blender/makesdna/DNA_material_types.h
index 1489593f7f6..060b1bf42d1 100644
--- a/source/blender/makesdna/DNA_material_types.h
+++ b/source/blender/makesdna/DNA_material_types.h
@@ -161,7 +161,7 @@ typedef struct Material {
 
 	int mapto_textured;	/* render-time cache to optimise texture lookups */
 	short shadowonly_flag;		/* "shadowsonly" type */
-	short pad;
+        short index;    /* custom index for render passes */
 
 	ListBase gpumaterial;		/* runtime */
 } Material;
diff --git a/source/blender/makesdna/DNA_scene_types.h b/source/blender/makesdna/DNA_scene_types.h
index 100a66d209f..f351a48b998 100644
--- a/source/blender/makesdna/DNA_scene_types.h
+++ b/source/blender/makesdna/DNA_scene_types.h
@@ -201,6 +201,7 @@ typedef struct SceneRenderLayer {
 #define SCE_PASS_RAYHITS		(1<<15)
 #define SCE_PASS_EMIT			(1<<16)
 #define SCE_PASS_ENVIRONMENT	(1<<17)
+#define SCE_PASS_INDEXMA	(1<<18)
 
 /* note, srl->passflag is treestore element 'nr' in outliner, short still... */
 
diff --git a/source/blender/makesrna/intern/rna_material.c b/source/blender/makesrna/intern/rna_material.c
index b86a91967a6..d90798e9b29 100644
--- a/source/blender/makesrna/intern/rna_material.c
+++ b/source/blender/makesrna/intern/rna_material.c
@@ -1675,7 +1675,12 @@ void RNA_def_material(BlenderRNA *brna)
 	RNA_def_property_flag(prop, PROP_EDITABLE);
 	RNA_def_property_ui_text(prop, "Light Group", "Limit lighting to lamps in this Group");
 	RNA_def_property_update(prop, 0, "rna_Material_update");
-	
+
+        prop= RNA_def_property(srna, "pass_index", PROP_INT, PROP_UNSIGNED);
+        RNA_def_property_int_sdna(prop, NULL, "index");
+        RNA_def_property_ui_text(prop, "Pass Index", "Index # for the IndexMA render pass");
+        RNA_def_property_update(prop, NC_OBJECT, NULL);
+
 	/* flags */
 	
 	prop= RNA_def_property(srna, "use_light_group_exclusive", PROP_BOOLEAN, PROP_NONE);
diff --git a/source/blender/makesrna/intern/rna_render.c b/source/blender/makesrna/intern/rna_render.c
index 3a6cebef178..3074508d6a7 100644
--- a/source/blender/makesrna/intern/rna_render.c
+++ b/source/blender/makesrna/intern/rna_render.c
@@ -388,7 +388,8 @@ static void rna_def_render_pass(BlenderRNA *brna)
 		{SCE_PASS_MIST, "MIST", 0, "Mist", ""},
 		{SCE_PASS_EMIT, "EMIT", 0, "Emit", ""},
 		{SCE_PASS_ENVIRONMENT, "ENVIRONMENT", 0, "Environment", ""},
-		{0, NULL, 0, NULL, NULL}};
+                {SCE_PASS_INDEXMA, "MATERIAL_INDEX", 0, "Material Index", ""},
+                {0, NULL, 0, NULL, NULL}};
 	
 	srna= RNA_def_struct(brna, "RenderPass", NULL);
 	RNA_def_struct_ui_text(srna, "Render Pass", "");
diff --git a/source/blender/makesrna/intern/rna_scene.c b/source/blender/makesrna/intern/rna_scene.c
index 0c136fc429b..a496e24143b 100644
--- a/source/blender/makesrna/intern/rna_scene.c
+++ b/source/blender/makesrna/intern/rna_scene.c
@@ -1515,7 +1515,13 @@ void rna_def_render_layer_common(StructRNA *srna, int scene)
 	if(scene) RNA_def_property_update(prop, NC_SCENE|ND_RENDER_OPTIONS, "rna_SceneRenderLayer_pass_update");
 	else RNA_def_property_clear_flag(prop, PROP_EDITABLE);
 
-	prop= RNA_def_property(srna, "use_pass_color", PROP_BOOLEAN, PROP_NONE);
+        prop= RNA_def_property(srna, "use_pass_material_index", PROP_BOOLEAN, PROP_NONE);
+        RNA_def_property_boolean_sdna(prop, NULL, "passflag", SCE_PASS_INDEXMA);
+        RNA_def_property_ui_text(prop, "Material Index", "Deliver material index pass");
+        if(scene) RNA_def_property_update(prop, NC_SCENE|ND_RENDER_OPTIONS, "rna_SceneRenderLayer_pass_update");
+        else RNA_def_property_clear_flag(prop, PROP_EDITABLE);
+
+        prop= RNA_def_property(srna, "use_pass_color", PROP_BOOLEAN, PROP_NONE);
 	RNA_def_property_boolean_sdna(prop, NULL, "passflag", SCE_PASS_RGBA);
 	RNA_def_property_ui_text(prop, "Color", "Deliver shade-less color pass");
 	if(scene) RNA_def_property_update(prop, NC_SCENE|ND_RENDER_OPTIONS, "rna_SceneRenderLayer_pass_update");
diff --git a/source/blender/nodes/intern/CMP_nodes/CMP_image.c b/source/blender/nodes/intern/CMP_nodes/CMP_image.c
index 3caaad26bae..91800897cb3 100644
--- a/source/blender/nodes/intern/CMP_nodes/CMP_image.c
+++ b/source/blender/nodes/intern/CMP_nodes/CMP_image.c
@@ -53,7 +53,8 @@ static bNodeSocketType cmp_node_rlayers_out[]= {
 	{	SOCK_RGBA, 0, "Refract",	0.0f, 0.0f, 0.0f, 0.0f, 0.0f, 1.0f},
 	{	SOCK_RGBA, 0, "Indirect",	0.0f, 0.0f, 0.0f, 0.0f, 0.0f, 1.0f},
 	{	SOCK_VALUE, 0, "IndexOB",	0.0f, 0.0f, 0.0f, 0.0f, 0.0f, 1.0f},
-	{	SOCK_VALUE, 0, "Mist",		0.0f, 0.0f, 0.0f, 0.0f, 0.0f, 1.0f},
+        {	SOCK_VALUE, 0, "IndexMA",	0.0f, 0.0f, 0.0f, 0.0f, 0.0f, 1.0f},
+        {	SOCK_VALUE, 0, "Mist",		0.0f, 0.0f, 0.0f, 0.0f, 0.0f, 1.0f},
 	{	SOCK_RGBA, 0, "Emit",		0.0f, 0.0f, 0.0f, 0.0f, 0.0f, 1.0f},
 	{	SOCK_RGBA, 0, "Environment",0.0f, 0.0f, 0.0f, 0.0f, 0.0f, 1.0f},
 	{	-1, 0, ""	}
@@ -211,7 +212,9 @@ static void outputs_multilayer_get(RenderData *rd, RenderLayer *rl, bNodeStack *
 		out[RRES_OUT_INDIRECT]->data= compbuf_multilayer_get(rd, rl, ima, iuser, SCE_PASS_INDIRECT);
 	if(out[RRES_OUT_INDEXOB]->hasoutput)
 		out[RRES_OUT_INDEXOB]->data= compbuf_multilayer_get(rd, rl, ima, iuser, SCE_PASS_INDEXOB);
-	if(out[RRES_OUT_MIST]->hasoutput)
+        if(out[RRES_OUT_INDEXMA]->hasoutput)
+                out[RRES_OUT_INDEXMA]->data= compbuf_multilayer_get(rd, rl, ima, iuser, SCE_PASS_INDEXMA);
+        if(out[RRES_OUT_MIST]->hasoutput)
 		out[RRES_OUT_MIST]->data= compbuf_multilayer_get(rd, rl, ima, iuser, SCE_PASS_MIST);
 	if(out[RRES_OUT_EMIT]->hasoutput)
 		out[RRES_OUT_EMIT]->data= compbuf_multilayer_get(rd, rl, ima, iuser, SCE_PASS_EMIT);
@@ -326,7 +329,7 @@ static CompBuf *compbuf_from_pass(RenderData *rd, RenderLayer *rl, int rectx, in
 		CompBuf *buf;
 		int buftype= CB_VEC3;
 
-		if(ELEM3(passcode, SCE_PASS_Z, SCE_PASS_INDEXOB, SCE_PASS_MIST))
+                if(ELEM4(passcode, SCE_PASS_Z, SCE_PASS_INDEXOB, SCE_PASS_MIST, SCE_PASS_INDEXMA))
 			buftype= CB_VAL;
 		else if(passcode==SCE_PASS_VECTOR)
 			buftype= CB_VEC4;
@@ -373,6 +376,8 @@ static void node_composit_rlayers_out(RenderData *rd, RenderLayer *rl, bNodeStac
 	  out[RRES_OUT_INDIRECT]->data= compbuf_from_pass(rd, rl, rectx, recty, SCE_PASS_INDIRECT);
    if(out[RRES_OUT_INDEXOB]->hasoutput)
 	   out[RRES_OUT_INDEXOB]->data= compbuf_from_pass(rd, rl, rectx, recty, SCE_PASS_INDEXOB);
+   if(out[RRES_OUT_INDEXMA]->hasoutput)
+           out[RRES_OUT_INDEXMA]->data= compbuf_from_pass(rd, rl, rectx, recty, SCE_PASS_INDEXMA);
    if(out[RRES_OUT_MIST]->hasoutput)
 	   out[RRES_OUT_MIST]->data= compbuf_from_pass(rd, rl, rectx, recty, SCE_PASS_MIST);
    if(out[RRES_OUT_EMIT]->hasoutput)
diff --git a/source/blender/render/intern/source/pipeline.c b/source/blender/render/intern/source/pipeline.c
index 1d4014aac3e..37226018a91 100644
--- a/source/blender/render/intern/source/pipeline.c
+++ b/source/blender/render/intern/source/pipeline.c
@@ -383,7 +383,11 @@ static const char *get_pass_name(int passtype, int channel)
 		if(channel==-1) return "IndexOB";
 		return "IndexOB.X";
 	}
-	if(passtype == SCE_PASS_MIST) {
+        if(passtype == SCE_PASS_INDEXMA) {
+                if(channel==-1) return "IndexMA";
+                return "IndexMA.X";
+        }
+        if(passtype == SCE_PASS_MIST) {
 		if(channel==-1) return "Mist";
 		return "Mist.Z";
 	}
@@ -448,6 +452,9 @@ static int passtype_from_name(char *str)
 	if(strcmp(str, "IndexOB")==0)
 		return SCE_PASS_INDEXOB;
 
+        if(strcmp(str, "IndexMA")==0)
+                return SCE_PASS_INDEXMA;
+
 	if(strcmp(str, "Mist")==0)
 		return SCE_PASS_MIST;
 	
@@ -631,7 +638,9 @@ static RenderResult *new_render_result(Render *re, rcti *partrct, int crop, int
 			render_layer_add_pass(rr, rl, 3, SCE_PASS_REFRACT);
 		if(srl->passflag  & SCE_PASS_INDEXOB)
 			render_layer_add_pass(rr, rl, 1, SCE_PASS_INDEXOB);
-		if(srl->passflag  & SCE_PASS_MIST)
+                if(srl->passflag  & SCE_PASS_INDEXMA)
+                        render_layer_add_pass(rr, rl, 1, SCE_PASS_INDEXMA);
+                if(srl->passflag  & SCE_PASS_MIST)
 			render_layer_add_pass(rr, rl, 1, SCE_PASS_MIST);
 		if(rl->passflag & SCE_PASS_RAYHITS)
 			render_layer_add_pass(rr, rl, 4, SCE_PASS_RAYHITS);
diff --git a/source/blender/render/intern/source/rendercore.c b/source/blender/render/intern/source/rendercore.c
index 6747784b21a..11ae721ad95 100644
--- a/source/blender/render/intern/source/rendercore.c
+++ b/source/blender/render/intern/source/rendercore.c
@@ -515,7 +515,15 @@ static void add_filt_passes(RenderLayer *rl, int curmask, int rectx, int offset,
 						*fp= (float)shi->obr->ob->index;
 				}
 				break;
-			case SCE_PASS_MIST:
+                        case SCE_PASS_INDEXMA:
+                                /* no filter */
+                                if(shi->vlr) {
+                                        fp= rpass->rect + offset;
+                                        if(*fp==0.0f)
+                                                *fp= (float)shi->mat->index;
+                                }
+                                break;
+                        case SCE_PASS_MIST:
 				/*  */
 				col= &shr->mist;
 				pixsize= 1;
diff --git a/source/blender/render/intern/source/shadeinput.c b/source/blender/render/intern/source/shadeinput.c
index 2702b7e5145..277cec1835a 100644
--- a/source/blender/render/intern/source/shadeinput.c
+++ b/source/blender/render/intern/source/shadeinput.c
@@ -1455,7 +1455,7 @@ int shade_samples(ShadeSample *ssamp, PixStr *ps, int x, int y)
 		shade_samples_do_AO(ssamp);
 		
 		/* if shade (all shadepinputs have same passflag) */
-		if(ssamp->shi[0].passflag & ~(SCE_PASS_Z|SCE_PASS_INDEXOB)) {
+                if(ssamp->shi[0].passflag & ~(SCE_PASS_Z|SCE_PASS_INDEXOB|SCE_PASS_INDEXMA)) {
 
 			for(samp=0; samp<ssamp->tot; samp++, shi++, shr++) {
 				shade_input_set_shade_texco(shi);
diff --git a/source/blender/render/intern/source/zbuf.c b/source/blender/render/intern/source/zbuf.c
index 98dbb796f5b..3ac6d2c33ff 100644
--- a/source/blender/render/intern/source/zbuf.c
+++ b/source/blender/render/intern/source/zbuf.c
@@ -3497,7 +3497,7 @@ static void add_transp_obindex(RenderLayer *rl, int offset, Object *ob)
 	RenderPass *rpass;
 	
 	for(rpass= rl->passes.first; rpass; rpass= rpass->next) {
-		if(rpass->passtype == SCE_PASS_INDEXOB) {
+                if(rpass->passtype == SCE_PASS_INDEXOB||rpass->passtype == SCE_PASS_INDEXMA) {
 			float *fp= rpass->rect + offset;
 			*fp= (float)ob->index;
 			break;
@@ -3820,7 +3820,7 @@ static int shade_tra_samples(ShadeSample *ssamp, StrandShadeCache *cache, int x,
 		shade_samples_do_AO(ssamp);
 		
 		/* if shade (all shadepinputs have same passflag) */
-		if(shi->passflag & ~(SCE_PASS_Z|SCE_PASS_INDEXOB)) {
+                if(shi->passflag & ~(SCE_PASS_Z|SCE_PASS_INDEXOB|SCE_PASS_INDEXMA)) {
 			for(samp=0; samp<ssamp->tot; samp++, shi++, shr++) {
 				shade_input_set_shade_texco(shi);
 				shade_input_do_shade(shi, shr);
@@ -4115,7 +4115,14 @@ unsigned short *zbuffer_transp_shade(RenderPart *pa, RenderLayer *rl, float *pas
 							add_transp_obindex(rlpp[a], od, obr->ob);
 					}
 				}
-				
+                                if(addpassflag & SCE_PASS_INDEXMA) {
+                                        ObjectRen *obr= R.objectinstance[zrow[totface-1].obi].obr;
+                                        if(obr->ob) {
+                                                for(a= 0; a<totfullsample; a++)
+                                                        add_transp_obindex(rlpp[a], od, obr->ob);
+                                        }
+                                }
+
 				/* for each mask-sample we alpha-under colors. then in end it's added using filter */
 				memset(samp_shr, 0, sizeof(ShadeResult)*osa);
 				for(a=0; a<osa; a++) {