Bugfix IRC report

Curves heavily scaled down will have render artifacts

Caused by precision issues when computing average normal map
for INDEX3 surface type. Now calculation happens in local object
space instead of world space.

1 files changed, 20 insertions, 6 deletions

diff --git a/source/blender/render/intern/source/convertblender.c b/source/blender/render/intern/source/convertblender.c
index 620f9d41818..67e899e425e 100644
--- a/source/blender/render/intern/source/convertblender.c
+++ b/source/blender/render/intern/source/convertblender.c
@@ -2820,7 +2820,7 @@ static void init_render_curve(Render *re, ObjectRen *obr, int timeoffset)
 	ListBase disp={NULL, NULL};
 	Material **matar;
 	float *data, *fp, *orco=NULL;
-	float n[3], mat[4][4];
+	float n[3], mat[4][4], nmat[4][4];
 	int nr, startvert, a, b;
 	int need_orco=0, totmat;
 
@@ -2835,6 +2835,11 @@ static void init_render_curve(Render *re, ObjectRen *obr, int timeoffset)
 	mult_m4_m4m4(mat, re->viewmat, ob->obmat);
 	invert_m4_m4(ob->imat, mat);
 
+	/* local object -> world space transform for normals */
+	copy_m4_m4(nmat, mat);
+	transpose_m4(nmat);
+	invert_m4(nmat);
+
 	/* material array */
 	totmat= ob->totcol+1;
 	matar= MEM_callocN(sizeof(Material*)*totmat, "init_render_surf matar");
@@ -2891,13 +2896,20 @@ static void init_render_curve(Render *re, ObjectRen *obr, int timeoffset)
 					zero_v3(n);
 					index= dl->index;
 					for (a=0; a<dl->parts; a++, index+=3) {
+						int v1 = index[0], v2 = index[1], v3 = index[2];
+						float *co1 = &dl->verts[v1 * 3],
+						      *co2 = &dl->verts[v2 * 3],
+						      *co3 = &dl->verts[v3 * 3];
+
 						vlr= RE_findOrAddVlak(obr, obr->totvlak++);
-						vlr->v1= RE_findOrAddVert(obr, startvert+index[0]);
-						vlr->v2= RE_findOrAddVert(obr, startvert+index[1]);
-						vlr->v3= RE_findOrAddVert(obr, startvert+index[2]);
+						vlr->v1= RE_findOrAddVert(obr, startvert + v1);
+						vlr->v2= RE_findOrAddVert(obr, startvert + v2);
+						vlr->v3= RE_findOrAddVert(obr, startvert + v3);
 						vlr->v4= NULL;
-						if (area_tri_v3(vlr->v3->co, vlr->v2->co, vlr->v1->co)>FLT_EPSILON10) {
-							normal_tri_v3(tmp, vlr->v3->co, vlr->v2->co, vlr->v1->co);
+
+						/* to prevent float accuracy issues, we calculate normal in local object space (not world) */
+						if (area_tri_v3(co3, co2, co1)>FLT_EPSILON10) {
+							normal_tri_v3(tmp, co3, co2, co1);
 							add_v3_v3(n, tmp);
 						}
 
@@ -2906,6 +2918,8 @@ static void init_render_curve(Render *re, ObjectRen *obr, int timeoffset)
 						vlr->ec= 0;
 					}
 
+					/* transform normal to world space */
+					mul_m4_v3(nmat, n);
 					normalize_v3(n);
 
 					/* vertex normals */