Finishing touch for hair strand shadows;

- raytracing code now uses cylinder-line intersect for strands. It used
  to intersect with the screen-aligned strand quads, giving too many
  misses for tracing.
  Note; mirror for hair is still not well supported!

- added in Materials a choice for whether a material is Traceable for
  raytracing or whether it is part of Shadow buffers. This way you can
  exclude hair strands from raytracing, but still get shadowbuffers for it.

source/blender/blenkernel/intern/material.c

@@ -117,7 +117,7 @@ void init_material(Material *ma)
 	ma->rampfac_spec= 1.0;
 	ma->pr_lamp= 3; // two lamps, is bits
 	
-	ma->mode= MA_TRACEBLE|MA_SHADOW|MA_RADIO|MA_TANGENT_STR;
+	ma->mode= MA_TRACEBLE|MA_SHADBUF|MA_SHADOW|MA_RADIO|MA_TANGENT_STR;
 }
 
 Material *add_material(char *name)

source/blender/blenloader/intern/readfile.c

@@ -5077,6 +5077,11 @@ static void do_versions(FileData *fd, Library *lib, Main *main)
 				ma->strand_sta= ma->strand_end= 1.0f;
 				ma->mode |= MA_TANGENT_STR;
 			}
+			/* remove this test before 2.40 too! pad is set to denote check was done */
+			if(ma->pad==0) {
+				if(ma->mode & MA_TRACEBLE) ma->mode |= MA_SHADBUF;
+				ma->pad= 1;
+			}
 		}
 	}
 	

source/blender/makesdna/DNA_material_types.h

@@ -155,6 +155,7 @@ typedef struct Material {
 #define MA_RAYBIAS		0x400000
 #define MA_FULL_OSA		0x800000
 #define MA_TANGENT_STR	0x1000000
+#define MA_SHADBUF		0x2000000
 
 /* diff_shader */
 #define MA_DIFF_LAMBERT		0

source/blender/render/intern/source/ray.c

@@ -632,7 +632,7 @@ void makeoctree(void)
 /* ************ raytracer **************** */
 
 /* only for self-intersecting test with current render face (where ray left) */
-static short intersection2(VlakRen *vlr, float r0, float r1, float r2, float rx1, float ry1, float rz1)
+static int intersection2(VlakRen *vlr, float r0, float r1, float r2, float rx1, float ry1, float rz1)
 {
 	VertRen *v1,*v2,*v3,*v4=NULL;
 	float x0,x1,x2,t00,t01,t02,t10,t11,t12,t20,t21,t22;
@@ -705,13 +705,64 @@ static short intersection2(VlakRen *vlr, float r0, float r1, float r2, float rx1
 	return 0;
 }
 
-static short intersection(Isect *is)
+/* ray - line intersection */
+static int intersection_strand(Isect *is)
+{
+	float *v1, *v2;		/* length of strand */
+	float axis[3], rc[3], nor[3], radline, dist, len;
+	
+	/* radius strand */
+	radline= 0.5f*VecLenf(is->vlr->v1->co, is->vlr->v2->co);
+	
+	v1= is->vlr->v2->co;
+	v2= is->vlr->v3->co;
+	
+	VECSUB(rc, v1, is->start);	/* vector from base ray to base cylinder */
+	VECSUB(axis, v2, v1);		/* cylinder axis */
+	
+	CROSS(nor, is->vec, axis);
+	len= VecLength(nor);
+	
+	if(len<FLT_EPSILON)
+		return 0;
+
+	dist= INPR(rc, nor)/len;	/* distance between ray and axis cylinder */
+	
+	if(dist<radline && dist>-radline) {
+		float dot1, dot2, dot3, rlen, alen, div;
+		float labda;
+		
+		/* calculating the intersection point of shortest distance */
+		dot1 = INPR(rc, is->vec);
+		dot2 = INPR(is->vec, axis);
+		dot3 = INPR(rc, axis);
+		rlen = INPR(is->vec, is->vec);
+		alen = INPR(axis, axis);
+		
+		div = alen * rlen - dot2 * dot2;
+		if (ABS(div) < FLT_EPSILON)
+			return 0;
+		
+		labda = (dot1*dot2 - dot3*rlen)/div;
+		
+		/* labda: where on axis do we have closest intersection? */
+		if(labda>=0.0f && labda<=1.0f)
+			return 1;
+	}
+	return 0;
+}
+
+/* ray - triangle or quad intersection */
+static int intersection(Isect *is)
 {
 	VertRen *v1,*v2,*v3,*v4=NULL;
 	float x0,x1,x2,t00,t01,t02,t10,t11,t12,t20,t21,t22,r0,r1,r2;
 	float m0, m1, m2, divdet, det1;
 	short ok=0;
 	
+	if(is->vlr->flag & R_STRAND) 
+		return intersection_strand(is);
+	
 	v1= is->vlr->v1; 
 	v2= is->vlr->v2; 
 	if(is->vlr->v4) {
@@ -986,7 +1037,7 @@ static Node *ocread(int x, int y, int z)
 	return NULL;
 }
 
-static short cliptest(float p, float q, float *u1, float *u2)
+static int cliptest(float p, float q, float *u1, float *u2)
 {
 	float r;
 
@@ -1017,7 +1068,7 @@ static short cliptest(float p, float q, float *u1, float *u2)
  
 /*
 
-in top: static short coh_nodes[16*16*16][6];
+in top: static int coh_nodes[16*16*16][6];
 in makeoctree: memset(coh_nodes, 0, sizeof(coh_nodes));
  
 static void add_coherence_test(int ocx1, int ocx2, int ocy1, int ocy2, int ocz1, int ocz2)

source/blender/render/intern/source/zbuf.c

@@ -2451,7 +2451,7 @@ void zbuffershad(LampRen *lar)
 		if(vlr->mat!= ma) {
 			ma= vlr->mat;
 			ok= 1;
-			if((ma->mode & MA_TRACEBLE)==0) ok= 0;
+			if((ma->mode & MA_SHADBUF)==0) ok= 0;
 		}
 		
 		if(ok && (vlr->flag & R_VISIBLE) && (vlr->lay & lay)) {

source/blender/src/buttons_shading.c

@@ -3065,7 +3065,9 @@ static void material_panel_shading(Material *ma)
 		uiBlockEndAlign(block);
 
 		uiBlockSetCol(block, TH_BUT_SETTING1);
-		uiDefButBitI(block, TOG, MA_TRACEBLE, 0,	"Traceable",		245,150,65,19, &(ma->mode), 0, 0, 0, 0, "Makes material to cast shadows or being detected by ray tracing");
+		uiBlockBeginAlign(block);
+		uiDefButBitI(block, TOG, MA_TRACEBLE, 0,"Traceable",		245,160,65,18, &(ma->mode), 0, 0, 0, 0, "Makes material to being detected by ray tracing");
+		uiDefButBitI(block, TOG, MA_SHADBUF, 0,	"Shadbuf",			245,142,65,18, &(ma->mode), 0, 0, 0, 0, "Makes material to cast shadows with shadow buffers");
 
 		uiBlockBeginAlign(block);
 		uiDefButBitI(block, TOG, MA_SHADOW, 0,	"Shadow",			245,120,65,19, &(ma->mode), 0, 0, 0, 0, "Makes material receive shadows");