Bugfix #3493

Replaced sqrt() with the safe version sasqrt() in anisotropic.
the formula (1 - n*n) should not give negative values for n = dotproduct
of normals, but float inaccuracy can make negative zeros, as we know!

This solves, hopefully, last annoying "blotches" in hair!

1 files changed, 11 insertions, 12 deletions

diff --git a/source/blender/render/intern/source/rendercore.c b/source/blender/render/intern/source/rendercore.c
index 303d83cde14..73d57e453b8 100644
--- a/source/blender/render/intern/source/rendercore.c
+++ b/source/blender/render/intern/source/rendercore.c
@@ -665,7 +665,6 @@ static float area_lamp_energy(float *co, float *vn, LampRen *lar)
 	return pow(fac*lar->areasize, lar->k);	// corrected for buttons size and lar->dist^2
 }
 
-
 float spec(float inp, int hard)	
 {
 	float b1;
@@ -717,7 +716,7 @@ float Phong_Spec( float *n, float *l, float *v, int hard, int tangent )
 	Normalise(h);
 	
 	rslt = h[0]*n[0] + h[1]*n[1] + h[2]*n[2];
-	if(tangent) rslt= sqrt(1.0 - rslt*rslt);
+	if(tangent) rslt= sasqrt(1.0 - rslt*rslt);
 		
 	if( rslt > 0.0 ) rslt= spec(rslt, hard);
 	else rslt = 0.0;
@@ -737,11 +736,11 @@ float CookTorr_Spec(float *n, float *l, float *v, int hard, int tangent)
 	Normalise(h);
 
 	nh= n[0]*h[0]+n[1]*h[1]+n[2]*h[2];
-	if(tangent) nh= sqrt(1.0 - nh*nh);
+	if(tangent) nh= sasqrt(1.0 - nh*nh);
 	else if(nh<0.0) return 0.0;
 	
 	nv= n[0]*v[0]+n[1]*v[1]+n[2]*v[2];
-	if(tangent) nv= sqrt(1.0 - nv*nv);
+	if(tangent) nv= sasqrt(1.0 - nv*nv);
 	else if(nv<0.0) nv= 0.0;
 
 	i= spec(nh, hard);
@@ -770,15 +769,15 @@ float Blinn_Spec(float *n, float *l, float *v, float refrac, float spec_power, i
 	Normalise(h);
 
 	nh= n[0]*h[0]+n[1]*h[1]+n[2]*h[2]; /* Dot product between surface normal and half-way vector */
-	if(tangent) nh= sqrt(1.0f - nh*nh);
+	if(tangent) nh= sasqrt(1.0f - nh*nh);
 	else if(nh<0.0) return 0.0;
 
 	nv= n[0]*v[0]+n[1]*v[1]+n[2]*v[2]; /* Dot product between surface normal and view vector */
-	if(tangent) nv= sqrt(1.0f - nv*nv);
+	if(tangent) nv= sasqrt(1.0f - nv*nv);
 	if(nv<=0.0) nv= 0.01;				/* hrms... */
 
 	nl= n[0]*l[0]+n[1]*l[1]+n[2]*l[2]; /* Dot product between surface normal and light vector */
-	if(tangent) nl= sqrt(1.0f - nl*nl);
+	if(tangent) nl= sasqrt(1.0f - nl*nl);
 	if(nl<=0.0) {
 		return 0.0;
 	}
@@ -817,7 +816,7 @@ float Toon_Spec( float *n, float *l, float *v, float size, float smooth, int tan
 	Normalise(h);
 	
 	rslt = h[0]*n[0] + h[1]*n[1] + h[2]*n[2];
-	if(tangent) rslt = sqrt(1.0f - rslt*rslt);
+	if(tangent) rslt = sasqrt(1.0f - rslt*rslt);
 	
 	ang = saacos( rslt ); 
 	
@@ -841,15 +840,15 @@ float WardIso_Spec( float *n, float *l, float *v, float rms, int tangent)
 	Normalise(h);
 
 	nh = n[0]*h[0]+n[1]*h[1]+n[2]*h[2]; /* Dot product between surface normal and half-way vector */
-	if(tangent) nh = sqrt(1.0f - nh*nh);
+	if(tangent) nh = sasqrt(1.0f - nh*nh);
 	if(nh<=0.0) nh = 0.001f;
 	
 	nv = n[0]*v[0]+n[1]*v[1]+n[2]*v[2]; /* Dot product between surface normal and view vector */
-	if(tangent) nv = sqrt(1.0f - nv*nv);
+	if(tangent) nv = sasqrt(1.0f - nv*nv);
 	if(nv<=0.0) nv = 0.001f;
 
 	nl = n[0]*l[0]+n[1]*l[1]+n[2]*l[2]; /* Dot product between surface normal and light vector */
-	if(tangent) nl = sqrt(1.0f - nl*nl);
+	if(tangent) nl = sasqrt(1.0f - nl*nl);
 	if(nl<=0.0) nl = 0.001;
 
 	angle = tan(saacos(nh));
@@ -1506,7 +1505,7 @@ void shade_lamp_loop(ShadeInput *shi, ShadeResult *shr)
 					x= MAX2(fabs(lvrot[0]/lvrot[2]) , fabs(lvrot[1]/lvrot[2]));
 					/* 1.0/(sqrt(1+x*x)) is equivalent to cos(atan(x)) */
 
-					inpr= 1.0/(sqrt(1+x*x));
+					inpr= 1.0f/(sqrt(1.0f+x*x));
 				}
 				else inpr= 0.0;
 			}