Fix issues with NaNs in tangent data from using normalize3fast on zero-length vectors and other data conditioning; also added assert to normalize3fast to make finding these problems easier in the future

1 files changed, 9 insertions, 0 deletions

diff --git a/indra/llmath/llvector4a.inl b/indra/llmath/llvector4a.inl
index 7c52ffef21..4589bac9fb 100755
--- a/indra/llmath/llvector4a.inl
+++ b/indra/llmath/llvector4a.inl
@@ -331,6 +331,9 @@ inline LLSimdScalar LLVector4a::dot4(const LLVector4a& b) const
 // Note that this does not consider zero length vectors!
 inline void LLVector4a::normalize3()
 {
+	// find out about bad math before it takes two man-days to track down
+	llassert(isFinite3() && !equals3(getZero()));
+
 	// lenSqrd = a dot a
 	LLVector4a lenSqrd; lenSqrd.setAllDot3( *this, *this );
 	// rsqrt = approximate reciprocal square (i.e., { ~1/len(a)^2, ~1/len(a)^2, ~1/len(a)^2, ~1/len(a)^2 }
@@ -379,6 +382,9 @@ inline void LLVector4a::normalize4()
 // Note that this does not consider zero length vectors!
 inline LLSimdScalar LLVector4a::normalize3withLength()
 {
+	// find out about bad math before it takes two man-days to track down
+	llassert(isFinite3() && !equals3(getZero()));
+
 	// lenSqrd = a dot a
 	LLVector4a lenSqrd; lenSqrd.setAllDot3( *this, *this );
 	// rsqrt = approximate reciprocal square (i.e., { ~1/len(a)^2, ~1/len(a)^2, ~1/len(a)^2, ~1/len(a)^2 }
@@ -404,6 +410,9 @@ inline LLSimdScalar LLVector4a::normalize3withLength()
 // Note that this does not consider zero length vectors!
 inline void LLVector4a::normalize3fast()
 {
+	// find out about bad math before it takes two man-days to track down
+	llassert(isFinite3() && !equals3(getZero()));
+
 	LLVector4a lenSqrd; lenSqrd.setAllDot3( *this, *this );
 	const LLQuad approxRsqrt = _mm_rsqrt_ps(lenSqrd.mQ);
 	mQ = _mm_mul_ps( mQ, approxRsqrt );