<HTML> <HEAD> <TITLE>refract</TITLE> <STYLE TYPE="text/css" MEDIA=screen> <!-- BODY { font-family: Arial,Helvetica; } BLOCKQUOTE { margin: 10pt; } H1,A { color: #336699; } /*** Top menu style ****/ .mmenuon { font-family: Arial,Helvetica; font-weight: bold; text-decoration: none; color: #ff6600; font-size: 10pt; } .mmenuoff { font-family: Arial,Helvetica; font-weight: bold; text-decoration: none; color: #ffffff; font-size: 10pt; } .cpyright { font-family: Arial,Helvetica; font-weight: bold; text-decoration: none; color: #ffffff; font-size: xx-small; } .cpyrightText { font-family: Arial,Helvetica; font-weight: bold; text-decoration: none; color: #ffffff; font-size: xx-small; } .sections { font-family: Arial,Helvetica; font-weight: bold; text-decoration: none; color: #336699; font-size: 11pt; } .dsections { font-family: Arial,Helvetica; font-weight: bold; text-decoration: none; color: #336699; font-size: 12pt; } .slink { font-family: Arial,Helvetica; font-weight: normal; text-decoration: none; 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half3 refract(half3 i, half3 n, half eta); float3 refract(float3 i, float3 n, float eta); </PRE> <H1><A NAME="PARAMETERS"><A NAME="3">PARAMETERS </A></A></H1> <DL> <DT><STRONG>i </STRONG></DT> <DD> <P> Incidence vector. </P> <DT><STRONG>n </STRONG></DT> <DD> <P> Normal vector. </P> <DT><STRONG>eta </STRONG></DT> <DD> <P> Ratio of indices of refraction at the surface interface. </P> </DD></DL> <H1><A NAME="DESCRIPTION"><A NAME="4">DESCRIPTION </A></A></H1> <P> Returns a refraction vector given an incidence vector, a normal vector for a surface, and a ratio of indices of refraction at the surface's interface. </P> <P> The incidence vector <I>i</I> and normal vector <I>n</I> should be normalized. </P> <H1><A NAME="REFERENCE_IMPLEMENTATION"><A NAME="5">REFERENCE IMPLEMENTATION </A></A></H1> <P> <B>reflect</B> for <B>float3</B> vectors could be implemented this way: </P> <PRE> float3 refract( float3 i, float3 n, float eta ) { float cosi = dot(-i, n); float cost2 = 1.0f - eta * eta * (1.0f - cosi*cosi); float3 t = eta*i + ((eta*cosi - sqrt(abs(cost2))) * n); return t * (float3)(cost2 > 0); } </PRE> <H1><A NAME="PROFILE_SUPPORT"><A NAME="6">PROFILE SUPPORT </A></A></H1> <P> <B>refract</B> is supported in all profiles. </P> <P> Support in the <A HREF="fp20.html">fp20</A> is limited. </P> <H1><A NAME="SEE_ALSO"><A NAME="7">SEE ALSO </A></A></H1> <P> <A HREF="abs.html"><I>abs</I></A>, <A HREF="cos.html"><I>cos</I></A>, <A HREF="dot.html"><I>dot</I></A>, <A HREF="reflect.html"><I>reflect</I></A>, <A HREF="sqrt.html"><I>sqrt</I></A> </P> </BLOCKQUOTE> </BODY>