<HTML> <HEAD> <TITLE>lit</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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half4 lit(half NdotL, half NdotH, half m); fixed4 lit(fixed NdotL, fixed NdotH, fixed m); </PRE> <H1><A NAME="PARAMETERS"><A NAME="3">PARAMETERS </A></A></H1> <DL> <DT><STRONG>NdotL </STRONG></DT> <DD> <P> The dot product of a normalized surface normal and a normalized light vector. </P> <DT><STRONG>NdotH </STRONG></DT> <DD> <P> The dot product of a normalized surface normal and a normalized half-angle vector (for Blinn-style specular) where the half-angle vector is the sum of the normalized view vector and normalized light vector. Alternatively, the dot product of a normlized light vector and a normalized view vector reflected by a normalized surface normal could be used (for Phong-style specular). </P> <DT><STRONG>m </STRONG></DT> <DD> <P> A specular exponent, typically described as a measure of shininess. The larger the exponent, the shinier the specular highlight, the smaller the exponent, the duller the specular highlight. </P> </DD></DL> <H1><A NAME="DESCRIPTION"><A NAME="4">DESCRIPTION </A></A></H1> <P> The <B>lit</B> function is a helper function useful to compute lighting coefficients for ambient, diffuse, and specular lighting contributions. The function efficiently maps to a native instruction for most GPUs. </P> <P> <B>lit</B> returns a 4-component vector arranged as follows: </P> <DL> <DT><STRONG>x </STRONG></DT> <DD> <P> The ambient coefficient that is always 1.0. </P> <DT><STRONG>y </STRONG></DT> <DD> <P> The diffuse coefficient that is zero if <I>NdotL</I> is less than zero, and <I>NdotL</I> otherwise. </P> <DT><STRONG>z </STRONG></DT> <DD> <P> The specular coefficient that is zero if either <I>NdotL</I> or <I>NdotH</I> are less than zero, and otherwise <I>NdotH</I> raised to the power <I>m</I>. </P> <DT><STRONG>w </STRONG></DT> <DD> <P> Always 1.0. </P> </DD></DL> <H1><A NAME="REFERENCE_IMPLEMENTATION"><A NAME="5">REFERENCE IMPLEMENTATION </A></A></H1> <P> <B>lit</B> accepting <float> parameters could be implemented this way: </P> <PRE> float4 lit(float NdotL, float NdotH, float m) { float specular = (NdotL > 0) ? pow(max(0.0, NdotH), m); return float4(1.0, max(0.0, NdotL), specular, 1.0); } </PRE> <H1><A NAME="PROFILE_SUPPORT"><A NAME="6">PROFILE SUPPORT </A></A></H1> <P> <B>lit</B> is supported in all profiles. </P> <H1><A NAME="SEE_ALSO"><A NAME="7">SEE ALSO </A></A></H1> <P> <A HREF="dot.html"><I>dot</I></A>, <A HREF="max.html"><I>max</I></A>, <A HREF="normalize.html"><I>normalize</I></A>, <A HREF="pow.html"><I>pow</I></A> </P> </BLOCKQUOTE> </BODY>