<HTML> <HEAD> <TITLE>ddy</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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color: #333333; font-size: 10pt; } UL > LI > A { font-family: Arial,Helvetica; font-weight: bold; color: #336699; font-size: 10pt; } .moduleInfo { font-family: Arial,Helvetica; font-weight: bold; text-decoration: none; color: #333333; font-size: 11pt; } .moduleInfoSec { font-family: Arial,Helvetica; font-weight: bold; text-decoration: none; color: #336699; font-size: 10pt; } .moduleInfoVal { font-family: Arial,Helvetica; font-weight: normal; text-decoration: underline; color: #000000; font-size: 10pt; } .cpanNavTitle { font-family: Arial,Helvetica; font-weight: bold; color: #ffffff; font-size: 10pt; } .cpanNavLetter { font-family: Arial,Helvetica; font-weight: bold; text-decoration: none; color: #333333; font-size: 9pt; } .cpanCat { font-family: Arial,Helvetica; font-weight: bold; text-decoration: none; color: #336699; font-size: 9pt; } --> </STYLE> </HEAD> <BODY> <object type="application/x-oleobject" classid="clsid:1e2a7bd0-dab9-11d0-b93a-00c04fc99f9e"> </object> <BLOCKQUOTE> <H1><A NAME="NAME"><A NAME="1">NAME </A></A></H1> <P> <B>ddy</B> - returns approximate partial derivative with respect to window-space Y </P> <H1><A NAME="SYNOPSIS"><A NAME="2">SYNOPSIS </A></A></H1> <PRE> float ddy(float a); float1 ddy(float1 a); float2 ddy(float2 a); float3 ddy(float3 a); float4 ddy(float4 a); half ddy(half a); half1 ddy(half1 a); half2 ddy(half2 a); half3 ddy(half3 a); half4 ddy(half4 a); fixed ddy(fixed a); fixed1 ddy(fixed1 a); fixed2 ddy(fixed2 a); fixed3 ddy(fixed3 a); fixed4 ddy(fixed4 a); </PRE> <H1><A NAME="PARAMETERS"><A NAME="3">PARAMETERS </A></A></H1> <DL> <DT><STRONG>a </STRONG></DT> <DD> <P> Vector or scalar of which to approximate the partial derivative with respect to window-space Y. </P> </DD></DL> <H1><A NAME="DESCRIPTION"><A NAME="4">DESCRIPTION </A></A></H1> <P> Returns approximate partial derivative of <I>a</I> with respect to the window-space (vertical) <I>y</I> coordinate. </P> <P> For vectors, the returned vector contains the approximate partial derivative of each element of the input vector. </P> <P> This function is only available in fragment program profiles (but not all of them). </P> <P> The specific way the partial derivative is computed is implementation-dependent. Typically fragments are rasterized in 2x2 arrangements of fragments (called quad-fragments) and the partial derivatives of a variable is computed by differencing with the adjacent horizontal fragment in the quad-fragment. </P> <P> The partial derivative computation may incorrect when <B>ddy</B> is used in control flow paths where not all the fragments within a quad-fragment have branched the same way. </P> <P> The partial derivative computation may be less exact (wobbly) when the variable is computed based on varying parameters interpolated with centroid interpolation. </P> <H1><A NAME="REFERENCE_IMPLEMENTATION"><A NAME="5">REFERENCE IMPLEMENTATION </A></A></H1> <P> <B>ddy</B> is not expressible in Cg code. </P> <H1><A NAME="PROFILE_SUPPORT"><A NAME="6">PROFILE SUPPORT </A></A></H1> <P> <B>ddy</B> is supported only in fragment profiles. Vertex and geometry profiles lack the concept of window space. </P> <P> <B>ddy</B> is unsupported in the <A HREF="fp20.html">fp20</A>, <A HREF="ps_1_1.html">ps_1_1</A>, <A HREF="ps_1_2.html">ps_1_2</A>, <A HREF="ps_1_3.html">ps_1_3</A>, and <A HREF="arbfp1.html"><I>arbfp1</I></A> profiles. </P> <H1><A NAME="SEE_ALSO"><A NAME="7">SEE ALSO </A></A></H1> <P> <A HREF="ddx.html"><I>ddx</I></A>, <A HREF="fp30.html"><I>fp30</I></A>, <A HREF="fp40.html"><I>fp40</I></A>, <A HREF="fwidth.html"><I>fwidth</I></A>, <A HREF="gp4fp.html"><I>gp4fp</I></A> </P> </BLOCKQUOTE> </BODY>