1<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"> 2<HTML> 3<HEAD> 4<META http-equiv="Content-Type" content="text/html; charset=windows-1252"> 5<META name="GENERATOR" content="Microsoft FrontPage 5.0"> 6<META http-equiv="Content-Style-Type" content="text/css"> 7<LINK rel="stylesheet" type="text/css" href="../../CSS/revolution.css"> 8<TITLE>GXInitLightDistAttn</TITLE> 9</HEAD> 10<BODY> 11<H1 align="left">GXInitLightDistAttn</H1> 12 13<H2>Syntax</H2> 14<dl><dd><pre class="construction"> 15#include <revolution/gx.h> 16 17void GXInitLightDistAttn( 18 <A href="../Structures/GXLightObj.html">GXLightObj</A>* lt_obj, 19 f32 ref_distance, 20 f32 ref_brightness, 21 <A href="../Enumerated_Types/GXDistAttnFn.html">GXDistAttnFn</A> dist_func ); 22</pre></dd></dl> 23 24<H2>Arguments</H2> 25<TABLE class="arguments" border="1" > 26 <TBODY> 27 <TR> 28<TH>lt_obj</TH> 29<TD>Pointer to a light object.</TD> 30 </TR> 31 <TR> 32<TH>ref_distance</CODE></TH> 33<TD>Distance between the light and the reference point.</TD> 34 </TR> 35 <TR> 36<TH>ref_brightness</CODE></TH> 37<TD>Brightness of the reference point.0 < <SPAN class="argument">ref_brightness</SPAN> < 1.</TD> 38 </TR> 39 <TR> 40<TH>dist_func</CODE></TH> 41<TD>Type of brightness reduction function. Accepted values are:<BR> 42 <TABLE class="arguments" border="1" > 43 <TBODY> 44 <TR> 45<TD bgcolor="#C0C0C0">Name</TD> 46<TD bgcolor="#C0C0C0">Type of distance attenuation function</TD> 47 </TR> 48 <TR> 49<TH>GX_DA_OFF</TH> 50<TD>No attenuation.</TD> 51 </TR> 52 <TR> 53<TH>GX_DA_GENTLE</TH> 54<TD rowspan="3">See the figures below.</TD> 55 </TR> 56 <TR> 57<TH>GX_DA_MEDIUM</TH> 58 </TR> 59 <TR> 60<TH>GX_DA_STEEP</TH> 61 </TR> 62 </TBODY> 63 </TABLE> 64 </TD> 65 </TR> 66 </TBODY> 67</TABLE> 68 69<H2>Return Values</H2> 70<P>None.</P> 71 72<H2>Description</H2> 73<P>This function sets coefficients for distance attenuation in light objects. These can be also set using the <A href="GXInitLightAttn.html"><CODE>GXInitLightAttn</CODE></A> function. This function uses three easy-to-control parameters instead of the <SPAN class="argument">k0</SPAN>, <SPAN class="argument">k1</SPAN> and <SPAN class="argument">k2</SPAN> parameters used in the <A href="GXInitLightAttn.html"><CODE>GXInitLightAttn</CODE></A> function.</P> 74<P>This function can specify the brightness on an assumed reference point. The <SPAN class="argument">ref_distance</SPAN> parameter is the distance between the light and the reference point. The <SPAN class="argument">ref_brightness</SPAN> parameter specifies the ratio of the brightness at the reference point. The value for <SPAN class="argument">ref_distance</SPAN> should be greater than 0. In addition, the value for <SPAN class="argument">ref_brightness</SPAN> must be within 0 < <SPAN class="argument">ref_brightness</SPAN> < 1. If not, distance attenuation will not work.</P> 75<P>The <SPAN class="argument">dist_func</SPAN> parameter defines the type of brightness decrease over distance. The following graphs show curve shape of the decreasing functions given by acceptable values for <SPAN class="argument">dist_func</SPAN>. The value <code>GX_DA_OFF</code> turns the distance attenuation feature off.</P> 76<DIV align="center"> 77<CENTER> 78<TABLE border="1" width="128" cellpadding="0"> 79 <TBODY> 80 <TR> 81 <TD><IMG src="DistFn1.gif" alt="DistFn1.gif (1605 bytes)" width="128" height="128"></TD> 82 <TD><IMG src="DistFn2.gif" alt="DistFn2.gif (1611 bytes)" width="128" height="128"></TD> 83 <TD><IMG src="DistFn3.gif" alt="DistFn3.gif (1600 bytes)" width="128" height="128"></TD> 84 </TR> 85 <TR> 86 <TD align="center"><CODE>GX_DA_GENTLE</CODE></TD> 87 <TD align="center"><CODE>GX_DA_MEDIUM</CODE></TD> 88 <TD align="center"><CODE>GX_DA_STEEP</CODE></TD> 89 </TR> 90 </TBODY> 91</TABLE> 92</CENTER> 93</DIV> 94<P>For more flexible control, use the <A href="GXInitLightAttn.html"><CODE>GXInitLightAttn</CODE></A> function and calculate the appropriate coefficients.</P> 95<P>Be aware that this function sets parameters only for distance attenuation. Parameters for angular attenuation should be set using the <A href="GXInitLightSpot.html"><CODE>GXInitLightSpot</CODE></A> or <A href="GXInitLightAttnA.html"><CODE>GXInitLightAttnA</CODE></A> function.</P> 96<P>This function does not load any hardware registers directly. To load a light object into a hardware light, use the <A href="GXLoadLightObjImm.html"><CODE>GXLoadLightObjImm</CODE></A> or <A href="GXLoadLightObjIndx.html"><CODE>GXLoadLightObjIndx</CODE></A> function.</P> 97 98<H2>See Also</H2> 99<P class="reference"> 100<A href="GXInitLightAttn.html">GXInitLightAttn</A>, 101<A href="GXGetLightAttnA.html">GXInitLightAttnA</A>, 102<A href="GXInitLightAttnK.html">GXInitLightAttnK</A>, 103<A href="GXInitLightSpot.html">GXInitLightSpot</A>, 104<A href="GXLightObjInitFlow.html">GXLightObj Initialization Flow</A> 105</P> 106 107<H2>Revision History</H2> 108<P> 1092006/03/01 Initial version.<br> 110</P> 111 112<hr><p>CONFIDENTIAL</p></body> 113</HTML>
