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>GXInitLightSpot</TITLE> 9</HEAD> 10<BODY> 11<H1 align="left">GXInitLightSpot</H1> 12 13<H2>Syntax</H2> 14<dl><dd><pre class="construction"> 15#include <revolution/gx.h> 16 17void GXInitLightSpot( 18 <A href="../Structures/GXLightObj.html">GXLightObj</A>* lt_obj, 19 f32 cutoff, 20 <A href="../Enumerated_Types/GXSpotFn.html">GXSpotFn</A> spot_func ); 21</pre></dd></dl> 22 23<H2>Arguments</H2> 24<TABLE class="arguments" border="1" > 25 <TBODY> 26 <TR> 27 <TH>lt_obj</TH> 28 <TD>Pointer to a light object.</TD> 29 </TR> 30 <TR> 31 <TH>cutoff</TH> 32 <TD>Spotlight cutoff angle (in degrees).0 < <SPAN class="argument">cutoff</SPAN> <= 90.</TD> 33 </TR> 34 <TR> 35 <TH>spot_func</TH> 36 <TD>Types of light volume distribution functions. Accepted values are:<BR> 37 <TABLE class="arguments" border="1" > 38 <tr> 39 <TD bgcolor="#C0C0C0">Name</TD> 40 <TD bgcolor="#C0C0C0">Spot (Angular Attenuation) Function Types</TD> 41 </tr> 42 <tr> 43 <TH>GX_SP_OFF</TH> 44 <TD>No attenuation.</TD> 45 </tr> 46 <tr> 47 <TH>GX_SP_FLAT</TH> 48 <TD rowspan="6">See the figures below.</TD> 49 </tr> 50 <tr> 51 <TH>GX_SP_COS</TH> 52 </tr> 53 <tr> 54 <TH>GX_SP_COS2</TH> 55 </tr> 56 <tr> 57 <TH>GX_SP_SHARP</TH> 58 </tr> 59 <tr> 60 <TH>GX_SP_RING1</TH> 61 </tr> 62 <tr> 63 <TH>GX_SP_RING2</TH> 64 </tr> 65 </TABLE> 66 </TD> 67 </TR> 68 </TBODY> 69</TABLE> 70 71<H2>Return Values</H2> 72<P>None.</P> 73 74<H2>Description</H2> 75<P>Sets coefficients for angular (spotlight) attenuation in light objects. This can be also set with the <A href="GXInitLightAttn.html"><CODE>GXInitLightAttn</CODE></A> function. This function uses two easy-to-control parameters instead of <SPAN class="argument">a0</SPAN>, <SPAN class="argument">a1</SPAN>, and <SPAN class="argument">a2</SPAN>, which are used by the <A href="GXInitLightAttn.html"><CODE>GXInitLightAttn</CODE></A> function.</P> 76<P>The <SPAN class="argument">cutoff</SPAN> argument specifies the spotlight's cutoff angle in degrees. The spotlight works when the angle between the ray for a vertex and the light direction given by the <a href="GXInitLightDir.html"><code>GXInitLightDir</code></a> function is smaller than this cutoff angle. The value used for <SPAN class="argument">cutoff</SPAN> should be 0 < <SPAN class="argument">cutoff</SPAN> <= 90.0. Otherwise, the given light object doesn't become a spotlight. (Some spotlight types require tighter range.) </P> 77<P>The <SPAN class="argument">spot_func</SPAN> argument defines the type of the illumination distribution to be used within the cutoff angle. The following graphs show the curves of the distribution functions given by acceptable values for <SPAN class="argument">spot_func</SPAN>. The value <CODE>GX_SP_OFF</CODE> turns the spotlight feature off even if the color channel setting uses <CODE>GX_AF_SPOT</CODE> (see the <A href="GXSetChanCtrl.html"><CODE>GXSetChanCtrl</CODE></A> function).</P> 78<DIV align="center"> 79<CENTER> 80<table border="1" cellpadding="3" cellspacing="0" width="474"> 81 82 <tr> 83 <td width="168" align="center">Graph</td> 84 <td width="144" align="center"> 85 <IMG src="SpotFn1.gif" alt="SpotFn1.gif (1403 bytes)" width="128" height="128"></td> 86 <td width="141" align="center"> 87 <IMG src="SpotFn2.gif" alt="SpotFn2.gif (1457 bytes)" width="128" height="128"></td> 88 <td width="166" align="center"> 89 <IMG src="SpotFn3.gif" alt="SpotFn3.gif (1465 bytes)" width="128" height="128"></td> 90 </tr> 91 <tr> 92 <td width="168" align="center">Type</td> 93 <td width="144" align="center"><code>GX_SP_FLAT</code></td> 94 <td width="141" align="center"><code>GX_SP_COS</code></td> 95 <td width="166" align="center"><code>GX_SP_COS2</code></td> 96 </tr> 97 <tr> 98 <td width="168" align="center">Valid Range</td> 99 <td width="144" align="center">0 < <SPAN class="argument">cutoff</SPAN> <= 90</td> 100 <td width="141" align="center">0 < <SPAN class="argument">cutoff</SPAN> <= 90</td> 101 <td width="166" align="center">0 < <SPAN class="argument">cutoff</SPAN> <= 90</td> 102 </tr> 103 <tr> 104 <td width="168" align="center">Graph</td> 105 <td width="144" align="center"> 106 <IMG src="SpotFn4.gif" alt="SpotFn4.gif (1460 bytes)" width="128" height="128"></td> 107 <td width="141" align="center"> 108 <IMG src="SpotFn5.gif" alt="SpotFn5.gif (1554 bytes)" width="128" height="128"></td> 109 <td width="166" align="center"> 110 <IMG src="SpotFn6.gif" alt="SpotFn6.gif (1557 bytes)" width="128" height="128"></td> 111 </tr> 112 <tr> 113 <td width="168" align="center">Type</td> 114 <td width="144" align="center"><code>GX_SP_SHARP</code></td> 115 <td width="141" align="center"><code>GX_SP_RING1</code></td> 116 <td width="166" align="center"><code>GX_SP_RING2</code></td> 117 </tr> 118 <tr> 119 <td width="168" align="center">Valid Range</td> 120 <td width="144" align="center">30 < <SPAN class="argument">cutoff</SPAN> <= 90</td> 121 <td width="141" align="center">30 < <SPAN class="argument">cutoff</SPAN> <= 90</td> 122 <td width="166" align="center">30 < <SPAN class="argument">cutoff</SPAN> <= 90</td> 123 </tr> 124 125</table> 126</CENTER> 127</DIV> 128<P>This function can generate only some kinds of simple spotlights. For more flexible control, use the <A href="GXInitLightAttn.html"><CODE>GXInitLightAttn</CODE></A> function and calculate the appropriate coefficients.</P> 129<P>This function sets parameters only for angular attenuation. Parameters for distance attenuation may be set using the <A href="GXInitLightDistAttn.html"><CODE>GXInitLightDistAttn</CODE></A> or <A href="GXInitLightAttnK.html"><CODE>GXInitLightAttnK</CODE></A> function.</P> 130<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> 131 132<H2>See Also</H2> 133<P> 134<A href="GXInitLightAttn.html"><CODE>GXInitLightAttn</CODE></A><BR> <A href="GXInitLightAttnA.html"><CODE>GXInitLightAttnA</CODE></A><BR> <A href="GXInitLightAttnK.html"><CODE>GXInitLightAttnK</CODE></A><BR> <A href="GXInitLightDistAttn.html"><CODE>GXInitLightDistAttn</CODE></A><BR> <A href="GXLightObjInitFlow.html"><CODE>GXLightObj</CODE> Initialization Flow</A> 135</P> 136 137<H2>Revision History</H2> 138<P> 1392006/03/01 Initial version. 140</P> 141 142<hr><p>CONFIDENTIAL</p></body> 143</HTML>
