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<H2>C Specification</H2> 13<DL> 14 <DD> 15 <PRE><CODE>#include <revolution/gx.h></CODE></PRE> 16 <DD> 17 <PRE><CODE>void 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 );</CODE></PRE> 21</DL> 22<H2>Arguments</H2> 23<TABLE border="1" cellpadding="3" cellspacing="0.1"> 24 <TBODY> 25 <TR> 26<TD width="120" bgcolor="#ffffe8"><EM><STRONG><CODE>lt_obj</CODE></STRONG></EM></TD> 27<TD width="520">pointer to a light object</TD> 28 </TR> 29 <TR> 30<TD width="120" bgcolor="#ffffe8"><EM><STRONG><CODE>cutoff</CODE></STRONG></EM></TD> 31<TD width="520">spotlight cutoff angle (in degrees)0 < <BR><CODE>cutoff<=90</CODE></TD> 32 </TR> 33 <TR> 34<TD width="120" bgcolor="#ffffe8"><EM><STRONG><CODE>spot_func</CODE></STRONG></EM></TD> 35<TD width="520">type of light volume distribution functions <BR>Accepted values are:<BR> 36 <TABLE width="500" border="1" cellspacing="0.1"> 37 38 <tr> 39<TD width="150" bgcolor="#C0C0C0">Name</TD> 40<TD width="350" bgcolor="#C0C0C0">Spot (Angular Attenuation) Function Types</TD> 41 </tr> 42 <tr> 43<TD width="150" height="7"><code>GX_SP_OFF</code></TD> 44<TD width="350" height="7">no attenuation</TD> 45 </tr> 46 <tr> 47<TD width="150" height="19"><code>GX_SP_FLAT</code></TD> 48<TD rowspan="6" height="43" width="350">refer to the figure below</TD> 49 </tr> 50 <tr> 51 <TD width="150"><code>GX_SP_COS</code></TD> 52 </tr> 53 <tr> 54 <TD width="150" height="22"><code>GX_SP_COS2</code></TD> 55 </tr> 56 <tr> 57 <TD width="150"><code>GX_SP_SHARP</code></TD> 58 </tr> 59 <tr> 60 <TD width="150"><code>GX_SP_RING1</code></TD> 61 </tr> 62 <tr> 63 <TD width="150"><code>GX_SP_RING2</code></TD> 64 </tr> 65 66 </TABLE> 67 </TD> 68 </TR> 69 </TBODY> 70</TABLE> 71<H2>Return Values</H2> 72<P>None.</P> 73<H2>Description</H2> 74<P>This function 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 the <EM><STRONG><CODE>a0</CODE></STRONG></EM>, <EM><STRONG><CODE>a1</CODE></STRONG></EM> and <EM><STRONG><CODE>a2</CODE></STRONG></EM> used by <a href="GXInitLightAttn.html"><code>GXInitLightAttn</code></a>.</P> 75<P>The parameter <EM><STRONG><CODE>cutoff</CODE></STRONG></EM> 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 <a href="GXInitLightDir.html"><code>GXInitLightDir</code></a> is smaller than this cutoff angle. The <EM><STRONG><CODE>cutoff</CODE></STRONG></EM> value should be 0 < <EM><STRONG><CODE>cutoff</CODE></STRONG></EM> <= 90.0. Otherwise, the given light object doesn't become a spotlight. (Some spotlight types require tighter range.) </P> 76<P>The parameter <EM><STRONG><CODE>spot_func</CODE></STRONG></EM> defines the type of the illumination distribution within cutoff angle. The following graphs show curve shape of the distribution functions given by acceptable values for <EM><STRONG><CODE>spot_func</CODE></STRONG></EM>. And 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 <a href="GXSetChanCtrl.html"><code>GXSetChanCtrl</code></a>).</P> 77<DIV align="center"> 78<CENTER> 79<table border="1" cellpadding="3" cellspacing="0" width="474"> 80 81 <tr> 82<td width="168" align="center">Graph</td> 83 <td width="144" align="center"> 84<IMG src="SpotFn1.gif" alt="SpotFn1.gif (1403 bytes)" width="128" height="128"></td> 85 <td width="141" align="center"> 86<IMG src="SpotFn2.gif" alt="SpotFn2.gif (1457 bytes)" width="128" height="128"></td> 87 <td width="166" align="center"> 88<IMG src="SpotFn3.gif" alt="SpotFn3.gif (1465 bytes)" width="128" height="128"></td> 89 </tr> 90 <tr> 91<td width="168" align="center">Type</td> 92<td width="144" align="center"><code>GX_SP_FLAT</code></td> 93<td width="141" align="center"><code>GX_SP_COS</code></td> 94<td width="166" align="center"><code>GX_SP_COS2</code></td> 95 </tr> 96 <tr> 97<td width="168" align="center">Valid Range</td> 98 <td width="144" align="center"> 99<p align="center">0<cutoff<=90</CODE> 100 </td> 101<td width="141" align="center">0<cutoff<=90</CODE></td> 102<td width="166" align="center">0<cutoff<=90</CODE></td> 103 </tr> 104 <tr> 105<td width="168" align="center">Graph</td> 106 <td width="144" align="center"> 107<IMG src="SpotFn4.gif" alt="SpotFn4.gif (1460 bytes)" width="128" height="128"></td> 108 <td width="141" align="center"> 109<IMG src="SpotFn5.gif" alt="SpotFn5.gif (1554 bytes)" width="128" height="128"></td> 110 <td width="166" align="center"> 111<IMG src="SpotFn6.gif" alt="SpotFn6.gif (1557 bytes)" width="128" height="128"></td> 112 </tr> 113 <tr> 114<td width="168" align="center">Type</td> 115<td width="144" align="center"><code>GX_SP_SHARP</code></td> 116<td width="141" align="center"><code>GX_SP_RING1</code></td> 117<td width="166" align="center"><code>GX_SP_RING2</code></td> 118 </tr> 119 <tr> 120<td width="168" align="center">Valid Range</td> 121 <td width="144" align="center"> 122<p align="center">30<<em><strong>cutoff</strong></em><=90 123 </td> 124<td width="141" align="center">30<<em><strong>cutoff</strong></em><=90</td> 125<td width="166" align="center">30<<em><strong>cutoff</strong></em><=90</td> 126 </tr> 127 128</table> 129</CENTER> 130</DIV> 131<P>This function can generate only some kinds of simple spotlights. For more flexible control, use <a href="GXInitLightAttn.html"><code>GXInitLightAttn</code></a> and calculate the appropriate coefficients.</P> 132<P>This function sets parameters only for angular attenuation. Parameters for distance attenuation should be set using <a href="GXInitLightDistAttn.html"><code>GXInitLightDistAttn</code></a> or <a href="GXInitLightAttnK.html"><code>GXInitLightAttnK</code></a>.</P> 133<P>This function does not load any hardware registers directly. To load a light object into a hardware light, use <a href="GXLoadLightObjImm.html"><code>GXLoadLightObjImm</code></a> or <a href="GXLoadLightObjIndx.html"><code>GXLoadLightObjIndx</code></a>.</P> 134<H2>See Also</H2> 135<P><CODE><A href="GXInitLightAttn.html">GXInitLightAttn</A><BR> <A href="GXInitLightAttnA.html">GXInitLightAttnA</A></CODE><BR> <A href="GXInitLightAttnK.html"><CODE>GXInitLightAttnK</CODE></A><BR> <CODE><A href="GXInitLightDistAttn.html">GXInitLightDistAttn</A></CODE></P> 136<P><A href="GXLightObjInitFlow.html"><CODE>GXLightObj</CODE> Initialization Flow</A></P> 137<H2>Revision History</H2> 138<P>2006/03/01 Initial version.</P> 139<hr> 140<P>CONFIDENTIAL</p> 141</BODY> 142</HTML>
