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>GXInitLightShininess</TITLE> 9</HEAD> 10<BODY> 11<H1 align="left">GXInitLightShininess</H1> 12<H2>C Specification</H2> 13<DL> 14 <DD> 15 <PRE><CODE>#include <revolution/gx.h></CODE></PRE> 16 <DD> 17 <PRE><CODE>#define GXInitLightShininess(lobj, shininess) \ 18 GXInitLightAttn(lobj, 0.0F, 0.0F, 1.0F, \ 19 (shininess)/2.0F, 0.0F, \ 20 1.0F-(shininess)/2.0F )</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>lobj</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>shininess</CODE></STRONG></EM></TD> 31<TD width="520">shininess parameter</TD> 32 </TR> 33 </TBODY> 34</TABLE> 35<H2>Return Values</H2> 36<P>None.</P> 37<H2>Description</H2> 38<P>This function sets the <em><strong><code>shininess</code></strong></em> of a per-vertex specular light. In reality, shininess is a property of the <em>material</em> being lit, not the light. However, in the graphics processor, the specular calculation is implemented by reusing the diffuse angle/distance attenuation function, so shininess is determined by the light attenuation parameters (see <A href="GXInitLightAttn.html"><CODE>GXInitLightAttn</CODE></A>). The arithmetic formula approximates the function (N*H)^<CODE><EM><STRONG>shininess</STRONG></EM></CODE> "(Normal vector (1/2 the line-of-sight and the light direction))^brightness" Since the attenuation formula is only a fraction of second degree equations, it cannot be used as an accurate exponential function. To enable specular calculations, the lighting channel attenuation parameter must be set to <CODE>GX_AF_SPEC</CODE> using <A href="GXSetChanCtrl.html"><CODE>GXSetChanCtrl</CODE></A> function.</P> 39<P>The graph below represents the attenuation curve for various shininess levels (<EM><STRONG><CODE>shininess</CODE></STRONG></EM>).</P> 40<P><IMG src="shininess.jpg" alt="shininess.jpg (30875 bytes)" width="571" height="421"></P> 41<P>As you can see from the graph, a larger value of shininess creates a narrower specular highlight.</P> 42<P>And the following image shows result samples.</P> 43<TABLE border="0" width="71%" cellspacing="0" cellpadding="0"> 44 <TBODY> 45 <TR> 46<TD width="21%"><IMG src="Spec004.gif" alt="Spec004.gif (8415 bytes)" width="160" height="160"></TD> 47<TD width="21%"><IMG src="Spec016.gif" alt="Spec016.gif (7761 bytes)" width="160" height="160"></TD> 48<TD width="21%"><IMG src="Spec064.gif" alt="Spec064.gif (6036 bytes)" width="160" height="160"></TD> 49<TD width="37%"><IMG src="Spec256.gif" alt="Spec256.gif (4218 bytes)" width="160" height="160"></TD> 50 </TR> 51 <TR> 52<TD width="21%" align="center"><strong><em>shininess</em></strong> = 4.0</TD> 53<TD width="21%" align="center"><strong><em>shininess</em></strong> = 16.0</TD> 54<TD width="21%" align="center"><strong><em>shininess</em></strong> = 64.0</TD> 55<TD width="37%" align="center"><strong><em>shininess</em></strong> = 256.0</TD> 56 </TR> 57 </TBODY> 58</TABLE> 59<H2>See Also</H2> 60<P><A href="GXLightObjInitFlow.html">GXLightObj Initialization Flow</A></P> 61<P><A href="GXSetChanCtrl.html"><code>GXSetChanCtrl</code></A></P> 62<H2>Revision History</H2> 63<P>2006/03/01 Initial version.</P> 64<hr> 65<P>CONFIDENTIAL</p> 66</BODY> 67</HTML>
