/*---------------------------------------------------------------------

  $Id: us2dex.c,v 1.1.1.1 2003/01/17 23:03:12 wheeler Exp $

  

  File : us2dex.c

  

  Coded     by Yoshitaka Yasumoto.   Mar 19, 1997.

  Copyright by Nintendo, Co., Ltd.           1997.

  ---------------------------------------------------------------------*/

#include	<ultra64.h>

#include	<PR/gs2dex.h>



/*

 *	Routines that support processing of S2DEX microcode

 */



/*

 *	guS2DInitBG

 *		Set BG screen draw parameters

 *

 *		If called at time of initialization, then it only needs to be 

 *		called again when changes made to imageFmt, imageSiz, imageLoad, *		imageW, frameW.  However, if  imageLoad == G_BGLT_LOADBLOCK and  *		only frameW is changed, another call is unnecessary.

 */

void	guS2DInitBg(uObjBg *bg)

{

  u16	tmemUse;

  u16	shift;

  u32	tsize;

  

  /*

   *	Get the useable volume for TMEM

   *		If imageFmt is CI then TLUT will use half

   */

  tmemUse = (bg->b.imageFmt == G_IM_FMT_CI) ? 256 : 512;

  

  /*

   *	Get shift volume for conversion to TMEM word

   */

  shift = 6 - bg->b.imageSiz;

  

  /*

   *	Set other parameters for Load Mode

   */

  if (bg->b.imageLoad == G_BGLT_LOADBLOCK){

    bg->b.tmemW      = bg->b.imageW >> shift;

    bg->b.tmemH      = (tmemUse / bg->b.tmemW) << 2;

    bg->b.tmemSizeW  = bg->b.tmemW << 1;

    bg->b.tmemSize   = bg->b.tmemH * bg->b.tmemSizeW;

    bg->b.tmemLoadSH = (bg->b.tmemSize>>1) - 1;

    bg->b.tmemLoadTH = GS_CALC_DXT(bg->b.tmemW);

  } else {

    bg->b.tmemW      = (bg->b.frameW >> shift) + 3;

    bg->b.tmemH      = (tmemUse / bg->b.tmemW) << 2;

    bg->b.tmemSizeW  = (bg->b.imageW >> shift) * 2;

    tsize = bg->b.tmemH * bg->b.tmemSizeW;

    bg->b.tmemSize   = tsize >> 16;

    bg->b.tmemLoadSH = tsize & 0xffff;

    bg->b.tmemLoadTH = bg->b.tmemH - 1;

  }

  return;

}



/*======== End of us2dex.c ========*/