/* interp.h */

/*
 * Mesa 3-D graphics library
 * Version:  1.2
 * Copyright (C) 1995  Brian Paul  (brianp@ssec.wisc.edu)
 *
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Library General Public
 * License as published by the Free Software Foundation; either
 * version 2 of the License, or (at your option) any later version.
 *
 * This library is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * Library General Public License for more details.
 *
 * You should have received a copy of the GNU Library General Public
 * License along with this library; if not, write to the Free
 * Software Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
 */


/*
$Id: interp.h,v 1.5 1995/06/12 15:43:57 brianp Exp $

$Log: interp.h,v $
 * Revision 1.5  1995/06/12  15:43:57  brianp
 * separate GLint and GLubyte interpolation functions
 *
 * Revision 1.4  1995/06/02  13:59:01  brianp
 * faster GL_INTERPOLATE() macro
 *
 * Revision 1.3  1995/05/22  20:59:34  brianp
 * Release 1.2
 *
 * Revision 1.2  1995/03/04  19:25:29  brianp
 * 1.1 beta revision
 *
 * Revision 1.1  1995/02/27  22:20:16  brianp
 * Initial revision
 *
 */


#ifndef INTERP_H
#define INTERP_H



extern void gl_interpolate_i( GLint n, GLint y0, GLint y1, GLint yspan[] );


extern void gl_interpolate_ub( GLint n, GLint y0, GLint y1, GLubyte yspan[] );


extern void gl_interpolate_rgba( GLint n,
				 GLint r0, GLint r1, GLint *ir,
				 GLint g0, GLint g1, GLint *ig,
				 GLint b0, GLint b1, GLint *ib,
				 GLint a0, GLint a1, GLint *ia );


extern void gl_interp_texcoords( GLuint n,
				 GLfloat eyez0, GLfloat eyez1,
				 GLfloat winz0, GLfloat winz1,
				 GLfloat s0, GLfloat s1,
				 GLfloat t0, GLfloat t1,
				 GLfloat s[], GLfloat t[], GLfloat *z );


#ifdef DEBUG

#define GL_INTERPOLATE_I(N,Y0,Y1,YSPAN)   gl_interpolate_i(N,Y0,Y1,YSPAN)

#define GL_INTERPOLATE_UB(N,Y0,Y1,YSPAN)  gl_interpolate_ub(N,Y0,Y1,YSPAN)

#else

#define GL_INTERPOLATE_I(N,Y0,Y1,YSPAN)	\
{					\
   switch (N) {				\
      case 1:				\
	 YSPAN[0] = Y0;			\
	 break;				\
      case 2:				\
	 YSPAN[0] = Y0;			\
	 YSPAN[1] = Y1;			\
	 break;				\
      case 3:				\
	 YSPAN[0] = Y0;			\
	 YSPAN[1] = ((Y0)+(Y1)) >> 1;	\
	 YSPAN[2] = Y1;			\
	 break;				\
      default:				\
	 if (Y0==Y1) {			\
	    register GLint i;		\
	    for (i=0;i<(N);i++) {	\
	       YSPAN[i] = Y0;		\
	    }				\
	 }				\
	 else {				\
	    register GLint i;		\
	    register GLint dx, dy;	\
	    register GLint a, b, d;	\
	    register GLint yy;		\
	    register GLint qa, qb;	\
	    dx = (N)-1;			\
	    dy = (Y1) - (Y0);		\
	    qa = dy / dx;		\
	    dy = dy % dx;		\
	    if (dy<0) {			\
	       dy = -dy;		\
	       qb = qa - 1;		\
	    }				\
	    else {			\
	       qb = qa + 1;		\
	    }				\
	    a = dy + dy;		\
	    d = a - dx;			\
	    b = d - dx;			\
	    yy = Y0;			\
	    for (i=0;i<(N);i++) {	\
	       YSPAN[i] = yy;		\
	       if (d<0) {		\
		  d += a;		\
		  yy += qa;		\
	       }			\
	       else {			\
		  d += b;		\
		  yy += qb;		\
	       }			\
	    }				\
	 }				\
   }					\
}


#define GL_INTERPOLATE_UB(N,Y0,Y1,YSPAN)   GL_INTERPOLATE_I(N,Y0,Y1,YSPAN)


#endif  /*DEBUG*/


#endif  /* INTERP_H */