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<HTML>
<HEAD>
<META name=vsisbn content="1576101746">
<META name=vstitle content="Michael Abrash's Graphics Programming Black Book, Special Edition">
<META name=vsauthor content="Michael Abrash">
<META name=vspublisher content="The Coriolis Group">
<META name=vspubdate content="07/01/97">
<META name=vscategory content="Web and Software Development: Game Development,Web and Software Development: Graphics and Multimedia Development">
<TITLE>Michael Abrash's Graphics Programming Black Book Special Edition: Fast 3-D Animation: Meet X-Sharp</TITLE>
<!-- HEADER -->
<!-- Empty Reference Subhead -->
<!--ISBN=1576101746//-->
<!--TITLE=Michael Abrash's Graphics Programming Black Book Special Edition//-->
<!--AUTHOR=Michael Abrash//-->
<!--PUBLISHER=The Coriolis Group, Inc.//-->
<!--CHAPTER=52//-->
<!--PAGES=981-984//-->
<!--UNASSIGNED1//-->
<!--UNASSIGNED2//--></HEAD><BODY LINK=#0000FF ALINK=#000099 VLINK=#0000FF BGCOLOR=#FFFFFF>
<CENTER>
<TABLE BORDER>
<TR>
<TD><A HREF="52-05.html">Previous</A></TD>
<TD><A HREF="index.html">Table of Contents</A></TD>
<TD><A HREF="52-07.html">Next</A></TD>
</TR>
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<P><BR></P>
<P><B>LISTING 52.9 L52-9.ASM</B></P>
<!-- CODE //-->
<PRE>
; 386-specific fixed point multiply and divide.
;
; C near-callable as: Fixedpoint FixedMul(Fixedpoint M1, Fixedpoint M2);
; Fixedpoint FixedDiv(Fixedpoint Dividend, Fixedpoint Divisor);
;
; Tested with TASM
;
.model small
.386
.code
public _FixedMul,_FixedDiv
; Multiplies two fixed-point values together.
FMparms struc
dw 2 dup(?) ;return address &amp pushed BP
M1 dd ?
M2 dd ?
FMparms ends
align 2
_FixedMul proc near
push bp
mov bp,sp
mov eax,[bp+M1]
imul dword ptr [bp+M2] ;multiply
add eax,8000h ;round by adding 2^(-16)
adc edx,0 ;whole part of result is in DX
shr eax,16 ;put the fractional part in AX
pop bp
ret
_FixedMul endp
; Divides one fixed-point value by another.
FDparms struc
dw 2 dup(?) ;return address &amp pushed BP
Dividend dd ?
Divisor dd ?
FDparms ends
align 2
_FixedDiv proc near
push bp
mov bp,sp
sub cx,cx ;assume positive result
mov eax,[bp+Dividend]
and eax,eax ;positive dividend?
jns FDP1 ;yes
inc cx ;mark it's a negative dividend
neg eax ;make the dividend positive
FDP1: sub edx,edx ;make it a 64-bit dividend, then shift
; left 16 bits so that result will be in EAX
rol eax,16 ;put fractional part of dividend in
; high word of EAX
mov dx,ax ;put whole part of dividend in DX
sub ax,ax ;clear low word of EAX
mov ebx,dword ptr [bp+Divisor]
and ebx,ebx ;positive divisor?
jns FDP2 ;yes
dec cx ;mark it's a negative divisor
neg ebx ;make divisor positive
FDP2: div ebx ;divide
shr ebx,1 ;divisor/2, minus 1 if the divisor is
adc ebx,0 ; even
dec ebx
cmp ebx,edx ;set Carry if remainder is at least
adc eax,0 ; half as large as the divisor, then
; use that to round up if necessary
and cx,cx ;should the result be made negative?
jz FDP3 ;no
neg eax ;yes, negate it
FDP3: mov edx,eax ;return result in DX:AX; fractional
; part is already in AX
shr edx,16 ;whole part of result in DX
pop bp
ret
_FixedDiv endp
end
</PRE>
<!-- END CODE //-->
<P><B>LISTING 52.10 POLYGON.H</B></P>
<!-- CODE //-->
<PRE>
/* POLYGON.H: Header file for polygon-filling code, also includes
a number of useful items for 3-D animation. */
#define MAX_OBJECTS 100 /* max simultaneous # objects supported */
#define MAX_POLY_LENGTH 4 /* four vertices is the max per poly */
#define SCREEN_WIDTH 320
#define SCREEN_HEIGHT 240
#define PAGE0_START_OFFSET 0
#define PAGE1_START_OFFSET (((long)SCREEN_HEIGHT*SCREEN_WIDTH)/4)
#define NUM_CUBE_VERTS 8 /* # of vertices per cube */
#define NUM_CUBE_FACES 6 /* # of faces per cube */
/* Ratio: distance from viewpoint to projection plane / width of
projection plane. Defines the width of the field of view. Lower
absolute values = wider fields of view; higher values = narrower */
#define PROJECTION_RATIO -2.0 /* negative because visible Z
coordinates are negative */
/* Draws the polygon described by the point list PointList in color
Color with all vertices offset by (X,Y) */
#define DRAW_POLYGON(PointList,NumPoints,Color,X,Y) \
Polygon.Length = NumPoints; Polygon.PointPtr = PointList; \
FillConvexPolygon(&ampPolygon, Color, X, Y);
#define INT_TO_FIXED(x) (((long)(int)x) &lt&lt 16)
#define DOUBLE_TO_FIXED(x) ((long) (x * 65536.0 + 0.5))
typedef long Fixedpoint;
typedef Fixedpoint Xform[3][4];
/* Describes a single 2D point */
typedef struct { int X; int Y; } Point;
/* Describes a single 3D point in homogeneous coordinates; the W
coordinate isn't present, though; assumed to be 1 and implied */
typedef struct { Fixedpoint X, Y, Z; } Point3;
typedef struct { int X; int Y; int Z; } IntPoint3;
/* Describes a series of points (used to store a list of vertices that
describe a polygon; each vertex is assumed to connect to the two
adjacent vertices; last vertex is assumed to connect to first) */
typedef struct { int Length; Point * PointPtr; } PointListHeader;
/* Describes the beginning and ending X coordinates of a single
horizontal line */
typedef struct { int XStart; int XEnd; } HLine;
/* Describes a Length-long series of horizontal lines, all assumed to
be on contiguous scan lines starting at YStart and proceeding
downward (used to describe a scan-converted polygon to the
low-level hardware-dependent drawing code). */
typedef struct { int Length; int YStart; HLine * HLinePtr;} HLineList;
typedef struct { int Left, Top, Right, Bottom; } Rect;
/* structure describing one face of an object (one polygon) */
typedef struct { int * VertNums; int NumVerts; int Color; } Face;
typedef struct { double RotateX, RotateY, RotateZ; } RotateControl;
typedef struct { Fixedpoint MoveX, MoveY, MoveZ, MinX, MinY, MinZ,
MaxX, MaxY, MaxZ; } MoveControl;
/* fields common to every object */
#define BASE_OBJECT \
void (*DrawFunc)(); /* draws object */ \
void (*RecalcFunc)(); /* prepares object for drawing */ \
void (*MoveFunc)(); /* moves object */ \
int RecalcXform; /* 1 to indicate need to recalc */ \
Rect EraseRect[2]; /* rectangle to erase in each page */
/* basic object */
typedef struct { BASE_OBJECT } Object;
/* structure describing a polygon-based object */
typedef struct {
BASE_OBJECT
int RDelayCount, RDelayCountBase; /* controls rotation speed */
int MDelayCount, MDelayCountBase; /* controls movement speed */
Xform XformToWorld; /* transform from object-&gtworld space */
Xform XformToView; /* transform from object-&gtview space */
RotateControl Rotate; /* controls rotation change over time */
MoveControl Move; /* controls object movement over time */
int NumVerts; /* # vertices in VertexList */
Point3 * VertexList; /* untransformed vertices */
Point3 * XformedVertexList; /* transformed into view space */
Point3 * ProjectedVertexList; /* projected into screen space */
Point * ScreenVertexList; /* converted to screen coordinates */
int NumFaces; /* # of faces in object */
Face * FaceList; /* pointer to face info */
} PObject;
extern void XformVec(Xform, Fixedpoint *, Fixedpoint *);
extern void ConcatXforms(Xform, Xform, Xform);
extern int FillConvexPolygon(PointListHeader *, int, int, int);
extern void Set320x240Mode(void);
extern void ShowPage(unsigned int);
extern void FillRectangleX(int, int, int, int, unsigned int, int);
extern void XformAndProjectPObject(PObject *);
extern void DrawPObject(PObject *);
extern void AppendRotationX(Xform, double);
extern void AppendRotationY(Xform, double);
extern void AppendRotationZ(Xform, double);
extern near Fixedpoint FixedMul(Fixedpoint, Fixedpoint);
extern near Fixedpoint FixedDiv(Fixedpoint, Fixedpoint);
extern void InitializeFixedPoint(void);
extern void RotateAndMovePObject(PObject *);
extern void InitializeCubes(void);
extern int DisplayedPage, NonDisplayedPage, RecalcAllXforms;
extern int NumObjects;
extern Xform WorldViewXform;
extern Object *ObjectList[];
extern Point3 CubeVerts[];
</PRE>
<!-- END CODE //-->
<P><BR></P>
<CENTER>
<TABLE BORDER>
<TR>
<TD><A HREF="52-05.html">Previous</A></TD>
<TD><A HREF="index.html">Table of Contents</A></TD>
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</TR>
</TABLE>
</CENTER>
<hr width="90%" size="1" noshade>
<div align="center">
<font face="Verdana,sans-serif" size="1">Graphics Programming Black Book &copy; 2001 Michael Abrash</font>
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