142 lines
5.1 KiB
NASM
142 lines
5.1 KiB
NASM
;
|
||
; Command & Conquer Red Alert(tm)
|
||
; Copyright 2025 Electronic Arts Inc.
|
||
;
|
||
; This program is free software: you can redistribute it and/or modify
|
||
; it under the terms of the GNU General Public License as published by
|
||
; the Free Software Foundation, either version 3 of the License, or
|
||
; (at your option) any later version.
|
||
;
|
||
; This program 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 General Public License for more details.
|
||
;
|
||
; You should have received a copy of the GNU General Public License
|
||
; along with this program. If not, see <http://www.gnu.org/licenses/>.
|
||
;
|
||
|
||
;***************************************************************************
|
||
;** C O N F I D E N T I A L --- W E S T W O O D A S S O C I A T E S **
|
||
;***************************************************************************
|
||
;* *
|
||
;* Project Name : Support Library *
|
||
;* *
|
||
;* File Name : FACING8.ASM *
|
||
;* *
|
||
;* Programmer : Joe L. Bostic *
|
||
;* *
|
||
;* Start Date : May 8, 1991 *
|
||
;* *
|
||
;* Last Update : February 6, 1995 [BWG] *
|
||
;* *
|
||
;*-------------------------------------------------------------------------*
|
||
;* Functions: *
|
||
;* Desired_Facing8 -- Determines facing to reach a position. *
|
||
;* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - *
|
||
|
||
|
||
IDEAL
|
||
P386
|
||
MODEL USE32 FLAT
|
||
|
||
|
||
GLOBAL Desired_Facing8 :NEAR
|
||
; INCLUDE "wwlib.i"
|
||
|
||
DATASEG
|
||
|
||
; 8 direction desired facing lookup table. Build the index according
|
||
; to the following bits:
|
||
;
|
||
; bit 3 = Is y2 < y1?
|
||
; bit 2 = Is x2 < x1?
|
||
; bit 1 = Is the ABS(x2-x1) < ABS(y2-y1)?
|
||
; bit 0 = Is the facing closer to a major axis?
|
||
NewFacing8 DB 1,2,1,0,7,6,7,0,3,2,3,4,5,6,5,4
|
||
|
||
CODESEG
|
||
|
||
;***************************************************************************
|
||
;* DESIRED_FACING8 -- Determines facing to reach a position. *
|
||
;* *
|
||
;* This routine will return with the most desirable facing to reach *
|
||
;* one position from another. It is accurate to a resolution of 0 to *
|
||
;* 7. *
|
||
;* *
|
||
;* INPUT: x1,y1 -- Position of origin point. *
|
||
;* *
|
||
;* x2,y2 -- Position of target. *
|
||
;* *
|
||
;* OUTPUT: Returns desired facing as a number from 0..255 with an *
|
||
;* accuracy of 32 degree increments. *
|
||
;* *
|
||
;* WARNINGS: If the two coordinates are the same, then -1 will be *
|
||
;* returned. It is up to you to handle this case. *
|
||
;* *
|
||
;* HISTORY: *
|
||
;* 07/15/1991 JLB : Documented. *
|
||
;* 08/08/1991 JLB : Same position check. *
|
||
;* 08/14/1991 JLB : New algorithm *
|
||
;* 02/06/1995 BWG : Convert to 32-bit *
|
||
;*=========================================================================*
|
||
; long Desired_Facing8(long x1, long y1, long x2, long y2);
|
||
|
||
PROC Desired_Facing8 C near
|
||
USES ebx, ecx, edx
|
||
|
||
ARG x1:DWORD
|
||
ARG y1:DWORD
|
||
ARG x2:DWORD
|
||
ARG y2:DWORD
|
||
|
||
xor ebx,ebx ; Index byte (built).
|
||
|
||
; Determine Y axis difference.
|
||
mov edx,[y1]
|
||
mov ecx,[y2]
|
||
sub edx,ecx ; DX = Y axis (signed).
|
||
jns short ??absy
|
||
inc ebx ; Set the signed bit.
|
||
neg edx ; ABS(y)
|
||
??absy:
|
||
|
||
; Determine X axis difference.
|
||
shl ebx,1
|
||
mov eax,[x1]
|
||
mov ecx,[x2]
|
||
sub ecx,eax ; CX = X axis (signed).
|
||
jns short ??absx
|
||
inc ebx ; Set the signed bit.
|
||
neg ecx ; ABS(x)
|
||
??absx:
|
||
|
||
; Determine the greater axis.
|
||
cmp ecx,edx
|
||
jb short ??dxisbig
|
||
xchg ecx,edx
|
||
??dxisbig:
|
||
rcl ebx,1 ; Y > X flag bit.
|
||
|
||
; Determine the closeness or farness of lesser axis.
|
||
mov eax,edx
|
||
inc eax ; Round up.
|
||
shr eax,1
|
||
|
||
cmp ecx,eax
|
||
rcl ebx,1 ; Close to major axis bit.
|
||
|
||
xor eax,eax
|
||
mov al,[NewFacing8+ebx]
|
||
|
||
; Normalize to 0..FF range.
|
||
shl eax,5
|
||
|
||
ret
|
||
|
||
ENDP Desired_Facing8
|
||
|
||
|
||
END
|
||
|
||
|