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Amiga ACS 1998 #6
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texmap
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tmap_16p.asm
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Assembly Source File
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1998-06-08
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4KB
|
205 lines
;THE COMPUTER CODE CONTAINED HEREIN IS THE SOLE PROPERTY OF PARALLAX
;SOFTWARE CORPORATION ("PARALLAX"). PARALLAX, IN DISTRIBUTING THE CODE TO
;END-USERS, AND SUBJECT TO ALL OF THE TERMS AND CONDITIONS HEREIN, GRANTS A
;ROYALTY-FREE, PERPETUAL LICENSE TO SUCH END-USERS FOR USE BY SUCH END-USERS
;IN USING, DISPLAYING, AND CREATING DERIVATIVE WORKS THEREOF, SO LONG AS
;SUCH USE, DISPLAY OR CREATION IS FOR NON-COMMERCIAL, ROYALTY OR REVENUE
;FREE PURPOSES. IN NO EVENT SHALL THE END-USER USE THE COMPUTER CODE
;CONTAINED HEREIN FOR REVENUE-BEARING PURPOSES. THE END-USER UNDERSTANDS
;AND AGREES TO THE TERMS HEREIN AND ACCEPTS THE SAME BY USE OF THIS FILE.
;COPYRIGHT 1993-1998 PARALLAX SOFTWARE CORPORATION. ALL RIGHTS RESERVED.
;
; $Source: f:/miner/source/texmap/rcs/tmap_16p.asm $
; $Revision: 1.4 $
; $Author: mike $
; $Date: 1994/11/30 00:56:40 $
;
; Perspective 16 bit per pixel texture mapper
;
; $Log: tmap_16p.asm $
; Revision 1.4 1994/11/30 00:56:40 mike
; optimization.
;
; Revision 1.3 1994/11/12 16:39:32 mike
; jae to ja.
;
; Revision 1.2 1993/11/22 10:24:43 mike
; *** empty log message ***
;
; Revision 1.1 1993/09/08 17:29:21 mike
; Initial revision
;
;
;
.386
include tmap_inc.asm
public asm_tmap_scanline_per_16_
_DATA SEGMENT DWORD PUBLIC USE32 'DATA'
extrn _fx_u:dword
extrn _fx_v:dword
extrn _fx_z:dword
extrn _fx_du_dx:dword
extrn _fx_dv_dx:dword
extrn _fx_dz_dx:dword
extrn _fx_y:dword
extrn _fx_xleft:dword
extrn _fx_xright:dword
extrn _pixptr:dword
extrn _x:dword
extrn _loop_count:dword
temp dd ?
_DATA ENDS
DGROUP GROUP _DATA
_TEXT SEGMENT PARA PUBLIC USE32 'CODE'
ASSUME DS:_DATA
ASSUME CS:_TEXT
; --------------------------------------------------------------------------------------------------
; Enter:
; _xleft fixed point left x coordinate
; _xright fixed point right x coordinate
; _y fixed point y coordinate
; _pixptr address of source pixel map
; _u fixed point initial u coordinate
; _v fixed point initial v coordinate
; _z fixed point initial z coordinate
; _du_dx fixed point du/dx
; _dv_dx fixed point dv/dx
; _dz_dx fixed point dz/dx
; for (x = (int) xleft; x <= (int) xright; x++) {
; _setcolor(read_pixel_from_tmap(srcb,((int) (u/z)) & 63,((int) (v/z)) & 63));
; _setpixel(x,y);
;
; u += du_dx;
; v += dv_dx;
; z += dz_dx;
; }
asm_tmap_scanline_per_16_:
pusha
; Setup for loop: _loop_count iterations = (int) xright - (int) xleft
; esi source pixel pointer = pixptr
; edi initial row pointer = y*320+x
; set esi = pointer to start of texture map data
mov esi,_pixptr
; set edi = address of first pixel to modify
mov edi,_fx_y
cmp edi,_window_bottom
ja _none_to_do
sub edi,_window_top
imul edi,_bytes_per_row
mov eax,_fx_xleft
sar eax,16
jns eax_ok
sub eax,eax
eax_ok:
sub eax,_window_left
add edi,eax
add edi,eax
add edi,write_buffer
; set _loop_count = # of iterations
mov eax,_fx_xright
sar eax,16
cmp eax,_window_right
jb eax_ok1
mov eax,_window_right
eax_ok1: cmp eax,_window_left
ja eax_ok2
mov eax,_window_left
eax_ok2:
mov ebx,_fx_xleft
sar ebx,16
sub eax,ebx
js _none_to_do
cmp eax,_window_width
jbe _ok_to_do
mov eax,_window_width
_ok_to_do:
;** dec eax ; don't write rightmost pixel
;** js _none_to_do
mov _loop_count,eax
; set initial values
mov ebx,_fx_u
mov ebp,_fx_v
mov ecx,_fx_z
; Usage in loop: eax division, pixel value
; ebx u
; ecx z
; edx division
; ebp v
; esi source pixel pointer
; edi destination pixel pointer
align 4
tmap_loop:
; cmp ecx,_max_ecx
; jl nonewmax
; mov _max_ecx,ecx
;nonewmax:
; cmp ecx,_min_ecx
; ja nonewmin
; mov _min_ecx,ecx
;nonewmin:
;** cmp ecx,0
;** jle skip
; compute u coordinate
mov eax,ebx ; get u
cdq
idiv ecx ; eax = (u/z)
and eax,3fh ; mask with width-1
mov temp,eax
; compute v coordinate
mov eax,ebp ; get v
cdq
idiv ecx ; eax = (v/z)
and eax,3fh ; mask with height-1
shl eax,6 ; multiply by 64 (bitmap width)
add eax,temp
; read/write pixel
mov ax,[esi+2*eax] ; get pixel from source bitmap
; update deltas
mov [edi],ax
add edi,2
skip: add ebp,_fx_dv_dx
add ebx,_fx_du_dx
add ecx,_fx_dz_dx
dec _loop_count
jns tmap_loop
_none_to_do: popa
ret
_TEXT ends
end