;File: rot_a1.asm ;================================================================= ; ;rotation drawing a rotated bitmap ;======== ; ; Input: following 68000-C convention ; L Address of monochrome source bitmap ; W Width of source bitmap in bytes ; WWWW xywh: Dimensions of source picture ; L Address of monochrome destination bitmap ; W Width of destination bitmap in bytes ; WW xy: Picture rotation point ; W Rotation angle phi ; ; Output: -- ; ; Changed registers: 01234567 ; D:------- ; A-------- ; .ABS .CARGS #13*4+4,sadr.l,swb.w,sxp.w,syp.w,swp.w,shp.w,tadr.l,twb.w,txp.w,typ.w,phi.w .TEXT rotat:: movem.l d1-d7/a0/a1/a3-a6,-(sp) move.w sxp(sp),d0 move.w syp(sp),d1 add.w shp(sp),d1 move.w swb(sp),d2 movea.l sadr(sp),a0 bsr cpos movea.l a0,a6 ; A6: Base address of first pixel move.w d0,d6 ; D6: Index of first valid bit move.w phi(sp),d0 bsr cosin movea.w d0,a0 ; A0: cos(phi) / 2 move.w phi(sp),d0 bsr sine movea.w d0,a1 ; A1: sin(phi) / 2 movea.l tadr(sp),a5 ; A5: Base address destination bitmap moveq.l #0,d5 ; D5: Start x/y coordinates move.w shp(sp),d7 ; D7: Lines counter .lines: bsr line ;Rotate straight addq.w #1,d5 ;y-coordinate + 1/2 bsr line ;Rotate straight (blur) addi.w #1,d5 ;y-coordinate + 1/2 suba.w swb(sp),a6 ; next straight .vloop: dbf d7,.lines movem.l (sp)+,d1-d7/a0/a1/a3-a6 rts ;============================================================================ ; ; line ; ==== ; ; Input: a6: Line start source picture ; d5: y coordinate ; Output: -- ; ; Changed registers: 01234567 ; D:::::'-' ; A---::--- ; also used: ; adr, tadr on stack line: swap.w d7 ; d7: Counter rows/columns move.w a0,d0 muls.w d5,d0 move.l d0,4+sadr(sp) ; sadr: y*cos(phi) move.w a1,d0 muls.w d5,d0 move.l d0,4+tadr(sp) ; tadr: y*sin(phi) swap.w d5 ; d5: y/x -coordinate clr.w d5 ;x-coordinate := 0 movea.l a6,a4 ;Initialise bitstream move.l (a4)+,d4 ;and prepare window lsl.l d6,d4 moveq.l #31,d3 sub.w d6,d3 move.w 4+swp(sp),d7 .dlne: lea.l clear(pc),a3 ;Set pixels or erase add.l d4,d4 ; Test pixel bcc .tst lea.l set(pc),a3 .tst: dbf d3,.rot ;Move window on move.l (a4)+,d4 moveq.l #31,d3 .rot: bsr dorot ;rotate pixel addq.w #1,d5 ; x-coordinate + 1/2 bsr dorot ;blur pixel addq.w #1,d5 ; x-coordinate + 1/2 .hloop: dbf d7,.dlne ;remaining pixels in line swap.w d5 swap.w d7 rts ;============================================================================ ; ; dorot ; ===== ; ; Input: a0: cos(phi) ; a1: sin(phi) ; a5: Base address destination bitmap ; d5.w: x ; tadr.l: y * sin(phi) ; sadr.l: y * sin(phi) ; txp: x coordinate rotation point ; typ: y coordinate rotation point ; twb: width of destination bitmap in bytes ; Output: -- ; ; Changed registers: 01234567 ; D:::----- ; A-------- ; dorot: move.w a0,d0 ;cos(phi)*x muls.w d5,d0 sub.l 8+tadr(sp),d0 ; - y*sin(phi) addi.l #$18000,d0 swap.w d0 add.w 8+txp(sp),d0 ;x' = x0 + [x*cos(p)-y*sin(phi)] move.w a1,d1 ;sin(phi)*x muls.w d5,d1 add.l 8+sadr(sp),d1 ; + cos(phi)*y addi.l #$18000,d1 swap.w d1 neg.w d1 add.w 8+typ(sp),d1 ;y' = y0 - [x*sin(phi)+y*cos(phi)] mulu.w 8+twb(sp),d1 ;calculate pixel position in destination bitmap ror.l #3,d0 ; andi.w #$1fff,d0 add.w d0,d1 clr.w d0 rol.l #3,d0 addq.w #1,d0 moveq.l #1,d2 ror.b d0,d2 jmp (a3) ;either set or erase pixel clear: not.w d2 ;erase pixel and.b d2,0(a5,d1.w) rts set: or.b d2,0(a5,d1.w) ;set pixel rts ;============================================================================ ; ; cpos Positioning the graphic cursor (Turtle) ; ==== ; ; Input: d0: x coordinate ; d1: y coordinate ; d2: width of bitmap in bytes ; a0: base address of bitmap ; Output: d1,a0: Turtle is positioned ; d0: Bit offset in word addressed ; ; Changed registers: 01234567 ; D::------ ; A:------- ; cpos:: muls.w d2,d1 ;calculate line offset adda.l d1,a0 ; + Base address ror.l #4,d0 ; + 2 * (x div 16) andi.w #$0fff,d0 lea.l 0(a0,d0.w),a0 lea.l 0(a0,d0.w),a0 clr.w d0 ;turtle position in word: x mod 16 rol.l #4,d0 ; counting bits from addq.w #1,d0 ; from the left! moveq.l #1,d1 ror.w d0,d1 subq.w #1,d0 rts PI equ 32767 ;============================================================================ ; ; cosin Cosine / Sine ; sine ; ===== ; ; Input: d0 : Angle phi/ã*32768 with -ã ó phi < ã ; Output: d0 : sin(phi)*32768 (fractional Format) ; cos(phi)*32768 ; CCR : XNZVC ; -**00 ; ; changed Registers: 01234567 ; D:------- ; A-------- ; cosin:: addi.w #PI/2,d0 ;cos(p)=sin(p+ã/2) sine: movem.l d1/a0,-(sp) ;save registers move.w d0,d1 ;and make copy bpl .quadr12 ;save: only I. and II. quadrant neg.w d0 ; if not: mirror angle ; along x axis .quadr12: cmpi.w #PI/2+1,d0 ;test, if II. Quadrant bcs .indexing ;no, then straight to table neg.w d0 ;yes, then into table from the end addi.w #PI,d0 .indexing: mulu.w #sinresol,d0 ;Calculate position of relevant tabel lsl.l #1,d0 ;element: angle * number of table elements swap.w d0 ; / 2^14 add.w d0,d0 ; * 2 (word table!) lea.l sintab(pc),a0 ;fetch sine value from table move.w 0(a0,d0.w),d0 lsl.w #1,d1 ; was angle in quadrant I or IV? bcc .return ; no, then leave alone neg.w d0 ; else expand negative sine .return: ext.l d0 ;to full word movem.l (sp)+,d1/a0 ; so there rts .PATH 'A:\' sintab: .IBYTES "SINE.DMP" ;read in table calculated in BASIC sinresol equ *-sintab ;gives length of table in bytes .END