159 lines
3.8 KiB
ArmAsm
159 lines
3.8 KiB
ArmAsm
.proc circle_help ; This is because jmp cant jump that long!
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.include "circle.inc"
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;;We have named the parts of the circle as such.
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;; * |
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;; qbb | qab
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;; |
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;; qba | qaa
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;;---------------X-----------------> X
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;; qca | qda
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;; |
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;; qcb | qdb
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;; | *
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;; v Y
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;; The q stands for quarter, whe have 4 quarter, and each quarter is split into 2
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draw_qaa:
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LDA byte_to_paint ;A byte containing a single 1. Coresponds to X position in the chunk.
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ORA (btp_mem_pos), Y
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STA (btp_mem_pos), Y
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;; something is wrong | well isue for another time
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draw_qcb:; xy swaped
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STY temp
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LDA byte_to_paint
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STA temp__
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;;modify Y_pos
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LDY #$00
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jmp goto_loop
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loop:
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INY
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goto_loop:
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ASL byte_to_paint; lsr asl
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BCC loop
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STY temp___
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revert_byte_to_paint:
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LDA temp__
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STA byte_to_paint
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;;modify X_pos
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LDX temp
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LDA binary_factor, X; (see END.s)
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LDY temp___
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ORA (btp_mem_pos_swop), Y
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STA (btp_mem_pos_swop), Y;
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draw_qdb:; xy swaped and y is inverted.
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;;modify X
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LDX temp
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LDA binary_factor, X; (see END.s)
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TAX
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LDA inverse_factor_value, X;; (see END.s)
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;;Uses modifyed Y from above
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ORA (btp_mem_pos_swop_inv_y), Y
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STA (btp_mem_pos_swop_inv_y), Y;
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LDY temp
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LDA temp__
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STA byte_to_paint
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draw_qab:; xy swoped + mirroring
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LDA btp_mem_pos_center_two
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SBC btp_mem_pos_swop
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STA btp_mem_pos_inv
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LDA btp_mem_pos_center_two + 1
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SBC btp_mem_pos_swop + 1
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STA btp_mem_pos_inv + 1
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SEC
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LDA #$07
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SBC temp___
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TAY
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LDA #$07
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SBC temp
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TAX
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LDA binary_factor, X; (see END.s)
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ORA (btp_mem_pos_inv), Y
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STA (btp_mem_pos_inv), Y
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LDY temp
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draw_qda:; y is inverted
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;; invert Y, this is shared with qca
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STY temp
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LDA #$07
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SBC temp
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TAY
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LDA byte_to_paint
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ORA (btp_mem_pos_inv_y), Y
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STA (btp_mem_pos_inv_y), Y
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draw_qca: ;;mirror technique
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;SEC
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LDA btp_mem_pos_center_two
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SBC btp_mem_pos
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STA btp_mem_pos_inv
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LDA btp_mem_pos_center_two + 1
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SBC btp_mem_pos + 1
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STA btp_mem_pos_inv + 1
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;; calculate byte_to_paint_inv 00000001 --> 10000000, 00000010 --> 01000000 ... etc
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;; uses a table!
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STX temp_
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LDX byte_to_paint
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LDA inverse_factor_value, X;; (see END.s)
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TAX ;; A is saved to x because qba use this as well
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; A = byte_to_paint_inv
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ORA (btp_mem_pos_inv), Y
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STA (btp_mem_pos_inv), Y
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;;Recover the Y value (we changed it because evrything is inverted)
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LDY temp
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draw_qba: ;;mirror_technique
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;SEC
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LDA btp_mem_pos_center_two
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SBC btp_mem_pos_inv_y
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STA btp_mem_pos_inv
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LDA btp_mem_pos_center_two + 1
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SBC btp_mem_pos_inv_y + 1
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STA btp_mem_pos_inv + 1
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TXA
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ORA (btp_mem_pos_inv), Y
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STA (btp_mem_pos_inv), Y
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increment_y_pos:
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INC Y_rel ; y++
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DEY
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BPL increment_y_pos_end
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move_8px_down:
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LDY #$07
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;; Switch to chunk bellow
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; So we subtract #$0140
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; C = 1 because branching!
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Sub_16 btp_mem_pos, btp_mem_pos + 1, #$40, #$01, ! ;-320
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;; Y is inverted
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Add_16 btp_mem_pos_inv_y, btp_mem_pos_inv_y + 1, #$40, #$01 ;+320
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;; X and Y has swopped
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Sub_16 btp_mem_pos_swop, btp_mem_pos_swop + 1, #$08, #$00
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;; X and Y has swoped and Y has inverted
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Add_16 btp_mem_pos_swop_inv_y, btp_mem_pos_swop_inv_y +1, #$08, #$00
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increment_y_pos_end:
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RTS
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.endproc
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