LDA K3 ; Set YY(1 0) to the pixel x-coordinate of the centre STA YY ; of the new sun, from K3(1 0) LDA K3+1 STA YY+1 LDY TGT ; Set Y to the maximum y-coordinate of the sun on the ; screen (i.e. the bottom of the sun), which we set up ; in part 1 LDA #0 ; Set the sub width variables to zero, so we can use STA sunWidth1 ; them below to store the widths of the sun on each STA sunWidth2 ; pixel row within each tile row STA sunWidth3 STA sunWidth4 STA sunWidth5 STA sunWidth6 STA sunWidth7 TYA ; Set A to the maximum y-coordinate of the sun, so we ; can apply the first AND below TAX ; Set X to the maximum y-coordinate of the sun, so we ; can apply the second AND below AND #%11111000 ; Each tile row contains 8 pixel rows, so to get the TAY ; y-coordinate of the first row of pixels in the tile ; row, we clear bits 0-2, so Y now contains the pixel ; y-coordinate of the top pixel row in the tile row ; containing the bottom of the sun LDA V+1 ; If V+1 is non-zero then we are doing the top half of BNE dsun11 ; the new sun, so jump down to dsun11 to work our way ; upwards from the centre towards the top of the sun ; If we get here then we are drawing the bottom half of ; of the sun, so we work our way up from the bottom by ; decrementing V for each pixel line, as V contains the ; vertical distance between the line we're drawing and ; the centre of the new sun, and it starts out pointing ; to the bottom of the sun TXA ; Set A = X mod 8, which is the pixel row within the AND #7 ; tile row of the bottom of the sun BEQ dsun8 ; If A = 0 then the bottom of the sun is only in the top ; pixel row of the tile row, so jump to dsun8 to ; calculate the sun's width on one pixel row CMP #2 ; If A = 1, jump to dsun7 to calculate the sun's width BCC dsun7 ; on two pixel rows BEQ dsun6 ; If A = 2, jump to dsun6 to calculate the sun's width ; on three pixel rows CMP #4 ; If A = 3, jump to dsun5 to calculate the sun's width BCC dsun5 ; on four pixel rows BEQ dsun4 ; If A = 4, jump to dsun4 to calculate the sun's width ; on five pixel rows CMP #6 ; If A = 5, jump to dsun3 to calculate the sun's width BCC dsun3 ; on six pixel rows BEQ dsun2 ; If A = 6, jump to dsun2 to calculate the sun's width ; on seven pixel rows ; If we get here then A = 7, so keep going to calculate ; the sun's width on all eight pixel rows, starting from ; row 7 at the bottom of the tile row, all the way up to ; pixel row 0 at the top of the tile row .dsun1 JSR PLFL ; Call PLFL to set A to the half-width of the new sun on ; the sun line given in V STA sunWidth7 ; Store the half-width of pixel row 7 in sunWidth7 DEC V ; Decrement V, the height of the sun that we use to work ; out the width, so this makes the line get wider, as we ; move up towards the sun's centre BEQ dsun12 ; If V is zero then we have reached the centre, so jump ; to dsun12 to start working our way up from the centre, ; incrementing V instead .dsun2 JSR PLFL ; Call PLFL to set A to the half-width of the new sun on ; the sun line given in V STA sunWidth6 ; Store the half-width of pixel row 6 in sunWidth6 DEC V ; Decrement V, the height of the sun that we use to work ; out the width, so this makes the line get wider, as we ; move up towards the sun's centre BEQ dsun13 ; If V is zero then we have reached the centre, so jump ; to dsun13 to start working our way up from the centre, ; incrementing V for the rest of this tile row .dsun3 JSR PLFL ; Call PLFL to set A to the half-width of the new sun on ; the sun line given in V STA sunWidth5 ; Store the half-width of pixel row 5 in sunWidth5 DEC V ; Decrement V, the height of the sun that we use to work ; out the width, so this makes the line get wider, as we ; move up towards the sun's centre BEQ dsun14 ; If V is zero then we have reached the centre, so jump ; to dsun14 to start working our way up from the centre, ; incrementing V for the rest of this tile row .dsun4 JSR PLFL ; Call PLFL to set A to the half-width of the new sun on ; the sun line given in V STA sunWidth4 ; Store the half-width of pixel row 4 in sunWidth4 DEC V ; Decrement V, the height of the sun that we use to work ; out the width, so this makes the line get wider, as we ; move up towards the sun's centre BEQ dsun15 ; If V is zero then we have reached the centre, so jump ; to dsun15 to start working our way up from the centre, ; incrementing V for the rest of this tile row .dsun5 JSR PLFL ; Call PLFL to set A to the half-width of the new sun on ; the sun line given in V STA sunWidth3 ; Store the half-width of pixel row 3 in sunWidth3 DEC V ; Decrement V, the height of the sun that we use to work ; out the width, so this makes the line get wider, as we ; move up towards the sun's centre BEQ dsun16 ; If V is zero then we have reached the centre, so jump ; to dsun16 to start working our way up from the centre, ; incrementing V for the rest of this tile row .dsun6 JSR PLFL ; Call PLFL to set A to the half-width of the new sun on ; the sun line given in V STA sunWidth2 ; Store the half-width of pixel row 2 in sunWidth2 DEC V ; Decrement V, the height of the sun that we use to work ; out the width, so this makes the line get wider, as we ; move up towards the sun's centre BEQ dsun17 ; If V is zero then we have reached the centre, so jump ; to dsun17 to start working our way up from the centre, ; incrementing V for the rest of this tile row .dsun7 JSR PLFL ; Call PLFL to set A to the half-width of the new sun on ; the sun line given in V STA sunWidth1 ; Store the half-width of pixel row 1 in sunWidth1 DEC V ; Decrement V, the height of the sun that we use to work ; out the width, so this makes the line get wider, as we ; move up towards the sun's centre BEQ dsun10 ; If V is zero then we have reached the centre, so jump ; to dsun18 via dsun10 to start working our way up from ; the centre, incrementing V for the rest of this tile ; row .dsun8 JSR PLFL ; Call PLFL to set A to the half-width of the new sun on ; the sun line given in V STA sunWidth0 ; Store the half-width of pixel row 0 in sunWidth0 DEC V ; Decrement V, the height of the sun that we use to work ; out the width, so this makes the line get wider, as we ; move up towards the sun's centre BEQ dsun9 ; If V is zero then we have reached the centre, so jump ; to dsun19 via dsun9 to start working our way up from ; the centre, incrementing V for the rest of this tile ; row JSR dsun28 ; Call dsun28 to draw all eight lines for this tile row TYA ; Set Y = Y - 8 to move up a tile row SEC SBC #8 TAY BCS dsun1 ; If the subtraction didn't underflow, then Y is still ; positive and is therefore still on-screen, so loop ; back to dsun1 to keep drawing pixel rows RTS ; Otherwise we have reached the top of the screen, so ; return from the subroutine as we are done drawing .dsun9 BEQ dsun19 ; Jump down to dsun19 (this is only used to enable us to ; use a BEQ dsun9 above) .dsun10 BEQ dsun18 ; Jump down to dsun18 (this is only used to enable us to ; use a BEQ dsun10 above) .dsun11 ; If we get here then we are drawing the top half of the ; sun, so we increment V for each pixel line as we move ; up the screen JSR PLFL ; Call PLFL to set A to the half-width of the new sun on ; the sun line given in V STA sunWidth7 ; Store the half-width of pixel row 7 in sunWidth7 LDX V ; Increment V, the height of the sun that we use to work INX ; out the width, so this makes the line get less wide, STX V ; as we move up and away from the sun's centre CPX K ; If V >= K then we have reached the top of the sun (as BCS dsun21 ; K is the sun's radius, so there are K pixel lines in ; each half of the sun), so jump to dsun21 to draw the ; lines that we have calculated so far for this tile row .dsun12 JSR PLFL ; Call PLFL to set A to the half-width of the new sun on ; the sun line given in V STA sunWidth6 ; Store the half-width of pixel row 6 in sunWidth6 LDX V ; Increment V, the height of the sun that we use to work INX ; out the width, so this makes the line get less wide, STX V ; as we move up and away from the sun's centre CPX K ; If V >= K then we have reached the top of the sun (as BCS dsun22 ; K is the sun's radius, so there are K pixel lines in ; each half of the sun), so jump to dsun22 to draw the ; lines that we have calculated so far for this tile row .dsun13 JSR PLFL ; Call PLFL to set A to the half-width of the new sun on ; the sun line given in V STA sunWidth5 ; Store the half-width of pixel row 5 in sunWidth5 LDX V ; Increment V, the height of the sun that we use to work INX ; out the width, so this makes the line get less wide, STX V ; as we move up and away from the sun's centre CPX K ; If V >= K then we have reached the top of the sun (as BCS dsun23 ; K is the sun's radius, so there are K pixel lines in ; each half of the sun), so jump to dsun23 to draw the ; lines that we have calculated so far for this tile row .dsun14 JSR PLFL ; Call PLFL to set A to the half-width of the new sun on ; the sun line given in V STA sunWidth4 ; Store the half-width of pixel row 4 in sunWidth4 LDX V ; Increment V, the height of the sun that we use to work INX ; out the width, so this makes the line get less wide, STX V ; as we move up and away from the sun's centre CPX K ; If V >= K then we have reached the top of the sun (as BCS dsun24 ; K is the sun's radius, so there are K pixel lines in ; each half of the sun), so jump to dsun24 to draw the ; lines that we have calculated so far for this tile row .dsun15 JSR PLFL ; Call PLFL to set A to the half-width of the new sun on ; the sun line given in V STA sunWidth3 ; Store the half-width of pixel row 3 in sunWidth3 LDX V ; Increment V, the height of the sun that we use to work INX ; out the width, so this makes the line get less wide, STX V ; as we move up and away from the sun's centre CPX K ; If V >= K then we have reached the top of the sun (as BCS dsun25 ; K is the sun's radius, so there are K pixel lines in ; each half of the sun), so jump to dsun25 to draw the ; lines that we have calculated so far for this tile row .dsun16 JSR PLFL ; Call PLFL to set A to the half-width of the new sun on ; the sun line given in V STA sunWidth2 ; Store the half-width of pixel row 2 in sunWidth2 LDX V ; Increment V, the height of the sun that we use to work INX ; out the width, so this makes the line get less wide, STX V ; as we move up and away from the sun's centre CPX K ; If V >= K then we have reached the top of the sun (as BCS dsun26 ; K is the sun's radius, so there are K pixel lines in ; each half of the sun), so jump to dsun26 to draw the ; lines that we have calculated so far for this tile row .dsun17 JSR PLFL ; Call PLFL to set A to the half-width of the new sun on ; the sun line given in V STA sunWidth1 ; Store the half-width of pixel row 1 in sunWidth1 LDX V ; Increment V, the height of the sun that we use to work INX ; out the width, so this makes the line get less wide, STX V ; as we move up and away from the sun's centre CPX K ; If V >= K then we have reached the top of the sun (as BCS dsun27 ; K is the sun's radius, so there are K pixel lines in ; each half of the sun), so jump to dsun27 to draw the ; lines that we have calculated so far for this tile row .dsun18 JSR PLFL ; Call PLFL to set A to the half-width of the new sun on ; the sun line given in V STA sunWidth0 ; Store the half-width of pixel row 0 in sunWidth0 LDX V ; Increment V, the height of the sun that we use to work INX ; out the width, so this makes the line get less wide, STX V ; as we move up and away from the sun's centre CPX K ; If V >= K then we have reached the top of the sun (as BCS dsun28 ; K is the sun's radius, so there are K pixel lines in ; each half of the sun), so jump to dsun28 to draw the ; lines that we have calculated so far for this tile row .dsun19 JSR dsun28 ; Call dsun28 to draw all eight lines for this tile row TYA ; Set Y = Y - 8 to move up a tile row SEC SBC #8 TAY BCC dsun20 ; If the subtraction underflowed, then Y is negative ; and is therefore off the top of the screen, so jump to ; dsun20 to return from the subroutine JMP dsun11 ; Otherwise we still have work to do, so jump up to ; dsun11 to keep working our way up the top half of the ; sun .dsun20 RTS ; Return from the subroutine .dsun21 ; If we jump here then we have reached the top of the ; sun and only need to draw pixel row 7 in the current ; tile row, so we zero sunWidth0 through sunWidth6 LDA #0 ; Zero sunWidth6 STA sunWidth6 .dsun22 ; If we jump here then we have reached the top of the ; sun and need to draw pixel rows 6 and 7 in the current ; tile row, so we zero sunWidth0 through sunWidth5 LDA #0 ; Zero sunWidth5 STA sunWidth5 .dsun23 ; If we jump here then we have reached the top of the ; sun and need to draw pixel rows 5 to 7 in the current ; tile row, so we zero sunWidth0 through sunWidth4 LDA #0 ; Zero sunWidth4 STA sunWidth4 .dsun24 ; If we jump here then we have reached the top of the ; sun and need to draw pixel rows 4 to 7 in the current ; tile row, so we zero sunWidth0 through sunWidth3 LDA #0 ; Zero sunWidth3 STA sunWidth3 .dsun25 ; If we jump here then we have reached the top of the ; sun and need to draw pixel rows 3 to 7 in the current ; tile row, so we zero sunWidth0 through sunWidth2 LDA #0 ; Zero sunWidth2 STA sunWidth2 .dsun26 ; If we jump here then we have reached the top of the ; sun and need to draw pixel rows 2 to 7 in the current ; tile row, so we zero sunWidth0 through sunWidth1 LDA #0 ; Zero sunWidth1 STA sunWidth1 .dsun27 ; If we jump here then we have reached the top of the ; sun and need to draw pixel rows 1 to 7 in the current ; tile row, so we zero sunWidth0 LDA #0 ; Zero sunWidth0 STA sunWidth0 ; So by this point sunWidth0 through sunWidth7 are set ; up with the correct widths that we need to draw on ; each pixel row of the current tile row, with some of ; them possibly set to zero ; We now fall through into dsun28 to draw these eight ; pixel rows and return from the subroutine .dsun28 ; If we jump here with a branch instruction or fall ; through from above, then we have reached the top of ; the sun and need to draw pixel rows 0 to 7 in the ; current tile row, and then we are done drawing ; ; If we call this code as a subroutine using JSR dsun28 ; then we need to draw pixel rows 0 to 7 in the current ; tile row, and when we return from the call we keep ; drawing rows ; ; In either case, we now need to draw all eight rows ; before returning from the subroutine ; ; We start by finding the smallest width out of ; sunWidth0 through sunWidth7 LDA sunWidth0 ; Set A to sunWidth0 as our starting point CMP sunWidth1 ; If A >= sunWidth1 then set A = sunWidth1, so this sets BCC dsun29 ; A = min(A, sunWidth1) LDA sunWidth1 .dsun29 CMP sunWidth2 ; If A >= sunWidth2 then set A = sunWidth2, so this sets BCC dsun30 ; A = min(A, sunWidth2) LDA sunWidth2 .dsun30 CMP sunWidth3 ; If A >= sunWidth3 then set A = sunWidth3, so this sets BCC dsun31 ; A = min(A, sunWidth3) LDA sunWidth2 .dsun31 CMP sunWidth4 ; If A >= sunWidth4 then set A = sunWidth4, so this sets BCC dsun32 ; A = min(A, sunWidth4) LDA sunWidth4 .dsun32 CMP sunWidth5 ; If A >= sunWidth5 then set A = sunWidth5, so this sets BCC dsun33 ; A = min(A, sunWidth5) LDA sunWidth5 .dsun33 CMP sunWidth6 ; If A >= sunWidth6 then set A = sunWidth6, so this sets BCC dsun34 ; A = min(A, sunWidth6) LDA sunWidth6 .dsun34 CMP sunWidth7 ; If A >= sunWidth7 then set A = sunWidth7, so this sets BCC dsun35 ; A = min(A, sunWidth7) LDA sunWidth7 ; So by this point A = min(sunWidth0 to sunWidth7), and ; we can now check to see if we can save time by drawing ; a portion of this tile row out of filled blocks BEQ dsun37 ; If A = 0 then at least one of the pixel rows needs to ; be left blank, so we can't draw the row using filled ; blocks, so jump to dsun37 to draw the tile row one ; pixel row at a time .dsun35 JSR EDGES ; Call EDGES to calculate X1 and X2 for the horizontal ; line centred on YY(1 0) and with half-width A, clipped ; to fit on-screen if necessary, so this gives us the ; coordinates of the smallest pixel row in the tile row ; that we want to draw BCS dsun37 ; If the C flag is set, then the smallest pixel row ; is off-screen, so jump to dsun37 to draw the tile row ; one pixel row at a time, as there is at least one ; pixel row in the tile row that doesn't need drawing ; If we get here then every pixel row in the tile row ; fits on-screen and contains some sun pixels, so we ; can now work out how to draw this row using filled ; tiles where possible ; ; We do this by breaking the line up into a tile at the ; left end of the row, a tile at the right end of the ; row, and a set of filled tiles in the middle ; ; We set P and P+1 to the pixel coordinates of the block ; of filled tiles in the middle LDA X2 ; Set P+1 to the x-coordinate of the right end of the AND #%11111000 ; smallest sun line by clearing bits 0-2 of X2, giving STA P+1 ; P+1 = (X2 div 8) * 8 ; ; This gives us what we want as each tile is 8 pixels ; wide LDA X1 ; Now to calculate the x-coordinate of the left end of ADC #7 ; the filled tiles, so set A = X1 + 7 (we know the C ; flag is clear for the addition as we just passed ; through a BCS) BCS dsun37 ; If the addition overflowed, then this addition pushes ; us past the right edge of the screen, so jump to ; dsun37 to draw the tile row one pixel row at a time as ; there isn't any room for filled tiles AND #%11111000 ; Clear bits 0-2 of A to give us the x-coordinate of the ; left end of the set of filled tiles CMP P+1 ; If A >= P+1 then there is no room for any filled as BCS dsun37 ; the entire line fits into one tile, so jump to dsun37 ; to draw the tile row one pixel row at a time STA P ; Otherwise we now have valid values for the ; x-coordinate range of the filled blocks in the ; middle of the row, so store A in P so the coordinate ; range is from P to P+1 CMP #248 ; If A >= 248 then we only have room for one block on BCS dsun36 ; this row, and it's at the right edge of the screen, ; so jump to dsun36 to skip the right and middle tiles ; and just draw the tile at the left end of the row JSR dsun47 ; Call dsun47 to draw the tile at the right end of this ; tile row JSR DrawSunRowOfBlocks ; Draw the tiles containing the horizontal line (P, Y) ; to (P+1, Y) with filled blocks, silhouetting any ; existing content against the sun .dsun36 JMP dsun46 ; Jump to dsun46 to draw the tile at the left end of ; this tile row, returning from the subroutine using a ; tail call as we have now drawn the middle of the row, ; plus both ends .dsun37 ; If we get here then we draw the current tile row one ; pixel row at a time SETUP_PPU_FOR_ICON_BAR ; If the PPU has started drawing the icon bar, configure ; the PPU to use nametable 0 and pattern table 0 TYA ; Set Y = Y + 7 CLC ; ADC #7 ; We draw the lines from row 7 up the screen to row 0, TAY ; so this sets Y to the pixel y-coordinate of row 7 LDA sunWidth7 ; Call EDGES-2 to calculate X1 and X2 for the horizontal JSR EDGES-2 ; line centred on YY(1 0) and with half-width sunWidth7, ; which is the pixel line for row 7 in the tile row ; ; Calling EDGES-2 will set the C flag if A = 0, which ; isn't the case for a straight call to EDGES BCS dsun38 ; If the C flag is set then either A = 0 (in which case ; there is no sun line on this pixel row), or the line ; does not fit on-screen, so in either case skip the ; following instruction and move on to the next pixel ; row JSR HLOIN ; Draw a horizontal line from (X1, Y) to (X2, Y) to draw ; pixel row 7 of the sun on this tile row, using EOR ; logic so anything already on-screen appears as a ; silhouette in front of the sun .dsun38 DEY ; Decrement the pixel y-coordinate in Y to row 6 in the ; tile row LDA sunWidth6 ; Call EDGES-2 to calculate X1 and X2 for the horizontal JSR EDGES-2 ; line centred on YY(1 0) and with half-width sunWidth6, ; which is the pixel line for row 6 in the tile row ; ; Calling EDGES-2 will set the C flag if A = 0, which ; isn't the case for a straight call to EDGES BCS dsun39 ; If the C flag is set then either A = 0 (in which case ; there is no sun line on this pixel row), or the line ; does not fit on-screen, so in either case skip the ; following instruction and move on to the next pixel ; row JSR HLOIN ; Draw a horizontal line from (X1, Y) to (X2, Y) to draw ; pixel row 6 of the sun on this tile row, using EOR ; logic so anything already on-screen appears as a ; silhouette in front of the sun .dsun39 DEY ; Decrement the pixel y-coordinate in Y to row 5 in the ; tile row LDA sunWidth5 ; Call EDGES-2 to calculate X1 and X2 for the horizontal JSR EDGES-2 ; line centred on YY(1 0) and with half-width sunWidth5, ; which is the pixel line for row 5 in the tile row ; ; Calling EDGES-2 will set the C flag if A = 0, which ; isn't the case for a straight call to EDGES BCS dsun40 ; If the C flag is set then either A = 0 (in which case ; there is no sun line on this pixel row), or the line ; does not fit on-screen, so in either case skip the ; following instruction and move on to the next pixel ; row JSR HLOIN ; Draw a horizontal line from (X1, Y) to (X2, Y) to draw ; pixel row 5 of the sun on this tile row, using EOR ; logic so anything already on-screen appears as a ; silhouette in front of the sun .dsun40 DEY ; Decrement the pixel y-coordinate in Y to row 4 in the ; tile row LDA sunWidth4 ; Call EDGES-2 to calculate X1 and X2 for the horizontal JSR EDGES-2 ; line centred on YY(1 0) and with half-width sunWidth4, ; which is the pixel line for row 4 in the tile row ; ; Calling EDGES-2 will set the C flag if A = 0, which ; isn't the case for a straight call to EDGES BCS dsun41 ; If the C flag is set then either A = 0 (in which case ; there is no sun line on this pixel row), or the line ; does not fit on-screen, so in either case skip the ; following instruction and move on to the next pixel ; row JSR HLOIN ; Draw a horizontal line from (X1, Y) to (X2, Y) to draw ; pixel row 4 of the sun on this tile row, using EOR ; logic so anything already on-screen appears as a ; silhouette in front of the sun .dsun41 DEY ; Decrement the pixel y-coordinate in Y to row 3 in the ; tile row LDA sunWidth3 ; Call EDGES-2 to calculate X1 and X2 for the horizontal JSR EDGES-2 ; line centred on YY(1 0) and with half-width sunWidth3, ; which is the pixel line for row 3 in the tile row ; ; Calling EDGES-2 will set the C flag if A = 0, which ; isn't the case for a straight call to EDGES BCS dsun42 ; If the C flag is set then either A = 0 (in which case ; there is no sun line on this pixel row), or the line ; does not fit on-screen, so in either case skip the ; following instruction and move on to the next pixel ; row JSR HLOIN ; Draw a horizontal line from (X1, Y) to (X2, Y) to draw ; pixel row 3 of the sun on this tile row, using EOR ; logic so anything already on-screen appears as a ; silhouette in front of the sun .dsun42 DEY ; Decrement the pixel y-coordinate in Y to row 2 in the ; tile row LDA sunWidth2 ; Call EDGES-2 to calculate X1 and X2 for the horizontal JSR EDGES-2 ; line centred on YY(1 0) and with half-width sunWidth2, ; which is the pixel line for row 2 in the tile row ; ; Calling EDGES-2 will set the C flag if A = 0, which ; isn't the case for a straight call to EDGES BCS dsun43 ; If the C flag is set then either A = 0 (in which case ; there is no sun line on this pixel row), or the line ; does not fit on-screen, so in either case skip the ; following instruction and move on to the next pixel ; row JSR HLOIN ; Draw a horizontal line from (X1, Y) to (X2, Y) to draw ; pixel row 2 of the sun on this tile row, using EOR ; logic so anything already on-screen appears as a ; silhouette in front of the sun .dsun43 DEY ; Decrement the pixel y-coordinate in Y to row 1 in the ; tile row LDA sunWidth1 ; Call EDGES-2 to calculate X1 and X2 for the horizontal JSR EDGES-2 ; line centred on YY(1 0) and with half-width sunWidth1, ; which is the pixel line for row 1 in the tile row ; ; Calling EDGES-2 will set the C flag if A = 0, which ; isn't the case for a straight call to EDGES BCS dsun44 ; If the C flag is set then either A = 0 (in which case ; there is no sun line on this pixel row), or the line ; does not fit on-screen, so in either case skip the ; following instruction and move on to the next pixel ; row JSR HLOIN ; Draw a horizontal line from (X1, Y) to (X2, Y) to draw ; pixel row 1 of the sun on this tile row, using EOR ; logic so anything already on-screen appears as a ; silhouette in front of the sun .dsun44 DEY ; Decrement the pixel y-coordinate in Y to row 0 in the ; tile row LDA sunWidth0 ; Call EDGES-2 to calculate X1 and X2 for the horizontal JSR EDGES-2 ; line centred on YY(1 0) and with half-width sunWidth0, ; which is the pixel line for row 0 in the tile row ; ; Calling EDGES-2 will set the C flag if A = 0, which ; isn't the case for a straight call to EDGES BCS dsun45 ; If the C flag is set then either A = 0 (in which case ; there is no sun line on this pixel row), or the line ; does not fit on-screen, so in either case skip the ; following instruction and return from the subroutine ; as we are done JMP HLOIN ; Draw a horizontal line from (X1, Y) to (X2, Y) to draw ; pixel row 0 of the sun on this tile row, using EOR ; logic so anything already on-screen appears as a ; silhouette in front of the sun, and return from the ; subroutine using a tail call as we have now drawn all ; the lines in this row .dsun45 RTS ; Return from the subroutine .dsun46 ; If we get here then we need to draw the tile at the ; left end of the current tile row SETUP_PPU_FOR_ICON_BAR ; If the PPU has started drawing the icon bar, configure ; the PPU to use nametable 0 and pattern table 0 LDX P ; Set X to P, the x-coordinate of the left end of the ; middle part of the sun row (which is the same as the ; x-coordinate just to the right of the leftmost tile) BEQ dsun45 ; If X = 0 then the leftmost tile is off the left of the ; screen, so jump to dsun45 to return from the ; subroutine TYA ; Set Y = Y + 7 CLC ; ADC #7 ; We draw the lines from row 7 up the screen to row 0, TAY ; so this sets Y to the pixel y-coordinate of row 7 LDA sunWidth7 ; Draw a pixel byte for the left edge of the sun at the JSR DrawSunEdgeLeft ; left end of pixel row 7 DEY ; Decrement the pixel y-coordinate in Y to row 6 in the ; tile row LDA sunWidth6 ; Draw a pixel byte for the left edge of the sun at the JSR DrawSunEdgeLeft ; left end of pixel row 6 DEY ; Decrement the pixel y-coordinate in Y to row 5 in the ; tile row LDA sunWidth5 ; Draw a pixel byte for the left edge of the sun at the JSR DrawSunEdgeLeft ; left end of pixel row 5 DEY ; Decrement the pixel y-coordinate in Y to row 4 in the ; tile row LDA sunWidth4 ; Draw a pixel byte for the left edge of the sun at the JSR DrawSunEdgeLeft ; left end of pixel row 4 DEY ; Decrement the pixel y-coordinate in Y to row 3 in the ; tile row LDA sunWidth3 ; Draw a pixel byte for the left edge of the sun at the JSR DrawSunEdgeLeft ; left end of pixel row 3 DEY ; Decrement the pixel y-coordinate in Y to row 2 in the ; tile row LDA sunWidth2 ; Draw a pixel byte for the left edge of the sun at the JSR DrawSunEdgeLeft ; left end of pixel row 2 DEY ; Decrement the pixel y-coordinate in Y to row 1 in the ; tile row LDA sunWidth1 ; Draw a pixel byte for the left edge of the sun at the JSR DrawSunEdgeLeft ; left end of pixel row 1 DEY ; Decrement the pixel y-coordinate in Y to row 0 in the ; tile row LDA sunWidth0 ; Draw a pixel byte for the left edge of the sun at the JMP DrawSunEdgeLeft ; left end of pixel row 0 and return from the subroutine ; using a tail call .dsun47 ; If we get here then we need to draw the tile at the ; right end of the current tile row SETUP_PPU_FOR_ICON_BAR ; If the PPU has started drawing the icon bar, configure ; the PPU to use nametable 0 and pattern table 0 LDX P+1 ; Set X1 to P+1, the x-coordinate of the right end of STX X1 ; the middle part of the sun row (which is the same as ; x-coordinate of the left end of the rightmost tile) TYA ; Set Y = Y + 7 CLC ; ADC #7 ; We draw the lines from row 7 up the screen to row 0, TAY ; so this sets Y to the pixel y-coordinate of row 7 LDA sunWidth7 ; Draw a pixel byte for the right edge of the sun at the JSR DrawSunEdgeRight ; right end of pixel row 7 DEY ; Decrement the pixel y-coordinate in Y to row 6 in the ; tile row LDA sunWidth6 ; Draw a pixel byte for the right edge of the sun at the JSR DrawSunEdgeRight ; right end of pixel row 6 DEY ; Decrement the pixel y-coordinate in Y to row 5 in the ; tile row LDA sunWidth5 ; Draw a pixel byte for the right edge of the sun at the JSR DrawSunEdgeRight ; right end of pixel row 5 DEY ; Decrement the pixel y-coordinate in Y to row 4 in the ; tile row LDA sunWidth4 ; Draw a pixel byte for the right edge of the sun at the JSR DrawSunEdgeRight ; right end of pixel row 4 DEY ; Decrement the pixel y-coordinate in Y to row 3 in the ; tile row LDA sunWidth3 ; Draw a pixel byte for the right edge of the sun at the JSR DrawSunEdgeRight ; right end of pixel row 3 DEY ; Decrement the pixel y-coordinate in Y to row 2 in the ; tile row LDA sunWidth1 ; Draw a pixel byte for the right edge of the sun at the JSR DrawSunEdgeRight ; right end of pixel row 2 ; ; This appears to be a bug (though one you would be ; hard-pressed to detect from looking at the screen), as ; we should probably be loading sunWidth2 here, not ; sunWidth1 ; ; As it stands, on each tile row of the sun, the right ; edge always has matching lines on pixel rows 1 and 2 DEY ; Decrement the pixel y-coordinate in Y to row 1 in the ; tile row LDA sunWidth1 ; Draw a pixel byte for the right edge of the sun at the JSR DrawSunEdgeRight ; right end of pixel row 1 DEY ; Decrement the pixel y-coordinate in Y to row 0 in the ; tile row LDA sunWidth0 ; Draw a pixel byte for the right edge of the sun at the JMP DrawSunEdgeRight ; right end of pixel row 0 and return from the ; subroutine using a tail callName: SUN (Part 2 of 2) [Show more] Type: Subroutine Category: Drawing suns Summary: Draw the sun: Starting from the bottom of the sun, draw the new sun line by line Deep dive: Drawing the sunContext: See this subroutine in context in the source code References: No direct references to this subroutine in this source file
This part erases the old sun, starting at the bottom of the screen and working upwards until we reach the bottom of the new sun.
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Subroutine DrawSunEdgeLeft (category: Drawing suns)
Draw a sun line in the tile on the left end of a sun row
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Subroutine DrawSunEdgeRight (category: Drawing suns)
Draw a sun line in the tile on the right end of a sun row
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Subroutine DrawSunRowOfBlocks (category: Drawing suns)
Draw a row of character blocks that contain sunlight, silhouetting any existing content against the sun
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Subroutine EDGES (category: Drawing lines)
Draw a horizontal line given a centre and a half-width
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Subroutine HLOIN (Part 1 of 5) (category: Drawing lines)
Draw a horizontal line from (X1, Y) to (X2, Y) using EOR logic
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Subroutine PLFL (category: Drawing suns)
Calculate the sun's width on a given pixel row
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Macro SETUP_PPU_FOR_ICON_BAR (category: PPU)
If the PPU has started drawing the icon bar, configure the PPU to use nametable 0 and pattern table 0
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Label dsun1 is local to this routine
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Label dsun10 is local to this routine
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Label dsun11 is local to this routine
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Label dsun12 is local to this routine
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Label dsun13 is local to this routine
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Label dsun14 is local to this routine
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Label dsun15 is local to this routine
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Label dsun16 is local to this routine
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Label dsun17 is local to this routine
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Label dsun18 is local to this routine
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Label dsun19 is local to this routine
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Label dsun2 is local to this routine
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Label dsun20 is local to this routine
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Label dsun21 is local to this routine
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Label dsun22 is local to this routine
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Label dsun23 is local to this routine
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Label dsun24 is local to this routine
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Label dsun25 is local to this routine
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Label dsun26 is local to this routine
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Label dsun27 is local to this routine
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Label dsun28 is local to this routine
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Label dsun29 is local to this routine
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Label dsun3 is local to this routine
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Label dsun30 is local to this routine
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Label dsun31 is local to this routine
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Label dsun32 is local to this routine
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Label dsun33 is local to this routine
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Label dsun34 is local to this routine
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Label dsun35 is local to this routine
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Label dsun36 is local to this routine
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Label dsun37 is local to this routine
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Label dsun38 is local to this routine
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Label dsun39 is local to this routine
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Label dsun4 is local to this routine
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Label dsun40 is local to this routine
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Label dsun41 is local to this routine
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Label dsun42 is local to this routine
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Label dsun43 is local to this routine
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Label dsun44 is local to this routine
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Label dsun45 is local to this routine
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Label dsun46 is local to this routine
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Label dsun47 is local to this routine
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Label dsun5 is local to this routine
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Label dsun6 is local to this routine
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Label dsun7 is local to this routine
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Label dsun8 is local to this routine
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Label dsun9 is local to this routine