.LAUN LDA #$00 ; Clear the screen and set the view type in QQ11 to $00 JSR ChangeToView ; (Space view with no fonts loaded) JSR HideMostSprites ; Hide all sprites except for sprite 0 and the icon bar ; pointer LDY #12 ; Call the NOISE routine with Y = 12 to make the first JSR NOISE ; sound of the ship launching from the station LDA #128 ; Set K+2 = 128 to send to DrawLaunchBox and STA K+2 ; DrawLightning as the x-coordinate of the centre of the ; boxes and lightning (so they are centred on-screen) LDA halfScreenHeight ; Set K+3 to half the screen height to send to STA K+3 ; DrawLaunchBox and DrawLightning as the y-coordinate of ; the centre of the boxes and lightning (so they are ; centred on-screen) LDA #80 ; Set XP to use as a counter for the duration of the STA XP ; hyperspace effect, so we run the following loop 80 ; times LDA #112 ; Set YP to use as a counter for when we show the STA YP ; lightning effect at the end of the tunnel, which we ; show when YP < 100 (so we wait until 13 frames have ; passed before drawing the lightning) ; ; Also, at the start of each frame, we keep subtracting ; 16 from STP until STP < YP, and only then do we start ; drawing boxes and, possibly, the lightning LDY #4 ; Wait until four NMI interrupts have passed (i.e. the JSR DELAY ; next four VBlanks) LDY #24 ; Call the NOISE routine with Y = 24 to make the second JSR NOISE ; sound of the ship launching from the station .laun1 JSR CheckForPause-3 ; Check whether the pause button has been pressed or an ; icon bar button has been chosen, and process pause or ; unpause if a pause-related button has been pressed JSR FlipDrawingPlane ; Flip the drawing bitplane so we draw into the bitplane ; that isn't visible on-screen LDA XP ; Set STP = 96 + (XP mod 16) AND #15 ; ORA #96 ; STA STP ; So over the course of the 80 iterations around the ; loop, STP starts at 96, then counts down from 112 to ; 96, and keeps repeating this countdown until XP is ; zero and STP is 96 ; ; The higher the value of STP, the closer together the ; lines in the tunnel, so this makes the tunnel lines ; move further away as the animation progresses, giving ; a feeling of moving forwards through the tunnel LDA #%10000000 ; Set bit 7 of firstBox so we can detect when we are on STA firstBox ; the first iteration of the laun2 loop ; We now draw the boxes in the launch tunnel effect, ; looping back to hype2 for each new line ; ; STP gets decremented by 16 for each box, so STP is ; set to the starting point (in the range 96 to 112), ; and gets decremented by 16 for each box until it is ; negative ; ; As STP decreases, the boxes get bigger, so this loop ; draws the boxes from the smallest in the middle and ; working out towards the edges .laun2 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 LDA STP ; Set STP = STP + 16 SEC ; SBC #16 ; And set A to the new value of STP BMI laun4 ; If STP is now negative, then jump to laun4 to move on ; to the next frame, so we stop drawing boxes in this ; frame STA STP ; Update STP with the new value CMP YP ; If STP >= YP, jump to laun2 to keep reducing STP until BCS laun2 ; STP < YP STA Q ; Set Q to the new value of STP ; We now calculate how far the top edge of this box is ; from the centre of the screen in a vertical direction, ; with the result being boxes that are closer together, ; the closer they are to the centre ; ; We space out the boxes using a reciprocal algorithm, ; where the distance of line n from the centre is ; proportional to 1/n, so the boxes get spaced roughly ; in the proportions of 1/2, 1/3, 1/4, 1/5 and so on, so ; the boxes bunch closer together as n increases ; ; STP also includes the iteration number, modded so it ; runs from 15 to 0, so over the course of the animation ; the boxes move away from the centre line, as the ; iteration decreases and the value of R below increases LDA #8 ; Set A = 8 to use in the following division JSR LL28 ; Call LL28 to calculate: ; ; R = 256 * A / Q ; = 256 * 8 / STP ; ; So R is the vertical distance of the current box top ; top from the centre of the screen ; ; The maximum value of STP is 112 - 16 = 96, and the ; minimum is 0 (the latter being enforced by the ; comparison above), so R ranges from 21 to 255 LDA R ; Set A = R - 20 SEC ; SBC #20 ; This sets the range of values in A to 1 to 235 ; We can now use A as half the height of the box to ; draw, to give us an effect where the boxes are more ; spread out as they get taller, and which get bigger ; as the animation progresses, with the difference in ; size between frames being more pronounced with the ; bigger boxes CMP #84 ; If A >= 84, jump to laun4 to move on to the next frame BCS laun4 ; as the box is outside the edges of the screen (so we ; can stop drawing lines in this frame as we have now ; drawn them all) STA K+1 ; Set K+1 = A to send to DrawLaunchBox and DrawLightning ; as half the height of the box/lightning LSR A ; Set K = 1.5 * K+1 to send to DrawLaunchBox and ADC K+1 ; DrawLightning as half the width of the box, so the box STA K ; is 50% wider than it is tall (as it's a space station ; slot) ASL firstBox ; Set the C flag to bit 7 of firstBox and zero firstBox ; (as we know that only bit 7 of firstBox is set before ; the shift) BCC laun3 ; If the C flag is clear then this is not the first ; iteration of the laun2 loop for this frame, so jump to ; laun3 to draw the box, skipping the lightning (so we ; only draw the lightning on the first iteration of ; laun2 for this frame ; If we get here then this is the first iteration of the ; laun2 loop for this frame, so we consider drawing the ; lightning effect at the end of the tunnel LDA YP ; If YP >= 100, jump to laun3 to skip drawing the CMP #100 ; lightning as the tunnel exit is too small to contain BCS laun3 ; the lightning effect LDA K+1 ; If K+1 >= 72, jump to laun5 to draw the lightning but CMP #72 ; without drawing any boxes, as the first box (which is BCS laun5 ; the smallest) doesn't fit on-screen LDA STP ; Store the value of STP on the stack so we can retrieve PHA ; it after the call to DrawLightning (as DrawLightning ; corrupts the value of STP) JSR DrawLightning_b6 ; Call DrawLightning to draw the lightning effect at the ; end of the tunnel, centred on the centre of the screen ; and in a rectangle with a half-height of K and a ; half-width of 1.5 * K (so it fits within the smallest ; launch box) PLA ; Restore the value of STP that we stored on the stack STA STP .laun3 JSR DrawLaunchBox_b6 ; Draw a box centred on the centre of the screen, with a ; half-height of K and a half-width of 1.5 * K JMP laun2 ; Loop back to laun2 to draw the next box .laun4 JSR DrawBitplaneInNMI ; Configure the NMI to send the drawing bitplane to the ; PPU after drawing the box edges and setting the next ; free tile number DEC YP ; Decrement the lightning counter in YP DEC XP ; Decrement the frame counter in XP BNE laun1 ; Loop back to laun1 to draw the next frame of the ; animation, until the frame counter runs down to 0 LDY #23 ; Call the NOISE routine with Y = 23 to make the third JMP NOISE ; sound of the ship launching from the station, ; returning from the subroutine using a tail call .laun5 ; We call this from the first iteration of the loop in ; this frame, and when K+1 >= 72, which means that the ; first box in this frame (which will be the smallest) ; is too big for the screen, so we just draw the ; lightning effect and don't draw any boxes LDA #72 ; Set K+1 = 72 to pass to DrawLightning as half the STA K+1 ; height of the lightning effect LDA STP ; Store the value of STP on the stack so we can retrieve PHA ; it after the call to DrawLightning (as DrawLightning ; corrupts the value of STP) JSR DrawLightning_b6 ; Call DrawLightning to draw the lightning effect at the ; end of the tunnel, centred on the centre of the screen ; and in a rectangle with a half-height of K and a ; half-width of 1.5 * K (so it fits within the smallest ; launch box) PLA ; Restore the value of STP that we stored on the stack STA STP JMP laun2 ; Loop back to laun2 to draw the next box RTS ; Return from the subroutineName: LAUN [Show more] Type: Subroutine Category: Flight Summary: Make the launch sound and draw the launch tunnelContext: See this subroutine in context in the source code References: This subroutine is called as follows: * DOENTRY calls LAUN * TT110 calls LAUN
This is shown when launching from or docking with the space station. This routine does a similar job to the routine of the same name in the BBC Master version of Elite, but the code is significantly different.
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Subroutine ChangeToView (category: Drawing the screen)
Clear the screen and set a new view type
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Entry point CheckForPause-3 in subroutine CheckForPause (category: Icon bar)
Set A to the number of the icon bar button in iconBarChoice so we check whether the pause button is being pressed
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Subroutine DELAY (category: Utility routines)
Wait until a specified number of NMI interrupts have passed (i.e. a specified number of VBlanks)
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Subroutine DrawBitplaneInNMI (category: Drawing the screen)
Configure the NMI to send the drawing bitplane to the PPU after drawing the box edges and setting the next free tile number
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Subroutine DrawLaunchBox_b6 (category: Flight)
Call the DrawLaunchBox routine in ROM bank 6
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Subroutine DrawLightning_b6 (category: Flight)
Call the DrawLightning routine in ROM bank 6
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Subroutine FlipDrawingPlane (category: Drawing the screen)
Flip the drawing bitplane
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Subroutine HideMostSprites (category: Drawing sprites)
Hide all sprites except for sprite 0 and the icon bar pointer
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Subroutine LL28 (category: Maths (Arithmetic))
Calculate R = 256 * A / Q
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Subroutine NOISE (category: Sound)
Make the sound effect whose number is in Y
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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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Variable halfScreenHeight in workspace ZP
Half the height of the drawable part of the screen in pixels (can be 72, 77 or 104 pixels)
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Label laun1 is local to this routine
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Label laun2 is local to this routine
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Label laun3 is local to this routine
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Label laun4 is local to this routine
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Label laun5 is local to this routine