LDA MJ \ If we are in witchspace, jump down to MA23S to skip BNE MA23S \ the following, as there are no space stations in \ witchspace LDA MCNT \ Fetch the main loop counter and calculate MCNT mod 32, AND #31 \ jumping to MA93 if it is on-zero (so the following BNE MA93 \ code only runs every 32 iterations of the main loop) LDA SSPR \ If we are inside the space station safe zone, jump to BNE MA23S \ MA23S to skip the following, as we already have a \ space station and don't need another TAY \ Set Y = A = 0 (A is 0 as we didn't branch with the \ previous BNE instruction) JSR MAS2 \ Call MAS2 to calculate the largest distance to the BNE MA23S \ planet in any of the three axes, and if it's \ non-zero, jump to MA23S to skip the following, as we \ are too far from the planet to bump into a space \ station \ We now want to spawn a space station, so first we \ need to set up a ship data block for the station in \ INWK that we can then pass to NWSPS to add a new \ station to our bubble of universe. We do this by \ copying the planet data block from K% to INWK so we \ can work on it, but we only need the first 29 bytes, \ as we don't need to worry about bytes #29 to #35 \ for planets (as they don't have rotation counters, \ AI, explosions, missiles, a ship line heap or energy \ levels) LDX #28 \ So we set a counter in X to copy 29 bytes from K%+0 \ to K%+28 .MAL4 LDA K%,X \ Load the X-th byte of K% and store in the X-th byte STA INWK,X \ of the INWK workspace DEX \ Decrement the loop counter BPL MAL4 \ Loop back for the next byte until we have copied the \ first 28 bytes of K% to INWK \ We now check the distance from our ship (at the \ origin) towards the point where we will spawn the \ space station if we are close enough \ \ This point is calculated by starting at the planet's \ centre and adding 2 * nosev, which takes us to a point \ above the planet's surface, at an altitude that \ matches the planet's radius \ \ This point pitches and rolls around the planet as the \ nosev vector rotates with the planet, and if our ship \ is within a distance of (192 0) from this point in all \ three axes, then we spawn the space station at this \ point, with the station's slot facing towards the \ planet, along the nosev vector \ \ This works because in the following, we calculate the \ station's coordinates one axis at a time, and store \ the results in the INWK block, so by the time we have \ calculated and checked all three, the ship data block \ is set up with the correct spawning coordinates INX \ Set X = 0 (as we ended the above loop with X as &FF) LDY #9 \ Call MAS1 with X = 0, Y = 9 to do the following: JSR MAS1 \ \ (x_sign x_hi x_lo) += (nosev_x_hi nosev_x_lo) * 2 \ \ A = |x_sign| BNE MA23S \ If A > 0, jump to MA23S to skip the following, as we \ are too far from the planet in the x-direction to \ bump into a space station LDX #3 \ Call MAS1 with X = 3, Y = 11 to do the following: LDY #11 \ JSR MAS1 \ (y_sign y_hi y_lo) += (nosev_y_hi nosev_y_lo) * 2 \ \ A = |y_sign| BNE MA23S \ If A > 0, jump to MA23S to skip the following, as we \ are too far from the planet in the y-direction to \ bump into a space station LDX #6 \ Call MAS1 with X = 6, Y = 13 to do the following: LDY #13 \ JSR MAS1 \ (z_sign z_hi z_lo) += (nosev_z_hi nosev_z_lo) * 2 \ \ A = |z_sign| BNE MA23S \ If A > 0, jump to MA23S to skip the following, as we \ are too far from the planet in the z-direction to \ bump into a space station LDA #192 \ Call FAROF2 to compare x_hi, y_hi and z_hi with 192, JSR FAROF2 \ which will set the C flag if all three are < 192, or \ clear the C flag if any of them are >= 192 BCC MA23S \ Jump to MA23S if any one of x_hi, y_hi or z_hi are \ >= 192 (i.e. they must all be < 192 for us to be near \ enough to the planet to bump into a space station) JSR WPLS \ Call WPLS to remove the sun from the screen, as we \ can't have both the sun and the space station at the \ same time JSR NWSPS \ Add a new space station to our local bubble of \ universe .MA23S JMP MA23 \ Jump to MA23 to skip the following planet and sun \ altitude checksName: Main flight loop (Part 14 of 16) [Show more] Type: Subroutine Category: Main loop Summary: Spawn a space station if we are close enough to the planet Deep dive: Program flow of the main game loop Scheduling tasks with the main loop counter Ship data blocks The space station safe zoneContext: See this subroutine in context in the source code Variations: See code variations for this subroutine in the different versions References: No direct references to this subroutine in this source file
The main flight loop covers most of the flight-specific aspects of Elite. This section covers the following: * Spawn a space station if we are close enough to the planet (every 32 iterations of the main loop)
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Subroutine FAROF2 (category: Maths (Geometry))
Compare x_hi, y_hi and z_hi with A
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Workspace K% (category: Workspaces)
Ship data blocks
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Label MA23 in subroutine Main flight loop (Part 16 of 16)
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Label MA23S is local to this routine
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Label MA93 in subroutine Main flight loop (Part 15 of 16)
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Label MAL4 is local to this routine
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Subroutine MAS1 (category: Maths (Geometry))
Add an orientation vector coordinate to an INWK coordinate
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Subroutine MAS2 (category: Maths (Geometry))
Calculate a cap on the maximum distance to the planet or sun
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Subroutine NWSPS (category: Universe)
Add a new space station to our local bubble of universe
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Subroutine WPLS (category: Drawing suns)
Remove the sun from the screen