.ApplyElevation LDA heightAboveTrack \ Set A = heightAboveTrack BEQ elev1 \ If heightAboveTrack = 0, jump to elev1 DEC yJumpHeight \ Set yJumpHeight = yJumpHeight - 2 DEC yJumpHeight JMP elev7 \ Jump to elev7 .elev1 \ If we get here then heightAboveTrack = 0 and A = 0 STA yJumpHeight \ Set yJumpHeight = 0 STA yGravityDelta \ Set yGravityDelta = 0 LDY liftFromTorque \ Set Y = liftFromTorque LDA gearNumber \ If gearNumber = 0, then we are in reverse, so jump to BEQ elev3 \ elev3 LDA throttleBrakeState \ If throttleBrakeState is negative, then there is no BMI elev3 \ brake or throttle key press, so jump to elev3 BEQ elev2 \ If throttleBrakeState = 0, then the brakes are being \ applied, so jump to elev2 \ If we get here then the throttle is being applied LDA engineTorque \ Set A to the engine torque BNE elev4 \ If the engine torque is non-zero, jump to elev4 to \ increment the lift in Y BEQ elev3 \ Jump to elev3 (this BEQ is effectively a JMP as A is \ always zero) .elev2 \ If we get here then we are not in reverse gear and the \ brakes are being applied LDA playerSpeedHi \ Set A = playerSpeedHi BNE elev5 \ If A is non-zero, then we are moving, so jump to elev5 \ to decrement the lift in Y .elev3 \ This part of the routine brings the car nose back \ towards the normal level, if it isn't there already \ \ We get here when any of the following are true: \ \ * In reverse \ \ * Not in reverse, no brake or throttle key press \ \ * Not in reverse, brakes are being applied, we are \ not moving \ \ * Not in reverse, no brakes, throttle is being \ applied, engine torque is zero \ \ In other words, we are not accelerating or braking, so \ we slowly cancel any rise or fall of the car nose that \ we may have applied previously, as follows: \ \ * If the lift in Y is positive, we decrement it \ towards zero via elev5 \ \ * If the lift in Y is negative, we increment it \ towards zero and then increment it again via elev4 \ \ This means the list increments towards zero at twice \ the rate that it decrements towards zero TYA \ Set A = Y \ = liftFromTorque BEQ elev7 \ If liftFromTorque = 0, jump to elev7 to move on to \ part 2 without updating liftFromTorque BPL elev5 \ If liftFromTorque > 0, jump to elev5 to decrement the \ lift in Y \ If we get here then liftFromTorque < 0, so the nose of \ the car is already being pushed up and the horizon is \ lower than it would normally be INY \ Set Y = Y + 1 \ = liftFromTorque + 1 \ \ So this pulls the nose of the car up, making the \ horizon fall back towards the normal level .elev4 \ This part of the routine pulls the nose of the car up \ by incrementing Y (to a maximum of 3), making the \ horizon fall \ \ We jump here if we are not in reverse, we are applying \ the throttle, and engine torque is non-zero INY \ Set Y = Y + 1 \ = liftFromTorque + 1 \ \ So this pulls the nose of the car up, making the \ horizon fall down BMI elev6 \ If Y is negative, jump to elev6 to set liftFromTorque \ to Y CPY #4 \ If Y < 4, jump to elev6 to set liftFromTorque = Y BCC elev6 LDY #3 \ Set Y = 3, so Y has a maximum value of 3 BCS elev6 \ Jump to elev6 (this BCS is effectively a JMP as we \ just passed through a BCC) .elev5 \ This part of the routine pushes the nose of the car \ down by decrementing Y (to a minimum of -5), making \ the horizon rise \ \ We jump here if we are not in reverse, we are applying \ the brakes, and we are moving DEY \ Set Y = Y - 1 \ \ So this pushes the nose of the car down, making the \ horizon rise up BPL elev6 \ If Y is positive, jump to elev6 to set liftFromTorque \ to Y CPY #&FB \ If Y >= -5, jump to elev6 to set liftFromTorque = Y BCS elev6 LDY #&FB \ Set Y = -5, so Y has a minimum value of -5 .elev6 STY liftFromTorque \ Set liftFromTorque = YName: ApplyElevation (Part 1 of 5) [Show more] Type: Subroutine Category: Driving model Summary: Calculate changes in the car's elevation Deep dive: The core driving model Jumps and dropsContext: See this subroutine in context in the source code References: This subroutine is called as follows: * ApplyDrivingModel calls ApplyElevation
Calculate the following: * liftFromTorque = the lift of the front of the car caused by accelerating or braking, in the range -5 to +3 A positive value of liftFromTorque means the horizon is drawn lower on the screen, which means the nose is being pulled up. The value of liftFromTorque is only changed if the car is on the ground. The logic is as follows: * Horizon goes down when we are not in reverse, we are applying the throttle and engine torque is non-zero (i.e. we pull the nose of the car up by incrementing liftFromTorque, to a maximum of 3) * Horizon goes up when we are not in reverse, we are applying the brakes and we are moving (i.e. we push the nose of the car down by decrementing liftFromTorque, to a minimum of -5) * Otherwise, gradually bring the nose back to the normal level of zero, with the value incrementing towards zero at twice the rate that it decrements towards zero (so the nose rises at twice the speed that it falls, as the suspension springs are more powerful than gravity)
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Label elev1 is local to this routine
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Label elev2 is local to this routine
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Label elev3 is local to this routine
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Label elev4 is local to this routine
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Label elev5 is local to this routine
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Label elev6 is local to this routine
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Label elev7 in subroutine ApplyElevation (Part 2 of 5)
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Variable engineTorque in workspace Zero page
The power being generated by the engine
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Variable gearNumber in workspace Zero page
The current gear number
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Variable heightAboveTrack in workspace Zero page
The car's height above the track, for when it is being dropped from the crane, or jumping from hitting the verge too fast
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Variable liftFromTorque (category: Driving model)
The lift of the front of the car caused by acceleration or braking
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Variable playerSpeedHi in workspace Zero page
High byte of the speed of the player's car along the track
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Variable throttleBrakeState in workspace Zero page
Denotes whether the throttle or brake are being applied
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Variable yGravityDelta in workspace Zero page
The distance in the y-axis that the car would fall if the track wasn't there, for use when calculating the outcome of jumps and being dropped from the crane
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Variable yJumpHeight in workspace Zero page
The height of the car's jump (or crane lift), in terms of track lines, which we use to alter the position of the horizon