Routines
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CE72: Compute Entity Approach Position
Used by the routine at Main_Game_Loop.
Computes the approach position and frame index for an intro entity. Entry at Compute_Entity_Approach_Position_Short skips the phase-5 scaling step. Both entry points are called from Main_Game_Loop.
Compute_Entity_Approach_Position CE72 LD E,A Skip the extended scaling step if the approach is not in phase 05.
CE73 LD A,($C4FF)
CE76 CP $05
CE78 LD A,E
CE79 JP NZ,Compute_Entity_Approach_Position_Short
CE7C SLA A Scale the approach velocity into the displacement byte.
CE7E SLA A
CE80 SLA A
CE82 SLA A
CE84 RR D
CE86 SLA A
CE88 RR D
CE8A SLA A
CE8C RR D
CE8E SLA A
CE90 RR D
CE92 SLA A
CE94 RR D
CE96 SRL D Halve the displacement three times to normalise the scale.
CE98 SRL D
CE9A SRL D
CE9C LD A,D Transfer the normalised displacement to A.
This entry point is used by the routine at Main_Game_Loop.
Compute_Entity_Approach_Position_Short CE9D RRA Deinterleave the packed approach position bytes.
CE9E RRA
CE9F RR D
CEA1 RRA
CEA2 RR E
CEA4 RRA
CEA5 RR D
CEA7 RRA
CEA8 RR E
CEAA XOR A Reassemble the screen position components via left rotation.
CEAB RL D
CEAD RLA
CEAE RL E
CEB0 RLA
CEB1 RL D
CEB3 RLA
CEB4 RL E
CEB6 RLA
CEB7 RET Return.
CEB8 RET Return.
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