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Routines |
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Used by the routine at TestWideOverlap.
Tests the entity against one axis of a block. TestGroupObjects patches the two edges in first. Bit 6 of the object's flags selects the x edges and the x extent; otherwise the y edges and the y extent are used. The overlap is stored for that axis, and for the player the side is mixed into the flags. No overlap on z sets the flags to 255.
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Bit 6 of the object's flags selects the axis. The two edges loaded below are patched by TestGroupObjects.
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| TestBlockOverlap | 55004 | LD A,(23768) | Read the object's flags. | |||||||
| 55007 | AND %01000000 | Use bit 6 of the flags. | ||||||||
| 55009 | JR Z,TestBlockOverlap_YAxis | Test the y edges when bit 6 is clear. | ||||||||
| 55011 | LD DE,0 | Take the patched x edges. | ||||||||
| 55014 | LD HL,0 | |||||||||
| 55017 | LD A,(IY+2) | Scale the object's byte and use the x extent. | ||||||||
| 55020 | ADD A,A | |||||||||
| 55021 | ADD A,A | |||||||||
| 55022 | ADD A,A | |||||||||
| 55023 | LD B,(IX+11) | |||||||||
| 55026 | JR TestBlockOverlap_Size | |||||||||
| TestBlockOverlap_YAxis | 55028 | LD DE,0 | Take the patched y edges. | |||||||
| 55031 | LD HL,0 | |||||||||
| 55034 | LD B,(IX+12) | Use the y extent. | ||||||||
| 55037 | LD A,(IY+2) | Read the object's byte. | ||||||||
| TestBlockOverlap_Size | 55040 | ADD A,A | Double that byte. | |||||||
| 55041 | AND %01110000 | Use bits 4-6. | ||||||||
| 55043 | ADD A,16 | Add 16 to make the size. | ||||||||
| 55045 | LD C,A | |||||||||
| 55046 | LD A,(23768) | Read the flags again. | ||||||||
| 55049 | AND %00100000 | Use bit 5 of the flags. | ||||||||
| 55051 | JR Z,TestBlockOverlap_Edge | Measure from the far edge when bit 5 is set. | ||||||||
| 55053 | EX DE,HL | Subtract the near edge from the far edge plus the size. | ||||||||
| 55054 | LD B,0 | |||||||||
| 55056 | ADD HL,BC | |||||||||
| 55057 | SBC HL,DE | |||||||||
| 55059 | XOR A | |||||||||
| 55060 | JR TestBlockOverlap_Mark | The marker for that side is zero. | ||||||||
| TestBlockOverlap_Edge | 55062 | LD C,B | Subtract the near edge from the far edge plus the extent. | |||||||
| 55063 | LD B,0 | |||||||||
| 55065 | ADD HL,BC | |||||||||
| 55066 | SBC HL,DE | |||||||||
| 55068 | LD A,4 | The marker for that side is 4. | ||||||||
| TestBlockOverlap_Mark | 55070 | LD (55177),A | Remember the marker. | |||||||
| 55073 | LD B,2 | Start with a count of two. | ||||||||
| 55075 | LD A,(23768) | Read the flags. | ||||||||
| 55078 | AND %00010000 | Use bit 4 of the flags. | ||||||||
| 55080 | JR NZ,TestBlockOverlap_Compare | Halve the overlap when bit 4 is clear. | ||||||||
| 55082 | DEC B | Halve the overlap and count one. | ||||||||
| 55083 | SRL H | |||||||||
| 55085 | RR L | |||||||||
| TestBlockOverlap_Compare | 55087 | LD DE,(54991) | Add the edge address. | |||||||
| 55091 | ADD HL,DE | |||||||||
| 55092 | LD DE,(54998) | Subtract the z coordinate. | ||||||||
| 55096 | SBC HL,DE | No overlap on z sets the flags to 255. | ||||||||
| 55098 | JR C,FlagOverlap | |||||||||
| 55100 | LD A,(56787) | The overlap has to reach the stored z overlap. | ||||||||
| 55103 | SUB L | |||||||||
| 55104 | JR C,TestBlockOverlap_0 | |||||||||
| 55106 | SUB 2 | An overlap below two clears the flags. | ||||||||
| 55108 | JR C,TestBlockOverlap_0 | |||||||||
| 55110 | LD H,255 | Remember an overlap of 255. | ||||||||
| 55112 | LD (56787),HL | |||||||||
| 55115 | LD A,(23768) | Read the flags. | ||||||||
| 55118 | AND %01000000 | Use bit 6 of the flags. | ||||||||
| 55120 | LD A,H | The x test records the overlap on x. | ||||||||
| 55121 | JR NZ,TestBlockOverlap_1 | |||||||||
| 55123 | LD (56785),A | Record the overlap on y. | ||||||||
| 55126 | LD A,(IX+0) | Only the player records the side. | ||||||||
| 55129 | DEC A | |||||||||
| 55130 | RET NZ | |||||||||
| 55131 | LD A,(55177) | Combine the marker with the count. | ||||||||
| 55134 | OR B | |||||||||
| 55135 | ADD A,A | Shift that side up by three. | ||||||||
| 55136 | ADD A,A | |||||||||
| 55137 | ADD A,A | |||||||||
| 55138 | LD B,A | Keep it for the flags. | ||||||||
| 55139 | ADD A,A | Shift it up by two more. | ||||||||
| 55140 | ADD A,A | |||||||||
| 55141 | AND %01100000 | Use bits 5-6. | ||||||||
| 55143 | LD C,A | Keep them for field 33. | ||||||||
| 55144 | LD A,(IX+30) | Read the flags. | ||||||||
| 55147 | AND %11000111 | Use the flag bits other than 3-5. | ||||||||
| 55149 | OR B | Mix the side into the flags. | ||||||||
| 55150 | LD (IX+30),A | |||||||||
| 55153 | LD A,(IX+33) | Read field 33. | ||||||||
| 55156 | AND %10011111 | Use the bits other than 5-6. | ||||||||
| 55158 | OR C | Mix the side into field 33. | ||||||||
| 55159 | LD (IX+33),A | |||||||||
| 55162 | RET | Return. | ||||||||
| TestBlockOverlap_0 | 55163 | XOR A | Clear the flags when the overlap is too small. | |||||||
| 55164 | LD (23768),A | |||||||||
| 55167 | RET | |||||||||
| TestBlockOverlap_1 | 55168 | LD (56783),A | Record the overlap on x. | |||||||
| 55171 | LD A,(IX+0) | Only the player records the side. | ||||||||
| 55174 | DEC A | |||||||||
| 55175 | RET NZ | |||||||||
| 55176 | LD A,0 | Combine the marker with the count. | ||||||||
| 55178 | OR B | |||||||||
| 55179 | LD B,A | Keep it. | ||||||||
| 55180 | RRCA | Shift the side down by three. | ||||||||
| 55181 | RRCA | |||||||||
| 55182 | RRCA | |||||||||
| 55183 | AND %01100000 | Use bits 5-6. | ||||||||
| 55185 | LD C,A | Keep them. | ||||||||
| 55186 | LD A,(IX+32) | Read field 32. | ||||||||
| 55189 | AND %10011111 | Use the bits other than 5-6. | ||||||||
| 55191 | OR C | Mix the side into field 32. | ||||||||
| 55192 | LD (IX+32),A | |||||||||
| 55195 | LD A,(IX+30) | Read the flags. | ||||||||
| 55198 | AND %11111000 | Use the top five bits of the flags. | ||||||||
| 55200 | OR B | Mix the count into the low bits of the flags. | ||||||||
| 55201 | LD (IX+30),A | |||||||||
| 55204 | RET | Return. | ||||||||
| Prev: 54990 | Up: Map | Next: 55205 |