Routines
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8B3C: Render an object with collision detection.
Two-phase rendering pipeline: (1) erase old sprite at previous_object_coordinates using XOR blending, (2) draw new sprite at object_coordinates using OR blending, checking for pixel collisions during the draw phase. Sprite frame is selected from E's lower bits for sub-pixel alignment.
Input
A Sprite width in tiles (1-3)
BC Sprite frame size in bytes
D Sprite height in pixels
E Screen attributes (lower bits also select animation frame)
HL Pointer to sprite data array (base of all frames)
render_object 8B3C PUSH DE Store width and set screen attributes for the sprite area.
8B3D LD ($8B1A),A
8B40 NOP
8B41 CALL set_sprite_attributes
8B44 LD A,E Select sprite frame from E's lower bits (sub-pixel alignment).
8B45 AND $07
8B47 SRL A
8B49 INC A
8B4A OR A
8B4B SBC HL,BC
render_object_frame_loop 8B4D ADD HL,BC
8B4E DEC A
8B4F JR NZ,render_object_frame_loop
8B51 LD ($8B10),HL Store selected frame pointer for both erase and draw passes.
8B54 LD ($8B16),HL
8B57 POP DE
This entry point is used by the routine at render_explosions.
render_object_entry 8B58 PUSH DE Calculate screen addresses for new and old positions.
8B59 LD BC,($8B0C)
8B5D CALL calculate_pixel_address
8B60 LD ($8B12),HL
8B63 LD BC,($8B0A)
8B67 CALL calculate_pixel_address
8B6A LD ($8B14),HL
8B6D JP adjust_old_screen_third_loop Jump to render loop.
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