Skip to navigation

Aviator on the BBC Micro

Visibility: ProcessLine (Part 4 of 7)

Name: ProcessLine (Part 4 of 7) [Show more] Type: Subroutine Category: Visibility Summary: Process bullet lines Deep dive: Visibility checks
Context: See this subroutine in context in the source code References: No direct references to this subroutine in this source file
.plin6 \ If we get here then the point is not part of a linked \ object, and object ID is in the range 12 to 15, so \ this is a bullet line PLA \ Pull the point ID from the stack and store it in GG STA GG LDA objectStatus,Y \ If bit 7 of the object's status byte is set, jump to BMI plin7 \ plin16 via plin7 \ If we get here then bit 7 of the object's status byte \ is clear LDA #%10000000 \ Set showLine to say that the line is not in view STA showLine RTS \ Return from the subroutine .plin7 JMP plin16 \ Jump down to plin16 with the bullet point ID in GG, to \ check distance and z-coordinates and return the final \ result