TUTORIAL #20 – SHPADR

 TUTORIAL #20 – SHPADR “Is used as a pointer for the SHAPE/TILE GRAPHICS used on the world map”. 

All the graphic-tiles/shapes in Ultima 1 are predefined within a database SHPADR.  These values consist of the type of shape used such as TREES, PLAINS, MOUNTAINS, OCEAN, etc…  They are structured and referenced exactly as the MAPADR data each shape on the map is defined by a value from 0 to 15.  This value is what represent a particular shape such as the fighter or the troll.

 

I will be going through the subroutine SHPADR line-by-line and explaining what each line of code is doing and how it affects the outcome of the program.

 

719  **********************************

 

This is just a comment line to separate each subroutine and helps to define the start of the subroutine. 

 

720  * LOAD SHAPE ADDRESSES INTO SHPADR, LOW BYTE FIRST

 

This comment line tells the user what type of data will be referenced. 

 

721  SHPADR              DFB   >SHAPE1

 

Line 721 is used to “[D]e[F]ine [B]ype” of SHAPE1 data location from the LOW byte side.  Each SHAPE location is defined by a HIGH and LOW byte, which in this case is the > character representing the LOW byte location for the map addresses in MAP1.  An example of a memory region address from the HIGH and LOW byte reference could be HEX $8000 or 32768.  The HIGH side would be the 80 and the LOW side would be the 00 of the HEX value $8000.

 

Also, line 721 has a header titled SHPADR, which allows it to be called as a separate subroutine from the main subroutine.

 

722                                DFB   <SHAPE1

 

Line 722 is used to “[D]e[F]ine [B]ype” of MAP1 data location from the HIGH byte side.  Each MAP location is defined by a HIGH and LOW byte, which in this case is the < character representing the HIGH byte location for the map addresses in SHAPE1.  SHAPE1 will call to a database that will hold all the graphic tile types for a space on the horizontal line of the world map.  By using a HIGH and LOW byte reference the map address is location in a memory region based on the byte reference and can be called to reference the necessary data of that map line.

 

 

723                               DFB   >SHAPE2

 

THRU

 

752                                DFB   <SHAPE16

 

Line 723 THRU 752 are all reference the same way with “[D]e[F]ine [B]ype” of SHAPE# data location.  Each MAP location is defined by a HIGH and LOW byte will be referenced the exact same way and hold all the world map data information to help draw out the entire Ultima World map.

These are the following shape/graphic tile reference values and their equivalent shape.

 

SHAPE1            =          SHIP

 

SHAPE2            =          RAFT

 

SHAPE3            =          PLAINS

 

SHAPE4            =          TREES

 

SHAPE5            =          CASTLE

 

SHAPE6            =          TOWN

 

SHAPE7            =          SIGNPOST

 

SHAPE8            =          CHARACTER

 

SHAPE9            =          TROLL 

 

SHAPE10         =          DUNGEON

 

SHAPE11         =          CART  

 

SHAPE12         =          HORSE

 

SHAPE13         =          SPEEDER         

 

SHAPE14         =          SPACE SHIP

 

SHAPE15         =          OCEAN

 

SHAPE16         =          MOUNTAIN

 

Please email me any questions you might have,

 

Ultima_revisited@yahoo.com

 

Joe “kingspud”