General notes
Whole structure operations Initialise
Draw
Load
Save
Append
Structure scanning Find
List
Structure value changes Set
Show
Translate
Zoom
Rotate
Data structure manipulation Create
Destroy
Insert
Delete
Miscellaneous CloseDown
MiscOp
Compress
Expand
Other BoundingSphere
Data structure manipulation
The following SWIs allow you to make changes to the data structure without
having to peek and poke the structure directly. Under normal circumstances
you will not need to use these at all, since the file is likely to be
created using the Euclid Editor, and will be loaded lock-stock-and-barrel
using Euclid_Load.
In all cases if the structure shifts because a chunk of the structure has
been removed, or a new section has been introduced, then all pointers in the
structure are relocated. If you hold pointers yourself, you must either
discard them after Destroy, Insert or Delete, or adjust them yourself.
Any new areas created are always blanked. Since zero pointers are always
interpreted by Euclid_Draw to mean 'do nothing' a created object can be
partially filled if you wish.
· Create
· Destroy
· Insert
· Delete
Data structure value changes
The following SWIs allow changes to the structure which do not move the structure about. It is often possible to avoid use of these SWIs completely by direct peeks/pokes to the structure. They are provided largely for use in BBC BASIC where calculation of the relevant offsets can be tedious.
· Set
· Show
· Translate
· Zoom
· Rotate
Euclid SWIs
The Euclid SWIs mostly take a pointer in R1 which points to a data structure
(detailed in another document) which actually defines the 3D scene. This
pointer can be set to zero if it is preceded by another call which also
requires it, since the module remembers the last pointer used between calls.
This is a useful feature when programming from BASIC, but is less so from
machine code. Under RISC OS the multitasking implies that a call using the
pointer value explicitly must be made after a Wimp_Poll call since other
tasks will be using different pointer values. A special version of
Euclid_Initialise is provided for this purpose - it simply sets the module's
'last block used' value, and performs no other function on the data
structure.
The SWIs fall into two main catagories. Those which are used to construct
the data structure, and those which operate on it, or search for information
in it. It is not necessary to know the exact form of the data structure for
some of the calls. As a consequence, details of the data structure can be
read after the description of the SWIs, although for some of the SWIs
knowledge of the data structure is useful.
[sh-index] Back to list of manuals
|
| |
