class HT_Selector

class HT_Selector

Selection renderers are special Heidi renderers for selecting geometry in 2D or 3D. They can be used for hit testing; for example, when a user is selecting geometry, closest to the cursor on the screen, to be translated or moved to a new location.

Like any Heidi renderer, a selection renderer first needs to be dynamically loaded using the HD_Load_Dynamic_Routine with a proper DLL name and the string "HD_Selector" as the first and second parameters respectively. Then, the application typically sets the desired selection region or volume via corresponding renderer options.

For a further description of the selection process , see chapter 7, "The Selection Renderer," and the Sprite sample application code.

See Also HT_Selector_Item, HT_Renderer Access Methods

include_crossing, set_include_crossing

Tells the selector to pick any items that are partially or completely inside the selection region.

one_per_key, set_one_per_key

Tells the selector to return no more than one selected item with the same key.

set_selection_key

Sets a unique ID that the user will apply to the object.

thin_line_limit, set_thin_line_limit

Controls when to tessellate wide lines.

show_next_selection_item

Shows the next selector item in the HT_Selector_Item list.

show_selection_count

Returns the number of primitives that have been selected. Constructor / Destructor

HT_Selector

Constructs an

HT_Selector

object.

HT_Selector::HT_Selector

Purpose

Constructs an HT_Selector object. Synopsis

HT_Selector ()

HT_Selector (HT_Selector_Data const * in)

HT_Selector::include_crossing, set_include_crossing

Purpose

Tells the selector to pick any items that are partially or completely inside the selection region. Synopsis

HT_Boolean include_crossing (void) const

void    set_include_crossing (HT_Boolean in)

Details This option, when enabled, tells the selector to pick any items that are completely or partially inside the selection region.

When disabled, the option, tells the selector to pick only items that are completely inside the selection region. The default value is HT_True ¾ enabled.

The first form returns the current setting.

The second form takes a boolean value as an input parameter and sets the option.

HT_Selector::one_per_key, set_one_per_key

Purpose

Tells the selector to return no more than one selected item with the same key. Synopsis

HT_Boolean one_per_key (void) cons

void    set_one_per_key (HT_Boolean in)

Details This option, when enabled, tells the selector to return no more than one selected item with the same key. It is typically used when there is more than one geometry carrying an identical key and the application is only interested in knowing if any one of the geometry is selected. The selector will examine every single geometry and pick only the best item of those within the selection region.

When disabled, this option will return all items that are selected even though they may have the same key.

The default value is HK_False ¾ disabled.

The second form takes a boolean value as an input parameter and sets the option.

HT_Selector::set_selection_key

Purpose

Sets a unique ID that the user will apply to the object.. Synopsis

void set_selection_key (long key)t

HT_Selector::show_next_selection_item

Purpose

Shows the next selector item in the HT_Selector_Item list. Synopsis

HT_Boolean show_next_selection_item (HT_Selector_Item alter * item)

Details Once the selection information is retrieved from show_selection_count, if the count comes back > 0, then the application iterates through the HT_Selector_Item list via show_next_selection_item.

HT_Selector::show_selection_count

Purpose

Returns the number of primitives that have been selected.. Synopsis

int show_selection_count (void)

Details The selection information is retrieved by calling show_selection_count which returns the number of primitives that have been selected.

HT_Selector::thin_line_limit, set_thin_line_limit

Purpose

Controls when to tessellate wide lines. Synopsis

int thin_line_limit (void) const

void    set_thin_line_limit (int in)

Details The default is one, in which case any line weight larger than one will be broken down into triangles and go through a slower yet more accurate selection path.

These methods are implemented as a speed enhancement for applications that do a lot of picking, wherein the pick window is known.
For example, if the pick window is known to be 5 pixels out on each side and a lot of picking is tested against weighted lines, it would save time to avoid tessellating these lines. Thus, if the lines are not very thick they can be treated as 0 weight lines to enhance picking speed.