SET HLHSR IDENTIFIER(3P) — Kubota Pacfic Computer Inc. (29 February 1991)

NAME

SET HLHSR IDENTIFIER − create a structure element to set the current hidden line/hidden surface removal attribute

SYNOPSIS

C Syntax

void
pset_hlhsr_id ( id )
Pintid;HLHSR identifier

Required PHIGS Operating States

(PHOP, ∗, STOP, ∗)

DESCRIPTION

Purpose

SET HLHSR IDENTIFIER creates a structure element containing a value for the Hidden Line and Hidden Surface Removal (HLHSR) primitive attribute. During traversal, this attribute replaces the current HLHSR identifier and is applied to all output primitives that follow in the structure network in a workstation-dependent way.

The HLHSR identifier in the structure network is used in conjunction with the HLHSR mode on the workstation during traversal. Presently, both must be one to enable Hidden Surface Removal.

If the current edit mode is INSERT, then a SET HLHSR IDENTIFIER element is inserted into the currently open structure after the element pointed to by the current element pointer. If the edit mode is REPLACE, then the new SET HLHSR IDENTIFIER element replaces the element pointed to by the element pointer. In either case, the element pointer is updated to point to the new element.

C Input Parameter

idThe HLHSR identifier value. Presently supported values are:

0PHIGS_HLHSR_ID_OFFRemove Nothing
1PHIGS_HLHSR_ID_ONRemove Hidden Surfaces and Hidden Lines Using Z-buffer

Execution

When the SET HLHSR IDENTIFIER element is traversed, the current HLHSR identifier entry in the traversal state list is set to HLHSR identifier. The current HLHSR identifier is applied to output primitives that follow in the structure network. The current HLHSR identifier traversal state from the structure network is compared to the current HLHSR mode on the workstation.

HLHSR is performed using a Z-buffer algorithm.

The Z-buffer processing does not work with primitives filled with hatches. When a hatched filled area-defining primitive is to be Z buffered, PEX-SI does not apply the Z-buffer process.

The HLHSR mode for a workstation is set with the SET HLHSR MODE function. The supported HLHSR modes are workstation-dependent.

For systems without Z-buffered hardware, HLHSR is done in software, but with a significant loss of performance.

A generic problem with Z-buffering is that edges on polygons can be drawn with missing pixels. When the high quality Z-buffer identifier is used, PEX-SI attempts to improve the quality of edges on polygons, possibly at the expense of lower performance. The severity of the problem and the amount of improvement is dependent on the hardware in use.

ERRORS

005Ignoring function, function requires state (PHOP, ∗, STOP, ∗)

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