0030126: Visualization, OpenGl_ShaderManager - define standard Lighting & Clipping within custom GLSL programs as template functions

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Date Submitted

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0030126

Open CASCADE

[OCCT] OCCT:Visualization

public

2018-09-11 14:12

2019-05-07 14:27

Reporter

kgv

Assigned To

kgv

Priority

normal

Severity

feature

Status

new

Resolution

open

Platform

OS Version

Product Version

Target Version

[OCCT] 7.4.0*

Fixed in Version

Summary

0030126: Visualization, OpenGl_ShaderManager - define standard Lighting & Clipping within custom GLSL programs as template functions

Description

Currently, defining a custom GLSL program requires redefining of all major blocks, including shading (lighting) and clipping.

This limits flexibility of custom programs at application level, since when lighting is required, significant code blocks have to be copied, complicating GLSL source code and its maintenance (considering that application requires a minor customization of shader code).

It is proposed redefining major portions of standard GLSL programs as reusable functions, which custom GLSL program can mark as blocks for template substitution at Shader Manager.

This conception is already used within some custom Shader Managers within OCC Products - the approach can be adapted and improved for OpenGl_ShaderManager, and ideally custom Shader Managers can be further replaced by standard one.

Another issue is optimization of custom GLSL programs depending on number of lights and clipping planes - currently, these optimizations (handful for low-end hardware) are applicable only to built-in GLSL programs, because custom GLSL has only one cached instance within current design.

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Relationships

related to	0030700	assigned	iko	Visualization, TKOpenGl - support PBR Metallic-Roughness shading model
child of	0024192	closed	abv	Adding support for shaders to OCCT visualization toolkit
child of	0025282	closed	bugmaster	Visualization, OpenGl_PrimitiveArray - provide built-in GLSL programs as alternative to FFP
child of	0030631	new	kgv	Visualization - Vulkan graphic driver prototype

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Issue History
Date Modified	Username	Field	Change
2018-09-11 14:12	kgv	New Issue
2018-09-11 14:12	kgv	Assigned To	=> kgv
2018-09-11 14:13	kgv	Relationship added	child of 0024192
2018-09-11 14:14	kgv	Description Updated	View Revisions
2018-09-11 14:15	kgv	Relationship added	child of 0025282
2019-04-17 14:11	kgv	Relationship added	child of 0030631
2019-05-07 14:27	kgv	Relationship added	related to 0030700