[vtk-developers] GLSL shader/shaderprogram etc

[John Biddiscombe]

Ken

Sending you files off list. If anyone else is interested, then I'll go 
back on list.

NB. ShaderProgram was modified because it has the central LoadExtensions 
call. Other than that it is untouched.

JB

> John,
> 
> I would like to see your changes before you check them in.  Your email
> was not exactly clear, but I am assuming you mean you added code to use
> the GL_ARB_vertex_program and GL_ARB_fragment_program extensions.  From
> what you described, I think I would like to see some changes before that
> code gets back into VTK.  Your description gives me two main
> reservations.
> 
> First, the vtkShaderProgram was meant to be agnostic to the
> implementation of the shader.  It should not matter if the
> implementation is Cg, GLSL, or GL_ARB_*_program.  Thus, you shouldn't
> need to make any changes to it.  That said, we may have forgotten some
> generic functionality that you require, for example a method to check to
> see if the current shader is supported by hardware.  Either way, I would
> like to see the code before it's checked in.
> 
> Second, the intention of the vtkShaderProgram hierarchy is to have a
> different vtkShaderProgram subclass for each shader API and method for
> specifying shader programs.  Thus, I think a better implementation is to
> leave vtkGLSLShaderProgram untouched and instead make a new class
> (vtkOpenGLShaderProgram?) that implements a shader using OpenGL 1.1
> extensions.  The VTK shader code was designed this way specifically to
> prevent "messy" (your word, not mine) code that has to handle multiple
> implementations with lots of conditionals.
> 
> -Ken
> 
>    ****      Kenneth Moreland
>     ***      Sandia National Laboratories
> ***********  
> *** *** ***  email: kmorel at sandia.gov
> **  ***  **  phone: (505) 844-8919
>     ***      fax:   (505) 845-0833
> 
> 
>> -----Original Message-----
>> From: vtk-developers-bounces+kmorel=sandia.gov at vtk.org 
>> [mailto:vtk-developers-bounces+kmorel=sandia.gov at vtk.org] On 
>> Behalf Of John Biddiscombe
>> Sent: Wednesday, May 03, 2006 5:59 AM
>> To: vtk-developers at vtk.org
>> Subject: [vtk-developers] GLSL shader/shaderprogram etc
>>
>> A while back, I made some changes to my copies of 
>> vtkShaderProgram.cxx ,vtkShaderProgram.h ,vtkGLSLShader.cxx 
>> ,vtkGLSLShader.h ,vtkGLSLShaderProgram.cxx
>>
>> so that they will function without OpenGL2 but instead use Gl 
>> Extensions (vertex program, shader program etc etc). I've 
>> been sitting on these changes for some time in the hope I'd 
>> get time to clean them and create some "proxy" or other 
>> delegate type object to make them a bit less messy
>> - they are full of if (opengl2supported) then {...} otherwise 
>> {...} but the functionality is essentially the same for either case.
>>
>> I'm going to check these changes in, because I don't think 
>> I'm ever going to find time to do a better job of it.
>>
>> It primarily lets on do GLSL stuff on some laptops and 
>> desktops that don't have gl2 drivers.
>>
>> any objections or comments, please send...
>>
>> JB
>>
>>
>>
>> -- 
>> John Biddiscombe,                            email:biddisco @ cscs.ch
>> http://www.cscs.ch/about/BJohn.php
>> CSCS, Swiss National Supercomputing Centre  | Tel:  +41 (91) 610.82.07
>> Via Cantonale, 6928 Manno, Switzerland      | Fax:  +41 (91) 610.82.82
>>
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>>
>>
> 


-- 
John Biddiscombe,                            email:biddisco @ cscs.ch
http://www.cscs.ch/about/BJohn.php
CSCS, Swiss National Supercomputing Centre  | Tel:  +41 (91) 610.82.07
Via Cantonale, 6928 Manno, Switzerland      | Fax:  +41 (91) 610.82.82