Re: [PyOpenGL-Users] Shading with Interpolated Normals

[Mike C. F. <mcf...@vr...>]

Mike C. Fletcher wrote:
> Chris Finley wrote:
>   

...
>> How do you read the "varying" attribute (pixel normal) that should be
>> passed into the function?
>>   
>>     
> My understanding is that you query for a "uniform" variable (a simple 
> integer) based on the name you use in your program, 
The function to do this, unfortunately, is currently not wrapped 
elegantly.  You'll have to append a "\000" to your program name to avoid 
memory-access failures when you use it...

            result = glGetUniformLocationARB( self.__shaderProgramID, 
variableName+'\000' )

because the array-type conversion will not automatically add the 
null-byte to signal the end of the variable name.  I'll try to get that 
fixed soon.
> then use the 
> glUniform* set of functions with that argument to pass the values into 
> your shader program.  You'll likely need to have the shader in "use" at 
> the time (glUseProgram*).
>   
I've just confirmed this.  You *must* have glUseProgram* called when you 
attempt to call the uniform-related functions, if you don't you'll get 
core-dumps (at least on Linux, with an Nvidia card).  Note that (e.g.) 
calls to glutMainloop() reset the glUseProgram, so you'll likely want to 
"use" the program close to where you do your uniform calls.

HTH,
Mike

-- 
________________________________________________
  Mike C. Fletcher
  Designer, VR Plumber, Coder
  http://www.vrplumber.com
  http://blog.vrplumber.com