[PD] use gl_VertexID

[Claude Heiland-Allen]

Hi Philippe,

On 14/06/18 10:51, Philippe Boisnard wrote:
> I continue to search to use gl_VertexID
>
> when I want to declare a version in vertex shader script, I want to declare for example
> #version 2.1 (it’s the openGL version when I check with print gemwin)
> but I have this in the PD_Terminal
> ERROR: 0:1: '' :  version '2' is not supported

The GL/GLSL version numbering is a bit obscure:

https://stackoverflow.com/questions/19021567/finding-supported-glsl-version#19022416

For OpenGL 2.1 you need this as first line of your shader:

#version 120

The good news is that gl_VertexID is supported in almost all GLSL versions:

http://docs.gl/sl4/gl_VertexID

For OpenGL ES (as found on embedded devices, eg mobile phones) you might 
not be so lucky:

http://docs.gl/el3/gl_VertexID

But I don't know if Gem supports attribute-less rendering (ie, just 
using gl_VertexID without any vertex data or element index buffers).


Claude
> Can I  use a version 2 for a vertex shader ?
>
> if I don’t declare a version
> gl_VertexID is not recognized
>
> Philippe
>
>
>
>> Le 14 juin 2018 à 06:27, Philippe Boisnard <philemon1 at mac.com> a écrit :
>>
>>
>> Hello
>>
>> I have a question about shader
>> I search to work with gl_VertexID in .vert script.
>> Some one have an example to implement this in .vert.
>> With gl_VertexID, you can have an array of vertex with no input array for VBO and you can detreminate in real time the size of VertexArray with no latencies.
>> I know that we can use this, but I have difficulties.
>>
>> best regards
>>
>> Philippe
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