Re: [Flightgear-devel] bring ShaderVG up to par with next

[Erik H. <er...@eh...>]

On 4/12/23 16:53, Scott Giese wrote:
> Hi Erik,
> 
> Can you provide a brief summary of the status to migrate from ShivaVG to 
> ShaderVG?

Good idea.

> Are there any significant challenges remaining?

At the moment there are 4 version of ShivaVG/ShaderVG in SimGear.

In next there is the ancient version of ShivaVG (probably OpenGL 
compatibility profile) and ShaderVG which is based on the ancient 
version of ShivaVG but adds shaders for rendering paths and color maps.

In the topics/shivavg_update branch there is an updated version of 
ShivaVG which requires OpenGL2.1 (and therefore I think leaves the 
OpenGL compatibility profile behind) and a version of ShaderVG where the 
changes between ShivaVG and ShaderVG have been applied on top of the new 
ShivaVG.

The state of both ShaderVG version is as such:
If I disable shader use in the code most of it seems to work properly.

But as soon as one or both of the shaders are used things get whacky, 
and I suspect it has something to do with what used to be the ModelView 
matrix which don't match between OpenSceneGraph and the shaders.

And to be honest, I don't know enough about both of them to fix this 
issue. So I would greatly appreciate it of someone with more knowledge 
on the subject could take a look.

The shaders have been moved from the code to FGSDATA/gui/shaders/

But the first thing to check, maybe, is to see whether the version of 
ShivaVG in the topics/shivavg_update branch is enough to get the core 
profile working. I suspect it might.

Erik

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