[Mesa-dev] How to get uniform components used by uniform variables

[Tapani Pälli]

On 02/22/2016 02:02 PM, Juan A. Suarez Romero wrote:
> On Mon, 2016-02-22 at 13:47 +0200, Tapani Pälli wrote:
>> Maybe one way would be to include these matrices in UBO or SSBO and
>> then
>> query BUFFER_DATA_SIZE for that buffer. That should return
>> "implementation-dependent minimum total buffer object size".
>>
>> https://www.opengl.org/registry/specs/ARB/program_interface_query.txt
>>
>
> Thank you!
>
> That API was one of the first thing I was checking :)
>
> But it doesn't provide what I'm looking for. Rather, seems to return
> the size it requires the UBO to store the content with a specific
> layout.
>
> For instance, having this UBO:
>
> uniform ubo1 {
>    float f;
> };
>
>
> And using the proper function from that extension to query "ubo1", it
> returns 16. Which is the size required to store a vec4, according to
> layout rules.
>
> If I modify the UBO and add another value:
>
> uniform ubo1 {
>    float f;
>    int i;
> };
>
> And querying again, it still returns 16, as both elements fits in that
> size.
>
> So rather than reporting the number of uniform components it is
> consuming, is reporting the bytes used in the layout.
>

Ah right, I see. Maybe you can query OFFSET then, this should differ 
then when matrix has a different type?

// Tapani