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Re: [css shaders] comment on grid dimensions

From: Dean Jackson <dino@apple.com>
Date: Tue, 04 Oct 2011 14:53:17 +1100
Cc: FX <public-fx@w3.org>
Message-id: <BCF9B0E6-A605-4B61-AC69-D8CECC0E3C36@apple.com>
To: Chris Lilley <chris@w3.org>

On 04/10/2011, at 8:38 AM, Chris Lilley wrote:

> Hello FX,
> 
> This is a comment on
> https://dvcs.w3.org/hg/FXTF/raw-file/tip/custom/index.html
> 
> In section 3.2.1. The ’vertexMesh' attribute, note 8 it says
> 
>  It may be confusing to have the vertexMesh attribute represent the
>  number of additional lines and columns. May be it should simply be
>  the number of lines and columns, default to 1 1 and require integral
>  values equal or superior to 1.
> 
> I agree it could be confusing, and I think it would be better to have
> the default be 1 1, meaning a grid of one row and
> one column.
> 
> So if I want a 7x4 grid I can just say 7 4 instead of 6 3.
> 
> CSS can and does restrict <number> values to positive numbers if
> needed (positive meaning zero is not allowed; the alternative is
> non-negative, which allows 0,1,2 etc).

I agree with Chris here. By default you should get a simple quad ("1 1" = 2 x 2 vertices), and think in terms of the holes in the grid, not the points.

However, I wonder why we even need to specify this alongside a reference to a shader. Do we expect authors to change this? It won't necessarily mean a better output with a higher input. I have a feeling that most effects will written with an assumption of some vague size of mesh input. Maybe it could be combined into the shader itself (or provide a default if the mesh isn't specified in the property)?

Or putting it another way, I could write a wave effect using a vertex shader or a fragment shader, or both. The vertex shader approach requires a mesh - the fragment shader approach does not. It would be nice if in both cases the author could just say filter: shader("wave") and get a nice default result.

Dean
Received on Tuesday, 4 October 2011 03:54:25 GMT

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