Impasto discussion

[Matthew Woehlke]

Dmitry Kazakov wrote:
> On Fri, Jul 9, 2010 at 8:44 PM, Matthew Woehlke<>  wrote:
>
>> I would make two suggestions. First, as Dmitry suggested, impasto should
>> be an additional channel, not a separate layer. Second, consider doing
>> the initial implementation as suggested, i.e. render impasto for each
>> layer before layer composition.
>>
>
> I think, instead of rendering every layer, it is better to use
> COMPOSITE_ALPHA_DARKEN for impasto channel. It'll be much cheaper. In such a
> case, the final impasto value of the point on projection will be equal to
> the value of the most opaque layer.

No, that doesn't work well, as I explained:
> That technique has obvious problems, since it effectively amounts to
> carving an alpha-mask-shaped hole in the underlying layers' impasto,
> rather than letting the layer as a whole float above the layers beneath.

To be honest, I'm not sure the method I described won't have the same 
problem. I think it should have less problem though, because you won't 
have artificial ridges in the impasto created at layer borders, as you 
would with Painter's technique (i.e. what you are suggesting).

Ultimately, I think any trivial implementation is doomed to have points 
of failure. I'm most comfortable with my idea because it has a 
real-world analogue, and its "failures" are rather more limitations.

(Also, it lets you do things like assign different materials to each 
layer. Different light source, even, though I don't know why you would 
want to do that. But I could see different materials.)

-- 
Matthew
Please do not quote my e-mail address unobfuscated in message bodies.
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