[Mesa-dev] [PATCH 3/9] glsl: Convert mix() to use a new ir_triop_lrp opcode.

[Aras Pranckevicius]

> Why did glsl implement this really as x * (1 - a) + y * a?
> The usual way for lerp would be (y - x) * a + x, i.e. two ops for most
> gpus (sub+mad, or sub+mul+add). But I'm wondering if that sacrifices
> precision


Yes.
http://fgiesen.wordpress.com/2012/08/15/linear-interpolation-past-present-and-future/



-- 
Aras Pranckevičius
work: http://unity3d.com
home: http://aras-p.info
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