This image above of Uglow's work, (one of his best) demonstrates the point. The small measuring points punctuate the painting's surface and attempt to define the three dimensional geometry of the model's body, in particular reducing the legs to interlocking planes. The clarity that ensues 'freezes' the moment, the model is not about to make that step, she never will, she is placed here forever. The interesting thing with this image however is that a second layer of visual language is starting to unfreeze the image. The yellow violet polarity creating a colour 'tick' and the flattened shadow image across the door starting to squeeze the space into a shallow pocket, punctuated by the door itself and the two rectangles that break into its geometry. These elements start to make the painting's heart beat. So Uglow wasn't all bad, but it was felt he was all the more dangerous because superficially his approach seemed as if he was engaged with the same struggle as Cezanne.
Conversely a hero of perceptual drawing was Giacometti, who's approach was seen as a 'proper' struggle.
The flicker of movement that takes you both across the space and creates the space was keeping the image 'alive' and recreating the moments of looking.
You can see the left sided back edge of the sideboard starting to lift as Giacometti discovers that the space it emerges into is part of a moving perceptual sphere. Visually this image is superficially quite close to some of Uglow's work, but a world away in reality. Uglow is searching for the frozen moment, trying to establish 'rightness', Giacometti is looking to recreate the experience of the phenomenology of looking. He represents a European Existentialist position, as opposed to Uglow's British Logical Positivism.