\section{Conclusion}
\label{conclusion}

\fig[0.6]{experiment/use_case}{%
  Illustration of the texture augmentation in \AR through an interior design scenario. %
  A user wearing an \AR headset and a wearable vibrotactile haptic device worn on their index is applying different virtual visuo-haptic textures to a real wall to compare them visually and by touch.
}

We investigated how users perceived visuo-haptic roughness texture augmentations on tangible surfaces seen in immersive OST-AR and touched directly with the index finger.
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The haptic roughness texture was rendered using a wearable vibrotactile haptic device worn on the middle phalanx, based on HaTT data-driven models and finger speed.
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Participants rated the coherence, realism and roughness of the combination of nine representative visuo-haptic texture pairs.
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The results showed that participants consistently identified and matched clusters of visual and haptic textures with similar perceived roughness.
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The texture rankings did indeed show that participants perceived the roughness of haptic textures to be very similar, but less so for visual textures, and the haptic roughness perception predominated the final roughness perception ranking of the original visuo-haptic pairs.
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There are still many improvements to be made to the respective renderings of the haptic and visual textures used in this work to make them more realistic for finger perception and immersive virtual environment contexts.
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However, these results suggest that \AR visual textures that augments tangible surfaces can be enhanced with a set of data-driven vibrotactile haptic textures in a coherent and realistic manner.
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This paves the way for new \AR applications capable of augmenting a real environment with virtual visuo-haptic textures, such as visuo-haptic painting in artistic, object design or interior design contexts.
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The latter is illustrated in \figref{experiment/use_case}, where a user applies different visuo-haptic textures to a wall to compare them visually and by touch.
