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Is the perception of 3D shape from shading based on assumed reflectance and illumination?

Todd JT, Egan EJ, Phillips F - Iperception (2014)

Bottom Line: A gauge figure adjustment task was used to measure observers' perceptions of local surface orientation on the depicted surfaces, and the probe points included 60 pairs of regions that both had the same orientation.The results show clearly that observers' perceptions of these three types of stimuli were remarkably similar, and that probe regions with similar apparent orientations could have large differences in image intensity.This latter finding is incompatible with any process for computing shape from shading that assumes any plausible reflectance function combined with any possible homogeneous illumination.

View Article: PubMed Central - PubMed

Affiliation: Department of Psychology, The Ohio State University, Columbus, OH; e-mail: todd.44@osu.edu.

ABSTRACT
The research described in the present article was designed to compare three types of image shading: one generated with a Lambertian BRDF and homogeneous illumination such that image intensity was determined entirely by local surface orientation irrespective of position; one that was textured with a linear intensity gradient, such that image intensity was determined entirely by local surface position irrespective of orientation; and another that was generated with a Lambertian BRDF and inhomogeneous illumination such that image intensity was influenced by both position and orientation. A gauge figure adjustment task was used to measure observers' perceptions of local surface orientation on the depicted surfaces, and the probe points included 60 pairs of regions that both had the same orientation. The results show clearly that observers' perceptions of these three types of stimuli were remarkably similar, and that probe regions with similar apparent orientations could have large differences in image intensity. This latter finding is incompatible with any process for computing shape from shading that assumes any plausible reflectance function combined with any possible homogeneous illumination.

No MeSH data available.


Related in: MedlinePlus

The distribution of test-retest differences between the first and second halves of Experiment 3 (black); the distribution of differences between corresponding probe points in all possible pairs of conditions (red); the distribution of differences between the ground truth and the average of observers' settings for each probe point in each condition (green); and the distribution of differences between the average settings of the matched probe points within a given condition (blue).
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Figure 8: The distribution of test-retest differences between the first and second halves of Experiment 3 (black); the distribution of differences between corresponding probe points in all possible pairs of conditions (red); the distribution of differences between the ground truth and the average of observers' settings for each probe point in each condition (green); and the distribution of differences between the average settings of the matched probe points within a given condition (blue).

Mentions: The results are presented in Figure 8. The black curve shows the distribution of test-retest differences between the first and second halves of the experiment; the red curve shows the distribution of differences between corresponding probe points in all possible pairs of conditions; the green curve shows the distribution of differences between the ground truth and the average of observers' settings for each probe point in each condition; and the blue curve shows the distribution of differences between the average settings of the matched probe points within a given condition. These findings indicate that: (1) observers judgments were highly reliable; (2) variations in the apparent shapes of the depicted surfaces among the different conditions were quite minimal; (3) observers' judgments were systematically distorted relative to the ground truth; and (4) there was a non-affine component to these perceptual distortions. In other words, the results were remarkably similar to those obtained in Experiment 1. In this case, however, the observers' judgments could not have been influenced by the presence of smooth occlusion contours, because the stimuli did not contain any occlusions.


Is the perception of 3D shape from shading based on assumed reflectance and illumination?

Todd JT, Egan EJ, Phillips F - Iperception (2014)

The distribution of test-retest differences between the first and second halves of Experiment 3 (black); the distribution of differences between corresponding probe points in all possible pairs of conditions (red); the distribution of differences between the ground truth and the average of observers' settings for each probe point in each condition (green); and the distribution of differences between the average settings of the matched probe points within a given condition (blue).
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4441026&req=5

Figure 8: The distribution of test-retest differences between the first and second halves of Experiment 3 (black); the distribution of differences between corresponding probe points in all possible pairs of conditions (red); the distribution of differences between the ground truth and the average of observers' settings for each probe point in each condition (green); and the distribution of differences between the average settings of the matched probe points within a given condition (blue).
Mentions: The results are presented in Figure 8. The black curve shows the distribution of test-retest differences between the first and second halves of the experiment; the red curve shows the distribution of differences between corresponding probe points in all possible pairs of conditions; the green curve shows the distribution of differences between the ground truth and the average of observers' settings for each probe point in each condition; and the blue curve shows the distribution of differences between the average settings of the matched probe points within a given condition. These findings indicate that: (1) observers judgments were highly reliable; (2) variations in the apparent shapes of the depicted surfaces among the different conditions were quite minimal; (3) observers' judgments were systematically distorted relative to the ground truth; and (4) there was a non-affine component to these perceptual distortions. In other words, the results were remarkably similar to those obtained in Experiment 1. In this case, however, the observers' judgments could not have been influenced by the presence of smooth occlusion contours, because the stimuli did not contain any occlusions.

Bottom Line: A gauge figure adjustment task was used to measure observers' perceptions of local surface orientation on the depicted surfaces, and the probe points included 60 pairs of regions that both had the same orientation.The results show clearly that observers' perceptions of these three types of stimuli were remarkably similar, and that probe regions with similar apparent orientations could have large differences in image intensity.This latter finding is incompatible with any process for computing shape from shading that assumes any plausible reflectance function combined with any possible homogeneous illumination.

View Article: PubMed Central - PubMed

Affiliation: Department of Psychology, The Ohio State University, Columbus, OH; e-mail: todd.44@osu.edu.

ABSTRACT
The research described in the present article was designed to compare three types of image shading: one generated with a Lambertian BRDF and homogeneous illumination such that image intensity was determined entirely by local surface orientation irrespective of position; one that was textured with a linear intensity gradient, such that image intensity was determined entirely by local surface position irrespective of orientation; and another that was generated with a Lambertian BRDF and inhomogeneous illumination such that image intensity was influenced by both position and orientation. A gauge figure adjustment task was used to measure observers' perceptions of local surface orientation on the depicted surfaces, and the probe points included 60 pairs of regions that both had the same orientation. The results show clearly that observers' perceptions of these three types of stimuli were remarkably similar, and that probe regions with similar apparent orientations could have large differences in image intensity. This latter finding is incompatible with any process for computing shape from shading that assumes any plausible reflectance function combined with any possible homogeneous illumination.

No MeSH data available.


Related in: MedlinePlus