What does the distance point mean in perspective?

The concept in perspective refers to two points on the eye level, which reflect the length of sight distance on the left and right sides of the central point, and are symmetrical about the central point, and the length is twice as long as the sight distance, marked as D.

Perspective in a broad sense refers to various methods of spatial expression; Narrow perspective refers to scientific perspective methods such as linear perspective of depicting objects and reproducing space, which were gradually established in the14th century. In modern times, due to the study of human visual perception, the scope and content of perspective have expanded.

Narrow perspective (that is, linear perspective) method is the product of Renaissance, that is, it reproduces the actual spatial position of objects in line with scientific laws. This method of systematically summarizing and studying the shape changes and laws of objects is the basis of linear perspective.

Extended data:

I. Other commonly used nouns

1, viewpoint-where the human eye is. Identified as S. (eye point)

2. Apparent horizon-horizontal line HL with the same height as the human eye. (HORIZOUTALLINE)

3. The imaginary connection between sight-viewpoint and any part of the object. (LINEOESIGHT)

4. Angle-the angle between the viewpoint and any two lines of sight. (visual angle)

5. Line of sight-the spatial range that the eyes can see.

6. Sight cone-a cone composed of viewpoints and countless lines of sight. (VISUALCONE)

7. Line of sight-the central axis of the cone. Also known as the middle point of view. (LINEOEVISUALCENTER)

8. Scene-the position where the audience stands. Also known as stopping. Identified as g. (standing point)

9. Sight distance-the vertical distance from the viewpoint to the center.

Second, the perspective glass

Widely used in prisons, interrogation rooms of public security organs, mental hospitals, research rooms of university scientific research institutions, large conference rooms, etc. You can achieve the effect that you can't see the inside from the outside, but you can see the outside from the inside.

A single mirror is actually a "double mirror". There is no difference in optical properties between the front and back of a single mirror. The reason why it can produce the effect of one-sided reflection is entirely because the two sides of the mirror are in different photometric environments. Let's first compare the structures of ordinary mirrors and single-sided mirrors. Ordinary mirrors are made of silver-plated glass.

The same is true for single-sided mirrors, except that only half of them are plated with silver. The method of "half" plating is that silver (not real silver, but other metals) is very thin, so that half of the light can pass through and the other half is reflected back. In actual use, the prisoner will face the mirror and be in a room with strong light.

Because there is enough light and more reflected light, the prisoner will see his own image in the mirror. At this time, the witness stood on the other side of the mirror, in a dimly lit room. Although part of the light in the witness's room can also pass through the single mirror, because of the low luminosity, the prisoner can't see the witness, but can only see his own image.

It's like we can't see fireflies under the strong light of street lamps, because the faint light emitted by fireflies is drowned by the light of street lamps. So the so-called one-sided reflection phenomenon is just a visual illusion.

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