Dimetriya — a type of an axonometrical projection. The axonometry allows to see by means of one volume image a subject in three dimensions at once. Receiving volume representation is followed by a certain distortion of the sizes of an object along axes. In a dimetriya the coefficients of distortion of the sizes on two axes are identical, from here and the name — a dimetriya.

## It is required to you

- - set of pencils of different hardness;
- - ruler;
- - square;
- - protractor;
- - eraser.

## Instruction

1. There are two types of a dimetriya: rectangular and oblique-angled frontal. When performing any dimetric projection all sizes along axis X are halved, and the sizes on axes Y and Z remain multiple to unit. T.e the distortion coefficient on axis X is accepted equal 0.5, and on axis Z and Y of distortion there are no sizes.

2. Draw axes for creation of the image of a detail in a dimetriya. In a rectangular dimetriya the corners between axes Z and X make 97o10'. Corners between axes Y and Z — 131o25'; corners between axes Y and X — 127o50'. In a frontal dimetriya the corners between axes Z and X make ninety degrees. And between axes Z and Y; X and Y — hundred thirty five degrees.

3. Apply axes on orthogonal projections of the represented detail according to the chosen provision of a detail for drawing in a dimetriya. It is reasonable to combine one of axes of an axonometrical projection with a detail axis.

4. Carry out construction in a dimetriya from the top side of a detail, consistently transferring the sizes from an orthogonal projection to the volume image. Having stopped transferring overall dimensions of a detail to the volume image, start performance of small elements on detail surfaces.

5. Circles in the different planes of a dimetric projection are represented by different ellipses. Without distortion on axes X and Z the big axis of an ellipse in all three planes of a projection is equal in a dimetriya 1.06 diameters of a circle. The small axis of an ellipse is equal in the XOZ plane 0.95 diameters of a circle, and in the ZOY and XOY planes makes 0.35 diameters of a circle. With distortion on axes X and Z the big axis of an ellipse in all three planes is equal in a dimetriya to diameter of a circle. The small axis of an ellipse is equal in the XOZ plane 0.9 diameters of a circle, and in the ZOY and XOY planes makes 0.33 diameters of a circle.

6. For obtaining more evident image it is possible to execute a cut of a part of a detail on a dimetric projection. Shading when drawing a cut of a part of a detail is put parallel to the square projection diagonal to the corresponding plane.