It is standard throughout Europe and Asia excluding Japan. To obtain this view without multiple rotations requires the principles of Descriptive Geometry. The principal planes of an object are used to project different views of the same object from different points of sight.
The location of the Ground Line in relation to the Horizon Line will determine how far above or below "eye level" the object will be viewed. If a model is made of the block in Fig. Extend a vertical line from the corner that touches the Picture Plane downward. These are drawn to scale so that measurements can be taken for any aspect necessary.
The box is then unfolded to view all of its exterior walls.
The same image, with views of object projected in the direction of sight onto walls using first-angle projection. Third angle projection is used. First and third angle projection are nothing but ways of describing what an object looks like from different directions.
Such a view might be desired for calculating clearances or for dimensioning purposes. Above, a technique is described that obtains varying views by projecting images after the object is rotated to a desired position.
The object is placed in the first quadrant for the first angle projection. Here is the construction of third angle projections of the same object as above.
The principal vanishing point is the vanishing point of all horizontal lines perpendicular to the picture plane.
Axonometric projection of a scheme displaying the relevant elements of a vertical picture plane perspective. The 3D object of interest is then placed into either quadrant I or III equivalently, the position of the intersection line between the two planes is shiftedobtaining first- and third-angle projections, respectively.
Overview[ edit ] Comparison of several types of graphical projectionincluding elevation and plan views To render each such picture, a ray of sight also called a projection line, projection ray or line of sight towards the object is chosen, which determines on the object various points of interest for instance, the points that are visible when looking at the object along the ray of sight ; those points of interest are mapped by an orthographic projection to points on some geometric plane called a projection plane or image plane that is perpendicular to the ray of sight, thereby creating a 2D representation of the 3D object.
Using the 6-sided viewing box, each view of the object is projected opposite to the direction sense of sight, onto the transparent exterior walls of the box; that is, each view of the object is drawn on the same side of the box.
The intersection of the vertical and horizontal planes give a line which is the ground line GL.Click here for an Introduction to Third Angle Orthographic Drawing. Click here for Third Angle Orthographic Drawing - an Example: Orthographic Projection is a way of drawing an object from different directions.
Usually a front, side and plan view are drawn so that a person looking at the drawing can see all the important sides. Orthographic projection is a method of projection to draw engineering 2D drawings for a part / object using parallel lines to project different views on to a plane.
Object can be placed in any of four quadrant. First angle projection and third angle projection are generally used for making engineering drawing. In technical drawing and computer graphics, a multiview projection is a technique of illustration by which a standardized series of orthographic two-dimensional pictures is constructed to represent the form of a three-dimensional object.
Up to six pictures of an object are produced (called primary views), with each projection plane parallel to one of the coordinate axes of the object.
Tutorial lesson on the step-by-step construction of a simple 2-point perspective grid with a horizon line, vanishing points, ground line and a POV picture plane used in creating technical illustrations, drawings and mechanical drafting. Every engineer must know how to read engineering drawings and the most integral part of this is knowing the difference between first and third angle projection.
A collection of 2D drawings can be used to. First Angle Projection is commonly used in all countries other than United States. The Indian Standard Institution (ISI) recommend the use of First Angle Projection method now in all the institutions. Third Angle Projection is commonly used in United States of America.Download