Orthographic Projection

  • Orthographic Projection

    Today students learned about Orthographic Projection. They drew a 3 view drawing of a persons face (front, side and top). They learned about the following terms:

    Orthographic The word orthographic as used in geometry refers to right angles and perpendicular lines.

    Projection Projection means to represent something on a plane much like a movie is projected onto a screen.

    Orthographic Projection Orthographic Projection is a method of representing the exact shape of an object by projecting lines onto a plane of vision. Three planes are usually projected to give an accurate presentation of the top, front and side.

    Object Lines Object lines are solid lines (drawn dark) representing the contour of an object as we see it.

    Extension Lines Extension lines are lines that are drawn lightly between views that transfer the proper proportions.

    Front view = frontal plane Side view = profile plane Top view = horizontal plane

    Today’s lesson deals with the creation of an Orthographic Projection. The word orthographic as used in geometry refers to right angles and perpendicular lines. Projection means to represent something on a plane much like a movie is projected onto a screen. Orthographic Projection is a method of representing the exact shape of an object by projecting lines onto a plane of vision. Three planes are usually projected to give an accurate presentation of the top, front and side.

     

    Activity:                                 Draw an Orthographic Projection of a Person’s Face

    1)     Take a plain piece of white drawing paper 8 ½ by 11 and fold it in half length-wise.
    2)     While folded in half length-wise fold the paper in half width-wise.
    3)     Unfold the paper. It should have four quadrants 4 ¼ by 5 ½.
    4)     In the bottom left hand corner write the words front view.
    5)    In the bottom left hand corner, draw a picture of a persons face looking directly at their nose. This picture should stay entirely   within the boundaries of the quadrant.

    The lines drawn in step # 5 are Object Lines. Object lines are solid lines (drawn dark) representing the contour of an object as we see it.  

    In order to keep all views in the correct proportion we need to draw extension lines from the following parts of the person’s face drawn in the front view: top of  the head, bottom of the chin, middle of the mouth, bottom of the nose, and middle of the eyes. Extension lines are lines that are drawn lightly between views that transfer the proper proportions (size) from one view to the next.  

    6)     Draw an extension line from the top of the head in the front view lightly across the paper into the side view.
    7)     Draw an extension line from the bottom of the chin in the front view lightly across the paper into the side view.
    8)     Draw an extension line from the bottom of the nose lightly across the paper into the side view.
    9)     Draw an extension line from the middle of the mouth lightly across the paper into the side view.
    10)   Draw an extension line from the middle of the eyes lightly across the paper into the side view.
    11)   Draw the side view of the face. The nose in the side view must be facing toward the nose in the front view. Use object lines to represent the face. It is important to keep all parts of the face within the boundary lines drawn in steps 6 & 7.

    We need to draw the top view next. This is done using extension lines from the front and side views.

    12)    Draw an extension line going from the right side of the face in the front view lightly up the paper through the top view.
    13)    Draw an extension line going from the left side of the face in the front view lightly up the paper through the top view.
    14)    Draw an extension line going from the middle of the nose in the front view lightly up the paper through the top view.
    15)    Place a 45 degree triangle on the fold line just above the side view. The bottom left hand portion of the triangle rests on the center of the paper (where all of the fold lines meet). Draw a 45 degree angle (along the top of the triangle) along the length of the triangle.
    16)    Draw an extension line going from the front of the nose in the side view lightly up to the diagonal drawn in step 15. Then draw an extension line lightly from the same line across  into the top view. A 90 degree angle is formed between these two lines where they intersect the diagonal.
    17)   Draw an extension line going from the front of the nose in the side view lightly up to the diagonal drawn in step 15. Then draw an extension line lightly from the same line across  into the top view. A 90 degree angle is formed between these two lines where they intersect the diagonal.
    18)   Draw an extension line going from the front of the nose in the side view lightly up to the diagonal drawn in step 15. Then draw an extension line lightly from the same line across  into the top view. A 90 degree angle is formed between these two lines where they intersect the diagonal.
    19)   Draw an extension line going from the back of the head in the side view lightly up to the diagonal drawn in step 15. Then draw an extension line lightly from the same line across  into the top view. A 90 degree angle is formed between these two lines where they intersect the diagonal.
    20)   Finish the drawing by the top view of the head. The nose in the top view should be facing the nose in the front view. These lines are object lines as they represent the face.

     

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