Oblique projection is a type of graphical projection used in technical drawing and computer graphics to represent three-dimensional objects on a two-dimensional plane. It is characterized by projecting the image of an object along parallel lines that are not perpendicular to the viewing plane, resulting in a skewed appearance where the front of the object is displayed in true scale, and the sides are distorted.
Key Features of Oblique Projection:
- Parallel Projection: Unlike perspective projection, where lines converge at a vanishing point, oblique projection uses parallel lines to project the object onto the drawing plane. This means that parallel lines in the object remain parallel in the projection.
- Angle of Projection: In oblique projection, the object’s front face is parallel to the drawing plane, and the other faces are projected at an angle, typically 45 degrees. The projection lines are usually drawn at a 30°, 45°, or 60° angle to the horizontal axis, but any angle can be used depending on the desired effect.
- Scaling: The front face of the object is drawn in true scale, meaning its dimensions are accurate and undistorted. However, the depth (or the sides of the object that recede into space) is typically scaled by a factor, often 0.5 or 1, to reduce distortion.
- Types of Oblique Projection:
- Cavalier Projection: The depth is scaled equally to the height and width, meaning the receding lines are drawn at full scale. This results in more distortion, where the object appears stretched along the depth axis.
- Cabinet Projection: The depth is scaled to half the height and width, making the receding lines shorter and reducing distortion. This is more commonly used because it produces a more realistic appearance.
- Applications: Oblique projection is often used in engineering drawings, architectural plans, and video games when a quick, straightforward depiction of an object is needed. It’s particularly useful for technical illustrations where a clear view of the front and side is required.
Characteristics of Oblique Projection:
- Simplification: It simplifies the drawing process since it doesn’t require complex calculations for perspective.
- Distortion: The side views are distorted, especially in Cavalier projection, which can make objects appear unrealistic.
- Ease of Interpretation: Because the front view is in true scale, it’s easier to interpret dimensions directly from the drawing, making it useful for technical and engineering purposes.
Oblique projection provides a practical way to visualize objects in 3D while keeping the technical drawing process relatively simple.