projection in computer graphics us.ppt
- 2. What is projection? projection is the process of transforming a 3D object or scene onto a 2D surface, typically the computer screen, while retaining certain properties such as shape and size relationships. This transformation is necessary because while the world exists in three dimensions (width, height, and depth), screens are two- dimensional. The type of projection defines how the 3D information is represented in 2D. Transform 3D objects on to a 2D plane using projections 2 types of projections Perspective projection Parallel projection 2
- 3. Perspective Projection 3 In perspective projection, object is transformed to the view plane along lines that converge to a point called projection reference point (center of projection)
- 4. • Perspective projection is a type of projection in computer graphics and geometry that simulates the way objects appear to the human eye, making objects look smaller as their distance from the observer increases. This type of projection is commonly used in 3D rendering to create realistic scenes. 4
- 5. General Terms • Center of projection: The point from where projection is taken. It can be either light source or eye. • Projection plane: The plane on which projection of object is formed. • Projectors: Line emerging from COP and hitting the projection plane. When projectors hit object and then hit projection plane the shadow of the object will be formed on projection plane. 5
- 6. Key Features of Perspective Projection • Vanishing Point: In a perspective projection, parallel lines appear to converge at a point in the distance, called the vanishing point. This creates a sense of depth. • Foreshortening: Objects closer to the viewer appear larger, while objects farther away appear smaller, even if their real-world dimensions are the same. • Depth Perception: Perspective projection is used to simulate depth, as objects farther from the viewer shrink and appear closer to the vanishing point. 6
- 7. Characteristics of perspective projection • Center of Projection (CP) is a finite distance from object • Projectors are rays (i.e., non-parallel) • Objects appear smaller as distance from CP (eye of observer) increases • Most realistic. 7
- 8. • Parallel projection is a type of projection used in computer graphics where all projection lines (rays) are parallel to each other, unlike perspective projection, where projection lines converge at a single point (the vanishing point). Parallel projection preserves the relative proportions of objects regardless of their distance from the viewer, making it particularly useful for technical drawings and CAD applications. 8
- 9. Parallel Projection 9 In parallel projection, coordinate positions are transformed to the view plane along parallel lines.
- 10. TYPES OF PARALLEL PROJECTION • Orthographic projection • Oblique projection 10
- 11. Key Features of Parallel Projection: • No Perspective Distortion: Objects retain their true dimensions and shape regardless of their distance from the camera. This means distant objects do not appear smaller, unlike in perspective projection. • Parallel Lines Stay Parallel: All parallel lines in the 3D scene remain parallel after the projection. There is no convergence at a vanishing point. • Proportionality: The relative proportions and sizes of objects are preserved, making parallel projection useful for tasks where accuracy and measurement are important. 11
- 12. • Perspective: – This type of projection is similar to human visual system... – In this system 'perspective foreshortening‘ occur. • size of object varies inversely with distance from the center of projection. Projection of a distant object are smaller than the projection of objects of the same size that are closer to the projection plane. • Parallel: It preserves relative proportion of object. – less realistic view because of no foreshortening – however, parallel lines remain parallel. Perspective v Parallel 12
- 13. when the projection is perpendicular to the view plane when the projection is not perpendicular to the view plane • Orthographic projection Oblique projection 13
- 14. – Front, side and rear orthographic projection of an object are called elevations. – all have projection plane perpendicular to a principle axes. – This type of projection is used in architectural drawings . • Different types of view can be shown by this type of projection. Orthographic (or orthogonal) projections: 14
- 15. Types of orthographic projections: • Multiview (or first-angle/third-angle projection) • Axonometric projection 15
- 16. Multiview (or first-angle/third- angle projection) • This method involves projecting the views of the object onto different planes (top, front, side, etc.) and placing these views together to represent the object from various angles. • In first-angle projection, the object is placed in the first quadrant, and views are projected onto adjacent planes. • In third-angle projection the object is placed in the third quadrant, and views are projected directly onto planes. 16
- 17. TYPES of Axonometric projection • This is a type of orthographic projection where the object is viewed from a skewed angle to show multiple sides at once. Common types include: – Isometric projection: The angles between the projection of the axes are equal (120°), providing a balanced view of the object. – Dimetric projection: Two of the three axes have the same scale or angle, while the third axis is different. – Trimetric projection: All three axes are scaled differently. 17
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