Transcription of Orthographic and Perspective Projection
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Orthographic and Perspective Projection
Chapter 10 Orthographic andPerspective Projectionraycastingobject space rendererprojectionscreen space rendererWe have been, until now, creating images by raycasting. By shooting rays fromthe eyepoint out into the scene, we determine what is visible at the screenpixel that the ray passes through. This type of renderer is called an object (orscene) space renderer, since all viewing calculations are done in the world spaceof the scene. This approach is depicted above to the left. We are about tobegin looking atOpenGL, which uses a very different approach. OpenGL usesa screen space rendering approach, as depicted above to the right, which worksby:1. transforming all scene objects from world coordinates to camera coordi-nates by a viewing transform,2. projecting all scene geometry into 2D screen space and then using thisprojection to produce a shaded 10. Orthographic AND Perspective PROJECTION123123 For example, consider the tetrahedron inthe picture to the we were toproject the tetrahedron onto the view plane,it might be that only two of the four trian-gular faces would be visible.
The view volume is the volume swept out by the screen through space in the projection system being used. For an orthographic projection, this is a rect-angular solid, as shown in Figure 10.1. We use the distance d n to denote the distance of the front face, or near plane, of the volume and d f to denote an arbitrary, or far plane depth of the ...
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