Lecture Notes

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4/15/02

¨      Rendering (continued)

o       While application programs are loaded from secondary memory into primary memory when they are opened, renderings, which are generated by a z-buffer sort (quickpaint), are stored entirely in primary memory (until saved).  The resulting display list is also stored in primary memory until the resulting image on the screen (whose actual pixels are stored in VRAM) is deleted.

o       Renderings are view dependent.  The resultant product depends on the eye point and center of interest.

§          The related model faces are arranged in the display list according to where they are in ‘space’ (which is dictated by the display list).

§          The fist face (furthest from the eye point) is sent to VRAM then displayed on screen, followed by the next furthest, and so on.

o       Shaded render solves many of the sorting problems seen in quickpaint.  This is because shaded render uses full boundary sort.  Sorting and the resulting list are based on every point, segment, and face, not simply the center of each face.

§          The user will pay for this increased accuracy with roughly four times the amount of time required to complete the rendering.

o       In both rendering types, curved surfaces are represented with facets, which approximate a curved surface.

o       Slight color differences displayed are based on position of the light source.  Those faces with their associated normals approaching zero degrees (pointing directly at the light source) will be lighter then those approaching 180 degrees from the light source (which will be represented as the darkest faces).

o       Shaded render (also known as Lambert’s shading) represents objects though color variation, without dark lines separating faces.

o       Shadows produced for renderings are projection routines.

§          All points and segments, and their spatial relationship to the light source, are considered.  The shadows are defined and created by the vectors created between these entities.

o       Renderzone.

§          Renderzone has a number of options.  The first is the rendering engine (mathematical routine) which will be used to generate the image.

The options include:  flat, gouard, phong, preview z-buffer, full z-buffer, preview raytrace, and full raytrace.