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Ray Traced Pictures
Ray traced pictures are computed directly from the geometry without the need to generate polygons as for the OpenGL 3D graphics. They can show cells not correctly rendered in the dynamic 3D plot because of complicated cell descriptions. Ray tracings are useful for showing fine detail in complicated models. Optional effects include etch lines at surface, material, cell, and/or lattice element boundaries, light source positioning and shadows, and use of a background picture. alpha semitransparency is supported, usually with better results than with OpenGL. The ray tracings use any clip planes defined for the dynamic 3D plot; the surfaces at the clip boundaries are always solid.
The visibility of cells is the same as in the OpenGL 3D plot. The same alpha values for semitransparency are used in both plots (Alpha Transparency must be checked on the Ray Trace Options property page). Cells drawn in wireframe in the OpenGL plot are treated as either solid and opaque or transparent for ray tracing according to the Wireframe Transparent setting on the Ray Trace Options property page. Only cells are ray traced—solid bodies, CAD models, particle tracks, and meshes are not.
A ray is a line of sight from the viewpoint to the geometry model. The properties of the surfaces encountered by the ray determine the color of the portion of the viewplane through which the ray passes. The ray terminates at the first opaque surface it encounters. The color of the cell on the other side of that surface and the angle the surface makes with the ray determine the color and intensity.
When the ray encounters a semitransparent cell, it continues. The RGB components of the colors of semitransparent cells along the ray are blended using the alpha values. The ray is terminated when the cumulative alpha along the path is >= 1. When coloring by material, the ray continues through cells of the same semitransparent material without modifying the color at the cell boundaries.
Ray tracing and OpenGL comparisons.
 White Rock Science http://www.whiterockscience.com/wrs.html 505 672 1105 |
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