Visualization Guide
Visualization Guide
Visualization Guide
Visualization Guide
Visualization Guide
Visualization Guide
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When creating photorealistic images, care should be taken with material definitions.
Unless a material is meant to be reflective or transparent, its Reflect and Transparency properties should be set to 0.
While the practical maximum value for both Reflect and Transparency is 100, larger values may be keyed-in to create certain types of effects. (This is true for the Ambient, Diffuse, and Specular settings, as well.)
If Transparency is off for a view, or in the Ray Tracing dialog box, transparent elements are rendered opaquely in that view.
Reflections and transparency are tinted by the Specular Color of the material. The degree of reflectivity also is modified by the Specular material property. For example, if Reflect is set to 0.9 and Specular is set to 0.4, the material is only 0.36 reflective as, essentially, the two fields are multiplied together. The reflectivity is further modified by the Specular Color. In this case, the RGB values of the reflections are the products of the above (0.36 reflective) further multiplied by the respective RGB values (between 0 and 1) of the Specular Color. The same holds true for Transmit.
Where there are no environment maps defined, a reflective object that does not see another object in its reflection will reflect the background color, as defined in the MicroStation color table. Thus, reflective objects will appear brighter when rendered with a white background than they would with a black background. Where environment maps are defined, then these will be reflected in place of the background color. Any background image that may be defined for a view, however, is not reflected.
 | Material tables for older existing DGN files may have Reflect set to a value other than 0.0. This means that more objects in a design may be reflective than intended, which can slow down ray tracing unnecessarily. Use the Material Editor dialog box to ensure that the reflectivity of only those objects that are intended to be reflective is set to a value greater than 0.0. |
When ray tracing a transparent surface (as opposed to a solid), if the element is defined in a clockwise order, transmitted rays bend as if they were leaving the element, as opposed to entering.
You can solve this problem by specifying a Thickness value for the material.
Other options are to use the reciprocal of the refraction value set for the element's material, or to reverse the surface normals using the Change Normal Direction tool in the Modify Surfaces tool box.
To achieve a realistic glass surface, the Diffuse Color should be relatively low (0.05). Clear glass actually is colorless (that is, its diffuse color is black, not white). Its Specular Color (the color of light that is reflected or transmitted) is white. Tinted glass can be obtained by modifying the specular color.
With both Radiosity solving and Particle Tracing, correct material definitions are even more important. For both these options, it is important that the Efficiency does not exceed 100%. In the real-world, materials generally range in efficiency from 30% to 70%.
For Radiosity solving, if efficiency is greater than 100%, then it is possible for more light energy to be reflected than was initially received, which is unrealistic and could result in a “never-ending” calculation with the light energy increasing rather than decreasing.
For Particle Tracing, this is not as drastic, but still should be considered. If the efficiency is above 100% then the process reduces the values for that material, on a pro-rata basis, back to 100%.
When the rendering process comes across a material definition, the four components — Diffuse, Specular, Transparency, and Ambient, all have an effect on the outcome.
Diffuse — the material's Base Color scaled by Diffuse, represents the percent of light (in each color) reflected by each light. This diffuse color determines how bright the material appears when illuminated, and how much light is reflected onto other surfaces for radiosity and particle tracing.
For materials that are pattern-mapped, Color is first blended with the pattern map, and then Diffuse is applied.
Specular — the Specular Color, scaled by Specular, represents the percent of light (in each color) that is reflected off a surface as a specular highlight, where you can “see” a reflection of each light source in the surface. When additionally scaled by Reflect, this yields the percent of light (in each color) that is seen in a reflection of a ray-traced object. When working with particle tracing, this value also represents the amount of light that will be reflected in the mirror direction onto other surfaces, accounting for caustics. Radiosity does not distribute specular light, and thus does not produce caustics.
Specular highlights are seen in radiosity solutions only when Ray Trace is chosen as the Final Display in the Display section of the Radiosity dialog box.
Specular highlights are seen in particle tracing solutions only when Ray Trace Specular Effects is enabled in the Display section of the Particle Tracing dialog box.
Transmit — the Specular Color scaled by Transmit, represents the percent of light (in each color) that passes through a surface. Note that this means that a material with a Specular Color of black will never transmit any light, even if Transmit is set at 1. This applies when the material is casting shadows and when objects are seen through the material.
Ambient — the ambient color of a material is its Color scaled by Ambient, and then by the Ambient Light from the Global Lighting dialog box. For Radiosity solving and Particle Tracing, Ambient usually should be 0.0, or you can have Ambient Lighting turned off. In general, Ambient should be used only for ray tracing (as well as Phong, Smooth, and the other rendering modes). It is used to compensate for reflected light that these renderers do not handle.