GRIME MANUAL: GRIME-NURBS

Grime-Polys examines the relations between individual polygons, therefore it is better for ‘griming’ objects made up of few large polygons (like the staircase in the tutorial section).

Gradient

Grime has a gradient feature which gives the user perfect control over the amount and location of dirt. Its spectrum has an unlimited number of values, which makes this feature a very flexible tool.

Fractal Noise

For the dirt to look even more realistic, Grime has a fractal noise feature which prevents the too-uniform application of dirt. It also makes it possible to create damp patches caused by leakage and other special kinds of dirt.

All Channels

With Grime the dirt effect can be applied to all surface channels (color, specularity, luminosity, reflectivity and transparency). Thus dirty parts of glossy objects can be made less glossy, dirty windowpanes less transparent, etc.

Now your objects will no longer look brand new, unless you want them to. Instead, they will have a much more interesting, real-life look.

GRAPHIC USER INTERFACE

The GUI is divided into three sections: the General Pptions, Set Tabs and Surface Channels Tabs.

Use existing geometry files

While processing a given object for the first time, Grime creates .grm files which contain object geometry data. During subsequent renderings, Grime uses those files for faster rendering. The default setting is ON.

Create missing geometry files

If there are no .grm files available, this option creates them. The default setting is ON.

In this section, users determine the dirt fractal properties (see the Grime-Nurbs section) and the relation between dirt application and the angle between polygons. Since Grime-Polys is capable of detecting protruding parts of objects, its GUI has two Peak pos / Zero scale / Peak pos / Max scale tables and charts. Additionally, it has Zero clip buttons which, if ON as in the default settings, produce a serrated, more natural edge of the fractal application area.

Example

Figure 1a - Here both Zero clip buttons are ON

Figure 1b - clip on

Figure 2a - Here both Zero clip buttons are OFF

Figure 2b - clip off

Edge parameters

Start value

This option determines the gradient value from which Grime starts to apply the effect, i.e. the value on the very edge (or at the bottom of the crack in Crack parameters). There are four values: Min angle, Max angle, Min value and Max value. The default angle settings are min 70° and max 90° (note that these values refer to angles between normals of polygons and not polygons themselves). Any edges between polygons whose angle is greater than the Max angle assume the Max value. Any edges between polygons whose angle is smaller than the Min angle assume the Min value. All edges the angles between whose normals are within the Max angle / Min angle range assume values linearly interpolated between Max value and Min value. These settings are graphically represented in the charts on the right.

Examples

Figure 3

Here the angle between normals of polygons is 90° . Since the angle is the same as Max angle, therefore Max value is assumed for the gradient value to be applied as start value. Here Max value is 1, therefore Start value is the brightest green (see figure 6 , click Back to return here). With Max value set to 0.5, Start value would be darker green from the middle of the edge gradient.

Figure 4

Here the angle between normals of polygons is 80° , i.e. it is exactly the average value between Max angle and Min angle. Therefore, Start value of the edge color is darker green from the middle of the edge gradient (see Figure 6, click Back to return here).

Figure 5

Here the angle between normals of polygons is 70° . Since the angle between is the same as the Min angle, Min value is assumed for the gradient value to be applied as start value. Here Min value is 0, and since opacity is set to 0, Start value is 0 and the effect is not applied to edges between polygons the angle between whose normals is 70° or less. With Min value set to 0.5, Start value would be darker green as in the middle of the edge gradient.

Figure 6 - click image to enlarge

This image shows which gradient values are assumed as start values for particular angles.

Start distance

This option determines the distance within which the Start value is applied. It is operated in the same way as the Start value option.

Examples

Figure 7

For 90° Max value is set to 0.5, therefore Start distance is 0.5 m (for the sake of clarity Decay distance is set to 0).

Decay distance

This option determines the distance within which Start value falls off. It is operated in the same way as the Start value option.

Example

Figure 9

For 90° Max value is set to 0.5, therefore decay distance is 0.5 m. (here Start distance is also set to 0.5 m).

Fast scaling

This option multiplies all the values in the table by a user defined number for fast scaling.

Crack parameters

See Edge parameters.

Effect

This gradient applies the color / luminosity / diffuse / specularity / transparency / reflectivity effect to concave / protruding parts of objects. By clicking on the gradient spectrum, users can select keyed values of the gradient, and then precisely adjust the positions of values using the numeric box with arrows and the Add and Del buttons below.

Flip button and Copy / Paste buttons

For easy editing, Grime’s GUI has Copy / Paste buttons and a Flip button. The copy / paste option allows users to copy settings of one surface channel into another surface channel (in LW 5.6 it is also possible to copy settings from one Grime into another if two or more have been opened). The Flip button reverts the gradient spectrum.

Set 1 pull-down menu

This option applies a fractal and a predefined relation between dirt application and the angle between polygons (as set in the Set Tabs Section) to the active surface channel. Four different settings are available.

Opacity

This gradient determines the opacity of the color / luminosity / diffuse / specularity / transparency / reflectivity effect. By clicking on the gradient spectrum, users can select keyed values of the gradient and then precisely adjust the positions of values using the numeric box with arrows and Add and Del buttons below.

Flip button and Copy / Paste buttons

The copy / paste option allows users to copy settings of one surface channel opacity into another surface channel (in LW 5.6 it is also possible to copy opacity settings from one Grime into another if two or more have been opened). The Flip button reverts the opacity gradient spectrum.

Set 1 pull-down menu

This option applies a fractal and a predefined relation between dirt application and the angle between polygons (as set in the Set Tabs Section) to the active surface channel. Four different settings are available.

KNOWN LIMITATIONS

While working with Grime-Polys, users should avoid using the Get/Put option of LightWave’s Modeler. LightWave saves object files in a template directory without modifying the original object stored in the hard disc and Objaccess.p uses the object information saved in the hard disc and not in the memory. Thus if the object is modified in any way in the meantime, the Get/Put option will disregard the modifications and load the original file from the hard disc.