# VRweb Display Settings

## Drawing Style

In the first part of the Display menu you can select the display mode:

- Wireframe (accelerator key ctrl-w)
- Hidden Line (accelerator key ctrl-h)
- Flat Shading (accelerator key ctrl-f)
- Smooth Shading (accelerator key ctrl-s)
- Texturing (accelerator key ctrl-t)

A similar pullright menu is available for the interactive display mode, which is applied during navigation.
(use the accelerator keys above, holding both the shift and ctrl key)

An extra item "the same" uses the same display mode during navigation and for still images.
(accelerator key ctrl-u)

The default display mode is Smooth Shading, meaning you have to change to Texturing yourself to display or load textures. The Mesa version by default uses Flat Shading and Wireframe during navigation.

## Display Options

- Line Antialiasing (accelerator key ctrl-a)

  toggles line antialiasing. Antialiasing is currently not supported by Mesa.

- Show Framerate

  displays the time it took to draw the last image and the frame-per-second rate. The time is measured from the completion of one drawing to the next and therefore also includes the time for putting the image on screen and event processing.

- Show Title

  switches back to the title or URL in the status line if hidden by navigation hints.

- Two-sided Polygons

  in VRML polygons are visible from both sides by default and there is a ShapeHint for showing polygons from the front only. Single-sided polygon rendering (known as backface culling) is faster (because only half of the polygons are visible), but requires properly oriented facets. With setting "on" or "off" you can force two-sided or single-sided polygons. The default "auto" tracks the ShapeHint.

## Lighting Options

- Lighting Calculations

  normally, under VRML, lighting calculations are always performed. However they can be computationally expensive and therefore there is a LightModel extension node to VRML, which is recognized by VRweb on setting "auto". With "on" or "off" you can force lighting calculations to be made always or never. Lighting calculations are usually turned off for prelit scenes. This yields faster rendering, but causes unrealistic effects in other scenes.

- ... on texturing

  The color of a texture map can be combined with the material color (if this option is active), or mapped directly to the object ignoring the material color (if this option is inactive). In the latter case lighting calculations are turned off for textures. Future versions will support a third option for performing light calculations using the color of the texture.

- Viewing Light

  toggles the use of an additional headlight. When viewing scenes that contain no light, the headlight is turned on automatically and this switch has no influence. Of course, when lighting calculations are turned off, light sources (incl. the headlight) have no influence. You can change the intensity or color of the headlight (see below).

## Gamma Correction

If you use the Mesa version, you can set up gamma correction to brighten up the drawings. Caveat: wireframes will be drawn much slower by Mesa when gamma correction is enabled. You have to set the environment variable `MESA_GAMMA` before starting VRweb. Some examples for uniform and non-uniform (RGB separately) gamma correction and deactivating it (depends on shell used):

       [csh/tcsh etc.:]  setenv MESA_GAMMA 2.0
                         setenv MESA_GAMMA "1.6 1.7 1.9"
                         unsetenv MESA_GAMMA
    [sh/ksh/bash etc.:]  MESA_GAMMA=2.0 ; export MESA_GAMMA
                         MESA_GAMMA="1.6 1.7 1.9" ; export MESA_GAMMA
                         unset MESA_GAMMA

SGI supports gamma correction via the Xserver (see man gamma), so there is no need to do it in Software. OpenGL itself provides no way to change gamma. Note: due to a small bug in the Mesa library you may have to use the "R G B" syntax also for uniform gamma correction to work properly.

## Anchor Settings

These options concern anchor display and appearance.

Display (accelerator key F9) toggles anchor highlighting.
Also available as button in the toolbar.

The effect of the different hightlighting methods are also described on the anchor page.

## Color Selection

Via Choose... you can open a dialog for interactive color selection. In the listbox in the top-right select the color you wish to change: Background, Heads-up Display, Anchor Faces (in mode color code), or the Viewing Light.

You can use the RGB or HLS color space for selections. Values can be changed with the sliders or by typing in the new values and entering Return. The field on the left side contains a predefined color map to choose from. With the Apply button you can test the changes; when finished, confirm them with OK or press Cancel to reject all changes.

The other items contain a set of predefined colors, e.g. for quick change of the background color to black, grey, lightgrey or white.

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