x11 - display driver for x11 1, 8, or 24 bit displays.

DESCRIPTION

X11 is a PhotoRealistic RenderMan display driver for the X11 24-bit DirectColor, 8-bit PseudoColor, or 1-bit monochrome displays under the X11 window system. When an image is displayed using the x11 driver, an X11 window pops up on the screen. The driver dynamically determines whether the X11 display system has a 24-bit DirectColor, or 8-bit PsuedoColor visual available and behaves appropriately for each. If neither of the above is available, the default visual is used as a 1-bit monochrome display. The size of the inside of the window is determined from the image resolution. The window can be moved, closed and reopened without affecting output.

After rendering is completed or aborted, the window remains on the screen. The window is removed only when the window is selected for focus and a “q” is typed on the keyboard. For 8- or 1-bit displays, after rendering is completed, an image-improvement process takes place and the image is redrawn. Monochrome images are dithered, and 8-bit images are redisplayed using a color map selected by the median cut color selection algorithm and dithered (see “Color Image Quantization for Frame Buffer Display,” Paul S. Heckbert, Proc. SIGGRAPH '82, pp. 297-307).

In order to view a color image properly, the colors should be adjusted for the monitor. If this isn't done, images will usually appear to be too dark. The x11 display driver does this using a technique called “gamma correction” using a “gamma” value of 2.0 to approximate the color response of most color monitors. A different gamma value can be used by setting the DSPYGAMMA environment variable; for example,

	DSPYGAMMA=2.6

will cause the driver to use a gamma value of 2.6 instead of the default. If the image appears washed out (bright), lower the gamma value (usually not below 1.0). If the image is too dark, raise the gamma value (usually not above 3.0). A gamma value of 1.0 will display the image unaltered on a display that has the color correction handled in another fashion.

DEFAULTS

resolution		512 × 384


pixel aspect ratio	1.0


gamma correction	2.0

ERROR MESSAGES

The following messages can be produced by the x11 display driver. Each of the following messages will be preceded by the generic message number D00001 and the string “Display error:”.

DspyOpen_x11: can not open display: name

The display referred to by the DISPLAY environment variable cannot be opened. Refer to the X11 window system documentation for your system to find the valid settings of this environment variable.

DspyOpen_x11: cannot allocate image memory

DspyOpen_x11: cannot allocate image buffer

The system failed to allocate memory for the image to be displayed. Either the image is inordinately large or your system is very low on swap space.

DspyOpen_x11: cannot create image structure

The X11 window system call to set up image data structures failed.

DspyOpen_x11: cannot open window

The X11 window system call to open the window failed.

DspyOpen_x11: unable allocate N cells in new colormap

The X11 window system call to allocate colormap cells failed for the PseudoColor visual.

DRIVER INSTALLATION NOTES

If the x11 display driver is not already installed in your display server, it may be possible to add it as described in the PhotoRealistic RenderMan Display Driver Installation Guide document. The file called /usr/local/prman/etc/dspyinst/d_x11.o must exist in order to install this display driver. The installation guide tells you how to modify the display server Makefile in order to add a display driver. The relevant symbols to add for this driver are as follows:

Add -DDISPLAY_X11 to DRIVERDEFS.

Add d_x11.o to DRIVEROBJS.

Add ${DLIB_X11} to DRIVERLIBS. If DLIB_X11 is not already defined, add the line (assuming libX11.a is in /usr/lib):

DLIB_X11= -lX11