<HTML> <TITLE>Off-screen Rendering</TITLE> <BODY text="#000000" bgcolor="#55bbff" link="#111188"> <H1>Off-screen Rendering</H1> <p> Mesa 1.2.4 introduced off-screen rendering, a facility for generating 3-D imagery without having to open a window on your display. Mesa's simple off-screen rendering interface is completely operating system and window system independent so programs which use off-screen rendering should be very portable. This feature effectively enables you to use Mesa as an off-line, batch-oriented renderer. </p> <p> The "OSMesa" API provides 3 functions for making off-screen renderings: OSMesaCreateContext(), OSMesaMakeCurrent(), and OSMesaDestroyContext(). See the Mesa/include/GL/osmesa.h header for more information. See the demos/osdemo.c file for an example program. There is no facility for writing images to files. That's up to you. </p> <p> If you want to generate large images (larger than 1280x1024) you'll have to edit the src/config.h file to change MAX_WIDTH and MAX_HEIGHT then recompile Mesa. Image size should only be limited by available memory. </p> <H2>Deep color channels</H2> <p> For some applications 8-bit color channels don't have sufficient accuracy (film and IBR, for example). If you're in this situation you'll be happy to know that Mesa supports 16-bit and 32-bit color channels through the OSMesa interface. When using 16-bit channels, channels are GLushorts and pixels occupy 8 bytes. When using 32-bit channels, channels are GLfloats and pixels occupy 16 bytes. </p> <p> To build Mesa/OSMesa with 16-bit color channels: <pre> cd Mesa-4.x/src make -f Makefile.X11 clean make -f Makefile.OSMesa16 linux-osmesa16 </pre> For 32-bit channels: <pre> cd Mesa-4.x/src make -f Makefile.X11 clean make -f Makefile.OSMesa16 linux-osmesa32 </pre> <p> If you're not using Linux, you can easily edit Make-config and add an appropriate configuration. </p> <p> The Mesa/tests/osdemo16.c file (available via CVS) demonstrates how to use this feature. </p> <p> BE WARNED: 16 and 32-bit channel support has not been exhaustively tested and there may be some bugs. However, a number of people have been using this feature successfully so it can't be too broken. </p> </BODY> </HTML>