From 62eb2e59097da8b0ec312d64363e0a12b55db7b4 Mon Sep 17 00:00:00 2001 From: Keith Whitwell Date: Thu, 20 Sep 2001 19:25:31 +0000 Subject: very brief overview of swrast --- src/mesa/swrast/NOTES | 55 +++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 55 insertions(+) create mode 100644 src/mesa/swrast/NOTES (limited to 'src') diff --git a/src/mesa/swrast/NOTES b/src/mesa/swrast/NOTES new file mode 100644 index 00000000000..f906e41b955 --- /dev/null +++ b/src/mesa/swrast/NOTES @@ -0,0 +1,55 @@ +INTRODUCTION + +Mesa's native software rasterizer. This module provides the fallback +paths for rasterization operations and states that aren't accelerated +in hardware drivers, and as the full rasterization engine in software +drivers. + +The swrast module 'stands alone', relying only on interfaces to core +mesa and it's own driver interface. It knows nothing about the tnl or +other modules, allowing it to be used for fallback paths in future tnl +schemes without modification. + +As well as providing triangle/line/point rasterization functionality, +the module provides implementations of the pixel operations +(ReadPixels, etc), and texture operations (CopyTexSubImage) which may +be plugged in to the core Mesa driver interface where accelerated +versions of these operations are unavailable. + + +STATE + +To create and destroy the module: + + GLboolean _swrast_CreateContext( GLcontext *ctx ); + void _swrast_DestroyContext( GLcontext *ctx ); + +This module tracks state changes internally and maintains derived +values based on the current state. For this to work, the driver +ensure the following funciton is called whenever the state changes and +the swsetup module is 'awake': + + void _swrast_InvalidateState( GLcontext *ctx, GLuint new_state ); + +There is no explicit call to put the swrast module to sleep. + + +CUSTOMIZATION + + void (*choose_point)( GLcontext * ); + void (*choose_line)( GLcontext * ); + void (*choose_triangle)( GLcontext * ); + +Drivers may add additional triangle/line/point functions to swrast by +overriding these functions. It is necessary for the driver to be very +careful that it doesn't return an inappropriate function, eg a +rasterization function in feedback mode. See the X11 driver for +examples. + +DRIVER INTERFACE + +The swrast device driver provides swrast primarily with span- and +pixel- level interfaces to a framebuffer, with a few additional hooks +for locking and setting the read buffer. + +See the definition of struct swrast_device_driver in swrast.h. \ No newline at end of file -- cgit v1.2.3