Added support for floating point depth buffers on Savage4-based

hardware. By also reversing the depth range this can compensate the loss
of accuracy of far objects caused by the projective transformation.
Software fallbacks work but are slightly slower since floats in a custom
(non IEEE) format have to be encoded and decoded. I havn't done anything
about polygon offsets yet. There doesn't seem to be an easy way do get
it right except making the offset unit as big as the lowest resolution
of depth values. For now float depth is disabled by default but can be
enabled through driconf (though I have seen only positive effects so
far).

1 files changed, 6 insertions, 4 deletions

diff --git a/src/mesa/drivers/dri/savage/savage_xmesa.c b/src/mesa/drivers/dri/savage/savage_xmesa.c
index f1798de134..e269705073 100644
--- a/src/mesa/drivers/dri/savage/savage_xmesa.c
+++ b/src/mesa/drivers/dri/savage/savage_xmesa.c
@@ -64,6 +64,7 @@ DRI_CONF_BEGIN
     DRI_CONF_SECTION_QUALITY
         DRI_CONF_TEXTURE_DEPTH(DRI_CONF_TEXTURE_DEPTH_FB)
         DRI_CONF_COLOR_REDUCTION(DRI_CONF_COLOR_REDUCTION_DITHER)
+        DRI_CONF_FLOAT_DEPTH(false)
     DRI_CONF_SECTION_END
     DRI_CONF_SECTION_PERFORMANCE
         DRI_CONF_MAX_TEXTURE_UNITS(2,1,2)
@@ -72,7 +73,7 @@ DRI_CONF_BEGIN
         DRI_CONF_NO_RAST(false)
     DRI_CONF_SECTION_END
 DRI_CONF_END;
-static const GLuint __driNConfigOptions = 4;
+static const GLuint __driNConfigOptions = 5;
 
 #ifdef USE_NEW_INTERFACE
 static PFNGLXCREATECONTEXTMODES create_context_modes = NULL;
@@ -308,6 +309,9 @@ savageCreateContext( const __GLcontextModes *mesaVis,
    driParseConfigFiles (&imesa->optionCache, &savageScreen->optionCache,
                         sPriv->myNum, "savage");
 
+   imesa->float_depth = driQueryOptionb(&imesa->optionCache, "float_depth") &&
+       savageScreen->chipset >= S3_SAVAGE4;
+   imesa->no_rast = driQueryOptionb(&imesa->optionCache, "no_rast");
    imesa->texture_depth = driQueryOptioni (&imesa->optionCache,
 					   "texture_depth");
    if (imesa->texture_depth == DRI_CONF_TEXTURE_DEPTH_FB)
@@ -407,7 +411,7 @@ savageCreateContext( const __GLcontextModes *mesaVis,
 
    imesa->hw_stencil = mesaVis->stencilBits && mesaVis->depthBits == 24;
    imesa->depth_scale = (imesa->savageScreen->zpp == 2) ?
-       (1.0F/0x10000):(1.0F/0x1000000);
+       (1.0F/0xffff):(1.0F/0xffffff);
 
    imesa->bufferSize = savageScreen->bufferSize;
    imesa->dmaVtxBuf.total = 0;
@@ -479,8 +483,6 @@ savageCreateContext( const __GLcontextModes *mesaVis,
 
    savageDDInitState( imesa );
 
-   imesa->no_rast = driQueryOptionb(&imesa->optionCache, "no_rast");
-
    driContextPriv->driverPrivate = (void *) imesa;
 
    return GL_TRUE;