draw,llvmpipe,util: add depth bias calculation for arb_depth_buffer_float

With this patch, the llvmpipe and draw modules will calculate the depth bias
according to floating point depth buffer semantics described in the
arb_depth_buffer_float specification, when the driver has a z buffer bound
with a format type of UTIL_FORMAT_TYPE_FLOAT.

By default, the driver will use the existing UNORM calculation for depth bias.

A new function, draw_set_zs_format, was added to calculate the Minimum
Resolvable Depth value and floating point depth sense for the draw module.

Reviewed-by: Jose Fonseca <jfonseca@vmware.com>
Reviewed-by: Roland Scheidegger <sroland@vmware.com>

1 files changed, 6 insertions, 10 deletions

diff --git a/src/gallium/auxiliary/util/u_format.c b/src/gallium/auxiliary/util/u_format.c
index 9ef3bb53ff2..6b602bf3262 100644
--- a/src/gallium/auxiliary/util/u_format.c
+++ b/src/gallium/auxiliary/util/u_format.c
@@ -215,9 +215,8 @@ util_format_is_supported(enum pipe_format format, unsigned bind)
  * default MRD will be 1.0 / ((1 << 24) - 1).
  */
 double
-util_get_depth_format_mrd(enum pipe_format format)
+util_get_depth_format_mrd(const struct util_format_description *desc)
 {
-   struct util_format_description *format_desc;
    /*
     * Depth buffer formats without a depth component OR scenarios
     * without a bound depth buffer default to D24.
@@ -225,23 +224,20 @@ util_get_depth_format_mrd(enum pipe_format format)
    double mrd = 1.0 / ((1 << 24) - 1);
    unsigned depth_channel;
 
-   format_desc = (struct util_format_description *)
-                     util_format_description(format);
-
-   assert(format_desc);
+   assert(desc);
 
    /*
     * Some depth formats do not store the depth component in the first
     * channel, detect the format and adjust the depth channel. Get the
     * swizzled depth component channel.
     */
-   depth_channel = format_desc->swizzle[0];
+   depth_channel = desc->swizzle[0];
 
-   if (format_desc->channel[depth_channel].type == UTIL_FORMAT_TYPE_UNSIGNED &&
-       format_desc->channel[depth_channel].normalized) {
+   if (desc->channel[depth_channel].type == UTIL_FORMAT_TYPE_UNSIGNED &&
+       desc->channel[depth_channel].normalized) {
       int depth_bits;
 
-      depth_bits = format_desc->channel[depth_channel].size;
+      depth_bits = desc->channel[depth_channel].size;
       mrd = 1.0 / ((1ULL << depth_bits) - 1);
    }