summaryrefslogtreecommitdiff
path: root/src/gallium/auxiliary/gallivm
diff options
context:
space:
mode:
authorJosé Fonseca <jfonseca@vmware.com>2010-10-08 15:50:28 +0100
committerJosé Fonseca <jfonseca@vmware.com>2010-10-08 15:50:28 +0100
commiteb605701aa4af9ea44004008256a5707e470738c (patch)
tree6895da786abb5ed7d5c455d9405a6ee0b233963d /src/gallium/auxiliary/gallivm
parentc8179ef5e8db46afd4efdf5cbb4d9c9d37e488f8 (diff)
gallivm: Implement brilinear filtering.
Diffstat (limited to 'src/gallium/auxiliary/gallivm')
-rw-r--r--src/gallium/auxiliary/gallivm/lp_bld_sample.c90
1 files changed, 89 insertions, 1 deletions
diff --git a/src/gallium/auxiliary/gallivm/lp_bld_sample.c b/src/gallium/auxiliary/gallivm/lp_bld_sample.c
index 754902891b..f23ede3319 100644
--- a/src/gallium/auxiliary/gallivm/lp_bld_sample.c
+++ b/src/gallium/auxiliary/gallivm/lp_bld_sample.c
@@ -39,12 +39,20 @@
#include "lp_bld_arit.h"
#include "lp_bld_const.h"
#include "lp_bld_debug.h"
+#include "lp_bld_printf.h"
#include "lp_bld_flow.h"
#include "lp_bld_sample.h"
#include "lp_bld_swizzle.h"
#include "lp_bld_type.h"
+/*
+ * Bri-linear factor. Use zero or any other number less than one to force
+ * tri-linear filtering.
+ */
+#define BRILINEAR_FACTOR 2
+
+
/**
* Does the given texture wrap mode allow sampling the texture border color?
* XXX maybe move this into gallium util code.
@@ -254,6 +262,79 @@ lp_build_rho(struct lp_build_sample_context *bld,
}
+/*
+ * Bri-linear lod computation
+ *
+ * Use a piece-wise linear approximation of log2 such that:
+ * - round to nearest, for values in the neighborhood of -1, 0, 1, 2, etc.
+ * - linear approximation for values in the neighborhood of 0.5, 1.5., etc,
+ * with the steepness specified in 'factor'
+ * - exact result for 0.5, 1.5, etc.
+ *
+ *
+ * 1.0 - /----*
+ * /
+ * /
+ * /
+ * 0.5 - *
+ * /
+ * /
+ * /
+ * 0.0 - *----/
+ *
+ * | |
+ * 2^0 2^1
+ *
+ * This is a technique also commonly used in hardware:
+ * - http://ixbtlabs.com/articles2/gffx/nv40-rx800-3.html
+ *
+ * TODO: For correctness, this should only be applied when texture is known to
+ * have regular mipmaps, i.e., mipmaps derived from the base level.
+ *
+ * TODO: This could be done in fixed point, where applicable.
+ */
+static void
+lp_build_brilinear_lod(struct lp_build_sample_context *bld,
+ LLVMValueRef lod,
+ double factor,
+ LLVMValueRef *out_lod_ipart,
+ LLVMValueRef *out_lod_fpart)
+{
+ struct lp_build_context *float_bld = &bld->float_bld;
+ LLVMValueRef lod_fpart;
+ float pre_offset = (factor - 0.5)/factor - 0.5;
+ float post_offset = 1 - factor;
+
+ if (0) {
+ lp_build_printf(bld->builder, "lod = %f\n", lod);
+ }
+
+ lod = lp_build_add(float_bld, lod,
+ lp_build_const_vec(float_bld->type, pre_offset));
+
+ lp_build_ifloor_fract(float_bld, lod, out_lod_ipart, &lod_fpart);
+
+ lod_fpart = lp_build_mul(float_bld, lod_fpart,
+ lp_build_const_vec(float_bld->type, factor));
+
+ lod_fpart = lp_build_add(float_bld, lod_fpart,
+ lp_build_const_vec(float_bld->type, post_offset));
+
+ /*
+ * It's not necessary to clamp lod_fpart since:
+ * - the above expression will never produce numbers greater than one.
+ * - the mip filtering branch is only taken if lod_fpart is positive
+ */
+
+ *out_lod_fpart = lod_fpart;
+
+ if (0) {
+ lp_build_printf(bld->builder, "lod_ipart = %i\n", *out_lod_ipart);
+ lp_build_printf(bld->builder, "lod_fpart = %f\n\n", *out_lod_fpart);
+ }
+}
+
+
/**
* Generate code to compute texture level of detail (lambda).
* \param ddx partial derivatives of (s, t, r, q) with respect to X
@@ -359,7 +440,14 @@ lp_build_lod_selector(struct lp_build_sample_context *bld,
}
if (mip_filter == PIPE_TEX_MIPFILTER_LINEAR) {
- lp_build_ifloor_fract(float_bld, lod, out_lod_ipart, out_lod_fpart);
+ if (BRILINEAR_FACTOR > 1.0) {
+ lp_build_brilinear_lod(bld, lod, BRILINEAR_FACTOR,
+ out_lod_ipart, out_lod_fpart);
+ }
+ else {
+ lp_build_ifloor_fract(float_bld, lod, out_lod_ipart, out_lod_fpart);
+ }
+
lp_build_name(*out_lod_ipart, "lod_ipart");
lp_build_name(*out_lod_fpart, "lod_fpart");
}