diff options
Diffstat (limited to 'src')
| -rw-r--r-- | src/gallium/auxiliary/gallivm/lp_bld_sample.c | 90 |
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 754902891b9..f23ede33197 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"); } |