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nouveau: Fix non-1x post-scale factor with DOT3 combiner 

Fixes long standing bug on NV10 and NV20 where using a non-1x RGB or A
post-scale with GL_DOT3_RGB or GL_DOT3_RGBA texture environment would
not work.

The old combiner math uses HALF_BIAS_NORMAL and HALF_BIAS_NEGATE.  The
GL_NV_register_combiners defines these as

    HALF_BIAS_NORMAL_NV       max(0.0, e) - 0.5
    HALF_BIAS_NEGATE_NV       -max(0.0, e) + 0.5

In order to get the correct result from the dot-product, the
intermediate dot-product must be multiplied by 4.  This is a literal
implementation of the GL_ARB_texture_env_dot3 spec.  It also requires
using the register combiner post-scale.  As a result, the post-scale
cannot be used for the post-scale set by the application.

The new combiner math uses EXPAND_NORMAL and EXPAND_NEGATE.  The
GL_NV_register_combiners defines these as

    EXPAND_NORMAL_NV          2.0 * max(0.0, e) - 1.0
    EXPAND_NEGATE_NV          -2.0 * max(0.0, e) + 1.0

Since this fully expands the value to [-1, 1] range, the intermediate
dot-product result is the desired value.  This leaves the register
combiner post-scale available for application use.

NOTE: I have not actually tested this.

Signed-off-by: Ian Romanick <ian.d.romanick@intel.com>
Acked-by: Ilia Mirkin <imirkin@alum.mit.edu>
This commit is contained in:
Ian Romanick 2016-08-18 10:57:44 +01:00
parent f926cf5bd0
commit a7d92c3c0b
1 changed files with 8 additions and 10 deletions
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18
src/mesa/drivers/dri/nouveau/nv10_state_frag.c
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@ -135,7 +135,7 @@ get_input_source(struct combiner_state *rc, int source)
/* Get the RC input mapping for the specified texture_env_combine
* operand, possibly inverted or biased. */
#define INVERT 0x1
#define HALF_BIAS 0x2
#define NORMALIZE 0x2
static uint32_t
get_input_mapping(struct combiner_state *rc, int operand, int flags)
@ -148,12 +148,12 @@ get_input_mapping(struct combiner_state *rc, int operand, int flags)
map |= RC_IN_USAGE(ALPHA);
if (is_negative_operand(operand) == !(flags & INVERT))
map |= flags & HALF_BIAS ?
RC_IN_MAPPING(HALF_BIAS_NEGATE) :
map |= flags & NORMALIZE ?
RC_IN_MAPPING(EXPAND_NEGATE) :
RC_IN_MAPPING(UNSIGNED_INVERT);
else
map |= flags & HALF_BIAS ?
RC_IN_MAPPING(HALF_BIAS_NORMAL) :
map |= flags & NORMALIZE ?
RC_IN_MAPPING(EXPAND_NORMAL) :
RC_IN_MAPPING(UNSIGNED_IDENTITY);
return map;
@ -270,12 +270,10 @@ setup_combiner(struct combiner_state *rc)
case GL_DOT3_RGB:
case GL_DOT3_RGBA:
INPUT_ARG(rc, A, 0, HALF_BIAS);
INPUT_ARG(rc, B, 1, HALF_BIAS);
INPUT_ARG(rc, A, 0, NORMALIZE);
INPUT_ARG(rc, B, 1, NORMALIZE);
rc->out = RC_OUT_DOT_AB | RC_OUT_SCALE_4;
assert(!rc->logscale);
rc->out = RC_OUT_DOT_AB;
break;
default: