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i965: expose sample positions

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Moves the definition of the sample positions out of
gen6_emit_3dstate_multisample, and unpacks them in
gen6_get_sample_position.

V2: Be consistent about `sample position` rather than `location`.

Signed-off-by: Chris Forbes <chrisf@ijw.co.nz>
Reviewed-by: Paul Berry <stereotype441@gmail.com>
Acked-by: Ian Romanick <ian.d.romanick@intel.com>
This commit is contained in:
Chris Forbes
2012-12-05 16:27:42 +13:00
parent 569c4a9f1c
commit 032896cbf9
3 changed files with 82 additions and 43 deletions
Download Patch File Download Diff File Expand all files Collapse all files
src/mesa/drivers/dri/i965/brw_context.c
+3
View File
@@ -95,6 +95,9 @@ static void brwInitDriverFunctions(struct intel_screen *screen,
functions->EndTransformFeedback = gen7_end_transform_feedback;
else
functions->EndTransformFeedback = brw_end_transform_feedback;
if (screen->gen >= 6)
functions->GetSamplePosition = gen6_get_sample_position;
}
bool
src/mesa/drivers/dri/i965/brw_context.h
+5
View File
@@ -1230,6 +1230,11 @@ void
gen6_emit_3dstate_sample_mask(struct brw_context *brw,
unsigned num_samples, float coverage,
bool coverage_invert, unsigned sample_mask);
void
gen6_get_sample_position(struct gl_context *ctx,
struct gl_framebuffer *fb,
GLuint index,
GLfloat *result);
/* gen7_urb.c */
void
src/mesa/drivers/dri/i965/gen6_multisample_state.c
+74 -43
View File
@@ -26,6 +26,77 @@
#include "brw_context.h"
#include "brw_defines.h"
/* Sample positions:
* 2 6 a e
* 2 0
* 6 1
* a 2
* e 3
*/
static uint32_t
sample_positions_4x[] = { 0xae2ae662 };
/* Sample positions are based on a solution to the "8 queens" puzzle.
* Rationale: in a solution to the 8 queens puzzle, no two queens share
* a row, column, or diagonal. This is a desirable property for samples
* in a multisampling pattern, because it ensures that the samples are
* relatively uniformly distributed through the pixel.
*
* There are several solutions to the 8 queens puzzle (see
* http://en.wikipedia.org/wiki/Eight_queens_puzzle). This solution was
* chosen because it has a queen close to the center; this should
* improve the accuracy of centroid interpolation, since the hardware
* implements centroid interpolation by choosing the centermost sample
* that overlaps with the primitive being drawn.
*
* Note: from the Ivy Bridge PRM, Vol2 Part1 p304 (3DSTATE_MULTISAMPLE:
* Programming Notes):
*
* "When programming the sample offsets (for NUMSAMPLES_4 or _8 and
* MSRASTMODE_xxx_PATTERN), the order of the samples 0 to 3 (or 7
* for 8X) must have monotonically increasing distance from the
* pixel center. This is required to get the correct centroid
* computation in the device."
*
* Sample positions:
* 1 3 5 7 9 b d f
* 1 5
* 3 2
* 5 6
* 7 4
* 9 0
* b 3
* d 1
* f 7
*/
static uint32_t
sample_positions_8x[] = { 0xdbb39d79, 0x3ff55117 };
void
gen6_get_sample_position(struct gl_context *ctx,
struct gl_framebuffer *fb,
GLuint index, GLfloat *result)
{
switch (fb->Visual.samples) {
case 1:
result[0] = result[1] = 0.5f;
break;
case 4: {
uint8_t val = (uint8_t)(sample_positions_4x[0] >> (8*index));
result[0] = (val & 0xf) / 16.0f;
result[1] = ((val >> 4) & 0xf) / 16.0f;
break;
}
case 8: {
uint8_t val = (uint8_t)(sample_positions_8x[index>>2] >> (8*(index & 3)));
result[0] = (val & 0xf) / 16.0f;
result[1] = ((val >> 4) & 0xf) / 16.0f;
break;
}
default:
assert(!"Not implemented");
}
}
/**
* 3DSTATE_MULTISAMPLE
@@ -47,52 +118,12 @@ gen6_emit_3dstate_multisample(struct brw_context *brw,
break;
case 4:
number_of_multisamples = MS_NUMSAMPLES_4;
/* Sample positions:
* 2 6 a e
* 2 0
* 6 1
* a 2
* e 3
*/
sample_positions_3210 = 0xae2ae662;
sample_positions_3210 = sample_positions_4x[0];
break;
case 8:
number_of_multisamples = MS_NUMSAMPLES_8;
/* Sample positions are based on a solution to the "8 queens" puzzle.
* Rationale: in a solution to the 8 queens puzzle, no two queens share
* a row, column, or diagonal. This is a desirable property for samples
* in a multisampling pattern, because it ensures that the samples are
* relatively uniformly distributed through the pixel.
*
* There are several solutions to the 8 queens puzzle (see
* http://en.wikipedia.org/wiki/Eight_queens_puzzle). This solution was
* chosen because it has a queen close to the center; this should
* improve the accuracy of centroid interpolation, since the hardware
* implements centroid interpolation by choosing the centermost sample
* that overlaps with the primitive being drawn.
*
* Note: from the Ivy Bridge PRM, Vol2 Part1 p304 (3DSTATE_MULTISAMPLE:
* Programming Notes):
*
* "When programming the sample offsets (for NUMSAMPLES_4 or _8 and
* MSRASTMODE_xxx_PATTERN), the order of the samples 0 to 3 (or 7
* for 8X) must have monotonically increasing distance from the
* pixel center. This is required to get the correct centroid
* computation in the device."
*
* Sample positions:
* 1 3 5 7 9 b d f
* 1 5
* 3 2
* 5 6
* 7 4
* 9 0
* b 3
* d 1
* f 7
*/
sample_positions_3210 = 0xdbb39d79;
sample_positions_7654 = 0x3ff55117;
sample_positions_3210 = sample_positions_8x[0];
sample_positions_7654 = sample_positions_8x[1];
break;
default:
assert(!"Unrecognized num_samples in gen6_emit_3dstate_multisample");