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/*
* Copyright © 2020 Raspberry Pi
*
* Permission is hereby granted, free of charge, to any person obtaining a
* copy of this software and associated documentation files (the "Software"),
* to deal in the Software without restriction, including without limitation
* the rights to use, copy, modify, merge, publish, distribute, sublicense,
* and/or sell copies of the Software, and to permit persons to whom the
* Software is furnished to do so, subject to the following conditions:
*
* The above copyright notice and this permission notice (including the next
* paragraph) shall be included in all copies or substantial portions of the
* Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
* THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
* FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
* IN THE SOFTWARE.
*/
#include "compiler/v3d_compiler.h"
#include "compiler/nir/nir_builder.h"
#include <math.h>
/**
* Lowers line smoothing by modifying the alpha component of fragment outputs
* using the distance from the center of the line.
*/
struct lower_line_smooth_state {
nir_shader *shader;
nir_variable *coverage;
};
static void
lower_line_smooth_intrinsic(struct lower_line_smooth_state *state,
nir_builder *b,
nir_intrinsic_instr *intr)
{
b->cursor = nir_before_instr(&intr->instr);
nir_ssa_def *one = nir_imm_float(b, 1.0f);
nir_ssa_def *coverage = nir_load_var(b, state->coverage);
nir_ssa_def *new_val = nir_fmul(b, nir_vec4(b, one, one, one, coverage),
intr->src[0].ssa);
nir_instr_rewrite_src(&intr->instr,
&intr->src[0],
nir_src_for_ssa(new_val));
}
static void
lower_line_smooth_func(struct lower_line_smooth_state *state,
nir_function_impl *impl)
{
nir_builder b;
nir_builder_init(&b, impl);
nir_foreach_block(block, impl) {
nir_foreach_instr_safe(instr, block) {
if (instr->type != nir_instr_type_intrinsic)
continue;
nir_intrinsic_instr *intr =
nir_instr_as_intrinsic(instr);
if (intr->intrinsic != nir_intrinsic_store_output ||
nir_intrinsic_base(intr) != 0 ||
intr->num_components != 4 ||
!intr->src[0].is_ssa)
continue;
lower_line_smooth_intrinsic(state, &b, intr);
}
}
}
static void
initialise_coverage_var(struct lower_line_smooth_state *state,
nir_function_impl *impl)
{
nir_builder b;
nir_builder_init(&b, impl);
b.cursor = nir_before_block(nir_start_block(impl));
nir_ssa_def *line_width = nir_load_line_width(&b);
nir_ssa_def *real_line_width = nir_load_aa_line_width(&b);
/* The line coord varies from 0.0 to 1.0 across the width of the line */
nir_ssa_def *line_coord = nir_load_line_coord(&b);
/* fabs(line_coord - 0.5) * real_line_width */
nir_ssa_def *pixels_from_center =
nir_fmul(&b, real_line_width,
nir_fabs(&b, nir_fsub(&b, line_coord,
nir_imm_float(&b, 0.5f))));
/* 0.5 - 1/√2 * (pixels_from_center - line_width * 0.5) */
nir_ssa_def *coverage =
nir_fsub(&b,
nir_imm_float(&b, 0.5f),
nir_fmul(&b,
nir_imm_float(&b, 1.0f / M_SQRT2),
nir_fsub(&b, pixels_from_center,
nir_fmul(&b,
line_width,
nir_imm_float(&b, 0.5f)))));
/* Discard fragments that aren’t covered at all by the line */
nir_ssa_def *outside = nir_fge(&b, nir_imm_float(&b, 0.0f), coverage);
nir_intrinsic_instr *discard =
nir_intrinsic_instr_create(state->shader,
nir_intrinsic_discard_if);
discard->src[0] = nir_src_for_ssa(outside);
nir_builder_instr_insert(&b, &discard->instr);
/* Clamp to at most 1.0. If it was less than 0.0 then the fragment will
* be discarded so we don’t need to handle that.
*/
nir_ssa_def *clamped = nir_fmin(&b, coverage, nir_imm_float(&b, 1.0f));
nir_store_var(&b, state->coverage, clamped, 0x1 /* writemask */);
}
static nir_variable *
make_coverage_var(nir_shader *s)
{
nir_variable *var = nir_variable_create(s,
nir_var_shader_temp,
glsl_float_type(),
"line_coverage");
var->data.how_declared = nir_var_hidden;
return var;
}
void
v3d_nir_lower_line_smooth(nir_shader *s)
{
assert(s->info.stage == MESA_SHADER_FRAGMENT);
struct lower_line_smooth_state state = {
.shader = s,
.coverage = make_coverage_var(s),
};
nir_foreach_function(function, s) {
if (function->is_entrypoint)
initialise_coverage_var(&state, function->impl);
lower_line_smooth_func(&state, function->impl);
}
}
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