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/*
* Copyright © 2022 Advanced Micro Devices, Inc.
*
* 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 "nir.h"
#include "nir_builder.h"
#include "nir_builtin_builder.h"
/**
* This NIR lowers pass for point smoothing by modifying the alpha value of
* fragment outputs using the distance from the center of the point.
* Anti-aliased points get rounded with respect to their radius.
*/
static bool
lower_point_smooth(nir_builder *b, nir_instr *instr, UNUSED void *_state)
{
if (instr->type != nir_instr_type_intrinsic)
return false;
nir_intrinsic_instr *intr = nir_instr_as_intrinsic(instr);
if (intr->intrinsic != nir_intrinsic_store_output &&
intr->intrinsic != nir_intrinsic_store_deref)
return false;
int out_src_idx;
if (intr->intrinsic == nir_intrinsic_store_output) {
int location = nir_intrinsic_io_semantics(intr).location;
if ((location != FRAG_RESULT_COLOR && location < FRAG_RESULT_DATA0) ||
nir_intrinsic_src_type(intr) != nir_type_float32)
return false;
out_src_idx = 0;
} else {
nir_variable *var = nir_intrinsic_get_var(intr, 0);
if ((var->data.location != FRAG_RESULT_COLOR &&
var->data.location < FRAG_RESULT_DATA0) ||
glsl_get_base_type(var->type) != GLSL_TYPE_FLOAT)
return false;
out_src_idx = 1;
}
assert(intr->src[out_src_idx].is_ssa);
assert(intr->num_components == 4);
b->cursor = nir_before_instr(&intr->instr);
nir_ssa_def *coord = nir_build_load_point_coord_maybe_flipped(b);
/* point_size = 1.0 / dFdx(gl_PointCoord.x); */
nir_ssa_def *point_size = nir_frcp(b, nir_fddx(b, nir_channel(b, coord, 0)));
/* radius = point_size * 0.5 */
nir_ssa_def *radius = nir_fmul_imm(b, point_size, 0.5);;
/**
* Compute the distance of point from centre
* distance = √ (x - 0.5)^2 + (y - 0.5)^2
*/
nir_ssa_def *distance = nir_fast_distance(b, coord,
nir_imm_vec2(b, 0.5, 0.5));
distance = nir_fmul(b, distance, point_size);
/* alpha = min(max(radius - distance, 0.0), 1.0) */
nir_ssa_def *coverage = nir_fsat(b, nir_fsub(b, radius, distance));
/* Discard fragments that are not covered by the point */
nir_discard_if(b, nir_feq(b, nir_imm_float(b, 0.0f), coverage));
/* Write out the fragment color*vec4(1, 1, 1, coverage)*/
nir_ssa_def *one = nir_imm_float(b, 1.0f);
nir_ssa_def *new_val = nir_fmul(b, nir_vec4(b, one, one, one, coverage),
intr->src[out_src_idx].ssa);
nir_instr_rewrite_src(instr, &intr->src[out_src_idx], nir_src_for_ssa(new_val));
return true;
}
bool
nir_lower_point_smooth(nir_shader *shader)
{
assert(shader->info.stage == MESA_SHADER_FRAGMENT);
return nir_shader_instructions_pass(shader, lower_point_smooth,
nir_metadata_loop_analysis |
nir_metadata_block_index |
nir_metadata_dominance, NULL);
}
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