1 /*
2 * Copyright © 2022 Advanced Micro Devices, Inc.
3 *
4 * Permission is hereby granted, free of charge, to any person obtaining a
5 * copy of this software and associated documentation files (the "Software"),
6 * to deal in the Software without restriction, including without limitation
7 * the rights to use, copy, modify, merge, publish, distribute, sublicense,
8 * and/or sell copies of the Software, and to permit persons to whom the
9 * Software is furnished to do so, subject to the following conditions:
10 *
11 * The above copyright notice and this permission notice (including the next
12 * paragraph) shall be included in all copies or substantial portions of the
13 * Software.
14 *
15 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
16 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
17 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
18 * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
19 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
20 * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
21 * IN THE SOFTWARE.
22 */
23
24 #include "nir.h"
25 #include "nir_builder.h"
26 #include "nir_builtin_builder.h"
27
28 /**
29 * This NIR lowers pass for point smoothing by modifying the alpha value of
30 * fragment outputs using the distance from the center of the point.
31 * Anti-aliased points get rounded with respect to their radius.
32 */
33
34 static bool
lower_point_smooth(nir_builder * b,nir_intrinsic_instr * intr,UNUSED void * _state)35 lower_point_smooth(nir_builder *b, nir_intrinsic_instr *intr,
36 UNUSED void *_state)
37 {
38 if (intr->intrinsic != nir_intrinsic_store_output &&
39 intr->intrinsic != nir_intrinsic_store_deref)
40 return false;
41
42 int out_src_idx;
43 if (intr->intrinsic == nir_intrinsic_store_output) {
44 int location = nir_intrinsic_io_semantics(intr).location;
45 if ((location != FRAG_RESULT_COLOR && location < FRAG_RESULT_DATA0) ||
46 nir_intrinsic_src_type(intr) != nir_type_float32)
47 return false;
48 out_src_idx = 0;
49 } else {
50 nir_variable *var = nir_intrinsic_get_var(intr, 0);
51 if ((var->data.location != FRAG_RESULT_COLOR &&
52 var->data.location < FRAG_RESULT_DATA0) ||
53 glsl_get_base_type(var->type) != GLSL_TYPE_FLOAT)
54 return false;
55 out_src_idx = 1;
56 }
57
58 assert(intr->num_components == 4);
59
60 b->cursor = nir_before_instr(&intr->instr);
61
62 nir_def *coord = nir_load_point_coord_maybe_flipped(b);
63
64 /* point_size = 1.0 / dFdx(gl_PointCoord.x); */
65 nir_def *point_size = nir_frcp(b, nir_ddx(b, nir_channel(b, coord, 0)));
66
67 /* radius = point_size * 0.5 */
68 nir_def *radius = nir_fmul_imm(b, point_size, 0.5);
69 ;
70
71 /**
72 * Compute the distance of point from centre
73 * distance = √ (x - 0.5)^2 + (y - 0.5)^2
74 */
75 nir_def *distance = nir_fast_distance(b, coord,
76 nir_imm_vec2(b, 0.5, 0.5));
77 distance = nir_fmul(b, distance, point_size);
78
79 /* alpha = min(max(radius - distance, 0.0), 1.0) */
80 nir_def *coverage = nir_fsat(b, nir_fsub(b, radius, distance));
81
82 /* Discard fragments that are not covered by the point */
83 nir_discard_if(b, nir_feq_imm(b, coverage, 0.0f));
84
85 /* Write out the fragment color*vec4(1, 1, 1, coverage)*/
86 nir_def *one = nir_imm_float(b, 1.0f);
87 nir_def *new_val = nir_fmul(b, nir_vec4(b, one, one, one, coverage),
88 intr->src[out_src_idx].ssa);
89 nir_src_rewrite(&intr->src[out_src_idx], new_val);
90
91 return true;
92 }
93
94 bool
nir_lower_point_smooth(nir_shader * shader)95 nir_lower_point_smooth(nir_shader *shader)
96 {
97 assert(shader->info.stage == MESA_SHADER_FRAGMENT);
98 return nir_shader_intrinsics_pass(shader, lower_point_smooth,
99 nir_metadata_loop_analysis |
100 nir_metadata_block_index |
101 nir_metadata_dominance,
102 NULL);
103 }
104