--- /dev/null
+/*
+ * 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);
+ }
+}
projects / mesa.git / commitdiff