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radv/rt: Reject hits within 10ULP of previous hits in emulated RT

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This is an alternative workaround that fixes double hits on shared edges
failing some watertightness CTS tests.

Fixes: e034ba1c44 ("radv/rt: Miss rays that hit the triangle's v edge")
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/24093>
This commit is contained in:
Friedrich Vock
2023-07-13 16:10:12 +02:00
committed by Marge Bot
parent f900b763b1
commit f8eec4c4e3
1 changed files with 17 additions and 8 deletions
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src/amd/vulkan/radv_rt_common.c
+17 -8
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@@ -258,13 +258,6 @@ intersect_ray_amd_software_tri(struct radv_device *device, nir_builder *b, nir_d
nir_def *cond = nir_inot(b, nir_iand(b, cond_back, cond_front));
/* If the ray is exactly on the edge where v is 0, consider it a miss.
* This seems to correspond to what the hardware is doing.
* Also, it avoids invoking hit shaders twice on a shared edge, which is
* discouraged by the spec.
*/
cond = nir_iand(b, cond, nir_fneu(b, v, nir_imm_float(b, 0.0f)));
nir_push_if(b, cond);
{
nir_def *det = nir_fadd(b, u, nir_fadd(b, v, w));
@@ -373,7 +366,9 @@ insert_traversal_triangle_case(struct radv_device *device, nir_builder *b, const
nir_def *div = nir_channel(b, result, 1);
intersection.t = nir_fdiv(b, intersection.t, div);
nir_push_if(b, nir_flt(b, intersection.t, nir_load_deref(b, args->vars.tmax)));
nir_def *tmax = nir_load_deref(b, args->vars.tmax);
nir_push_if(b, nir_flt(b, intersection.t, tmax));
{
intersection.frontface = nir_fgt_imm(b, div, 0);
nir_def *switch_ccw =
@@ -408,6 +403,20 @@ insert_traversal_triangle_case(struct radv_device *device, nir_builder *b, const
nir_def *divs[2] = {div, div};
intersection.barycentrics = nir_fdiv(b, nir_channels(b, result, 0xc), nir_vec(b, divs, 2));
nir_def *hit_t = intersection.t;
/* t values within 10 ULP of the current hit t are most likely duplicate hits along shared edges, which
* might occur with emulated RT. The Vulkan spec discourages double-hits along shared-edges, so reject them
* here by subtracting 10 ULP from t.
*/
if (radv_emulate_rt(device->physical_device)) {
nir_def *abs_t = nir_fabs(b, hit_t);
nir_def *sign_t = nir_fsign(b, hit_t);
nir_def *tm1 = nir_iadd(b, hit_t, nir_imul_imm(b, nir_f2i32(b, sign_t), -10));
nir_def *tm2 = nir_fmul(b, nir_isub_imm(b, 10, abs_t), nir_fneg(b, sign_t));
intersection.t = nir_bcsel(b, nir_ige_imm(b, abs_t, 10), tm1, tm2);
}
args->triangle_cb(b, &intersection, args, ray_flags);
}
nir_pop_if(b, NULL);