Cycles: support spread angle 0 for area lights
Ref: T87053
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blender-bot
2024-02-23 12:55:24 +01:00
Referenced by pull request #118584, Fix Cycles area light using MIS when the spread is zero Referenced by commit1d8ec32473
, Fix Cycles area light using MIS when the spread is zero Referenced by commit95d11b0d33
, Fix Cycles area light using MIS when the spread is zero
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@ -97,6 +97,11 @@ ccl_device float area_light_spread_attenuation(const float3 D,
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/* Model a soft-box grid, computing the ratio of light not hidden by the
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* slats of the grid at a given angle. (see D10594). */
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const float cos_a = -dot(D, lightNg);
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if (tan_half_spread == 0.0f) {
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/* cos(0.05°) ≈ 0.9999997 */
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/* The factor M_PI_F comes from integrating the radiance over the hemisphere */
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return (cos_a > 0.9999997f) ? M_PI_F : 0.0f;
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}
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const float sin_a = safe_sqrtf(1.0f - sqr(cos_a));
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const float tan_a = sin_a / cos_a;
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return max((tan_half_spread - tan_a) * normalize_spread, 0.0f);
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@ -128,8 +133,8 @@ ccl_device bool area_light_spread_clamp_light(const float3 P,
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const bool is_round = !(*sample_rectangle) && (*len_u == *len_v);
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/* Whether we should sample the spread circle. */
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bool sample_spread;
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if (is_round) {
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bool sample_spread = (r_spread == 0.0f);
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if (is_round && !sample_spread) {
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/* Distance between the centers of the disk light and the valid region circle. */
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const float dist = len(make_float2(spread_u, spread_v));
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@ -168,7 +173,7 @@ ccl_device bool area_light_spread_clamp_light(const float3 P,
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sample_spread = (spread_area < circle_area);
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}
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}
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else {
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else if (!is_round && !sample_spread) {
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/* Compute rectangle encompassing the circle that affects the shading point,
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* clamped to the bounds of the area light. */
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const float min_u = max(spread_u - r_spread, -*len_u * 0.5f);
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@ -210,6 +215,7 @@ ccl_device bool area_light_spread_clamp_light(const float3 P,
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}
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if (sample_spread) {
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*sample_rectangle = false;
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*lightP = *lightP + *axis_u * spread_u + *axis_v * spread_v;
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*len_u = r_spread * 2.0f;
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*len_v = r_spread * 2.0f;
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@ -280,9 +286,16 @@ ccl_device_inline bool area_light_sample(const ccl_global KernelLight *klight,
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P, &ls->P, sample_axis_u, sample_len_u, sample_axis_v, sample_len_v, randu, randv, true);
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}
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else {
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ls->P += ellipse_sample(
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sample_axis_u * sample_len_u * 0.5f, sample_axis_v * sample_len_v * 0.5f, randu, randv);
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ls->pdf = 4.0f * M_1_PI_F / (sample_len_u * sample_len_v);
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if (klight->area.tan_half_spread == 0.0f) {
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ls->pdf = 1.0f;
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}
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else {
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ls->P += ellipse_sample(sample_axis_u * sample_len_u * 0.5f,
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sample_axis_v * sample_len_v * 0.5f,
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randu,
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randv);
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ls->pdf = 4.0f * M_1_PI_F / (sample_len_u * sample_len_v);
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}
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}
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inplane = ls->P - old_P;
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}
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@ -313,7 +326,7 @@ ccl_device_inline bool area_light_sample(const ccl_global KernelLight *klight,
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ls->D, ls->Ng, klight->area.tan_half_spread, klight->area.normalize_spread);
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}
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if (!sample_rectangle) {
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if (!sample_rectangle && klight->area.tan_half_spread > 0) {
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ls->pdf *= lamp_light_pdf(Ng, -ls->D, ls->t);
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}
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@ -420,7 +433,10 @@ ccl_device_inline bool area_light_sample_from_intersection(
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ray_P, &light_P, sample_axis_u, sample_len_u, sample_axis_v, sample_len_v, 0, 0, false);
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}
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else {
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ls->pdf = 4.0f * M_1_PI_F / (sample_len_u * sample_len_v) * lamp_light_pdf(Ng, -ray_D, ls->t);
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ls->pdf = klight->area.tan_half_spread == 0.0f ?
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1.0f :
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4.0f * M_1_PI_F / (sample_len_u * sample_len_v) *
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lamp_light_pdf(Ng, -ray_D, ls->t);
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}
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ls->eval_fac = 0.25f * invarea;
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@ -429,12 +445,9 @@ ccl_device_inline bool area_light_sample_from_intersection(
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/* Area Light spread angle attenuation */
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ls->eval_fac *= area_light_spread_attenuation(
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ls->D, ls->Ng, klight->area.tan_half_spread, klight->area.normalize_spread);
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if (ls->eval_fac == 0.0f) {
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return false;
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}
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}
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return true;
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return ls->eval_fac > 0;
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}
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template<bool in_volume_segment>
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@ -1038,9 +1038,10 @@ void LightManager::device_update_lights(Device *device, DeviceScene *dscene, Sce
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float invarea = (area != 0.0f) ? 1.0f / area : 1.0f;
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float3 dir = light->dir;
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/* Clamping to a minimum angle to avoid excessive noise. */
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const float min_spread = 1.0f * M_PI_F / 180.0f;
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const float half_spread = 0.5f * max(light->spread, min_spread);
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/* Clamp angles in (0, 0.1) to 0.1 to prevent zero intensity due to floating-point precision
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* issues, but still handles spread = 0 */
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const float min_spread = 0.1f * M_PI_F / 180.0f;
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const float half_spread = light->spread == 0 ? 0.0f : 0.5f * max(light->spread, min_spread);
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const float tan_half_spread = light->spread == M_PI_F ? FLT_MAX : tanf(half_spread);
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/* Normalization computed using:
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* integrate cos(x) * (1 - tan(x) / tan(a)) * sin(x) from x = 0 to a, a being half_spread.
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@ -472,7 +472,7 @@ static void rna_def_area_light(BlenderRNA *brna)
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prop = RNA_def_property(srna, "spread", PROP_FLOAT, PROP_ANGLE);
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RNA_def_property_float_sdna(prop, NULL, "area_spread");
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RNA_def_property_range(prop, DEG2RADF(1.0f), DEG2RADF(180.0f));
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RNA_def_property_range(prop, DEG2RADF(0.0f), DEG2RADF(180.0f));
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RNA_def_property_ui_text(
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prop,
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"Spread",
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