maszyna/rendering/opengl46/opengl46sky.cpp

/*
This Source Code Form is subject to the
terms of the Mozilla Public License, v.
2.0. If a copy of the MPL was not
distributed with this file, You can
obtain one at
http://mozilla.org/MPL/2.0/.
*/

#include "stdafx.h"
#include "rendering/opengl46/opengl46sky.h"

#include <cstring>

#include "environment/skydome.h"
#include "model/Texture.h"
#include "utilities/Globals.h"
#include "utilities/utilities.h"

namespace
{

// irradiance of a radiance given as spherical harmonics, divided by pi (the units of the ambient light of the shading:
// under a uniform sky of radiance L it is L): the coefficients of band l are scaled by A_l / pi (Ramamoorthi, Hanrahan 2001)
float const SH_IRRADIANCE_BAND[3]{1.f, 2.f / 3.f, 0.25f};
int const SH_BAND[gl::SKY_SH_COEFFICIENTS]{0, 1, 1, 1, 2, 2, 2, 2, 2};
float const SH_Y00{0.282095f};
float const SH_Y1{0.488603f};
float const PI{3.14159265359f};

// real spherical harmonics of order 2 in a world space direction, in the order of light_common.glsl
std::array<float, gl::SKY_SH_COEFFICIENTS> sh_basis(glm::vec3 const &n)
{
	return {SH_Y00,
	        SH_Y1 * n.y,
	        SH_Y1 * n.z,
	        SH_Y1 * n.x,
	        1.092548f * n.x * n.y,
	        1.092548f * n.y * n.z,
	        0.315392f * (3.f * n.z * n.z - 1.f),
	        1.092548f * n.x * n.z,
	        0.546274f * (n.x * n.x - n.y * n.y)};
}

float luminance(glm::vec3 const &Color)
{
	return glm::dot(Color, glm::vec3{0.2126f, 0.7152f, 0.0722f});
}

glm::vec3 desaturate(glm::vec3 const &Color, float const Amount)
{
	return glm::mix(Color, glm::vec3{luminance(Color)}, Amount);
}

// the response of color.frag to the vertex colours of the dome, so the light taken from the dome is the light it shows
glm::vec3 sky_shoulder(glm::vec3 const &Color)
{
	float const knee{0.25f};
	float const range{0.95f - knee};
	auto const excess{glm::max(Color - glm::vec3{knee}, glm::vec3{0.f})};
	return glm::min(Color, glm::vec3{knee}) + range * (glm::vec3{1.f} - glm::exp(-excess / range));
}

// the atmosphere is calibrated against the old sky: these scales make a sky of the atmosphere, with the sun 15 to 60 degrees
// high on a clear day, as bright as the old Perez dome is drawn on average, and the ambient light and the sunlight as strong
// as the old ones, with the default ground albedo (measured on the tables worked out by the same shaders on a software
// renderer, see the notes of the plan, stage S2)
float const ATMOSPHERE_SKY_SCALE{16.f};
float const ATMOSPHERE_AMBIENT_SCALE{44.f};
float const ATMOSPHERE_SUN_SCALE{1.45f};
// sun elevations (degrees) between which the sky goes over from the old model (night, twilight) to the atmosphere. the
// atmosphere darkens at dusk much faster than the old model, which the rest of the lighting was tuned to
float const ATMOSPHERE_FADE_START{-6.f};
float const ATMOSPHERE_FADE_END{10.f};
// the shading scales the sunlight and the ambient light by these (light_common.glsl), so the light the sun gives the
// ground, in the units of the ambient light, is the diffuse colour times their ratio
float const SHADING_SUN_TO_AMBIENT{1.5f / 0.65f};

// parameters of the earth's atmosphere after Hillaire 2020 (km, 1/km)
glm::vec3 const RAYLEIGH_SCATTERING{5.802e-3f, 13.558e-3f, 33.1e-3f};
float const RAYLEIGH_SCALE_HEIGHT{8.f};
float const MIE_SCATTERING{3.996e-3f};
float const MIE_EXTINCTION{4.440e-3f};
float const MIE_SCALE_HEIGHT{1.2f};
float const MIE_ASYMMETRY{0.8f};
glm::vec3 const OZONE_ABSORPTION{0.650e-3f, 1.881e-3f, 0.085e-3f};
float const OZONE_ALTITUDE{25.f};
float const OZONE_HALF_WIDTH{15.f};
float const BOTTOM_RADIUS{6360.f};
float const TOP_RADIUS{6460.f};

} // namespace

opengl46_sky::~opengl46_sky()
{
	GLuint const tables[]{m_transmittance_table, m_multiscattering_table, m_skyview_table};
	for (auto const table : tables)
	{
		if (table != 0)
			glDeleteTextures(1, &table);
	}
}

GLuint opengl46_sky::create_table(GLsizei const Width, GLsizei const Height)
{
	GLuint table{0};
	glCreateTextures(GL_TEXTURE_2D, 1, &table);
	glTextureStorage2D(table, 1, GL_RGBA16F, Width, Height);
	glTextureParameteri(table, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
	glTextureParameteri(table, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
	glTextureParameteri(table, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE);
	glTextureParameteri(table, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE);
	float const black[4]{0.f, 0.f, 0.f, 0.f};
	glClearTexImage(table, 0, GL_RGBA, GL_FLOAT, black);
	return table;
}

void opengl46_sky::init()
{
	auto const make_compute = [](std::string const &Name) {
		gl::shader shader(Name);
		return std::make_unique<gl::program>(std::vector<std::reference_wrapper<const gl::shader>>{shader});
	};
	m_transmittance_program = make_compute("atmosphere_transmittance.comp");
	m_multiscattering_program = make_compute("atmosphere_multiscattering.comp");
	m_skyview_program = make_compute("atmosphere_skyview.comp");
	m_ambient_program = make_compute("atmosphere_ambient.comp");
	m_prefilter_program = make_compute("envmap_prefilter.comp");

	m_sky_ssbo = std::make_unique<gl::ssbo>(sizeof(gl::sky_data), gl::SKY_SSBO_BINDING);
	m_sky_ssbo->update(m_sky_data);
	m_atmosphere_ubo = std::make_unique<gl::ubo>(sizeof(gl::atmosphere_ubs), gl::ATMOSPHERE_UBO_BINDING);
	m_atmosphere_result_ssbo = std::make_unique<gl::ssbo>(sizeof(gl::atmosphere_result), gl::ATMOSPHERE_RESULT_SSBO_BINDING);

	m_transmittance_table = create_table(gl::ATMOSPHERE_TRANSMITTANCE_WIDTH, gl::ATMOSPHERE_TRANSMITTANCE_HEIGHT);
	m_multiscattering_table = create_table(gl::ATMOSPHERE_MULTISCATTERING_SIZE, gl::ATMOSPHERE_MULTISCATTERING_SIZE);
	m_skyview_table = create_table(gl::ATMOSPHERE_SKYVIEW_WIDTH, gl::ATMOSPHERE_SKYVIEW_HEIGHT);

	// a valid atmosphere for the sky shader from the start, the tables stay black until the first update
	m_atmosphere.rayleigh = glm::vec4{RAYLEIGH_SCATTERING, RAYLEIGH_SCALE_HEIGHT};
	m_atmosphere.mie = glm::vec4{MIE_SCATTERING, MIE_EXTINCTION, MIE_SCALE_HEIGHT, MIE_ASYMMETRY};
	m_atmosphere.ozone = glm::vec4{OZONE_ABSORPTION, OZONE_ALTITUDE};
	m_atmosphere.ground = glm::vec4{glm::vec3{Global.gfx_ambient_groundalbedo}, OZONE_HALF_WIDTH};
	m_atmosphere.sun_direction = glm::vec4{0.f, 1.f, 0.f, 0.f};
	m_atmosphere.bottom_radius = BOTTOM_RADIUS;
	m_atmosphere.top_radius = TOP_RADIUS;
	m_atmosphere.observer_radius = BOTTOM_RADIUS + 0.2f;
	m_atmosphere_ubo->update(m_atmosphere);
}

void opengl46_sky::bind()
{
	m_sky_ssbo->bind_base();
	m_atmosphere_ubo->bind_uniform();
	m_atmosphere_result_ssbo->bind_base();
}

opengl46_sky::sh_coefficients opengl46_sky::dome_directional(CSkyDome const &Skydome, glm::vec3 const &Ambient, glm::vec3 const &Sunlight, float const Sunheight) const
{
	sh_coefficients radiance{};
	auto const &vertices{Skydome.vertices()};
	auto const &colors{Skydome.colors()};
	// the vertices make a grid even in the elevation and the azimuth, so the solid angle of a vertex goes with the cosine of
	// its elevation. the bottom ring lies a little under the horizon and is taken as the horizon
	float totalweight{0.f};
	for (std::size_t i = 0; i < vertices.size() && i < colors.size(); ++i)
	{
		auto direction{glm::normalize(vertices[i])};
		// the dome darkens its colours towards the top and brightens the band above the horizon for the looks
		// (CSkyDome::RebuildColors), which would make the zenith almost black and the horizon the main source of light.
		// both are undone here, so the light comes from the sky the Perez model describes
		auto const height{std::max(direction.y, 0.05f)};
		auto const horizonband{std::clamp(1.f - height / 0.2f, 0.f, 1.f)};
		auto const looks{std::clamp(1.f - height * 0.75f, 0.25f, 1.f) * std::lerp(1.f, 1.5f + 0.75f * m_overcast, horizonband)};
		direction.y = std::max(direction.y, 0.f);
		direction = glm::normalize(direction);
		auto const weight{std::sqrt(std::max(1.f - direction.y * direction.y, 0.f))};
		auto const color{sky_shoulder(glm::pow(glm::max(colors[i] / looks, glm::vec3{0.f}), glm::vec3{2.2f}))};
		auto const basis{sh_basis(direction)};
		for (std::size_t c = 0; c < radiance.size(); ++c)
			radiance[c] += color * (basis[c] * weight);
		totalweight += weight;
	}
	if (totalweight <= 0.f)
		return {};
	for (auto &coefficient : radiance)
		coefficient *= 2.f * PI / totalweight;

	// the ground, lit by the sky and the sun, fills the lower hemisphere with uniform light (see atmosphere_ambient.comp).
	// the dome is in its own units: the light of the sky on an upward facing surface is taken to be the ambient light,
	// which converts the sunlight to them
	auto const up{sh_basis(glm::vec3{0.f, 1.f, 0.f})};
	glm::vec3 skyup{0.f};
	for (std::size_t c = 0; c < radiance.size(); ++c)
		skyup += radiance[c] * (SH_IRRADIANCE_BAND[SH_BAND[c]] * up[c]);
	auto const tosky{luminance(skyup) / std::max(luminance(Ambient), 1e-4f)};
	auto const groundradiance{Global.gfx_ambient_groundalbedo * (skyup + Sunlight * SHADING_SUN_TO_AMBIENT * std::max(Sunheight, 0.f) * tosky)};
	radiance[0] += groundradiance * (SH_Y00 * 2.f * PI);
	radiance[1] += groundradiance * (SH_Y1 * -PI);

	// to the irradiance, scaled so its average over all directions is the ambient light, channel by channel
	sh_coefficients directional{};
	glm::vec3 const average{radiance[0] * SH_Y00};
	auto const scale{Ambient / glm::max(average, glm::vec3{1e-4f})};
	for (std::size_t c = 1; c < radiance.size(); ++c)
		directional[c] = radiance[c] * SH_IRRADIANCE_BAND[SH_BAND[c]] * scale;
	return directional;
}

void opengl46_sky::update_atmosphere(glm::vec3 const &Sundirection)
{
	// aerosols grow with the turbidity the weather sets (3 clear .. 9 overcast)
	auto const turbidity{std::clamp(Global.fTurbidity, 3.f, 9.f)};
	auto const miescale{Global.gfx_atmosphere_haze * (1.f + 0.5f * (turbidity - 3.f))};
	glm::vec4 const medium{miescale, Global.gfx_ambient_groundalbedo, Global.gfx_atmosphere_altitude, 0.f};
	auto const mediumchanged{!m_tables_medium || *m_tables_medium != medium};
	// the sky-view table follows the sun when it moved by more than about a twentieth of a degree
	auto const sunchanged{!m_tables_sun || glm::dot(*m_tables_sun, Sundirection) < 0.9999995f};
	if (!mediumchanged && !sunchanged)
		return;

	m_atmosphere.mie = glm::vec4{MIE_SCATTERING * miescale, MIE_EXTINCTION * miescale, MIE_SCALE_HEIGHT, MIE_ASYMMETRY};
	m_atmosphere.ground = glm::vec4{glm::vec3{Global.gfx_ambient_groundalbedo}, OZONE_HALF_WIDTH};
	m_atmosphere.sun_direction = glm::vec4{Sundirection, 0.f};
	m_atmosphere.observer_radius = BOTTOM_RADIUS + std::max(Global.gfx_atmosphere_altitude, 0.f) * 0.001f + 0.001f;
	m_atmosphere_ubo->update(m_atmosphere);
	m_atmosphere_ubo->bind_uniform();
	m_atmosphere_result_ssbo->bind_base();

	m_atmosphere_timer.begin();
	if (mediumchanged)
	{
		glBindImageTexture(gl::ATMOSPHERE_TRANSMITTANCE_UNIT, m_transmittance_table, 0, GL_FALSE, 0, GL_WRITE_ONLY, GL_RGBA16F);
		m_transmittance_program->dispatch((gl::ATMOSPHERE_TRANSMITTANCE_WIDTH + 7) / 8, (gl::ATMOSPHERE_TRANSMITTANCE_HEIGHT + 7) / 8);
		glMemoryBarrier(GL_TEXTURE_FETCH_BARRIER_BIT | GL_SHADER_IMAGE_ACCESS_BARRIER_BIT);

		glBindTextureUnit(gl::ATMOSPHERE_TRANSMITTANCE_UNIT, m_transmittance_table);
		glBindImageTexture(gl::ATMOSPHERE_MULTISCATTERING_UNIT, m_multiscattering_table, 0, GL_FALSE, 0, GL_WRITE_ONLY, GL_RGBA16F);
		m_multiscattering_program->dispatch(gl::ATMOSPHERE_MULTISCATTERING_SIZE, gl::ATMOSPHERE_MULTISCATTERING_SIZE);
		glMemoryBarrier(GL_TEXTURE_FETCH_BARRIER_BIT | GL_SHADER_IMAGE_ACCESS_BARRIER_BIT);
	}

	glBindTextureUnit(gl::ATMOSPHERE_TRANSMITTANCE_UNIT, m_transmittance_table);
	glBindTextureUnit(gl::ATMOSPHERE_MULTISCATTERING_UNIT, m_multiscattering_table);
	glBindImageTexture(gl::ATMOSPHERE_SKYVIEW_UNIT, m_skyview_table, 0, GL_FALSE, 0, GL_WRITE_ONLY, GL_RGBA16F);
	m_skyview_program->dispatch((gl::ATMOSPHERE_SKYVIEW_WIDTH + 7) / 8, (gl::ATMOSPHERE_SKYVIEW_HEIGHT + 7) / 8);
	glMemoryBarrier(GL_TEXTURE_FETCH_BARRIER_BIT | GL_SHADER_IMAGE_ACCESS_BARRIER_BIT);

	glBindTextureUnit(gl::ATMOSPHERE_SKYVIEW_UNIT, m_skyview_table);
	m_ambient_program->dispatch(1);
	glMemoryBarrier(GL_BUFFER_UPDATE_BARRIER_BIT | GL_SHADER_STORAGE_BARRIER_BIT);
	m_atmosphere_timer.end();

	// the units the passes used are below the ones of the texture cache, which is told they changed
	for (GLuint unit : {gl::ATMOSPHERE_TRANSMITTANCE_UNIT, gl::ATMOSPHERE_MULTISCATTERING_UNIT, gl::ATMOSPHERE_SKYVIEW_UNIT})
		glBindTextureUnit(unit, 0);
	opengl_texture::reset_unit_cache();

	m_result_readback.push(*m_atmosphere_result_ssbo);
	m_tables_medium = medium;
	m_tables_sun = Sundirection;
}

void opengl46_sky::update(opengl46_light &Sunlight, glm::vec3 &Fogcolor, CSkyDome const &Skydome, glm::vec3 const &Sundirection, float const Sunangle)
{
	// the light the simulation set, which is kept where the atmosphere is not used
	glm::vec3 const oldambient{Sunlight.ambient};
	glm::vec3 const olddiffuse{Sunlight.diffuse};
	glm::vec3 const oldfog{Fogcolor};
	m_overcast = std::clamp(Global.Overcast, 0.f, 1.f);

	// atmosphere
	m_weight = 0.f;
	if (Global.gfx_atmosphere)
	{
		update_atmosphere(glm::normalize(Sundirection));
		gl::atmosphere_result result;
		if (m_result_readback.pop(&result))
			m_result = result;
		if (m_result)
			m_weight = glm::smoothstep(ATMOSPHERE_FADE_START, ATMOSPHERE_FADE_END, Sunangle);
	}

	sh_coefficients directional{};
	if (Global.gfx_ambient_sh)
	{
		// the dome changes with the sun, the weather and the light the simulation works out from them
		std::array<glm::vec4, 3> const key{glm::vec4{Sundirection, Sunlight.direction.y}, glm::vec4{oldambient, m_overcast}, glm::vec4{olddiffuse, Global.gfx_ambient_groundalbedo}};
		if (!m_dome_key || *m_dome_key != key)
		{
			m_dome_sh = dome_directional(Skydome, oldambient, olddiffuse, -Sunlight.direction.y);
			m_dome_key = key;
		}
		directional = m_dome_sh;
	}

	m_sunlight = olddiffuse;
	m_ambient = oldambient;
	m_fog = oldfog;
	m_sun_disc_color = glm::vec3{1.f};
	if (m_weight > 0.f)
	{
		auto const &result{*m_result};
		// the camera's white balance: the sun high in the sky is white
		auto const balance{1.f / glm::max(glm::vec3{result.zenith_transmittance}, glm::vec3{1e-3f})};
		m_white_balance = balance / std::max(luminance(balance), 1e-4f);

		// the atmosphere has no clouds: the overcast takes away the sunlight, greys the sky and evens out its light
		auto const sun{glm::vec3{result.sun_transmittance} * m_white_balance * (ATMOSPHERE_SUN_SCALE * Global.gfx_atmosphere_sun) * (1.f - 0.65f * m_overcast)};
		auto const ambientscale{ATMOSPHERE_AMBIENT_SCALE * Global.gfx_atmosphere_ambient};
		auto const ambient{desaturate(glm::vec3{result.radiance_sh[0]} * SH_Y00 * m_white_balance * ambientscale, 0.5f * m_overcast)};
		m_sky_scale = ATMOSPHERE_SKY_SCALE * Global.gfx_atmosphere_sky;
		auto const fog{desaturate(glm::vec3{result.horizon} * m_white_balance * m_sky_scale, 0.5f * m_overcast)};
		m_sky_flat_luminance = luminance(glm::vec3{result.average} * m_white_balance * m_sky_scale);

		m_sunlight = glm::mix(olddiffuse, sun, m_weight);
		m_ambient = glm::mix(oldambient, ambient, m_weight);
		m_fog = glm::mix(oldfog, fog, m_weight);
		auto const sundisc{glm::vec3{result.sun_transmittance} * m_white_balance};
		m_sun_disc_color = sundisc / std::max({sundisc.r, sundisc.g, sundisc.b, 1e-4f});

		if (Global.gfx_ambient_sh)
		{
			auto const evenness{1.f - 0.75f * m_overcast};
			for (std::size_t c = 1; c < directional.size(); ++c)
			{
				auto const atmosphere{desaturate(glm::vec3{result.radiance_sh[c]} * m_white_balance * (SH_IRRADIANCE_BAND[SH_BAND[c]] * ambientscale * evenness), 0.5f * m_overcast)};
				directional[c] = glm::mix(directional[c], atmosphere, m_weight);
			}
		}

		Sunlight.diffuse = glm::vec4{m_sunlight, Sunlight.diffuse.a};
		Sunlight.ambient = glm::vec4{m_ambient, Sunlight.ambient.a};
		Fogcolor = m_fog;
	}

	// directional part of the ambient light for the shading
	gl::sky_data skydata{};
	for (std::size_t c = 1; c < directional.size(); ++c)
		skydata.ambient_sh[c] = glm::vec4{directional[c] * Global.gfx_ambient_sh_strength, 0.f};
	if (!m_sky_data_uploaded || std::memcmp(&skydata, &m_sky_data, sizeof(skydata)) != 0)
	{
		m_sky_data = skydata;
		m_sky_ssbo->update(m_sky_data);
		m_sky_data_uploaded = true;
	}
}

void opengl46_sky::setup_sky(gl::model_ubs &Model) const
{
	glBindTextureUnit(gl::SKY_VIEW_TEX, m_skyview_table);
	Model.param[0] = glm::vec4{m_weight, m_sky_scale, 0.75f * m_overcast, m_sky_flat_luminance};
	Model.param[1] = glm::vec4{m_white_balance, 0.f};
}

glm::vec3 opengl46_sky::sun_disc_color(glm::vec3 const &Oldcolor) const
{
	return glm::mix(Oldcolor, m_sun_disc_color, m_weight);
}

void opengl46_sky::prefilter(gl::cubemap const &Source)
{
	if (!m_prefiltered)
	{
		m_prefiltered = std::make_unique<gl::cubemap>();
		m_prefiltered->alloc_levels(GL_RGBA16F, static_cast<int>(gl::ENVMAP_GGX_SIZE), static_cast<int>(gl::ENVMAP_GGX_LEVELS));
	}

	m_prefilter_timer.begin();
	Source.bind(GL_TEXTURE0 + gl::ENV_TEX);
	glActiveTexture(GL_TEXTURE0);
	for (std::size_t level = 0; level < gl::ENVMAP_GGX_LEVELS; ++level)
	{
		auto const size{static_cast<int>(gl::ENVMAP_GGX_SIZE >> level)};
		auto const roughness{gl::ENVMAP_GGX_ROUGHNESS_MIN + (1.f - gl::ENVMAP_GGX_ROUGHNESS_MIN) * static_cast<float>(level) / static_cast<float>(gl::ENVMAP_GGX_LEVELS - 1)};
		glBindImageTexture(0, *m_prefiltered, static_cast<GLint>(level), GL_TRUE, 0, GL_WRITE_ONLY, GL_RGBA16F);
		glProgramUniform1f(*m_prefilter_program, 0, roughness);
		glProgramUniform1i(*m_prefilter_program, 1, size);
		glProgramUniform1f(*m_prefilter_program, 2, static_cast<float>(gl::ENVMAP_SIZE));
		glProgramUniform1i(*m_prefilter_program, 3, 64);
		auto const groups{static_cast<GLuint>((size + gl::ENVMAP_GGX_GROUP_SIZE - 1) / gl::ENVMAP_GGX_GROUP_SIZE)};
		m_prefilter_program->dispatch(groups, groups, 6);
	}
	glMemoryBarrier(GL_TEXTURE_FETCH_BARRIER_BIT | GL_SHADER_IMAGE_ACCESS_BARRIER_BIT);
	m_prefilter_timer.end();
	glBindImageTexture(0, 0, 0, GL_FALSE, 0, GL_WRITE_ONLY, GL_RGBA16F);
	m_prefiltered_ready = true;
}

std::string opengl46_sky::info_times()
{
	std::string text;
	if (auto const time = m_atmosphere_timer.result())
		text += " atmosphere: " + to_string(static_cast<double>(*time) / 1000000.0, 3) + " ms\n";
	if (auto const time = m_prefilter_timer.result())
		text += " envmap ggx: " + to_string(static_cast<double>(*time) / 1000000.0, 3) + " ms\n";
	return text;
}

void opengl46_sky::draw_debug_ui()
{
	ImGui::Checkbox("directional ambient light (gfx.ambient.sh)", &Global.gfx_ambient_sh);
	ImGui::SliderFloat("directional strength", &Global.gfx_ambient_sh_strength, 0.f, 2.f);
	ImGui::SliderFloat("ground albedo", &Global.gfx_ambient_groundalbedo, 0.f, 1.f);
	ImGui::Checkbox("GGX prefiltered reflections (gfx.envmap.ggx)", &Global.gfx_envmap_ggx);
	ImGui::Checkbox("physical atmosphere (gfx.atmosphere)", &Global.gfx_atmosphere);
	ImGui::SliderFloat("sky", &Global.gfx_atmosphere_sky, 0.f, 4.f);
	ImGui::SliderFloat("ambient", &Global.gfx_atmosphere_ambient, 0.f, 4.f);
	ImGui::SliderFloat("sun", &Global.gfx_atmosphere_sun, 0.f, 4.f);
	ImGui::SliderFloat("haze", &Global.gfx_atmosphere_haze, 0.f, 8.f);
	ImGui::SliderFloat("altitude (m)", &Global.gfx_atmosphere_altitude, 0.f, 3000.f);
	ImGui::Text("atmosphere share %.2f%s", m_weight, (Global.gfx_atmosphere && !m_result) ? " (waiting for the first read back)" : "");
	ImGui::Text("sun %.3f %.3f %.3f", m_sunlight.r, m_sunlight.g, m_sunlight.b);
	ImGui::Text("ambient %.3f %.3f %.3f", m_ambient.r, m_ambient.g, m_ambient.b);
	ImGui::Text("fog %.3f %.3f %.3f", m_fog.r, m_fog.g, m_fog.b);
	ImGui::Text("up / down ambient %.3f / %.3f", luminance(m_ambient + glm::vec3{m_sky_data.ambient_sh[1]} * SH_Y1), luminance(m_ambient - glm::vec3{m_sky_data.ambient_sh[1]} * SH_Y1));
}