pbrt/src/lights/goniometric.rs

use crate::core::image::{Image, ImageIO, ImageMetadata};
use crate::core::light::{CreateLight, lookup_spectrum};
use crate::core::spectrum::spectrum_to_photometric;
use crate::core::texture::FloatTexture;
use crate::utils::sampling::PiecewiseConstant2D;
use crate::utils::{Arena, FileLoc, ParameterDictionary, resolve_filename};
use shared::core::image::ImageBase;
use shared::core::light::{Light, LightBase, LightType};
use shared::core::medium::{Medium, MediumInterface};
use shared::core::spectrum::Spectrum;
use shared::core::texture::SpectrumType;
use shared::lights::GoniometricLight;
use shared::spectra::RGBColorSpace;
use shared::utils::Transform;
use shared::utils::containers::Array2D;

impl CreateLight for GoniometricLight {
    fn new(
        render_from_light: Transform,
        medium_interface: MediumInterface,
        le: Spectrum,
        scale: shared::Float,
        shape: Option<shared::utils::Ptr<Shape>>,
        alpha: Option<shared::utils::Ptr<FloatTexture>>,
        image: Option<shared::utils::Ptr<Image>>,
        image_color_space: Option<shared::utils::Ptr<RGBColorSpace>>,
        two_sided: Option<bool>,
        fov: Option<shared::Float>,
    ) -> Self {
        let base = LightBase::new(
            LightType::DeltaPosition,
            render_from_light,
            medium_interface,
        );

        let iemit = lookup_spectrum(le);
        let d = image.unwrap().get_sampling_distribution_uniform();
        let distrib = PiecewiseConstant2D::new_with_data(d);
        Self {
            base,
            iemit,
            scale,
            image,
            distrib,
        }
    }

    fn create(
        arena: &mut Arena,
        render_from_light: Transform,
        medium: Medium,
        params: &ParameterDictionary,
        loc: &FileLoc,
        shape: &Shape,
        alpha_text: &FloatTexture,
        colorspace: Option<&RGBColorSpace>,
    ) -> Light {
        let i = params.get_one_spectrum(
            "I",
            colorspace.unwrap().illuminant,
            SpectrumType::Illuminant,
        );
        let lemit_data = lookup_spectrum(&i_spectrum_def);
        let sc = params.get_one_float("scale", 1.);
        let filename = resolve_filename(params.get_one_string("filename", ""));
        let mut image: Option<Image> = None;

        if filename.is_empty() {
            println!(
                "{}: Both \"L\" and \"filename\" specified for DiffuseAreaLight.",
                loc
            )
        } else {
            let im = Image::read(filename, None).expect("Could not load image");
            let loaded_img: Image = im.image;
            let res = loaded_img.resolution();
            let metadata: ImageMetadata = im.metadata;
            if loaded_img.has_any_infinite_pixels() {
                panic!(
                    "{:?}: Image '{}' has NaN pixels. Not suitable for light.",
                    loc, filename
                );
            }
            if res.x() != res.y() {
                panic!(
                    "{:?}: Image resolution ({}, {}) is non square. Unlikely that this is an equal area map.",
                    loc,
                    res.x(),
                    res.y(),
                    y()
                );
            }
            let rgb_desc = loaded_img.get_channel_desc(&["R", "G", "B"]);
            let y_desc = loaded_img.get_channel_desc(&["Y"]);
            if let Ok(rgb) = rgb_desc {
                if y_desc.is_ok() {
                    panic!(
                        "{:?}: Image '{}' has both RGB and Y channels. Ambiguous.",
                        loc, filename
                    );
                }

                let mut y_pixels = Vec::with_capacity((res.x * res.y) as usize);

                for y in 0..res.y {
                    for x in 0..res.x {
                        let r = loaded_img.get_channel(Point2i::new(x, y), 0);
                        let g = loaded_img.get_channel(Point2i::new(x, y), 1);
                        let b = loaded_img.get_channel(Point2i::new(x, y), 2);

                        y_pixels.push((r + g + b) / 3.0);
                    }
                }

                loaded_img = Some(Image::new(
                    PixelFormat::F32,
                    res,
                    &["Y"],
                    ColorEncoding::Linear,
                ));
            } else if y_desc.is_ok() {
                image = Some(loaded_img);
            } else {
                panic!(
                    "{:?}: Image '{}' has neither RGB nor Y channels.",
                    loc, filename
                );
            }
        }

        scale /= spectrum_to_photometric(&lemit_data);
        let phi_v = params.get_one_float("power", -1.0);

        if phi_v > 0.0 {
            if let Some(ref img) = image {
                let mut sum_y = 0.0;
                let res = img.resolution();

                for y in 0..res.y {
                    for x in 0..res.x {
                        sum_y += img.get_channel(Point2i::new(x, y), 0);
                    }
                }

                let k_e = 4.0 * PI * sum_y / (res.x * res.y) as Float;
                scale *= phi_v / k_e;
            }
        }

        let swap_yz: [Float; 16] = [
            1., 0., 0., 0., 0., 0., 1., 0., 0., 1., 0., 0., 0., 0., 0., 1.,
        ];
        let t = Transform::from_flat(swap_yz);
        let final_render_from_light = render_from_light * t;

        let d: Array2D<Float> = image.get_sampling_distribution();
        distrib = PiecewiseConstant2D::new_with_data(d);

        let specific = GoniometricLight::new(
            render_from_light,
            medium_interface,
            le,
            scale,
            None,
            None,
            Some(image),
            None,
            None,
            None,
        );

        Light::Goniometric(specific)
    }
}