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use crate::core::*;
use crate::renderer::*;

///
/// A material that renders the isosurface defined by the voxel data in the [IsosurfaceMaterial::voxels] and the [IsosurfaceMaterial::threshold].
/// The surface is defined by all the points in the volume where the red channel of the voxel data is equal to the threshold.
/// This material should be applied to a cube with center in origo, for example [CpuMesh::cube].
///
#[derive(Clone)]
pub struct IsosurfaceMaterial {
    /// The voxel data that defines the isosurface.
    pub voxels: std::rc::Rc<Texture3D>,
    /// Threshold (in the range [0..1]) that defines the surface in the voxel data.
    pub threshold: f32,
    /// Base surface color. Assumed to be in linear color space.
    pub color: Color,
    /// A value in the range `[0..1]` specifying how metallic the surface is.
    pub metallic: f32,
    /// A value in the range `[0..1]` specifying how rough the surface is.
    pub roughness: f32,
    /// The size of the cube that is used to render the voxel data. The texture is scaled to fill the entire cube.
    pub size: Vec3,
    /// The lighting model used when rendering this material
    pub lighting_model: LightingModel,
}

impl Material for IsosurfaceMaterial {
    fn fragment_shader_source(&self, _use_vertex_colors: bool, lights: &[&dyn Light]) -> String {
        let mut output = lights_shader_source(lights, self.lighting_model);
        output.push_str(include_str!("shaders/isosurface_material.frag"));
        output
    }
    fn use_uniforms(
        &self,
        program: &Program,
        camera: &Camera,
        lights: &[&dyn Light],
    ) -> ThreeDResult<()> {
        for (i, light) in lights.iter().enumerate() {
            light.use_uniforms(program, i as u32)?;
        }
        program.use_uniform("cameraPosition", camera.position())?;
        program.use_uniform("surfaceColor", self.color)?;
        program.use_uniform("metallic", self.metallic)?;
        program.use_uniform_if_required("roughness", self.roughness)?;
        program.use_uniform("size", self.size)?;
        program.use_uniform("threshold", self.threshold)?;
        program.use_uniform(
            "h",
            vec3(
                1.0 / self.voxels.width() as f32,
                1.0 / self.voxels.height() as f32,
                1.0 / self.voxels.depth() as f32,
            ),
        )?;
        program.use_texture_3d("tex", &self.voxels)
    }
    fn render_states(&self) -> RenderStates {
        RenderStates {
            blend: Blend::TRANSPARENCY,
            ..Default::default()
        }
    }
    fn is_transparent(&self) -> bool {
        true
    }
}

impl FromCpuVoxelGrid for IsosurfaceMaterial {
    fn from_cpu_voxel_grid(context: &Context, cpu_voxel_grid: &CpuVoxelGrid) -> ThreeDResult<Self> {
        Ok(Self {
            voxels: std::rc::Rc::new(Texture3D::new(&context, &cpu_voxel_grid.voxels)?),
            lighting_model: LightingModel::Blinn,
            size: cpu_voxel_grid.size,
            threshold: 0.15,
            color: Color::WHITE,
            roughness: 1.0,
            metallic: 0.0,
        })
    }
}