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

///
/// Used for rendering the distance from the camera to the object with this material in each pixel.
/// Can be used for debug purposes but is also used to create shadow maps from light sources.
///
#[derive(Default, Clone)]
pub struct DepthMaterial {
    /// The minimum distance from the camera to any object. If None, then the near plane of the camera is used.
    pub min_distance: Option<f32>,
    /// The maximum distance from the camera to any object. If None, then the far plane of the camera is used.
    pub max_distance: Option<f32>,
    /// Render states.
    pub render_states: RenderStates,
}

impl FromCpuMaterial for DepthMaterial {
    fn from_cpu_material(_context: &Context, _cpu_material: &CpuMaterial) -> Self {
        Self::default()
    }
}

impl Material for DepthMaterial {
    fn id(&self) -> u16 {
        0b1u16 << 15 | 0b10u16
    }

    fn fragment_shader_source(&self, _lights: &[&dyn Light]) -> String {
        include_str!("shaders/depth_material.frag").to_string()
    }

    fn fragment_attributes(&self) -> FragmentAttributes {
        FragmentAttributes {
            position: true,
            ..FragmentAttributes::NONE
        }
    }

    fn use_uniforms(&self, program: &Program, camera: &Camera, _lights: &[&dyn Light]) {
        program.use_uniform(
            "minDistance",
            self.min_distance.unwrap_or_else(|| camera.z_near()),
        );
        program.use_uniform(
            "maxDistance",
            self.max_distance.unwrap_or_else(|| camera.z_far()),
        );
        program.use_uniform("eye", camera.position());
    }

    fn render_states(&self) -> RenderStates {
        self.render_states
    }

    fn material_type(&self) -> MaterialType {
        MaterialType::Opaque
    }
}