gemini-engine 1.2.0

A 2D/3D monospaced ASCII rendering engine for the terminal
Documentation 
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use crate::mesh3d::Vec3D;

/// Characters for brightness. The first character is the darkest and the last character is the brightest
pub const BRIGHTNESS_CHARS: &str = ".,-~:;=!*(%#$@";

/// Type of light, determines how the normal of a face affects its illumination
#[derive(Debug, Clone, Copy, PartialEq)]
pub enum LightType {
    /// Lights the entire scene equally. It's good to have at least one of these so your models don't go completely dark.
    Ambient,

    /// Lights the scene from a specific direction. A surface facing the specified direction will be lit with the most intensity and a surface facing away from the direction will be lit with the least intensity or no intensity at all
    Directional {
        /// The direction the light is pointing
        direction: Vec3D,
    },

    /// Light comes from a postion in 3D space. This light type does not currently dissipate over distance, so can be represented with a single position
    Point {
        /// The position from which the light emanates
        position: Vec3D,
    },
}

/// A light object used to define a scene's lighting. Used by [`DisplayMode::Illuminated`](super::DisplayMode::Illuminated)
#[derive(Debug, Clone, Copy, PartialEq)]
pub struct Light {
    /// The type of light and the way it affects faces based on their normals
    pub light_type: LightType,
    /// The intensity of the light
    pub intensity: f64,
}

impl Light {
    /// Create a new ambient light
    #[must_use]
    pub const fn new_ambient(intensity: f64) -> Self {
        Self {
            light_type: LightType::Ambient,
            intensity,
        }
    }

    /// Create a new directional light
    #[must_use]
    pub const fn new_directional(intensity: f64, direction: Vec3D) -> Self {
        Self {
            light_type: LightType::Directional { direction },
            intensity,
        }
    }

    /// Create a new point light
    #[must_use]
    pub const fn new_point(intensity: f64, position: Vec3D) -> Self {
        Self {
            light_type: LightType::Point { position },
            intensity,
        }
    }

    fn calculate_intensity_for_direction(&self, normal: Vec3D, direction: Vec3D) -> f64 {
        let n_dot_l = normal.dot(direction);
        if n_dot_l > 0.0 {
            self.intensity * n_dot_l / (normal.length() * direction.length())
        } else {
            0.0
        }
    }

    /// Calculate the intensity of the light as it affects a surface with the given normal
    #[must_use]
    pub fn calculate_intensity(&self, point: Vec3D, normal: Vec3D) -> f64 {
        match self.light_type {
            LightType::Ambient => self.intensity,

            LightType::Directional { direction } => {
                self.calculate_intensity_for_direction(normal, direction)
            }

            LightType::Point { position } => {
                let direction = point - position;

                self.calculate_intensity_for_direction(normal, direction)
            }
        }
    }
}