R2LightPositional.h File Reference

Functions and types related to positional lighting. More...

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Data Structures
struct	R2_light_positional_vectors_t
	Vectors used when calculating positional lighting. More...
struct	R2_light_positional_t
	A positional light type. More...

Functions
R2_light_positional_vectors_t	R2_lightPositionalVectors (const R2_light_positional_t light, const vec3 p, const vec3 n)
float	R2_lightPositionalAttenuation (const R2_light_positional_t light, const float distance)

Detailed Description

Functions and types related to positional lighting.

Definition in file R2LightPositional.h.

Function Documentation

R2_lightPositionalAttenuation()

float R2_lightPositionalAttenuation	(	const R2_light_positional_t	light,
		const float	distance
	)

Given a light at distance from the current point on the lit surface, calculate the amount of attenuation. The returned value is 1.0 for "no attenuation" and 0.0 for "fully attenuated".

Parameters

light	The light
distance	The distance from the light to the surface

Returns

An attenuation value in the range [0.0, 1.0]

Definition at line 78 of file R2LightPositional.h.

{
  float linear      = distance * light.inverse_range;
  float exponential = pow (linear, light.inverse_falloff);
  return 1.0 - clamp (exponential, 0.0, 1.0);
}

R2_lightPositionalVectors()

R2_light_positional_vectors_t R2_lightPositionalVectors	(	const R2_light_positional_t	light,
		const vec3	p,
		const vec3	n
	)

Calculate the vectors required to calculate positional lighting.

Parameters

light	The light parameters
p	The surface position (eye-space)
n	The surface normal (eye-space)

Returns

A set of lighting vectors

Definition at line 46 of file R2LightPositional.h.

{
  vec3 position_diff       = p - light.position;
  vec3 observer_to_surface = normalize (p);
  vec3 light_to_surface    = normalize (position_diff);
  vec3 surface_to_light    = -light_to_surface;
  float distance           = length (position_diff);

  return R2_light_positional_vectors_t (
    observer_to_surface,
    surface_to_light,
    light_to_surface,
    n,
    distance
  );
}