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100 行
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using System;
using System.Collections.Generic;
using System.Linq;
namespace UnityEngine.Experimental.Rendering.HDPipeline
{
public class LightUtils
{
// Physical light unit helper
// All light unit are in lumen (Luminous power)
// Punctual light (point, spot) are convert to candela (cd = lumens / steradian)
// For our isotropic area lights which expect radiance(W / (sr* m^2)) in the shader:
// power = Integral{area, Integral{hemisphere, radiance * <N, L>}},
// power = area * Pi * radiance,
// radiance = power / (area * Pi).
// We use photometric unit, so radiance is luminance and power is luminous power
// Ref: Moving Frostbite to PBR
// Also good ref: https://www.radiance-online.org/community/workshops/2004-fribourg/presentations/Wandachowicz_paper.pdf
// convert intensity (lumen) to candela
public static float ConvertPointLightIntensity(float intensity)
{
return intensity / (4.0f * Mathf.PI);
}
// angle is the full angle, not the half angle in radiant
// convert intensity (lumen) to candela
public static float ConvertSpotLightIntensity(float intensity, float angle, bool exact)
{
return exact ? intensity / (2.0f * (1.0f - Mathf.Cos(angle / 2.0f)) * Mathf.PI) : intensity / Mathf.PI;
}
// angleA and angleB are the full opening angle, not half angle
// convert intensity (lumen) to candela
public static float ConvertFrustrumLightIntensity(float intensity, float angleA, float angleB)
{
return intensity / (4.0f * Mathf.Asin(Mathf.Sin(angleA / 2.0f) * Mathf.Sin(angleB / 2.0f)));
}
// convert intensity (lumen) to nits
public static float ConvertSphereLightIntensity(float intensity, float sphereRadius)
{
return intensity / ((4.0f * Mathf.PI * sphereRadius * sphereRadius) * Mathf.PI);
}
// convert intensity (lumen) to nits
public static float ConvertDiscLightIntensity(float intensity, float discRadius)
{
return intensity / ((discRadius * discRadius * Mathf.PI) * Mathf.PI);
}
// convert intensity (lumen) to nits
public static float ConvertRectLightIntensity(float intensity, float width, float height)
{
return intensity / ((width * height) * Mathf.PI);
}
// convert intensity (lumen) to nits
public static float CalculateLineLightIntensity(float intensity, float lineWidth)
{
//Line lights expect radiance (W / (sr * m^2)) in the shader.
//In the UI, we specify luminous flux (power) in lumens.
//First, it needs to be converted to radiometric units (radiant flux, W).
//Then we must recall how to compute power from radiance:
//radiance = differential_power / (differrential_projected_area * differential_solid_angle),
//radiance = differential_power / (differrential_area * differential_solid_angle * <N, L>),
//power = Integral{area, Integral{hemisphere, radiance * <N, L>}}.
//Unlike tube lights, our line lights have no surface area, so the integral becomes:
//power = Integral{length, Integral{sphere, radiance}}.
//For an isotropic line light, radiance is constant, therefore:
//power = length * (4 * Pi) * radiance,
//radiance = power / (length * (4 * Pi)).
return intensity / (4.0f * Mathf.PI * lineWidth);
}
public static void CalculateAnglesForPyramid(float aspectRatio, float spotAngle, out float angleA, out float angleB)
{
// Since the smallest angles is = to the fov, and we don't care of the angle order, simply make sure the aspect ratio is > 1
if (aspectRatio < 1.0f)
aspectRatio = 1.0f / aspectRatio;
angleA = spotAngle * Mathf.Deg2Rad;
var halfAngle = angleA * 0.5f; // half of the smallest angle
var length = Mathf.Tan(halfAngle); // half length of the smallest side of the rectangle
length *= aspectRatio; // half length of the bigest side of the rectangle
halfAngle = Mathf.Atan(length); // half of the bigest angle
angleB = halfAngle * 2.0f;
}
}
}