76 lines
2.8 KiB
HLSL
76 lines
2.8 KiB
HLSL
#ifndef UNITY_PHYSICAL_CAMERA_INCLUDED
|
|
#define UNITY_PHYSICAL_CAMERA_INCLUDED
|
|
|
|
// Has to be kept in sync with ColorUtils.cs
|
|
|
|
// References:
|
|
// "Moving Frostbite to PBR" (Sebastien Lagarde & Charles de Rousiers)
|
|
// https://seblagarde.files.wordpress.com/2015/07/course_notes_moving_frostbite_to_pbr_v32.pdf
|
|
// "Implementing a Physically Based Camera" (Padraic Hennessy)
|
|
// https://placeholderart.wordpress.com/2014/11/16/implementing-a-physically-based-camera-understanding-exposure/
|
|
|
|
float ComputeEV100(float aperture, float shutterSpeed, float ISO)
|
|
{
|
|
// EV number is defined as:
|
|
// 2^ EV_s = N^2 / t and EV_s = EV_100 + log2 (S /100)
|
|
// This gives
|
|
// EV_s = log2 (N^2 / t)
|
|
// EV_100 + log2 (S /100) = log2 (N^2 / t)
|
|
// EV_100 = log2 (N^2 / t) - log2 (S /100)
|
|
// EV_100 = log2 (N^2 / t . 100 / S)
|
|
return log2((aperture * aperture) / shutterSpeed * 100.0 / ISO);
|
|
}
|
|
|
|
float ComputeEV100FromAvgLuminance(float avgLuminance, float calibrationConstant)
|
|
{
|
|
const float K = calibrationConstant;
|
|
return log2(avgLuminance * 100.0 / K);
|
|
}
|
|
|
|
float ComputeEV100FromAvgLuminance(float avgLuminance)
|
|
{
|
|
// We later use the middle gray at 12.7% in order to have
|
|
// a middle gray at 18% with a sqrt(2) room for specular highlights
|
|
// But here we deal with the spot meter measuring the middle gray
|
|
// which is fixed at 12.5 for matching standard camera
|
|
// constructor settings (i.e. calibration constant K = 12.5)
|
|
// Reference: http://en.wikipedia.org/wiki/Film_speed
|
|
const float K = 12.5; // Reflected-light meter calibration constant
|
|
return ComputeEV100FromAvgLuminance(avgLuminance, K);
|
|
}
|
|
|
|
float ConvertEV100ToExposure(float EV100, float exposureScale)
|
|
{
|
|
// Compute the maximum luminance possible with H_sbs sensitivity
|
|
// maxLum = 78 / ( S * q ) * N^2 / t
|
|
// = 78 / ( S * q ) * 2^ EV_100
|
|
// = 78 / (100 * s_LensAttenuation) * 2^ EV_100
|
|
// = exposureScale * 2^ EV
|
|
// Reference: http://en.wikipedia.org/wiki/Film_speed
|
|
float maxLuminance = exposureScale * pow(2.0, EV100);
|
|
return 1.0 / maxLuminance;
|
|
}
|
|
|
|
float ConvertEV100ToExposure(float EV100)
|
|
{
|
|
const float exposureScale = 1.2;
|
|
return ConvertEV100ToExposure(EV100, exposureScale);
|
|
}
|
|
|
|
float ComputeISO(float aperture, float shutterSpeed, float targetEV100)
|
|
{
|
|
// Compute the required ISO to reach the target EV100
|
|
return ((aperture * aperture) * 100.0) / (shutterSpeed * pow(2.0, targetEV100));
|
|
}
|
|
|
|
float ComputeLuminanceAdaptation(float previousLuminance, float currentLuminance, float speedDarkToLight, float speedLightToDark, float deltaTime)
|
|
{
|
|
float delta = currentLuminance - previousLuminance;
|
|
float speed = delta > 0.0 ? speedDarkToLight : speedLightToDark;
|
|
|
|
// Exponential decay
|
|
return previousLuminance + delta * (1.0 - exp2(-deltaTime * speed));
|
|
}
|
|
|
|
#endif // UNITY_PHYSICAL_CAMERA_INCLUDED
|