Rendering a scene

We show how to render a scene using different illuminants, and then we show how to render an HDR scene.

We generally think og rendering as calculating the CIE XYZ values for the spectral data. We do this by first calculating the radiance signal for the surfaces under daylight (think of this as color balancing) Then we calculate the xyz values and use an xyz to linear sRGB final step should be to pass the linear rgb into a display gamma lut

See also: hdrRender, sceneShowImage, sceneFromFile, scenePlot, ieReadSpectra, sceneAdjustIlluminant, scenePlot

Copyright ImagEval Consultants, LLC, 2012

Contents

ieInit

Read in the scene

wList = [400:10:700];
fullFileName = fullfile(isetRootPath,'data','images','multispectral','StuffedAnimals_tungsten-hdrs.mat');
scene = sceneFromFile(fullFileName ,'multispectral',[],[],wList);

% Have a look at the image (just mapping different spectral bands into rgb)
ieAddObject(scene); sceneWindow;

% Plot the illuminant
scenePlot(scene,'illuminant photons roi')

Reading multispectral data with mcCOEF.
Saved using svd method
No ROI needed unless spatial spectral illluminant

ans = 

  struct with fields:

       wave: [31×1 double]
    photons: [31×1 single]
    comment: 'tungsten illuminant in lab'

Transform the current illuminant to daylight

notice that daylight is defined only out to ~700 nm try to find a spectral power distribution for daylight out to 950 nm

% Read illuminant energy.
wave  = sceneGet(scene,'wave');
daylight = ieReadSpectra('D75.mat',wave);

% Adjust function.  In this case daylight is a vector of illuminant
% energies at each wavelength.
scene = sceneAdjustIlluminant(scene,daylight);
scene = sceneSet(scene,'illuminantComment','Daylight (D75) illuminant');

% Have a look
ieAddObject(scene); sceneWindow;
scenePlot(scene,'illuminant photons roi')

No ROI needed unless spatial spectral illluminant

ans = 

  struct with fields:

       wave: [31×1 double]
    photons: [31×1 single]
    comment: 'Daylight (D75) illuminant'

HDR

%The FX-Window data
fname = fullfile(isetRootPath,'data','images','multispectral','Feng_Office-hdrs.mat');
s = sceneFromFile(fname,'multispectral');
ieAddObject(s); sceneWindow;

srgb = sceneShowImage(s,0);
res = hdrRender(srgb);
vcNewGraphWin; imagesc(res); axis image; axis off

Reading multispectral data with mcCOEF.
Saved using svd method

Standard image

fname = fullfile(isetRootPath,'data','images','multispectral','StuffedAnimals_tungsten-hdrs.mat');
s = sceneFromFile(fname,'multispectral');
srgb = sceneShowImage(s,0);

res = hdrRender(srgb);
vcNewGraphWin; imagesc(res); axis image; axis off

Reading multispectral data with mcCOEF.
Saved using svd method

Published with MATLAB® R2024a