How do I use the basecurve in Darktable to make sure that the final output is linear? That is, if the irradiance E is received at the front lens, I want the pixel values in the final values to be k*E, where k is constant. Does the default curve compensate for any non-linearities, or is the input already assumed to be linear, so the curve should be used to create a certain look?
The purpose of the images are for textures, and I want to have a linear workflow all the way until the final render, where the appropriate curves should be applied.
In other words, a non-tonemapped image is required, such that the image may be used in other programs that expect linear images.