Currently, the double rendering option sets the top layer to become transparent in regions where the rendered quantity falls outside the colour bar, which is a hard cutoff. It would be nice to implement double rendering such that the top layer follows a "transparency/alpha bar" where the transparency scales with the rendered quantity.
An example use case is to indicate the hydrogen partial ionisation region on top of density as follows: Render density on the bottom layer (not necessarily with a grayscale colorbar), and render hydrogen ionisation fraction (between 0 and 1) on the top layer in some other colour, but with that colour fading away towards 0 and 1 so that the regions with ionisation fraction near 0.5 are most opaque.
Currently, the double rendering option sets the top layer to become transparent in regions where the rendered quantity falls outside the colour bar, which is a hard cutoff. It would be nice to implement double rendering such that the top layer follows a "transparency/alpha bar" where the transparency scales with the rendered quantity.
An example use case is to indicate the hydrogen partial ionisation region on top of density as follows: Render density on the bottom layer (not necessarily with a grayscale colorbar), and render hydrogen ionisation fraction (between 0 and 1) on the top layer in some other colour, but with that colour fading away towards 0 and 1 so that the regions with ionisation fraction near 0.5 are most opaque.