I think it was Micha who originally came up with the clever idea for faking IES lights and Andeciuala who mastered
it for SU, so all credit goes to them, but it still took me about 3 days of experimenting before I got satisfactory
results for faking IES so I thought I’d document the process here in T,T & T.
Andeciuala’s thread which covers the basics and has some excellent transparency maps to start with is here:
a) Editing transparency maps in PS for different effects.
b) Making six distinct recessed luminaire components which could be placed in the ceiling of any model.
c) Reducing poly count while also reducing light leaks.
The main trick to this method turned out to be using a 0,0,0 black material on all faces of the luminaire which couldn’t be seen. The reflector doesn’t actually focus any light, so it’s just a 12 sided cone with white material applied to bounce as much light out as possible without creating artefacts/splotches (as a mirror material would). I also intersected some faces so rather than meeting perfectly with the ceiling they continued through it for 2mm (notice the inner edge of the luminaire extends slightly above the outer edge). These two tricks reduced light leaks enormously which can be a major problem when using high intensity omnis within very small geometry. This in turn allows you to keep your visopt settings pretty fast.
For clarity the attached sections show a regular (but scaled down) VfSU omni light inside the luminaire, but this presents a problem: how do you get at the VfSU omni to edit it’s settings? In my actual components I solved this problem by editing the geometry inside the VfSU omni component as the polyhedron geometry inside a VfSU omni component doesn’t actually do anything other than give you something to see and grab onto in SU. I edited it so rather than the default coloured polyhedron you see in the images below I have an upside-down pyramid, with its point at the dead centre of the VfSU omni component. The reason for editing the standard VfSU omni polyhedron is that it allows you to easily select the VfSU omni from above the ceiling (as the “base” of the upside-down pyramid extends well above the reflector cone) for editing intensity, decay, etc, but none of the omni is visible below the ceiling which would make for an ugly SU model (ceiling with big omni balls all over it).
I also added SU text to each VfSU omni stating what the intensity and decay was so that it’s easy to keep track of settings, but that’s not really necessary. You can also then adjust the “focus” of each luminaire by moving this omni up (tighter spot) or down (wider flood) within the component.
You can load any square texture into the SU material slot for the tranparency map of the luminaires as it will be overidden by the effect of the VfSU omni shining through the VfSU transparency map, but I chose to use a simple one with a dark dot at the centre so in the SU model it looks vaguely like a spotlight reflector. I created 6 clones of this SU material, called IES Map 1, IES Map 2, etc for each distinct luminaire component and then (even though they have identical diffuse maps) loaded different fake IES maps in the VfSU tranparency slot. This way I have six different IES patterns for six different luminaire components which can all be edited simultaneously by editing their respective VfSU material transparency maps.
You can easily create coloured lights by adjusting the colour settings for your VfSU omnis and you can create multi-coloured light patterns by editing the transparency maps in PS, see below. The only real limitation of these simple fake IES lights is that you can’t focus the light at a certain distance like you can with a real reflector or lense.
Phew, was that everthing? Not sure how much sense that all made. After all my experimenting I was actually a little irritated to hear that true IES lights will be supported in the next VfSU version LOL.
Here is my render with your maps and the cone like you have. I changed the radius of the omni light to .1 for some softer shadows. I think it looks pretty good. This was rendered for the IES effect.
