domalicious

thats right, don't take any guff from that swine...

Scripto Saturday night special. Get it whiles it's hot. I decided to write a skylight generator. "What's a skylight generator? and what will it do for me?" I hear you all bay. Well if you shut your yap for five seconds I'll tell you!

Now, a skylight generator is a tool that allows you to light your scene using information from a bitmap. The wholes scene is surrounded by a hemisphere of light, each light getting it's colour and brightness information from the bitmap. It gives your renders a radiosity like look for next to no cost. When I say radiosity I mean the flattened diffusy kinda look. But lest break it down into pro's and con's.

What it's not :-

A way to light your scene in five seconds that requires no talent. You will still need to key light your scene, and that takes time and knowledge. This merely provided a good base.

Any sort of "real" radiosity. It's just a big fudge with lots of lights using the standard renderer. You won't get any diffuse interreflection going on here.

A tool for all situations. It's main use is to make stuff outside look more like it's lit from the sky (ie, it's a skylight) it's no good for indoor scenes. Although you may be able to bodge an indoor look from a bitmap.

What it is :-

A way of generating complex ambient. You can make a much more subtle accurate ambient this way and still keep all your ambient setting black.

Funky and easy. There are some other scripts a bit like this one around. But I found them all too much hassle. This is small and easy to get good results out of. It's not a scene object but a utility that you call the renderer though. So it's easy to use it or not when you do a render.

You may be using another script for this at the moment, and if your getting on fine with that, then there will probably be no reason for you to change to this one. But if you like it's look and want to give it a try then all the better. I'm not trying to undermine other peoples work here. Just provide an alterative.

Installation a go-go

Read this bit, lest you cock it all up. The domelight consists of three scripts.

1.builddomelights.ms. This should live in a directory called "callbacks" which you will need to make inside your "UI" directory
2.Chugg_domelight.mcr This is the frontend and lives in your "UI\macroscripts" directory.
3.Chugg_global_setum.ms this is the global render structure used by the callback, it lives in your "stdplugs\stdscripts" directory.

When this is all done and you restart Max, you should find in your customize ui menu that there is a category called "Chugg's Tools". This is where you will find the domelight. I suggest that you put it in the render menu.

Thankyou for flying Chuggnut airways, we hope you have a pleasant flight

Just a quick guided tour of the interface.

A.This is your dome control section. It controls the size of the dome and how many light rows are placed in it. Lights are placed at regular intervals X distance apart. You can change X here as well with the spacing control. The build dome geometry does exactly what it says on the tin. The dome is reversed and base clipped for immediate use. This section also contains B. This is where you specify the bitmaps used on the dome.

As you can see you can add as many bitmaps as you like with a multiplier for each. To get an average effect change the multiplier to reflect the average of the number of bitmaps used ie, if using 2 bitmaps have each set to 0.5. For a more additive effect leave the multiplier at 1.0 or more. The colour will max out much quicker, but for all lights the colour is clamped at white with greater values increasing the light multiplier. So you can have a light that is brighter than white by stacking bitmaps together or putting their multipliers up. You can also see the size of each bitmap and a wee thumbnail (ahhhhh eesa widdle cootsy wootsy!) Double clicking on the bitmap in the list allows you to change it for another. Just close the window when all you bitmaps are selected.

Section C in the main window is all the light controls. All pretty standard, just like the usual light options. Also here is the exclude button. Press it to get this.....

Works just like the standard exclude dialogue.

Section D is, wait for it, the render section. When all your setting are done, press render to call the standard render dialogue up. The domlight will render only for the next render session. If you go to the render dialogue again or do a last render, the domelight will not be active. Call the renderer again from the render button on the main panel to get it to do a domelight render. This section also contains some useful info. Total light s to be made, amount of memory used by the shadow maps and the total average light colour from the bitmaps.

It's time to do some good

Well thats all the posturing out the way. Lets look at what it can do. These are all done (obviously) with the same simple scene. One key light set to overshoot and specular only. This is needed as the light from the dome, by design, has no real direction. So specular highlights need to be added

All that was really changed in all three were the bitmaps. The first uses two bitmaps in combination, (I think they were just two randomly chosen gradients in photoshop). The second two using one bitmap. All use a multiplier of around 3.0 except the third one which has a multiplier of 5.0. Don't be afraid to use quite a high multiplier. The light intensity as read from a bitmap will nearly always be much lower that you expect from looking at the map. All three also use a shadow map size of around 128, and in the order of 90 lights. Pre render setup time on my athlon 750Mhz was about three to four seconds. Render time was slowed by the fact I had raytraced reflections on two objects.

You may find that some of your images have patterns or faults in the shadows. This is mainly due to uneven light placement. You need to balance the spacing of the dome with the segments to provide an all round dome of light. If you have too many in the radial direction (spacing) and not enough in the vertical (segments) then you'll have gaps in your dome which will show up as shadows with harsh lines or gaps in.

Shadows with a small size will not always fit the bottom of angular objects that intersect. ie if you have a lot of boxy object resting on the floor, make sure that your map size is large enough, or after sampling the shadow will spill over or not meet up to the edge.

For environment map use the build dome button and place the same bitmap your using for light values on it. It's ready setup for this purpose. The UV's on the dome geometry match those of the light dome.

Better provide you with a link to this bad boy then....

Dome light

Domelight mini gallery