View Full Version : Baking global illumination highlights?

02-17-2003, 08:57 PM
So when I do bake global illumination according to the tutorials, my object starts at a default 100% white, and the darkest areas are colored in various shades of black and grey.

This is great to find the shadows of an object, but suppose I want to also bake the highlights on an object?

Now, this brings up a few questions. I suspect I could get more range of values with a HDRI (I know very little about HDRI and how it works, but I understand the general premise.) If you all can confirm to me that I can bake the highlights/raised areas of an object with a HDRI then my second question, is is HDRI manipulatable in photoshop?

I ask this because these images must be baked for games, so I don't so much need a HDRI as much as I need to compress the information into a standard LDRI.

I would be doing more exploring and less asking, but my few tests of baking/rendering a HDRI has resulted in a black image which dosen't help me at all. I'm not sure where to start to ensure that a HDRI gives me usable results.

Also, if I'm completely on the wrong track to be using a HDRI, somebody please tell me. All I want is a baked illumination map that will give me raised areas as well as shodows so I can apply it as a layer for a game engine.

Thanks for sitting through my rambling mess of a post. Any help appreciated.

02-18-2003, 04:35 AM
First, you can't bake a highlight (assuming you mean specular highlight) since it is camera angle dependant (same as bump and reflections)

Second, i have no experience baking HDRI, what you could though is trying to bake to RPF or FLX file (these support floating point and thus allow you to pass the 0-255 limit 8 bit images offer you)

02-18-2003, 07:52 AM
I'm not sure what you actually want to bake...the whole surface (color, illumination etc)?
If you bake everything you get an image that represents the final surface color, so where it would render 50% white the image is 50% white etc.

You can save baked surfaces as .hdr or LogLuv .tif to keep the dynamic range (don't know about FLX and RPF, actually i couldn't even find RPF in the list...)

But if you want to use it in games as anyway but find it hard to handle the lighting strength, you can edit the image within LW (i just found out it gets loaded in the render display :D newer really baked anything), so change the exposure etc and save it in any format you like.
Photoshop can not handle HDR images (unless i missed something)

btw, bumpmaps do get baked, only things that depend on the viewing angle obviously can't be baked.

02-18-2003, 10:09 AM
RPF is found under Image filter tab (Extended RPF/RLA Export), you can adjust the settings using the Deluxe RLA (not sure it does these settings on RPF aswell, come to think of it...ahwell, might try that later.)

As for FLX, i believe it is a native format to LW.

02-18-2003, 02:14 PM
I'd like to bake illumination. I do everything in layers, for post editing in photoshop, so I don't want everything baked down to one image map. Until I'm done working in photoshop that is.

As for exposure control... I found I could alter it by changing the color of the background... Makes sense, but even that's not what I need.

I dunno how to explain this... But you know how corners of objects pick up a highlight? It would seem to me that if I have a global illumination light that is recording my shadow information, it'd highlight all my sharp angles evenly... But like I said, GI seems only good for shadow information, so I'm adding the angle highlights in photoshop.

02-19-2003, 06:44 AM
I have a workaround to specular baking and will write a short tut on this, however, right now i have no web space (my server ditched me.)

I can tell you however to play around with gradients applied to the diffuse channel.
Set the input for these gradients to Light Incidence and choose the light you want to create speculars.
More specular sources mean more layers and gradients.

here's a setting:
Diffuse value, normal for your object in general (say 80%)
Open the Texture Editor on your diffuse and add a Layer.

Layer Type : Gradient
Blending mode : Additive
Layer Opacity : 100% or jazz it up for brighter spots (might give errors, have to find this out yet.)
Input Parameter : Light Incidence
Light : choose one

Gradient Parameters:

1: Value 100%, Alpha 0%, Parameter 0
2: Value 100%, Alpha 0%, Parameter 78 for example
3: Value 500%, Alpha 100%, Parameter 90 for example

Parameter 1 and 2 are Alpha so you can stack without screwing up your initial diffuse settings.
Parameter 2 and 3 define the specular.
Parameter 2 is where the specular begins (at its lowest value)
Parameter 3 is the brightest spot of your specular

Adjust 2 and 3 (Parameters) to get a bigger or smaller spot.
Moving 3 towards 2 gives a smaller rolloff and thus results in a sharper specular.

This technique even bakes the influence of bumpmaps (might require Raytracing)

This sofar is 'as is', i haven't tested too much with this yet and it is a workaround, thus might not always be sufficient...
I was writting a tut on this, but my server trashed my account...so until then i can't post anything (i might send it to NewTek though when it is finished...)

Hope this helped a bit

02-20-2003, 12:09 PM
Really slick Red. That'll work real nice when I have to bake environments. Not quite so good for global illuminated characters... I could create a fake global illumination rig to get the results necessary, but that's almost more trouble then it's worth.

Guess I'll stick with photoshoping in highlights for a while.

But thanks again Red, that's really usefull for environmental setups.