DeleD Community Edition

Paul-Jan

I am posting this not only as an answer to a question, but also as a reference for everyone that works with the DeleD Lightmapper.

In some other thread, not too long ago, Vampyre Dark posted a screenshot similar to the one below (you might notice how I removed most of the vases so that I didn't have to get coffee everytime I gave the lightmapper a testrun Razz

). Notice the black line of shadow along the skirtig (baseboard). Also notice how the black line discontinues underneath the window.

Unfortunately, this is not a bug in the lightmapper, but simply a shortcoming of the techniques used. The skirting casts a shadow on the back wall, and because of the low resolution of the lightmap, the shadow texel (one pixel on the lightmap) is actually bigger than the skirting. What you see is the edge of that texel.

Now why doesn't that happen on the wall below the window? Because that polygon is smaller, so the corresponding lightmap is smaller, so the shadow texel stays below the skirting. As a prove, here is the same screenshot, but now with the skirting removed:

Although rendering lightmaps at a higher (and dynamic) resolution makes this problem less pronounced, it won't go away completely. The only real solution is to adept your geometry. Don't stack your geometry, only model the faces that are actually visible. If you would remove the part of the wall that is hidden behind the skirting, the artifact would disappear.

Daaark · Posted: Thu Dec 09, 2004 2:13 pm Post subject:

Okay, question.

I would usually deleted all the unseen faces in my scenes. But when I made that, I left all the wall peices as boxes, because I figured I needed something to block the light from the outside.

In other lightmappers I have used, if the otherside of the wall wasn't there, the light would have shined right through. The 1 side of the wall wouldn't block it, because the normal was facing the other way. Is this the case with deled? If I had deled all the other faces of the wall, would it shine through the back?

The size of the faces was also never an issue, because they would be sliced to fit.

It would be nice to know all the little 'rules' of the Deled lightmapper. Nothing complex. Maybe just a list of do's and don'ts.

granada · Posted: Thu Dec 09, 2004 2:30 pm Post subject:

khris · Posted: Thu Dec 09, 2004 6:10 pm Post subject:

Paul-Jan · Posted: Thu Dec 09, 2004 8:33 pm Post subject:

The 'rules' is exactly why I started this thread, as issues come up I'll post things here. I actually don't know of any other rules atm, so that's why there is only one Smile

Don't get me wrong, you were right to include the outside facing polygons as well, because the DeleD lightmapper (don't shoot me on this one, I changed it a few times during development and I am rather sleepy at the moment) also does 'culling' intersection tests, as they are called.

In the example above however, you have _4_ layers of geometry instead of two. I'll try to explain things below using curley braces (yeah like that will make things any clearer Very Happy

):

khris · Posted: Thu Dec 09, 2004 10:45 pm Post subject:

yeh i kno what u mean PJ. just model all extruding surfaces like skirting boards or any object that overlaps another as a nice, easy to handle poly, instead of being lazy and jus sticking another cube over the front of the wall for example. im tired too so sorry if the interpretation sucks a little. maybe ur line drawings will help explain it better lol.

khris

Daaark · Posted: Fri Dec 10, 2004 5:27 am Post subject:

Paul-Jan · Posted: Fri Dec 10, 2004 3:24 pm Post subject:

*lol* I know you guys pretty much understand these kinda problems, I am trying to create a reference here for people that don't.

@Vampyre, if you find the time to create a screenshot and all, could you post it outside this thread? Because if it is the problem I think it is, it is a 'bug' (at least, an artifact that I believe might be fixable), and I want to reserve this thread for things that are problems that can not be solved in the code, so have to be taken into account by the modeller. But by all means, do POST the problem, I need all the problem-cases I can get my hands on.

Paul-Jan · Posted: Sun Dec 12, 2004 10:29 am Post subject:

Another feature/shortcoming of the lightmapping technique you might want to take into account while modelling:

A the moment, DeleD doesn't support 'normal groups', and lightmapping doesn't support normal smoothing. This makes the lightmapping ok for indoor scenes (you don't want light to be smoothed around the corners of a wall), but could be kinda bad for landscapes or curved surfaces. The light would change abrubtly from one face to the next.

This features will surely be added to the lightmapper at some point in the future, but I am not quite sure how the smoothing groups should be controlled by the user. Maybe it would even be enough to assume normals should always be smoothed, unless an angle is < 100 degrees or something.