Ridiculously simple lighting problem

[johnke]

Hi guys… longtime lurker, firsttime poster.

I’m experimenting with the lighting in Blender, trying to get a column of light pouring in through a wall. With a spotlight coming through a hole in a wall (plane) and projecting onto a floor, it turns out okay. When I change the hole in the wall into a doorway, the light starts ‘bleeding’ around the base in a really nasty way.

I’ve played about with the Clipsta and Clipend settings, as well as Halo Step, but none seem to have an effect. I know this is a simple thing, but I just can’t figure it out.

Anyone got any suggestions?

[Spin]

I know exactly what you mean. I have had the same problems doing baseboards and kick plates. I don’t have a direct answer.

Download this BLEND file…
http://mysite.verizon.net/vze3nvj6/bfda/door.zip
Right-click and SAVE

It is your door, with some slight lighting modification. I hope you have a fast PC.

<EDIT>I decided to elaborate on this and will post a modified picture of the door later today

[z3r0_d]

decrease the bias option and/or give the wall some thickness

[johnke]

Spin: Thanks for the .blend! I’m looking to do something like this in an animation, and I don’t know if 5-minute render times are something I could really use right now. But it’s early days. And I’ll be picking apart your .blend for a while anyway

z3r0 d: Cheers - I extruded the back wall a little and got rid of that ‘bleeding’. Unfortunately, using ‘soft’ shadows, a little light creeps under the wall of the doorway (even with bias down as low as I can put it), which looks, well… slightly unnatural.

Still… it’s given me somewhere to start. Cheers, guys!

[Spin]

Okay, I had some fun with this doorway…

Click URL for big Picture…
http://mysite.verizon.net/vze3nvj6/Blender/forum/room001.jpg

Ambient Occulant setting was used here. Long time to render.
This image shows the doorway and room. I added walls behind the camera. These walls are out of view and have a high EMIT setting, to add some ambient glow. The color of the walls match the glowing lantern. The purpose for the silver ball is tpo let me see the light sources.

Click URL for big Picture…
http://mysite.verizon.net/vze3nvj6/Blender/forum/room002.jpg

No Ambient Occulant. Quick time to render.
This image is without the Ambient Occulant setting. I added a regular default lamp and set it bright enough to illuminate the room. This is a quicker way to render and to do your adjustments with meshes and textures, before you use the Ambient Occulant method (or Yafray too).

Final Picture

Ambient Occulant setting was used here. Long time to render
Final touches were made. I did not SMOOTH any of the wall meshes, because I find that the shadows from the outside light faded away and lost the night-time effect.
I also removed the EMIT effect from the walls hidden behind the camera, but forgot to change the color back to white (instead of matching the candle). This is not a bad thing though, it actually helps.

Commentary: I made the floor shiny, to let the outside sky be seen without actually seeing the sky. It is a cold color and feels like night time. The glowing lantern was added for some warm indoor visual effect and a way to brighten the room too. Notice that the light coming inside is RAY traced, yet has a soft shadow-edge on the floor near the arch. I positioned the light just right, taking advantage of the faded edging. The glowing lantern has a tiny spotlight aimed at the floor. I wish I could have used SMOOTHING on the walls and in the arch, but in this dim lighting, it is almost not needed. I beveled the edges and corners.

You can download this project here…
http://mysite.verizon.net/vze3nvj6/Blender/forum/Doorway.zip

UNZIP it to drive C, don’t change the sub-folder name.
It will look like this c:\zBlend_Door
If you don’t, then you will have to manually load the images for the stone floor and the wooden baseboards.

“It is a sloppy project, but I did it on the fly for fun”.

[Spin]

I was just checking back. I haven’t seen any follow-ups on that door yet.

Any progress yet?

[johnke]

Hey Spin,

I was playing with your .blend over the weekend and it all finally clicked with me. Now I’m getting some pretty good renders (with reasonable render times), so I can almost certainly use this process in my animation!

Thanks for all your help

[sundialsvc4]

When light leaks under a doorway, I usually just extend the plane of the wall right through the floor. Or put a small scrim in the middle of the wall to block the light.

“Practical” lighting effects like this (that is: you can see the light emitter as part of the on-screen set), including “a beam of light coming in through smoke,” can also be added as a composite-layer. (That definitely is how I would do “smokiness.”) This gives you a lot of control when you need it.

Another argument for compositing is: in my experience “the number and complexity of the lights is the main determinant of render-time.” Practical-lighting requirements are where a lot of that comes from. The time required to generate four composite layers, plus the insignificant amount of time required to composite them, can be much less than the time required to render them all in one pass. (And of course, each layer can now be tweaked individually.)