Creating recessed strip lighting

I am experimenting with a G warehouse model for a future job that will need recessed lighting. Using the 'create light fixture' I create a narrow rectangle for the entire length of the recess on all sides. however when rendering it seems to be rendered as spots rather than the whole length. Any thoughts?

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Permalink Reply by Render Plus on February 28, 2011 at 9:58am

Let it render for more passes. Points are randomly selected from the rectangular light for each pass, so it needs several passes to smooth out.

See:Cove Lighting

Here is a cove lighting example after 6 passes:

And after hundreds of passes:

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Permalink Reply by marco alvarez on February 28, 2011 at 9:59am

ok, many thanks

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Permalink Reply by marco alvarez on March 10, 2011 at 9:53am

I'm still not having any joy with this cove lighting. The image below has been rendered for 7 hours and 50 passes yet the lighting is still a long way from approaching completion and I simply dont have the time to wait that long for this job. Where am i going wrong or how can I speed up the process. This render attempt was only 800 pixels wide, imagine I attempted a high res version!

appreciate the help, thanks

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Permalink Reply by Render Plus on March 10, 2011 at 10:02am

How many passes did you get in 7 hours?

Also, right click the top of the render window and select statistics to see how many lights you have. Sometimes
lights placed on a surface in SketchUp will create too many physical lights.

Send the model to support@renderplus.com and we will try it here and see if we can improve it.

(For example, you can place more shorter lights in the cove to get them to process faster, or use more lights per pass. Still it is going to take some time to get a good rendering with recessed lighting)

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Permalink Reply by marco alvarez on March 10, 2011 at 10:23am

Only 50 passes in 7 hours. the statistics tell me 221 lights. the strip lights are rectangular lights, 4 of them placed on a surface in the recess on all 4 sides. Im not sure where the 221 lights comes from unless as you say it is creating many physical lights as apparent in the image above. I have sent the model file to the address provided

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Permalink Reply by Render Plus on March 10, 2011 at 10:59am

It turns out that this lamp is processed as 26 lights. (There are 8 in the model, even though only two are visible in this room) Each triangle of theround lamp surface is being created as a separate light. (This is not your problem, and we will try to fix it. Sometimes are we read the individual parts of a SketchUp surface we wind up thinking they are not connected and creating too many "lights")

I moved the 8 ceiling lights to a hidden layer, and placed two IRender nXt ceiling lights in the room. Then when I rendered it, I only have 15 "lights"

Then I set it to use 100% of the lights per pass. My pixel rendering is taking about 1 minute per pass

- So, a tip to speed up the rendering - if there are rooms in your model with lights which do not effect the current scene, place these rooms in layers which you can turn off. We have to process the lights even though the don't effect the scene because we can't be certain they do not effect the scene (some light could come from down a hall - or, heaven forbid, through a keyhole - so we have to waste time processing the other lights.

Here is the result after 3 passes and 3 minutes. I will post another image, with more passes, later.

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Permalink Reply by Render Plus on March 10, 2011 at 11:16am

Also, the Path Tracer (a rendering engine option different than Packet Mode) seems to process the recessed light better, but will also take a lot of passes to resolve.

Here is a Path Tracer result after 5 passes and 5 minutes - the lights are smoother - but it will take an hour or two for it to make a good image. (The path tracer processes light for eack pixel individually - from a random direction - so it take many passes before it starts to converge into a good image)

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Permalink Reply by Render Plus on March 10, 2011 at 3:55pm

Here is the Path Tracer after 190 passes and about 3 hours:

Here is Packet mode after 340 passes and 3 hours (on a faster CPU):

They would both look pretty good after another 3 hours or so.

We will try to fix the problem with your original light, so you can use it in the future.

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Permalink Reply by Render Plus on March 11, 2011 at 8:36am

I have started a separate thread about how to use omni-directional rather then diffuse lighting for the ceiling lamp to cut down on the number of "lights" which are created by each ceiling lamp

Diffuse vs OmniDirectional lighting

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Permalink Reply by Render Plus on March 11, 2011 at 8:59am

Here is a rendering with the new ceiling lamps after 14 passes:

It will still need many more passes to resolve the cove lights, but it is running much faster with the new ceiling lights.

Roy adds some tips:

1. The cove lights will converge faster if you place multiple, shorter faces in the recessed ceiling.

(If you place 8 0.50 meter faces, rather than 1 4.00 meter face, than 8 lights will be used per pass rather than 1 - this will make the recessed lghts smooth out faster. nWith more lights each pass will take longer - but you will need fewer passes)

2. The Path Tracer might work better for this scene.

3.Make sure glossy materials are tagged as glossy.

"Glossy" causes a surface to have highlights from lighting, but to not reflect other things in it. It will help a scene render faster because it does not have to process direct reflection. See: Glossy Materials

(Teapot with Glossy reflection - light is highlighted, but other items are not reflected):