Light/reflection processing

Hi, We have made a component of 1 single square light and placed a grid underneath it that has a reflective material on it. As we render, only some of the pieces of the grid show up as reflecting. As more passes go by, more reflections show up. We were planning on using this in large models that are very slow to render, however we have no idea how many passes it would take before these fixtures are displayed properly. What is the best way to see as much of the lights & reflections in fewer passes? Ive attached images of our test at 10,30,& 50 passes. You can see that still not all parts are properly visible. The light processing was set at 100% with a minimum setting of default 5 (although we aren't quite sure what that "minimum" setting means.

10 passes

30 passes

50 passes

what would be the best way to handle using these fixtures without having the ability to render for many days.

Thanks for your help.

Alan

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Permalink Reply by Render Plus on May 9, 2012 at 3:17pm

The reason it takes multiple passes to show all the grid pieces as reflecting is that we sample a single, random point in the light during each pass to calculate the reflections - so it will take at least 36 passes (or more if you are not processing all lights on each pass. The default is only to process about 1/3rd of the lights per pass)

You had set lights per pass to 100% - which requires fewer passes, but takes longer per pass. The minimum of 5 is for cases where there are only say 3 lights - then it is probably not worth processing only 30% or one light per pass.

One approach here is to render just one light to get the reflective appearance you want, and then place the rendered image of the light on a square in the ceiling as the light. The image texture will have the appearance you want and will product light from the light places and less light from the darker parts of the image. (Yu could also render the entire ceiling once, and place it as an image on the ceiling marked as a light source for rendering the rest of the geometry)

Another way to handle this would be to make each square light grid into 36 smaller lights - but then each pass would take about 36 times longer. (This is probably not a good idea)

The real answer is that you simply need to give it enough passes.

You can also try the Path Tracer Engine rather than the Packet Engine. It will start showing the light and reflection much faster - but will still require hundreds of passes to process a scene like this.

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Permalink Reply by EHRC Arch. on May 10, 2012 at 7:15am

Thanks for the info. Do you have an example that we could see where someone has used the first method? Rendering the light/ceiling separate and placing its image as a light.

Also is there any user guide/manual for irender nxt that we could print out to have on hand that explains what all the settings and options for rendering acutally do?

Thanks

Alan