Area Lamps and Sun Lamps

I wonder if anyone can help…

I’ve run into a problem with rendering lamps. I have a daylight scene, interior shot, a sun lamp giving lovely crisp shadows. When I introduce a number of small area lamps (not mesh lamps, as these show up on the render either directly or in reflections) it seems to reduce the sun lamp’s importance, as my strong sunlight is gone!!! When I remove the area lights, the sunlight comes back.

I have already tried a simplified test scene to see if the problem is duplicated on a fresh blend file and it does. Basically put, the more mesh lights you use, the less light the camera seems to pick up from the sun.

Is there any workaround anyone knows for this?

Many many thanks in advance for your help!

R

Put all objects on two scene layers. Put area lamps on only one of these two scene layers and sun lamp on both (done via the relations tab in the Object properties buttons via selecting multiple layers via the “Layers:” field). In the compositor you’ll need two render layers. Your main render layer will be set to render the scene layer containing all objects and lights. This render layer needs only the combined pass enabled. You’ll also need to cli8ck the camera icon next to the shadow pass in order to exclude shadows from the combined pass. The second render layer will be set to render the scene layer containing all objects but only the sun lamp. This render layer needs only the shadow pass enabled. Now add a mix node to the compositor and set it to multiply with a factor of 1.0. Add the Combined pass render layer to the top image slot and the shadow only render layer to the bottom slot connect the result to the composite node and render away.

There you have it.

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Sometimes I think of lamp energy as a total. So if I have 1 lamp in the scene it gets 1.0 if I have two lamps in the scene I set each lamp’s energy to 0.5, etc…

You can also come up with other math formulas like say the Sun gets 0.5 of all lighting, then the other 0.5 is divided among the remaining lights.

Compositing is a great way to manage lighting, as is a combination of both light-lamps and shadow-only lamps.

First, establish by some means the “basic” lighting; what contributes about 75% to 80% of the light; the “ambiance.” Use a lighting scheme that doesn’t cast shadows.

Then, add additional lights, set relatively low,which either add light to that baseline value, or, as the case may be, subtract it.

This lets you put the highlights where you want them, and the (largely, fake) shadows where you want them also.

Use render-layers as previously described. The three components of the lighting (“zero,” “plus,” and “minus,” are now three separate and isolated channels of data which you can manipulate independently. For example, the area identified by a shadow-only spot can also be used to inject a dim blue gradient so that the shadowed area now also appears to capture some blue-sky light.