Below you can see a render (and settings for render), there is a single sun light outside the gallery.

Sun Setting

Infinite
intensity 850%

red    0.9
green     0.9
blue    0.9

Shadow  1

shadow blur radius = 3
Shadow Samples       = 100
Shadows min bias   = 0.8

Under red arrows you can see the trouble
 

If you deselect 'Use Irradiance Cache' it will get rid of the artefacts at the expense of a much longer render time.

Yes cspear

deselect 'Use Irradiance Cache' may solve the trouble but rendering times become impossible, perhaps speak more than one hour just for this simple scene

there is a different way?

I'm going crazy to solve this problem

Try lowering the  IDL irradiance cache.  I'd also add a bounce or two.

As an aside, are you using an environment sphere?  I ask becausae the intensity of the sun is very high; looking at the lit area, it looks like an atomic bomb has just gone off.  I usually use an infinite light with intensity of around 65% for outdoor sun when using BB's environment sphere with a sky texture applied. 

OK, a couple of other suggestions:

1. a bit of supplemental lighting, maybe a (weak) point light in the alcove

2. this one's a cheat, but before getting into that, why do you have the couch texture plugged into diffuse value? Pull it out of there and plug it into Ambient Color, make Ambient Color white and make the Ambient Value very small: try 0.5 and see if it helps the splodgy shadows without making the couch noticeably luminous. Increase or decrease Ambient Value as necessary.

cspear

Making test following your setting.

WandW

I'm not using an environment sphere. I'm setting the scene for rendering it from under the alcove, so the sun light may be more hard.

Making test following your setting too.  

couch material setting seems me not good, it's not real.

IDL really works best in an enclosed space.  An evironment sphere will throw some more light into the alcove, so you can then turn down the Sun...

I think there is not the way.

Do you have a map on the sphere?

Note that your blotches are gone; try cranking up the sun...

the problems on the couch are coming back rising the sun

couch materials very bad, like poser 4 materials.  it should be using the alt diffuse node; simple diffuse node is for preview.  wait for snarly's soon-to-be-released easymat product.  to get better interior lighting with only single infinite lite (sun), I prefer 16 or 32 bounces, in addition to bill's enviro-sphere.

Quote - wait for snarly's soon-to-be-released easymat product. 

What you are talking about ?

Quote - I prefer 16 or 32 bounces, in addition to bill's enviro-sphere.

Indirect light bounces ?

Quote - What you talkin bout ? 

 http://www.renderosity.com/mod/forumpro/showthread.php?thread_id=2876212

Quote - Indirect light bounces ?

yes.  use text entry field for >12 IDL bounce.

Quote - #### cspear  

couch material setting seems me not good, it's not real.

Use BBlightmeter and make sure you don't let it show yellow or red.

The picture with 85% light intensity on the direct light looks great with the envsphere set at 1.0 ...

The 150% intensity is simulating another planet where its sun burns brighter than that of the sun orbiting the earth. 

I agree with Trepleen, the picture with the 85% light intensity and the envsphere set at 1.0 is closer to what you want. But I would like to add that our Sun is not a blue-white star. Our Sun's light is slightly yellow. Clouds in the atmopshere can make it a whiter light when it's overcast and you're getting more diffuse light, but I think with bright sunlight like you're trying for could use a tiny bit of yellow in it. Also check the textures on all your patio set. If they're plugged into the diffuse channel, then the channel needs to be set to .85 not 1.0, otherwise, more advanced shaders would do the furniture good. I'd do a search on BB in the forum and start collecting shaders he's freely published.

P.S. Just looked closer at the render settings you posted up top......is there a typo on your bucket size?????!!!!!

Quote - But I would like to add that our Sun is not a blue-white star. Our Sun's light is slightly yellow. Clouds in the atmopshere can make it a whiter light when it's overcast and you're getting more diffuse light, but I think with bright sunlight like you're trying for could use a tiny bit of yellow in it.

You have it backwards. The sun's light is basically almost pure white (as photos showing the sun taken in space clearly demonstrate). It appears slightly yellowish because blue and violet is scattered by the atmosphere, making the light that reaches the ground lacking at that end of the spectrum, however you then have the light that's been scattered mixing back in so you're pretty much back to white.

The sun's visible output, when you measure it, is actually strongest in green.

Any photos that show a colour other than white (and doesn't involve scattering due to atmosphere) has either been altered or wasn't taken properly.

For the more scientifically-inclined, the sun is essentially a black-body radiator: the temperature of the emitter determines the colour of light you see. At 1000K, it will be red, at 10,000 kelvin blue-white. The color temperature of sunlight just above the  surface is 5900K, which is basically white.

Okay, I stand corrected. I was going by something I read here in the forums a year or so ago.