Strange beundhavior with alpha gr

Maybe there is something I didn't understand about shadows on the ground.

I wanted to see shadows on my backround image.

So I selected "ground ON" and checked "alpha" to not see it of course.

If you look at the following image, just up the umbrella, you can see the backround image lighter on the lower side than on the upper side.

Now if you look at the image below where I unchecked alpha parameter, you can see this lighter area corresponds to the ground position.

I already saw this problem in version KK30 and I noticed this problem only occurs in packet mode, not in path tracer.

What's the problem?

Alain

▶ Reply to This

Replies to This Discussion

Permalink Reply by Render Plus on December 22, 2011 at 12:59pm

My first guess is that the "ground" is set to transparent in SketchUp (this is the default for SketchUp)

The whole effect will be easier to see if you use a solid colored background image - e.g. white or light yellow. - that will make it easier to see what effect the ground is having as you toggle it on and off.

The white background will let us see exactly what the alpha ground looks like.

▶ Reply

Permalink Reply by Rich Hart on December 22, 2011 at 1:05pm

I thought I saw this happen...but now I can't duplicate it.

Can you send us that model and that background image to see if we can reproduce it consistently?

▶ Reply

Permalink Reply by Alain Bonnefoy on December 22, 2011 at 2:55pm

Ok, I'll prepare the model and bkgd image tomorrow to send it to you.

I said I don't get the problem in path tracer mode. It's true but I get another one.

In the image below, after 300 passes, we can see a fine black line exactly where was the limit between normal and lighter area.

▶ Reply

Permalink Reply by Alain Bonnefoy on December 31, 2011 at 3:48am

Hello,

Did you find something about this problem with the model I sent to you?

Alain

▶ Reply

Permalink Reply by Render Plus on December 31, 2011 at 9:32am

We received a model by YouSendIt labelled "My House" - was that yours?

Whenever you send a model with YouSendIt - be sure to add a comment about what it is.

Otherwise, all we get is an email address, which does not necesserily coorespond to your handle on the forum, or tell us why the model was uploaded to us.