Transparent wall rendered more like glass.

Hi again,

I need to understand if I am doing something wrong, or if this is "as-designed" behaviour.

I have a wall that has a material on one side, transparent on the other. I would expect that if I render the image so it is looking through the transparent wall, then I shouldn't see the wall at all. In other words, it should behave as if the wall is completely invisible. But it doesn't. It seems to render it as if it was glass; darkening things that can be seen behind the transparent wall, compared to things that can be seen through the doorway.

Obviously one solution is to stick the wall in a Layer so I can easily control the layer's visibility. But sadly I can't do that because the animation takes you through that wall. (Using a scene to split it doesn't work so well, as it is very hard to position the camera to keep a fluid motion)

To date my solution has been painful: I need to render the animation twice: Once with the wall visible (when camera is on the "inside") and a second time when the camera moves to the outside. Then I take the frames I want from each and splice them together to get a good animation.

Is there a better way? Is there something wrong with my "transparent" material which is causing it not to be truly transparent? Is iRender supposed to treat "100% transparent" as invisible?

regards,

-randall

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Permalink Reply by Rich Hart on August 13, 2012 at 6:04pm

I would have thought that 100% would have worked for you, but you also might have to turn off Refraction and have the color of the material be pure white.

I know that colored class isn't really 100% clear, and refraction adds some reflection, so it's not really 100% clear.

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Permalink Reply by Randy S on August 14, 2012 at 6:10am

Hi Rich,

Thanx for the tip. Setting the colour to pure white seems to have resolved it. I'm just running a test now to see if refraction plays a part or not. But I don't think so. Here are a few files so you can see for yourself. Note that rendering time varies across the models.

The key thing to look at is the shower door. Note how in this first image it is 2 different colours. This is because the LHS is behind the transparent wall, the RHS is not:

Below, I've only set the colour to pure white:

And finally, below is the same as above, but refraction set to 1 (previous was default of 1.5 or something like that):

Now we know!

-randall

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Permalink Reply by Render Plus on August 14, 2012 at 8:40am

And, or course, if you have ever taken a flash picture directly in front of a window, you know that glass is rarely 100% transparent and without reflections.

I think the refraction setting is the only way for us to distinguish between glass and a truly transparent material.