CGTalk - Fusion Questions

dark_tranquiltiy

03-12-2008, 06:21 AM

Hi,

I am new to Fusion and have just stared to building my comp up. Now I am rendering passes out of 3dmax. I am using the gbuffer with vray, which splits the channels up. e.g

I have my ambient pass (no alpha) but I can save the alpha out separately in the alpha tab of frame buffer.

So I bring the 2 renders into Fusion and build this over my sky background pass, seeing as the ambient pass has no alpha channel it covers the sky completely, how do I then use the alpha to affect the geometry only in the ambient pass? (this will need to be used in every other pass also)

My second question is how to make a background node go from a colour like white to transparent. (In a gradient like a gradient in Photoshop).

Lastly, in the colour correct modifier how do you invert the values (currently my shadow pass is the work way). I had done it once before but cant seem to do it again.

Any help would be much appreciated

Thanks

Jim.

mental

03-13-2008, 04:25 AM

1) Add a bitmap mask to the ambient sequence and then connect the alpha to that bitmap using either the luminance or alpha channel.

2) Duplicate the Background Node. Set the gradient to go from Black to White (or visa versa) Then follow the same steps mentioned above for the bitmap mask.

3) Tools > Color > Channel Booleans > Operation 'Negative'. Remember to set the Alpha Channel option to 'Do Nothing'

You may also use the Channel Boolean node to copy the luminance or alpha channel of one image or sequence to that of another image's alpha channel instead of using a bitmap mask. It all depends on the options needed and the size of the Flow.

dark_tranquiltiy

03-13-2008, 11:36 PM

hey thanks alot man, how about inverting a colour correct? Currently my shadow pass is the wrong way around.

Thanks

mental

03-14-2008, 12:30 AM

I'm not 100% certain what your situation is so try one of the following:

1) You can invert the alpha channel of any image by going to the Common Controls tab (The nuclear hazard symbol) on that loader and selecting 'Apply Mask Inverted'.

2) You can invert the value of just the Color Correction node by adding or subtracting 0.5 to the current Tint value.

dark_tranquiltiy

03-14-2008, 07:50 AM

My situation is that that the render from max has shadows where the light is and light where the shadows should be, so I just need to invert the information (I havent checked the alpha) but I will check it out when I get home and try your theroy.

Thanks again, Jim.

dprgb

03-14-2008, 03:34 PM

You should really check out vfxpedia.com, a lot of these questions can be answered by a quick look through the help and tool references...

To invert the shadow pass, just pipe it into a channel boolean, set the operator to 'negative,' and set the alpha to 'do nothing.'

The easier way is to download the free set of plugins from www.komkomdoorn.com, there's an invert node in there (along with some other useful stuff).

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