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Ultimatum
12-08-2005, 03:12 PM
Hi,

When I render an object with FPrime without background, thereīs white pixels all around the object in the final picture.

I save as TIFF32 + alpha.

Itīs not so much of a problem coz itīs quite easy to get rid of those with PS, but if somebody knows a way to render without these pixels it would be great.


- ult

Zarathustra
12-08-2005, 03:31 PM
I've always used targa 32 bit and have had no troubles.

Make sure you're using the renderer and not the previewer, click the '+ alpha' button and set your quality level high enough. I generally set quality to a min of 10 and max of 30, mostly going with 30.

Worst case, don't set your background color to white. :hmm:

brap
12-09-2005, 02:43 PM
This is an interesting question. I did a quick test, and at least with fprime 2.1 and AE, rendering with a white background and precomposing with white seems to give the best result. The file format does not seem to make a difference. Am I right that there is no way to get a 'straight' render out of fprime, or am I just having another friday morning brainfart? This test was done using the fprime renderer to quality 40:

http://www.sentientdigital.com/DL/test/MattingTest2.jpg

Panikos
12-09-2005, 04:40 PM
I am sorry to say that you have no idea what Premultiplied means.

You use Premultiplied when you have a source with alpha channel where the element you want to composite is surrounded with a colour other than black.
In this case, if the element has motionblur and the you want the composite to extract the motionblur while key, you defire the dominating colour as premultiplied otherwise you get a composite with an undesired colourful halo.

If you render something on black and you defire the premultiplied color as white, or vice versa, of course you will get an outline as in the image you supplied.

brap
12-10-2005, 12:29 AM
Panikos, my test was intended to show the results of different options when comped in AE, and to clear up the question of whether or not the file format had any effect on the outcome. Also, I checked with Worley Labs, and they confirmed that fprime cannot generate an RGB which is not premultiplied, which you can do in some other renderers. For example, using the LW renderer you can use Fader Alpha mode or Sprite Edger image filter to generate an RGB which will comp properly in straight alpha mode.

Panikos
12-10-2005, 01:31 AM
I.C

But the premultiplied colour is the source's dominating colour you want to get rid from the edges. If you use two different colours, you will have such borders.

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