- Sun Apr 29, 2007 12:52 am
#222935
Here's a quick and dirty tutorial. I couldn't reproduce your problems with your alpha mask, so for this example, assume that it's bad. Because of some special circumstance in your scene (the semi-transparent figures in front of the windows), I will be using part of it though.
First, I rendered out my RGB channel, with the glass slightly tinted so you can see the dividing line between the outside and inside lighting. After it was done, I hid the glass in the scene and rendered out the Alpha and Object ID channels (making sure to re-name my output file to make sure my RGB image does not get over-written by accident). These won't need to render very long in order for them to clear up. Here are the three channels I used for this example:
First, I added the forest image as a new layer to my RGB picture. I blurred this layer slightly so it's not so sharp.
I then duplicated the room layer and moved it over the top of the forest layer and gave it an Alpha channel. Opening up my object ID image, I first select the black window areas, invert my selection, and fill the rest of the image with white. I select the entire image and copy it to the clipboard. Going back to the RGB image, I'll paste this into the alpha channel I created for the duplicate room layer. You'll now see the forest through the windows. In order to get the colors to match a bit better, I selected the forest layer, and played with it's layer effects (in this case I used the Darken feature).
Now, we still have the problem that we don't see the forest in the transparent figure that overlaps the window behind it. For this, I open up the rendered out alpha channel, select the gray part that indicated this overlapping region, fill it with white, invert the selection, and fill the rest of the image with black. Again, I'll select the entire image and copy it to the clipboard.
Going back to the room image, I'll create a copy of the forest layer (setting it's properties back to Normal, and past the clipboard as a new alpha channel for this layer. I then set it's Opacity to around 15%, just so you could barely see it, and put this layer at the top of my layer stack. Here's a screenshot to show how the layers are arranged:
I can now flatten my layers, and adjust the levels, curves, or whatever to achieve the look I want:
There's all sorts of things you can use with the Object ID (or Material ID) channel. For example, if you wanted to de-noise just a specific part of your scene (the floor for example), you can easily create a mask using the Object ID channel. Another example is a night-time rendering of a room, where you have a lot of visible reflections on the windows. You can create a couple of layers with masks so you can insert a night-time cityscape as your background, and another layer of the windows with reflections. Each could be adjusted separately to achieve the look you want.
Hope this made sense. If you have any specific questions, feel free to ask!
First, I rendered out my RGB channel, with the glass slightly tinted so you can see the dividing line between the outside and inside lighting. After it was done, I hid the glass in the scene and rendered out the Alpha and Object ID channels (making sure to re-name my output file to make sure my RGB image does not get over-written by accident). These won't need to render very long in order for them to clear up. Here are the three channels I used for this example:
First, I added the forest image as a new layer to my RGB picture. I blurred this layer slightly so it's not so sharp.
I then duplicated the room layer and moved it over the top of the forest layer and gave it an Alpha channel. Opening up my object ID image, I first select the black window areas, invert my selection, and fill the rest of the image with white. I select the entire image and copy it to the clipboard. Going back to the RGB image, I'll paste this into the alpha channel I created for the duplicate room layer. You'll now see the forest through the windows. In order to get the colors to match a bit better, I selected the forest layer, and played with it's layer effects (in this case I used the Darken feature).
Now, we still have the problem that we don't see the forest in the transparent figure that overlaps the window behind it. For this, I open up the rendered out alpha channel, select the gray part that indicated this overlapping region, fill it with white, invert the selection, and fill the rest of the image with black. Again, I'll select the entire image and copy it to the clipboard.
Going back to the room image, I'll create a copy of the forest layer (setting it's properties back to Normal, and past the clipboard as a new alpha channel for this layer. I then set it's Opacity to around 15%, just so you could barely see it, and put this layer at the top of my layer stack. Here's a screenshot to show how the layers are arranged:
I can now flatten my layers, and adjust the levels, curves, or whatever to achieve the look I want:
There's all sorts of things you can use with the Object ID (or Material ID) channel. For example, if you wanted to de-noise just a specific part of your scene (the floor for example), you can easily create a mask using the Object ID channel. Another example is a night-time rendering of a room, where you have a lot of visible reflections on the windows. You can create a couple of layers with masks so you can insert a night-time cityscape as your background, and another layer of the windows with reflections. Each could be adjusted separately to achieve the look you want.
Hope this made sense. If you have any specific questions, feel free to ask!
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