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Old 12-12-2010, 07:21 PM   #16
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Moved to modeling

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Old 03-02-2011, 11:44 PM   #17
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**UPDATE**


I continued playing with displacement to add the "lego" text on the top of all the pegs and forgot to post the results. I am still figuring out displacement. There is a significant difference in behavior between mental ray and maya materials.

I still do not have a handle on how to displace inward. All my attempts to do so resulted in my entire model being inflated. In the end I just went with a black and grey disp map image and controlled the positive displacement with the alpha gain.

My original plan was to inset part of the label. So I went with the image in the network below and set the alpha gain offset to -.5. The idea was to shift the 0-1 range to -.5 to .5, but I could not get it to work and have to continue experimenting to understand what is going on better. The shader network below has the image that was not working. In the end I just used a black and grey image and a alpha gain of .07 and alpha gain offset of 0.



The resulting render with alpha gain set to 0.07.



Note that rendering with displacement significantly increases render time!
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Old 04-02-2011, 12:47 AM   #18
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Im watching this ct....interesting. Would it not then be prudent to just use a bump map if the render times are so large??..or are you trying to displace the geo for a reason? close up shots etc?

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Old 04-02-2011, 01:56 AM   #19
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Precisely! I use displacement for close ups and for shots where the displaced surfaces would be visible in silhouette. These are the to conditions where bump mapping and normal mapping fail.

You can get some performance gain by using mental ray approximation nodes at render time as they will adjust the tessellation dynamically.

Another option for this problem is to model the text as separate objects using the bevel plus tool but that would add a lot of geometry, especially in the case of legos where there could theoretically be lots of blocks.

This is primarily an exercise to understand displacement mapping. I personally prefer creating the geometry myself. However, I am rarely time constrained on my projects. If the schedule was tight and the additional render time was acceptable displacement is an option.
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Old 04-02-2011, 02:50 AM   #20
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Depending on what you were doing (ie still model/animation) you could forgo the DM and use bump if anything at all? as you would only need the DM on the parts you can see?.same same with the text Rick? working out which pieces that are seen might be a brain buster though LOL especially if it is a disintergrating/reintergrate model...might need a coffee or 3 with that.

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