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How does one go from a simple clay render to a fantastic fur render?

Assigning fur to a ball or a plane is as easy as drag n’ drop, but a furry bear? That’s asking for trouble.

The beginningMy first venture into fur was in the form of a few tests; to look at the possibilities of using it for this project, which I thought would be a good idea, just so I would know what I would be getting myself into.

I used a few polygon doughnuts and messed around with various fur attributes to see what I could come up with.

My first major concern was render time, the second was to decide whether or not to make it move dynamically or to leave it static. Thirdly was how easy was it to make the fur look good on a character. After all there’s a big difference between a doughnut and a bear!

Dynamic Vs StaticGoing back to those doughnut tests, I experimented with both dynamic and non dynamic. To make fur move dynamically in Maya, it needs to be controlled by Maya’s hair system.

This gave some amazing results, but my experience of dynamics has taught me that test’s is one thing and actual scenarios is another.

A decision had to be made now, and I chose static. When thinking about it, with all the other technical aspects of the fur, this was just one too many things to be worrying about.

Technical Document on Maya Fur

Fur Render

Clay Render

Dynamic Hair Curves Controlling Fur

By Ethan Shilling

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Render timesIt’s no good saying “I’m going to have a furry bear in every shot”, if its going to take until next year to render it. I had to find out how to achieve render speeds that were realistic for the project, while still maintaining reasonable looking fur.

A technique I discovered was to decrease the density of fur while increasing the fur base width. Together with the skins background colour matching the fur colour, it gave the appearance of denser fur. I also found out that the Mental Ray renderer has two methods of rendering fur. Fur Primitive (default) and Volume Fur.I switched to rendering with Volume Fur, and although it didn’t necessarily speed up render times, it did give it a softer look, which seemed to help add to the fluffiness.

In total, one furry bear averaged about 20 seconds per frame. So much better than a possible 1 minute 30!

Stylising FurThe biggest challenge was still to come.

Fur assigned to the bear with no fur maps controlling direction, length and colour looked pretty horrendous!

The bulk of this technical document lies here, with fur stylising.

Painting the fur direction was one of the most important things that needed to be done as without it, the fur would be angled in one direction, and the fur would never look right.

Maya has it’s own way of ‘painting’ on 3D objects. This is how you are supposed to paint fur direction, only as I very soon found out, this was not a very good way.

Limitations of the software really made this an impossible task.

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Visible Seams without painting fur direction

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Having ten strands of fur over one bear isn’t exactly enough detail to paint fur direction. My first attempts at painting in 3D showed that to be able to see what you are painting, you need to increase the display fur samples.Setting that to 128 was just about enough. Any higher and Maya just couldn’t handle displaying such dense fur in the preview.

What I also found out is that you should be painting at a decent resolution so I made the map size 1024 by 1024, both in the fur settings and in the painting settings.

Painting in Maya was proving to be a nightmare. Visible seams, random smudges that didn’t seem to disappear. This was when I decided to look at the map file and see what I was painting.

I discovered that Maya was painting at a 128 resolution on a map file of 1028 resolution. I also saw plenty of random patches which were the obvious cause of the smudges.

The main thing that I found out is that the display settings for previewing in Maya actually determines the resolution of the map, regardless of the actual resolution that is set for the map file!

This was when I decided to paint the map manually in Photoshop, but first I had to understand what the black to White values represented.

This is a diagram that I created to help me understand how fur direction is represented. White and black are down, and all the levels of grey are the 360 degrees of rotation. With that knowledge I was able to paint a map file that worked.

Maya’s Direction Map File

Painting Fur Direction In Maya

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To achieve an even rotation of fur around the head I used one of Photoshop’s least used gradient tools. The one that paints black to white in 360 degrees.

Painting the fur base and tip colour was far easier. I made the nose have darker fur.

Direction Map Painted In Photoshop

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Lastly was the fur length to consider. For example, the hands had way to much fur at that moment as did the soles of the feet. I painted a greyscale map to control the fur length. The darker the colour, the shorter the fur became.

To complete my technical discoveries, I found out one last thing about Maya’s fur system, when ‘baking’ all the attributes, any and all map files plugged in get up scaled to the resolution of the map. So those 128 resolution images get smoothed out.

This of course had a negative effect on my maps as it would blur the seams between black and white (which are technically the same value) causing grey to appear in the middle, causing a visible seam in the render. This was then avoided by not baking the attributes and all was well in the end.