Heretic Hides: Skinning Tutorial, part 2

Skinning Tutorial

Getting to Know the Polygons

The image to the left shows how the various polygons on the Corvus model are unwrapped to create the skin. Click on the thumbnail for the larger image, which is shown at twice normal size for clarity.
The red lines across the body indicate where the waist meets up across the different torso parts. The red line running down the leg will be facing forward on the model. The next image shows the standard Corvus skin overlaying the polygons. Again, this is twice actual size.
It's a good idea to always include an overlap beyond the polygon boundaries, to avoid black lines appearing between body parts. Compare Corvus' usual face (right) with what actually gets applied to the skin (left).

The tricky parts of creating skins are in matching up different body parts so the design continues smoothly across them. For instance, if you don't align the belt properly on the front, back and side of the torso, it won't match up on the model. By measuring where the red lines are on the first wireframe image(512x512), you can divide the number of pixels by two to work out where they would be on a standard 256x256 pixel skin (which is the size used in Heretic II). On this image, the waist line for the back of the torso is 146 pixels down from the top. On the front it is 436 pixels down, and the side of the torso it is at 448. That translates to 73, 218 and 224 pixels from the top on a 256x256 pixel image. An easy way to align the side of the torso with the front is to remember that where the belt on the side joins to the front it is 6 pixels lower. Remember that the belt on the side of the torso slopes upwards slightly to meet with the back.
A more accurate way would be to match the edges of the polygons up. This image shows how the various parts of the torso match. Notice how they are all at slightly different scales (the back is larger, the front and side are similar). Red parts will wrap under the groin area.
The polygons that make up Corvus' hair are complex, but the following is a basic template that should allow you to alter it as you like. Simple single-coloured hair is easy enough to do, but if you want a stripe running down the centre, or to convert the hair into a metal helmet, then you need to know exactly which parts end up where on the model. The inset shows how the template maps onto the model, in both front and rear views.

Getting to Know the Polygons
	The image to the left shows how the various polygons on the Corvus model are unwrapped to create the skin. Click on the thumbnail for the larger image, which is shown at twice normal size for clarity.
	The red lines across the body indicate where the waist meets up across the different torso parts. The red line running down the leg will be facing forward on the model. The next image shows the standard Corvus skin overlaying the polygons. Again, this is twice actual size.
It's a good idea to always include an overlap beyond the polygon boundaries, to avoid black lines appearing between body parts. Compare Corvus' usual face (right) with what actually gets applied to the skin (left).

The tricky parts of creating skins are in matching up different body parts so the design continues smoothly across them. For instance, if you don't align the belt properly on the front, back and side of the torso, it won't match up on the model. By measuring where the red lines are on the first wireframe image(512x512), you can divide the number of pixels by two to work out where they would be on a standard 256x256 pixel skin (which is the size used in Heretic II). On this image, the waist line for the back of the torso is 146 pixels down from the top. On the front it is 436 pixels down, and the side of the torso it is at 448. That translates to 73, 218 and 224 pixels from the top on a 256x256 pixel image. An easy way to align the side of the torso with the front is to remember that where the belt on the side joins to the front it is 6 pixels lower. Remember that the belt on the side of the torso slopes upwards slightly to meet with the back.
A more accurate way would be to match the edges of the polygons up. This image shows how the various parts of the torso match. Notice how they are all at slightly different scales (the back is larger, the front and side are similar). Red parts will wrap under the groin area.
The polygons that make up Corvus' hair are complex, but the following is a basic template that should allow you to alter it as you like. Simple single-coloured hair is easy enough to do, but if you want a stripe running down the centre, or to convert the hair into a metal helmet, then you need to know exactly which parts end up where on the model. The inset shows how the template maps onto the model, in both front and rear views.