UV Mapping to avoid texture flaws and enable proper shading

Transcription

1 UV Mapping to avoid texture flaws and enable proper shading Foreword: Throughout this tutorial I am going to be using Maya s built in UV Mapping utility, which I am going to base my projections on individual faces, rather than an entire group in the way that programs such as UV Mapper do. After you have a mesh made, UV Mapping it and correctly applying a texture to it can be tedious work. It s not something I would consider hard, just time consuming. In this tutorial I will walk you through correctly laying out the UV Map and texture, and then giving it some realistic shading in Photoshop via a simple cabinet mesh. Mapping the Mesh First off, let s look over the mesh and see what the best way to map it would be. There are many places that can use the same texture space, such as the tops and bottoms of both shelves, as well as the top and bottom of the cabinet, the left and right outsides of the cabinet, etc. There are many areas this can be done, I ll explain each one as we go along. About how the mesh was made: I started with a cube and scaled it down so that it is the appropriate thickness for the cabinet. I extruded (but did not actually move) the front face and scaled it inwards, then extruded that face again and this time moved it back so that it inset into the cabinet. The shelves are also cubes that have scaled down to the right height and thickness to fit into the cabinet. To start the UV Mapping, let s give the main inside face a planar project along the Z Axis. As personal preference I start filling the UV Map from the top left, and work my way down. Feel free to start the layout however you want, just be sure to pay attention so that you keep up with yours and won t confuse your UV Map with mine. Page - 1 -

2 Next, I m going to do each side of the insides on the cabinet. There is nothing special or different on one side that isn t on the other, so therefore I m going to map them both to the same space by selecting them both and giving them an X Axis planar projection. To make texturing easier, I plan on just using a wood grain that goes in one direction. When something is elongated (not square), as are all the faces we have mapped so far, the wood grain usually goes in that direction, in this case, vertically. So for the rest of the faces, I m going to have to remember the direction I m going to make the wood grain go, and rotate them accordingly. Because the texture is going to be going up and down, and the sides are going up and down, I won t have to change them. Once I have the insides mapped, I ll put it on the top, right next to the face we have already mapped. For the next part I ll do the shelves, both the tops and bottoms of both can be in the same space, as well as the bottom and top of the inside of the cabinet. They will all get a planar projection on the Y Axis. Now, because the planar projection maps them going from side-toside, and the texture goes from top-to-bottom, we have to rotate their part of the UV Map 90 degrees counter-clockwise so that the back part of the shelves are on the left side. Again, I will place it on the top of the UV Map next to the other faces. Page - 2 -

3 Next, let s UV Map the left and right outsides of the cabinet. Select both the sides, and give them an X Axis planar map. They should both be using the same texture space, as again, there is nothing significantly different about one side that isn t on the other. Because the faces are already vertical, we don t have to rotate them. In keeping with the current key, if you could call it that, I'm rotating the faces so that the back edge is towards the right, so when we have to shade it later, it s easy to remember what needs to be shaded where. I'm going to place the sides next to the shelves, which now will be in the top right. The back part of the cabinet, where there will be a slight shadow later, is towards the right. For the next part, let s do the front four faces around the outside of the cabinet, and the front of the shelves. To start with, I'm only going the top and bottom face, and the front of the two shelves. Give them a planar map along the Z axis. However, now if you look at the map, each face has a lot of space between it. Select the top face on the UV Map, and move it down so that its on top of the bottom face, sharing the same texture space. Now do the same for the two faces on the front of each shelf, moving them so they share a texture space. What appears to be one face on the top is actually the two shelf fronts, the bottom two with the crossing edges are the top and bottom. Page - 3 -

4 Now to do the left and right sides, give them a Z Axis planar map as well. Too keep the wood grain looking natural, we will have rotate them 90 degrees (clockwise or counter-clockwise, it doesn t really matter for this) and move them down either above or on top of the left and right sides. Here we have everything that we have mapped so far. To keep it more separated, I ve placed the most recently mapped left and right side above the shelve fronts and top/bottom. The only we have left to map is the back of the cabinet, and the top and the bottom. Let s go ahead and select the top and bottom faces of the cabinet, and give them a planar map on the Y Axis. It will appear horizontal on the map. We will have to rotate it 90 degrees counter-clockwise so the back is towards the right side. However, after it s rotated, there isn t anywhere it will fit. Scale it down vertically, so that is somewhat more square, and it should fit somewhere in the gap we have in the middle of the UV Map. About scaling and un-proportionately resizing parts of a UV Map: It causes stretching. On some textures it will hardly be noticeable, such as wood, since wood is streaky to start with. Now if we were making a couch or a chair, or something that would use a patterned texture, it s a bad idea to scale parts of the UV Map unless you do it proportionally (keeping it the same shape, only resizing it as a whole) because then the texture will stretch in a rather unsightly manner, unless you scale down the texture too for that part of it. I ve gone and placed the UV Map for the top and bottom of the cabinet on the very right side, so that I can save the larger area towards the left for the back of the cabinet, since it is a bigger face. Page - 4 -

5 Because the front face we already mapped will have shadows around the inside edges, we can t make it use the same texture space as the back of the cabinet, since there is nothing on the back that would really cause that shadowing. Select the back face and give it a planar map on the Z Axis. It should already be standing up vertically since that is how the cabinet itself is. If we scale it down to the point that it fits where we have empty space, it gets pretty small. If it gets too small, that will cause the texture to stretch out overall and blur, which we don t want. By compromising the size of the front face, we will be able to balance the front and back out so that they both receive approximately the same amount of texture space, as seen here. At this stage there are a few faces left on the mesh that we haven t UV Mapped, because they are hidden inside the mesh. There are 6 total, 3 on each shelf. There is a face on each side of each shelf, as well as on the back, that is hidden within the sides of the main cabinet. There are a couple of options of what you can do with these faces. Because they are hidden and no one will see them anyways, you can just delete them. I ve gone ahead and deleted them. It can be tricky to select them though going into wireframe mode and selecting them that way. The other option is to just leave them be. However if you do that, make sure they are somewhere on the UV Map (doesn t matter where, just scale them down really tiny and stick them in a corner somewhere where they are not in the way) because SimPE will not accept a mesh that isn t fully UV Mapped. Now if you look at the UV Map, there s a gaping hole in the middle that isn t being used for anything. There is no reason why this won t work, but it is a waste of space. I m going to go back on what I said earlier, and make part of the texture horizontal instead of vertical. Select the top and bottom faces that we resized earlier, and rotate them 90 degrees clockwise. Scale them back out horizontally so that it fits in the gap we had. The right side should now be along the bottom, so we will have to remember that we rotated this. Now save the UV Map to an image file, I'm going to use 512x512 for the resolution so there is ample room for shading. Page - 5 -

6 Making the Texture Open the UV Map in your graphics program (I m using Photoshop) and place your texture on a new layer above the UV Map. Lower the opacity so that we can see the UV Map, and get the Rectangle Marquee to select the area that will go over the top and bottom of the cabinet (That we rotated sideways) and the long edges we have mapped at the very bottom of the texture, and press the delete key on your keyboard to clear the selection. Add another new layer, above the UV Map but below the texture, and add your texture to it. Rotate this layer 90 degrees either clockwise or counter-clockwise (It doesn t really matter for this, as long as the grain is going horizontally). Raise the opacity of the layer back to 100 and your texture should look something like this. By deleting that area of the texture, it made a window onto the layer below, which saves us the trouble of trying to rotate just that of the texture, since we could just rotate the entire layer. To keep everything slightly organized, I'm going to merge the two layers with the wood texture. Now let s lower the opacity back down to around 50%. Add a new layer, which is where we will add the shading. With the rectangle marquee tool, draw a box carefully around the top left face. You ll want to try to be as accurate as possible, so that your shading turns out correctly. Select the paint brush tool, and get a basic round brush about 15 pixels wide with a pure black color. Click in one corner of the marquee (you want to paint right up to the very edge, so it helps to have the brush over hang outside the marquee a bit) and hold shift (to keep a straight line) then paint all the way across one of the edges. Without deselecting the rectangle, apply a Gaussian blur of about 10 pixels. (Now you can deselect the rectangle.) Page - 6 -

7 Now, if you want to you can add a new layer for each shadow you make, but you don t have to. To keep it simple, I'm just going to put them all on the same layer. With the rectangle marquee again, select the first rectangle to the right of the shadow we have done. Hold the shift key (or switch your selection mode to add to selection ), and select the one next to it, and the third one next to it as well. With the brush tool again, paint a straight line down the right side of each box. Without deselecting them, apply a Gaussian blur of 10 pixels again. Now deselect these three rectangles. Select instead the rectangle below them, which we rotated earlier so that the back of the face is towards the bottom. Draw another straight line along the bottom, and also apply the 10 pixel Gaussian blur to it. Lastly, we need to shade the bottom three faces. To keep it simple, just draw one big rectangle around them with the rectangle marquee tool. Because we are dealing with the odd angles on the sides, I'm going to bump my brush up to around 27 pixels wide and draw a straight line down the left and right side of the box. Apply the 10 pixel Gaussian blur to it, and deselect it. This is the last part of shading that we need to do to this particular object. Bump the opacity on the texture layer back to up to 100% and check out the texture. The very bottom part of the shading looks dark, but it s hard to tell if it s too dark without checking it out on the mesh. Save the texture as a JPG file with the highest quality setting, but don t actually close the layered version of the document. If your program flattened the image before saving, go back in the history and un-flatten it. If you have the ability to apply textures to your mesh within your 3D editor, you can do so now. If not, you ahead and import your mesh and texture into SimPE to preview it. Here is how mine turned out. It s not too bad, but there are still some obvious problems, the main one being the shading at the corners. Go back to your graphics program, and with the rectangle marquee select the bottom shading that we did last. With the Rectangle Marquee tool still selected, right click within the selection and if you are in Photoshop, you will have the option of Layer via Cut. This cuts that part of the texture off that layer and adds it to a new one. If not in Photoshop, simply copy that segment of the texture, add a new layer, and paste it in. Page - 7 -

8 Now that this part of the texture is on its own layer, we can change the opacity of it independent of the rest of the shadows. You don t want to get rid of it completely, so just lower the opacity of that layer some. I have mine at 30% and it looks decent, however what you need to do may vary depending on how dark your version is. One other thing that I see that could stand to be fixed a bit, is that the shading on the shelves is hardly noticeable. To fix that, let s go back and add those shadows again. Lower the opacity on the texture layer to around half so that you can see the UV Map below, and add a new layer that our extra shading will go on. Out of the top three rectangles on the top of the texture, the middle on is the shelf. Select it with the rectangle marquee and get the brush tool again. Bump the brush size back down to 15, and paint a straight line down the right side, and now let s also do the top and bottom. Apply the 10 pixel Gaussian blur. Raise the texture layer back to 100% and save it out to JPG again. Load the texture back onto your mesh to see how it looks. We now (hopefully) have shadows around the inside, around the edges of the shelf, around the seam between the shelves and the cabinet, and a very faint shadow around the back of the cabinet to simulate the shadow if it was against a wall. Here is the final mesh, with everything that was mentioned above. There could be a few more things done to it, like shadows on the back and sides of the cabinet itself where the shelves join up, or maybe more shadows under the shelves, but getting that to look right can be quite a bit of work, and I wanted to keep this fairly simple. I hope you didn t have too much trouble with this, and that you ve something along the way Page - 8 -