Applying simple or procedural materials to objects is not difficult. But it gets more complicated when the surface needs to display some kind of texture on it. Any texture maps are placed in the material's Diffuse slot, but rendering results may be unpredictable. That's why we need to understand how 3DMAX applies textures to 3D objects, what a UVW map is, and why it is "unwrapped".
This article is for those who are learning 3DMAX, but already know the basics: interface, modeling, modifiers and materials. This is a step-by-step tutorial: we won't explain what all the buttons do, but show the most commonly used ones.
Let's start with a simple dining table model. Its geometry will help us learn standard tools. You can use any simple box or cylindrical model to achieve clear and easy to see results. Assign it a simple material - depending on the render engine you use, it could be Standard, VRayMtl or CoronaMtl. Add a bitmap to the diffuse slot and apply a texture (you can also drag and drop a texture into the slot). In our case, we downloaded a free wood texture from Arroway Textures. In the bitmap's settings, click the "Show shaded material in viewport" checkbox and the texture will become visible.
The texture is clearly overstretched and doesn't show properly on the sides and legs. By default, 3DS MAX will try to project the texture onto the 3D object as if it were a simple plane, and then stretch the pixels on the edges to get the height. To define how to display our texture correctly we need a UV map.
The 3D software "unwraps" the 3D object onto a plane, then links each pixel with a matching pixel on the texture. The process of linking these pixels together is called UV mapping. In 3DS MAX this is done with UVW mapping and the Unwrap UVW modifier. After that you can render your project.
UVW mapping: for simple shapes and objects
Applies a UVW Map modifier to the object. The Length, Width, and Height values control the size of the texture projection gizmo. When using a square seamless texture, we can enter the size of the material displayed on the texture. This is easier when our material has certain elements whose dimensions we know (e.g. floors, bricks). This way, the size of the texture is calculated by multiplying the width/length of a single element by the number of elements. Otherwise, you have to guess or estimate a suitable value. Our texture is 1200 x 1600 pixels in size and we don't know the size of the material on it in millimeters (our system units). Let's try to fit these values into the gizmo dimensions - 1200 x 1600 x 1200 mm. The results were good enough for our case. When guessing the value, make sure to keep the aspect ratio constant between dimensions.
Note: If you are using an existing material from the Corona material library or the VRay material library, check the "Real world map size" checkbox in the UVW map preferences. Texture sizes are already built into these materials so you don't have to guess them.
Our texture now looks much better, but it's rotated the wrong way around on the table leg. The texture's rotation is controlled by the object's gizmo; to change it, open the modifier's scroller and select it. You can move, rotate, or scale a gizmo just like a normal object. Use the Angle Snap tool to rotate the gizmo 90 degrees by one of its axes (X or Y, depending on your object).
This is an excellent result for subjects in the background or those that are far from the focus of the lens. Experiment with different UVW map types to see which one works best for your objects. For example, if we used Cylinder, Shrink Wrap or Sphere projections, our table would look like this.
Unwrap UVW: Manually change UV maps
Our table has a simple shape, but the texture still doesn't look perfect after applying the UVW map. There is a seam in the middle of the leg, which will become more visible once we change the texture. These imperfections will be more apparent if we assign UVW maps to objects that have many elements that don't fit into standard gizmos. In this case we need to use the Unwrap UVW modifier instead.
Unwrap UVW has so many tools for creating and editing UV maps, it's not easy to figure out how it works. First, let's click the Open UV Editor button; here we can see our current map. This one was created with the UVW Map modifier applied before Unwrap UVW. If the object was not created from primitives, the map will be empty.
Elements of a UV map can interact via vertices, edges, and faces, the same as edit poly. If you select a face on the UV map it will be highlighted in the viewport and vice versa. To select an entire UV-mapped element, use the Select By Element UVs toggle located next to the Faces icon. This can be used with any selection mode.
Now, with all the map elements stacked on top of each other, it's hard to tell which is which. Select all polygons (Ctrl+A or via area selection) and click Pack Normalize. Elements are now distributed throughout the map, and we can edit each element individually.
Try clicking on different polygons to see them highlight in the viewport. You can see that the table legs are divided into several parts, that's why we see the seam there. Let's sew them together. Select an edge in the middle - it will be highlighted in red, while the adjacent one will turn blue. Right-click the highlighted edge and choose Stitch Selected. Elements will join, edges will become one and seams will disappear.
Continue stitching the edges together wherever you want to remove the seam. This is not always possible and sometimes you may make the wrong decision. If the unwrap doesn't work well and you can no longer undo it, just delete the modifier and start over. In our case, we separated the bottom of the table from the top, and sewed the sides and legs of the table together in two pieces.
Once the elements are stitched together, select all the polygons again and click Pack: Custom. Now the elements are packed together, without intersections, and blend neatly into the texture. However, we want to see our wood texture instead of the pawns, so let's select it in the top right menu. Ideally, you'd use a seamless texture - this way you scale all texels outside the bounding box to set the appropriate size. In our case, the results were good enough.
Here are our results so far:
Note: You can create interesting material layouts by using multiple UVW Map modifiers on different faces selected in Edit Poly. For example, this is what you would get by applying a cylinder gizmo to the table legs, a box to the sides, and a sphere to the top face.
Unwrap UVW: create UV maps from scratch
When you have a complex object, it's not efficient to start splicing elements manually. The UVW Map modifier doesn't handle shapes outside of primitives very well: it creates seams in the middle of elements, cutting them in unexpected places, and complicating an already difficult job. Standard Unwrap UWV tools often split an object into too many elements (try Tools → Flatten Map to see an example). In this case, it will be easier to cut the seams yourself.
Let's make a low poly model of this creature, which we'll name Crab. Apply a checkered texture to it using a UVW map with a Sphere gizmo.
The textures on Crabby's legs and eyes are stretched because those elements don't fit into the sphere. It's best to make them separately from the rest of the body. Apply Unwrap UVW to see the green seams in the viewport created by the UVW map. We don't need them, so let's click Reset Peel to clear the UV map.
Now let's create new stitches. Select the edges to become seams, and click Convert Edge Selection to Seams. Make seams around each leg and eye stalk, on the belly and back of the crab. Finding the right place to cut may be difficult for you at first, but don't give up. Remember to reset the stripping tool if you don't like your results and would rather start over.
Our seam looks like this:
NOTE: It will take a lot of practice to learn how to properly cut complex 3D models into patches for unfolding. Consider textures when modeling objects, and be mindful of where you can stitch them later. Unwrap low poly models: This means you have fewer polys to worry about; UV mapping will work properly after applying Turbosmooth.
After you have marked all the seams, select a polygon on the surface and click to extend the polygon selection to the seams. It selects the entire element bounded by our new seam. With this selection, click Quick Peel - you will create a UV map of this element. You could select all elements at once and UV maps would be created for all of them, but we're trying to make sure we've made enough seams, so let's repeat this for each element individually. It turns out that we need to add a seam to the eye stalk, otherwise the unfolded element will get deformed. Undo the unfold, create a new seam, and try again.
All elements are now expanded, but they're clearly not scaled correctly. Select all faces and click Rescale Elements to fix it.
The facial edges on Crabby's body look overly tense. Select the element, open the Tools menu, and choose Relax. Click "Start Relax" - the faces gradually start to change their shape and position to better fit the original model. When it looks good, click Stop Relax and Apply. If the UV map contains nodes and overstretched polygons, use a higher Stretch value and Amount - this will speed up the relaxation process. Apply Relax to all other elements of our map for practice.
The final UV map should fit the texture, so select all faces and click Pack: Custom. Some elements that don't require unique textures can be placed one above the other to save space. Let's put the crab's legs and eye stalks together, but keep the eyes separate so we can color them in different shades later. Remember, you can move and rotate elements to make them fit together better. But if you want to scale them, scale all elements at the same time, otherwise they lose their relative proportions.
Turns out we did too many seams on the crab's belly, so let's stitch them together via Stitch Selected. Our final UV map looks like this:
To paint our texture, let's export this map. From the Tools menu, choose Render UVW Template. In the window that opens you can set the image size, color and line thickness. Click Render UV Template and save the image in your favorite format. Now we can paint textures for Crabby in any paint application.
Create a new material with this map in the diffuse slot and apply it to the model. The crab is over! UV maps are available for both low poly and high poly models.
In this tutorial we learned how to create UV maps in three different ways. In practice, they can be used together or individually. Every 3D artist or studio will have their own method of unwrapping UVs. Do some more practice and experimentation to find what works best for your workflow. Good luck!
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