UV Unwrapping Basics

Getting started with UV Unwrapping.

01. Overview

In this tutorial, we will be showing you step by step how to unwrap a few simple objects to help you get to grips
with the basics of the UV unwrapping process in 3DS Max. You can use this file to start the tutorial.

02. Collect product references

We rely on product images to model accurately create out models. The more images and information you can get, the better. Now, with this example model there are no source images, but in general it’s really useful to have source images when laying out your UV’s. This is because the way your UVs are laid out will inform how textures are shown on the model.

a. For example, the direction of wood grain on a model can tell you which way the UV’s should be laid out. In the example below we can see that the UV map and texture on the front of the drawers needs to be somewhat square, but the UV map and texture on the side needs to be long and skinny.

03. Apply the unwrap UVW Modifier

As you have learned from the previous modeling tutorials, objects are built out of individual pieces (a lot like real life!). To start Unwrapping, choose one piece to start with. We’ll start with the chair back and bottom, which in this model are a single piece.

a. Select the back of the chair (Chair_Body) and check its modifier stack.

Notice that there is only an Editable Poly modifier in it. When applying a Unwrap UVW, make sure to add it below TurboSmooth, if it’s present. It’s easier to create UVs with less complex geometry. You generally want to do a Unwrap UVW right above the Editable Poly modifier.

b. Add the Unwrap UVW Modifier from the Modifier List.
At Wayfair we encourage artists to use the Unwrap UVW modifier for creating UV maps. While the other automatic maps are faster, they give less control and it’s harder to see what exactly they’re doing.

c. Once the modifier is applied, let’s open up the UV Editor by clicking the “Open UV Editor” button.

i. Opening the UV Editor without changing anything will display the default UV maps assigned to the currently selected map channel. You can change this channel by changing the number under the “Channel” tab. One object can have as many UV maps as you want by using different channels for each map. You can think of them like Red, Green and Blue channels in an image, if that helps.

d. Once the editor is open we get our look at the UV’s – they’re a mess! This is because they are created on the fly by the software as we model and are generally not very good. That’s fine because we will replace them.

i. To navigate in the UV Editor window, press and hold the scroll wheel to pan, and roll the scroll wheel forward and back to zoom. To switch between sub object selection modes (like in 3D modeling), press 1 for vertices, 2 for edges, and 3 for faces.

ii. For more information the UV Editor window and layout, you can visit this help center article on the Autodesk Knowledge Network.

04. Start by applying a basic map to “reset” the UV’s.

Now that we’ve applied the Unwrap UVW modifier, the first thing to do is fix the terrible default UVs. To do this, we will first apply a basic projection map from within the modifier.

a. With the “Chair_Body” object selected and the Unwrap UVW modifier selected, enable the Polygon subobject selection mode (shortcut: 4). To make it easier to select the entire body, we also want to enable the Select By Element X/Y Toggle as well. There can be multiple elements (groups of connected polygons) within a single object.

b. With these two options enabled, click on the chair body. 3DS Max will select the entire element.

c. We will use the Box Map auto-unwrap mode, because this chair’s shape is relatively similar to a box. Under the Unwrap UVW Modifier, toggle the “Box Map” mode. Then click “Open UV Editor”. If you do not see your new UV’s it means that they might be too big for the view area. Use the scroll wheel to zoom out until you see them or press Z to zoom to selected objects. Note that you have to click the “Box” Projection button a second time to stop the tool. Otherwise you will not be able to use anything else until the projection mode is toggled off.

d. Now that you have created UVs for the object, select the “Pack: Custom” option to pack them into the available UV space. Then zoom back in to look at the available UV area or press Z to zoom to the selected objects.

e. Congratulations! You have created a rough UV map to start from.

05. Apply a UV checkermap to the model so you can check for distortion

We need to make sure our UV’s are not distorted. If they are, it will make our textures look distorted as well, giving our models an unrealistic appearance. Distortion occurs when a UV island (a group of connected polygons in 2D UV space) is not the same shape and aspect ratio as they are in 3D space.

a. Create a new blank material in the material editor and assign the supplied Wayfair UV test map to the diffuse slot.

b. Assign the material to the model. To see its effects, enable display of textures in the Viewport by going to the Shading Modes menu. Go to this menu, then Materials -> Shaded (or Realistic) Materials with Maps. Now you should see the material on the model in the viewport.

c. The pattern should be small enough to see repetition. In the image to the left, the pattern is huge on the model which makes it hard to see the shape of the circles and the lines. This can be changed in the texture properties.

d. Go into the Material Editor and select the texture map. Under its properties, disable “Use Real-World Scale” and change the tiling value to 5.0 in both directions (U and V). This will make the texture smaller when applied to the model.

e. Now take a look at the model. The texture will appear smaller and repeat more times, making it easier to determine the shape of individual circles and better see distortion in the map as we work.

f. One last thing we can do is turn on the display of the new texture map in the UV window. This is helpful for aligning the UV islands with wood grains or specific patterns on an object, since we can match the UV island’s orientation with the orientation of the texture. Notice the drop down box in the top right hand corner of the UV Editor.

g. In this dropdown box, select the texture map that you added to the material in the previous steps. If you do not see the texture map then select “Reset Texture List” to refresh it. Once this is done, the texture map.

h. Once complete, the image will show up as the background. If you want to use the regular CheckerPattern, you can just switch back using the dialogue.

06. Join related parts of the UV map together

As you’ll notice, our UV map is OK but it isn’t perfect. The chair has seams that are in weird places, splitting up continuous surfaces with green lines called seams. These lines indicate where the UV map splits the polygon faces into separate islands. You should always minimize the amount of seams and keep continuous surfaces attached together in the UV editor if possible. The areas highlighted below should be continuous, but extra seams are splitting them apart. If your polygons are different, that’s fine – we are trying to merge continuous and planar areas of the model’s UV map together. So look for areas that could be coplanar (like the chamfer on the side of the chair and the side of the chair itself) for disrupted seams.

a. Select the areas on the model that are split off and non-continuous in the 3D View. This will also highlight them in the UV Editor window. If you closed the window, open it again by pressing the “Open UV Editor” button.

b. Middle click in the UV Editor workspace to focus the window. Since these polygons are attached to the wrong islands, we will have to break them off in order to move them around without distorting the polygons they’re attached to. To break the UV’s off, go to Tools -> Break or just press Ctrl-B on your keyboard.

c. After breaking off the polygons, press W to activate the Move tool, click and hold on one of the polygons and move them around by dragging the mouse.

d. With the polygons still selected, you will notice that some of the other edges in the UV space have turned blue. These blue edges are the same ones as the edges of the polygon you have selected. We will stitch these together.

e. Make note of which lines are blue and then deselect the polygons. Switch to Edge mode (Shortcut: 2) and select one of the blue edges on a main island – I’m using the side of the seat. You’ll notice that once you select it, one of the edges on the broken-off polygon will turn blue. Note that in this screenshot I have moved one of the broken off polygons closer to the side of the seat so you can see it more easily.

f. One thing to note here is that the blue highlighted edge is on the left side of the polygon, and the red selected edge is also on the left side of the polygon. This means that the broken off polygon is flipped relative to what we want to attach it to, and we need to reverse it. We can do this by selecting the polygon in polygon selection mode (Shortcut: 4), then going to “Mirror Vertically Selected Subobjects” at the top of the interface. Clicking and holding on this button will also give you options to mirror horizontally and other tools.

g. Once this is done, switching back to edge select mode and selecting the same edge as before will highlight the appropriate side of the broken off polygon.

h. Now all we have to do is use the “Stitch: Custom” button with the edge that we want to stitch to selected. Once you press it, the polygon island with the blue edge will move and attach itself to the island with the red selected edge. In the screenshot below, notice that not only did it move, but the edge turned white, indicating that it is no longer a seam.

i. Continue stitching the corner area together by selecting edges and using the Stitch: Custom tool.

j. Once you’ve stitched all these edges together, continue around the rest of the side of the seat. When you’re done, take a look at your model in the viewport. The texture will be continuous across the entire side of the seat and not split up by the seams. However you might have some distortion. Notice how the circles are stretched and the lines are no longer straight in the image below:

07. Fixing UV distortion

Now we must remove the distortion from our UV map. This is relatively easy and 3DS Max has some automated tools to help out.

a. Select the UV island that you want to un-distort using the polygon select mode. You can make it easier by enabling the “Select by Element UV Toggle” option in the UV Editor window.

b. Once you’ve selected the island that you want to un-distort, go to the Tools menu and select “Relax” from the drop down list. This will open the Relax Tool dialog. You can read about this dialog and its functions on Autodesk’s Knowledge Base here.

c. 3DS Max has three auto relax options – Relax by Edge Angles, Polygon Angles, and Centers. Relaxing will move each vertice closer to its neighboring vertice, based on these rules. Generally you only need to select the first two, Relax by Edge or Relax by Polygon, and generally Edge Angles will produce the best results.

d. Press “Start Relax” with the default settings and “Relax by Edge Angles” selected. You will see the island begin to spin around and distort slightly. It’s being relaxed, but not very well. Press the button again to stop the relax process.

e. Change the process to Relax by Polygon Angles and run the tool again. Stop it when it seems to stop moving the vertices.

Why did we run the Edge Angles first and then Polygon Angles, when Edge Angles clearly doesn’t work?

This is because sometimes, running one relax method and then another will produce better results than running just one. In this case it might not have been necessary, but it’s important that you know you can do this.

f. Now that the UV island has been relaxed, rotate it so that its edges are roughly vertical and horizontal. This’ll just make it easier for aligning the texture image to the model and for fitting multiple UV islands into the UV space. Take a look at the mesh and you’ll see the texture is now free of distortion and all the circles are properly sized.

08. Fixing UV distortion

So far, we’ve unwrapped an object with a single poly element. It’s possible for a single “object” to have multiple elements inside of it. There’s very little difference between this workflow and unwrapping an object that contains a single element.

a. Select the “Cushions” object and add an Unwrap UVW modifier to it. Enable the Polygon selection mode toggle and the Select By Element XY Toggle. Select the top cushion.

b. Use the Box Map to auto-unwrap this element. Notice that the Box Map will only apply to the element you have selected. Once both elements have been unwrapped select all of them and then run the Pack: Custom tool. This will lay them all out in UV space.

c. Once the elements are laid out and packed, join them together like in the image below, where 1 is the front of the top cushion and 2 is the top of the bottom cushion. Note that doing it this way will produce some slight warping around the corners but it’s such a small amount that it’s fine in this case. If you get strong warping then you would need to make sure that the outer vertices at each corner are split so that the UV map can relax completely flat.

d. Now we need to scale these elements. Since 1 and 2 are going to be visible, they need to take up the most room on the UV map so that they can get the most detail. To scale these elements you can either use the Scale tools or the Freeform Mode.

e. The Scale tool has three separate modes, accessible by clicking and holding on the button – scale uniformly, horizontally, or vertically.

f. The Freeform Mode allows you to intuitively scale, move, or rotate the UV island by clicking and dragging on one of the square boxes that surround the object once the tool is activated.

g. Scale the UV objects so that they are the proper size, with objects that require more detail being larger on the map than objects that require less detail. An object that requires little to no detail is the back of the cushion, or the underside of a couch, for instance. Note that with tiling textures (textures that are just a repeating pattern), it is OK to overlap your UV islands. However, for atlas textures (textures with specific detail in certain spots that lines up with individual islands) this is not OK. Since Wayfair never uses atlas textures, you should feel comfortable overlapping UVs if necessary.

09. UV unwrapping using alternative auto-unwrap methods

We have used the box map so far, but let’s use something else. Generally when you are choosing which auto-unwrap to use, you want to pick one that matches the shape of your object as much as possible. The legs on this chair are cylinders, so let’s try a cylindrical map!

a. Select the Leg_Prime object. The other legs are all instances of this leg, so modifying one will modify the others.

b. Add an Unwrap UVW modifier. Select the entire leg using the polygon select tool, and apply a cylindrical map. Use the “Align Options” to make sure that the cylinder is vertical, just like the legs are.

c. You will get something like this. Obviously it’s not exactly right – you will need to make sure that it is a square by breaking off the polygons and moving things around.

d. You will end up with something like this. Notice that to repair the green seams where two edges are directly on top of each other, you will have to click once to select the edges, and then run the Stitch: Custom tool. Do not click more than once or click and drag to select these edges, as you will select both at once and confuse the software when you try to stitch the seam.

f. Now that we’ve fixed the seam issue on the main body of the leg, let’s turn our attention to those straight lines on the top and bottom of the map. These are actually the top and bottom faces of the leg projected from the side.

To fix them it’s really easy. Select them using the polygon select mode in either the UV Editor or the Viewport.

Then activate the Planar Projection Map mode. This will reproject these selected faces onto the UV map. Now just scale them to fit with the cylindrical body of the leg and you’re all set!

10. Some final notes

If you would like to compare your model against ours, you can download the final model here.
At Wayfair we use tiling textures for most of our materials. Tiling textures are images that have a repetitive pattern that repeat over and over again on the model. The image below shows a tiling texture:

Because of this, we do not care if your UV maps fit inside the available UV square. Outside of the UV square the texture will automatically start to repeat. Since our textures are designed to repeat, this is acceptable.

Going forward we are standardizing all of our textures and materials to be at a real world size. This means that it is important for your entire model to be uniformly unwrapped. In the example image on the first page and the “BasicUV_Tut_FINISH.max” file included with this tutorial, all the separate sub-objects of the model display the tiling “R” texture at the same size.

In order to do this we had to make some of the UVs extend beyond the available square in UV space. This is acceptable because again, the textures will start to repeat. Since our textures are designed to repeat, this is not an issue. The important thing is to have a uniform unwrap and then scale the texture using the “Tiling” option in the Bitmap node.