Tutorial, creating a tyre sidewall bump map
Tutorial on how to create your own detailed sidewall bump map.
To create the sidewall texture, you really have two options, you can trace reference image in Photoshop or download an already created one from the internet. For this tutorial, I’m going to use the reference image I’ve already used for my previous tyre modeling tutorial.
Start by creating a nice high resolution square document in Photoshop. Go to File > New and type 4096 into both the Width: and Height: boxes and click OK.
You’ll want to be able to create black sections for parts that will push into the sidewall and white bits for parts that will extrude out of it. Fill the canvas with 50% grey colour. Click Set foreground color in the toolbox > set S: to 0 and B: to 50 %. Select the Paint Bucket Tool (shortcut: G) and click anywhere on the canvas.
Open up your sidewall reference image and copy it into the new document. Press Ctrl + A to select the whole image and Ctrl + C to copy it to the clipboard. Go back to your new blank document and press Ctrl + V to paste it as a new layer.
Fit the reference image to the canvas. Make sure that snapping is turned on by going to View and checking that there is a tick mark next to the word Snap. If the reference image isn’t perfectly aligned, turn snapping off.
Scale the image so that the circle of the tyre sits perfectly within the document boundaries. Press Ctrl + T and drag the corner handles out to the corners of the document. If you need to skew the image a bit to get it right. hold down Ctrl while clicking and dragging on the corners.
To change the layer names, double click on their names in the Layers window. Change the top layer to Reference.
One thing that makes this extra difficult is the fact that everything is shaped around a circle. Fortunately, Photoshop has a filter called Polar Coordinates that will flatten everything out for you. Once you’ve created all the shapes for the texture, you can transform everything back into a circle again.
To get a nice, wide and easy to work with straightened reference image, first double the width of the image. Image > Image Size…, make sure Constrain Proportions in unticked and type 8192 into the Width: box. Click OK.
Make sure the reference layer is selected and go to Filter > Distort > Polar Coordinates… Make sure Polar to Rectangular is ticked and click OK.
The reference is all straightened out but all the text is upside down. To correct this, go to Image > Image Rotation > 180°.
If the seam at the edges of the document cuts through something useful, you can go to Filter > Other > Offset….
Adjust the horizontal offset so that the seam doesn’t cut through anything important.
It may be possible to download some of the text required as a vector image. I googled ‘Bridgestone EPS’ and was able to find a bunch of sources for the logo. Unfortunately, I was not so lucky with ‘Potenza’.
Go to File > Place… and locate the eps file you downloaded and click Place. Click the tick button at the top or press Enter to apply. This imports the vector image as a smart object. A smart object uses vector data and can scale up and down while always keeping clean edges.
Press Ctrl + T and transform the logo to fit over the reference logo. One thing to note is that all the letters of the logo are the same height in the reference image but the logo file has a bigger ‘B’. For the moment, just match the scale of the main body of letters.
Select the Polygonal Lasso Tool from the toolbox. Create a selection around the ‘ridgestone’ section of the word.
Click the Add layer mask button at the bottom of the Layers window. This will make a mask that only reveals the part of the layer selected with the lasso tool from the previous step.
Duplicate the logo layer: Click on and drag the logo layer onto the Create new layer button at the bottom of the Layers window.
Invert the layer mask. Select the layer mask for the new layer by clicking on the black and white thumbnail of the mask in the Layers window. Press Ctrl + I to invert the mask.
Now the top layer should just be the ‘B’ and the one below it should be the ‘ridgestone’. Press Ctrl + T with the top layer selected and adjust the ‘B to the correct size. Press Enter to apply.
Select both Bridgestone layers in the Layers window (select one, hold down Shift, select the other). Press Ctrl + E to combine the layers into one.
You’re going to have to trace the rest of the larger shapes and logos by hand.
Open the Paths (Window > Paths) and click on the Create new path icon at the bottom of that window.
Select the Pen Tool from the toolbox (shortcut: P) and start tracing around one of the shapes or logos. Click on a corner to place a ‘hard’ corner, click and drag to create a ‘soft’ or curved section. Once you’ve already placed a marker, you can hold down Ctrl, click and drag on the marker to move it around.
If you’re working on something that has a hole (e.g., the letter ‘O’), make sure Exclude overlapping path areas is selected in the options bar and work from the outside in (e.g. the bigger circle in the ‘O’, then the smaller one). You can do this on multiple levels, e.g. it will work to cut out the shape around the ‘S001’.
If you need to duplicate a particular path, select it with the Path Selection Tool, hold down Alt + Shift and click and drag.
When you’ve completed a particular shape or logo, create a new path in the Paths window and move onto the next one.
When it comes to the smaller shapes, some of them are solid and some just need an outline, make sure you do these in different shape layers.
If you’ve finished an open shape and want to move onto a new one while still working in the same layer, first you need to deselect it in the Paths window. You do this by clicking in the empty space below all the layers. Then you can select the layer you were working in and keep going.
The next step is to create all the text layers. In the Layers window, make a new group by clicking on the little folder at the bottom of the window. Call it ‘Text’.
For the moment, make all the text white (make white the foreground color).
Select the Horizontal Type Tool from the toolbox. Type out the letters you’re trying to replicate.
Open the Character window (Windows > Character) and play with all the options in there until you get the text looking right. Try and find a font that’s close enough. If you want to find the exact font, you can use a website like identifont to help identify it.
To get the size just right, press Ctrl + T and, just as you did with the logo before, adjust the text to be just the right size.
Repeat the above steps to create text for all the appropriate locations.
Now it’s time to create the ridges inside the larger shapes. There are two different patterns, one where the ridges all go in a straight line and another where they form an arrow shape.
In the Layers window, create a new group called ‘Ridges1’ . Create a new layer inside the group and create a new shape layer. Trace one of the straight lines with the Pen Tool.
Make sure white is still the foreground color. Select the Brush Tool from the toolbox (or just press B).
In the Options bar, make the brush small and soft.
In the Paths window, click on the Stroke path with brush button at the bottom. Deselect the path.
Press Ctrl + Alt + T and move the newly created line over, next to the old one. Hold down Shift to ensure you move it in a straight line.
With Ctrl + Alt + Shift held down, tap the T button and new lines will be created next to the old ones. Keep tapping the T button until the lines reach all the way across a large part of the image.
Select the ‘Ridges1’ group and press Ctrl + E to condense it all into one layer.
If you need to, hold down Alt + Shift to duplicate and move the lines over onto another part of the image.
Repeat the above steps for the arrow shape ridges.
Now, it’s time to cut out the ridges and adjust everything to the right shades of gray.
Create a new group called ‘Bridgestone Group’. Click and drag the ‘Ridges’ layer (the one over the Bridgestone logo) onto the new group. This places that layer into the group. Also bring the ‘Bridgestone Logo’ layer and the layer with the ridges over the Potenza logo into the group. Click the little eye next to the ‘Bridgestone Logo’ layer to hide it.
Hold down Ctrl and click on the ‘Bridgestone Logo’ layer. Select the ‘Bridgestone Group’ group and press the Add layer mask button at the bottom of the Layers window. This applies a layer mask to everything inside the group.
Now you need to add the Potenza logo and any other logos to the layer mask.
In the Paths window, select the path that has the Potenza logo outline in it.
Click the Load path as a selection button at the bottom of the window.
Select the Paint Bucket Tool from the toolbox. Make sure white is the foreground color and click anywhere within the selection boundaries (the ‘marching ants’).
Do the same for any other logos or shapes that need the straight ridges.
Create a new layer called ‘BlackBG’. Click and drag it so that it is underneath everything in the ‘BridgestoneGroup’ but still inside the group. Check that the thumbnail for the layer is indented slightly like everything else inside the group.
Make the foreground color black and fill the whole layer using the Paint Bucket Tool.
At the moment, the troughs of the ridges would be below the surface of the tyre wall because they are black and the peaks would be above the surface because they are white and brighter than the surface colour. Looking at the reference, this isn’t the case, the ridges don’t appear to get as high as the surface.
Select the ridges layer and lower the opacity to about 40%
Create a new group for the arrow shaped ridges.
Repeat the above steps for all the shapes that have the arrow ridges in them.
You should be pretty close now.
Make a new layer called ‘SolidShapes’. In the Paths window, select one of the paths with shapes that need to be solid.
At the bottom of the Shapes window, make sure the foreground color is white and click the Fill path with foreground color button.
Repeat the above step for any other shape layers with solid shapes in them.
Make a new layer called ‘OutlineShapes’. In the Paths window, select one of the paths with shapes that need to be an outline.
At the bottom of the Shapes window, make sure the foreground color is white. Select the Brush Tool and make the brush small and hard. Click the Stroke path with brush button at the bottom of the Shapes window.
Again, repeat the above step for any other shape layers with outline shapes in them.
In this example, the some of the text should have an outline instead of being solid filled. First select the text layer that should have an outline.
In the Layers window, make the Fill opacity 0%. This will make it so that the layer itself will be completely transparent but the effects from the layer style that you’re about to add will be visible.
Click the Add a layer style button at the bottom of the Layers window and choose Stroke.
Make the Color white and experiment with the settings to get a result that looks about right. Click OK when you’re done
Now check the reference, do some bits of of the text not protrude less far than other? Are some indented into the surface and thus should be less than 50% grey? Check everything and adjust the colour of the text as necessary. To change the colour of a text layer, simply select the layer you want to change and change the foreground color to what you want it to be.
Now it’s just a matter of re-distorting this image back into a circle again. The straightened version is much easier to work on however a good idea is to save the steps to make it into a circle as an action. That way it’s possible to keep on working on the straightened version and whenever you need to save it out to test it in a 3D program, you can just run the action instead of doing all the steps yourself every time.
Click File > Save and save it as ‘TyreMaster_01’.
Click Window > Actions. Make a new action by clicking the Create a new action button in the Actions window. Name it ‘TyreCircleBump’ and click Record.
Again, click File > Save.
Click Layer > Flatten Image. If a dialogue box comes up asking to discard hidden layers, click ‘OK’.
Click Image > Image Rotation > 180°
Click Filter > Distort > Polar Coordinates…, check Rectangular to Polar and click OK
Click Image > Image Size…, make sure Constrain Proportions is unticked and change the Width: back to 4096 to make it square. Click OK.
Click File > Save As…. In the Format: menu, choose PNG. Name it TyreBump_01 and click OK.
Click File > Close.
Click File > Open…, Navigate to the ‘TyreMaster_01.psd’ file, select it and click Open.
Hit the Stop recording button at the bottom of the Actions window.
Now you can keep working on the straightened PSD file and whenever you want to update the texture file, you just need to click the ‘TyreCircleBump’ action in the Actions window and click the Play selection button. When you click on the little arrow in the Actions window, you can see a list of all the individual steps included in an action. If you don’t want to include one of the steps when you run the action, just untick that step.
Now you just need to add the PNG texture to the bump slot of your tyre shader. You’ll be one step closer to creating killer car renders.