Photorealistic Rock and Stone Textures
Simulating any material in Photoshop and getting it to look real is largely a matter of surface texture and lighting. This tutorial will show you a very easy method for making rock and stone that’s incredibly photorealistic. No special artistic skills are required here. We’ll just be using Photoshop’s built-in filters and tools. Here’s a look at what we’ll be creating:
Render Clouds, Difference Clouds, Noise, Alpha Channels, Displacement Map, Lighting Effects, Layer Mask
Start with an empty canvas. I choose 500×500 pixels, but this technique works with any size. We will also pick two colors that will make up our rock at this point. Earth tones work best when trying to make realistic looking rock, however you can pick other colors if you’re making more fanciful looking rocks. I chose a dark gray (color #4b4d4d) and a dull brown/orange (color #795b32). Set these as your foreground and background colors, then choose Filter->Render->Clouds to give us a nice randomized mix of color that one would find in true rock or stone. You’ll get something that looks like this:
Now we’ll randomized the surface a bit further by adding some noise. Use Filter->Noise->Add Noise. The settings shown to the right generally work quite well. This will yield the look below.
The next step will be to create a displacement map that will let us create a rough surface texture. This will give the look of an uneven surface and rough edges one expects to see in rock. In Photoshop, displacement maps are expressed as Alpha Channels. The white areas represent raised areas in the image and the black areas represent depressions in the surface. Since a rock surface has a random roughness to it, we’ll render clouds again to simulate the random nature.
First, click on the Channels tab and create a new alpha channel by clicking the new channel icon . The new channel will automatically be filled with black. Double click the channel name and change it to “Displace Map” so we can keep track of it. Your channel palette should like the one to the right. Now pick Filter->Render->Difference Clouds. This will give you an image similar to this:
Next we’ll randomize the displacement map a bit more by using Filter->Noise->Add Noise. Use the same settings as in Step 2. Now select Edit->Fade Add Noise and set the opacity to 50% to tone it down a little bit. Now select Filter->Render->Difference Clouds once again. Hit cmd-F (control-F on Windows) to reapply the filter two or three more times until you get a pattern where the light and dark areas seems balanced. If you want the surface to be smoother or rougher, you can apply a Levels adjustment at this point. If you increase the contrast between the light and dark areas, then the surface will be rougher. Reducing the contrast makes it smoother. Here’s what mine looks like:
Go back to the layers palette now by clicking on the Layers tab. Duplicate the original layer by right-clicking on it and selecting Duplicate Layer. This will eventually serve as a highlights layer, so double click on the layer name for this new layer and rename it “Highlights”. For the moment, turn off the visibility of this layer by clicking on the “eye” icon. Your layers palette should look like the one to the right at this point.
This is where things get fun. We’re going to work on Layer 1 now, so click that layer to make it active. We will apply the displacement map to the image by using a lighting effect. Select Filter->Render->Lighting Effects. Below are the options I used. Try these to get started. Once you get the hang of how it works, feel free to vary the settings to get the lighting the way you want.
The important setting is to select the Displace Map alpha channel we created earlier for the Texture Channel. Without this, the image would remain flat. The combination of the displacement map and the lighting is what creates the realistic rock texture. As you can see, the result is amazingly realistic looking:
You can now see how the displacement map works. Looking at the alpha channel we created in Step 4, the dark areas cause depressions in the rock and light areas cause ridges. The lighting effect uses this map to figure out where the shadows will fall.
If you like what you have already, you can stop here. I’m going to go on a bit further and show how to add a highlight to the surface that gives something of a wet look. It just makes it a little more shiny looking.
To begin, click on the Highlights layer we created back in Step 5. Click on the eye icon to make the layer visible. Select Filter->Render->Lighting Effect again. Use the same settings as in Step 6 except increase the Gloss value to about -50. This yields a much more shiny version of the surface as shown below. We’ll tone it down in the next step.
We’ll use a layer mask to control how much of this new shiny layer shows through. Create an empty mask with Layer->Layer Mask->Reveal All. This adds a layer mask to the layer and fills the mask with white. White in a layer mask causes the corresponding pixels in the layer to show through. Your layers palette will look like the one to the right at this point.
The layer mask you just created should be highlighted (has a border around it as shown above). If it’s not, just click in the white area of the mask icon to select it. Selecting it tells Photoshop we plan to draw in the mask as opposed to the image in the layer. Now choose Filter->Render->Difference Clouds to once again to give us a random pattern in the mask. Hit cmd-F (control-F on Windows) three times to reapply the filter further. This gives a nice random cloudy pattern in the mask. Where ever the mask is black, it causes the pixels in the Highlights layer to become transparent. Shades of gray going towards white cause the pixels to become less and less transparent. The end effect is that this allows just random portions of the highlight layer to show through. This nicely tones down the gloss since the layer mask only lets it show through here and there, and gives us something that looks very nice; not too dry looking and not too wet. It’s uncanny how quickly we can create a photorealistic rock texture in Photoshop. Here’s the final result: