I often get asked how I get extra colour, vibrancy and texture into my 3D work.
Often 3D renders can come out a bit flat and boring. The key to vibrancy is comping and mixing lots of renders ( passes ) in a program such a photoshop, that allows you to blend your various renders layers.
For this tutorial I'm using Blender and Photoshop, but the same principles can be applied to other 3D and comping software.
For this tutorial you can use a 3D illustration you have already made.
I'm using this image from my "un-game-land" project.
In Blender we are going to render the image with 4 passes, the default render, mist, ao, and gloss. When you image is rendered, save each pass separately and name them.
After our default pass we have ambient occlusion or ( ao for short ) next. This is a version of our image with shadow information basically based on the proximity of objects to each other.
Next we have a gloss pass, this is a render of only the reflections in our scene.
For the mist pass in Blender you will need to add some extra nodes. These are Map value and colour ramp. You connect Them in sequence to the mist pass. This results in a greyscale image of your scene where the front is dark and the back light. Other software will have a different way of achieving this.
We are going to add two extra passes. First we are going to add a glow to our default render. In blender you can use a glare node, there will be different setting in other software but the principle will be the same. We want the lights to have a glow around them.
HOW TO MAKE A RIM LIGHT MATERIAL IN BLENDER
The next will involve some more work. We need to render the whole scene again, but with a single material that has a glow on the edges. This gives us a sort of artificial rim light.Again different 3D programs will have various ways of achieving this. In Blender we create a new material. We make it black and add gloss and emission to the edges by using fresnel mix factors. These are set very low so we only highlight the edges.
Next we render the whole scene with just this material applied to everything. In Blender you can do this by selecting the material in the martial setting in the scene menu. This applies it to your entire render. In the example I've called this material Rim.
Then save this render pass. It should look like the whole image is black with white edges on everything.
Next I open all my render passes in Photoshop. You can use other programs to comp your files, but I find each program uses blend modes in slightly different ways. So you will have to play around a bit to get the same results.
I also create a new document ( the same size as our renders ) and place all the renders into the new file, this is excluding the mist pass, I'll come to that latter.
The above image shows the basic order I layer the passes, though this can vary according to the look you want to achieve.
At the bottom we have the default render, then above that the ao pass, this I've duplicated as I will blend it in two ways. First one gets a multiply blend, you find this option in your layers panel in Photoshop. The next layer gets an overlay blend. I also colourise both these layers and adjust the levels. I want darker darker shadows and whiter light areas. This helps increase contrast.
Next I adjust the opacity of these layers. I will often have a play around with opacity and the colour values to get an interesting look. There are no hard and fast rules here so experiment.
Next I add Layer with a colour fill. This will be our mist, so the colour and blend mode will be based on whether we want our mist darker or lighter.
HOW TO USE AN IMAGE AS LAYER MASK IN PHOTOSHOP
We mix this layer by using a mask, this will be made from our mist pass. The way we do this is to open the mist pass file in photoshop, use the marquee select tool to select the whole image then copy it. Then we go back to our main file, and select the layer mask option on the layer with our colour fill. Then we click the channels button in our layers panel. There you will see an empty layer at the bottom, that is our mask. We select that layer and paste.
We now have our mist layer. If we go back to the layers panel in Photoshop we will see this take effect. We can adjust the blending mode and opacity, and also play with the levels of our mask to create various effects. This often adds a lot of depth and interest to our image.
My next layer is the gloss pass. Now I don't always use this, it again depends on the image, but it can help bring out some extra highlights. I use a colour dodge add blending mode here and reduce opacity quite a lot, maybe down to 9%.
Next up is our glow pass. Again I use a colour dodge add blend, this time I create a layer mask and fill with a gradient, I also use the pen tool to mask off or highlight certain areas.
I fact with any of these layers it often helps to use layer masks on bits that don't work so well. For example we don't want or gloss layer to make thing shiny that shouldn't be shiny so we just mask those areas off.
Next layer is our rim material pass. This goes on top, and uses a colour dodge add blend. You'll often find you image really "pops" at this point. We can recolour this layer to good effect and I often bring the opacity down until we only just notice the effect. Again mask of areas you don't want to highlight.
I also use a adjustment layer or two at this point. This can be found at the bottom of the layers panel and is a round icon. I use curves and vibrancy layers to tweak the image. I often go back and fore tweaking each layer and the settings until I'm happy.
When I'm happy I save this image as jpg and open in Photoshop again. This is because I need to make adjustments to the whole image without the layers. Here we can do some final tweaks to the image. With this new Duplicate the image into a new layer and create a layer mask with the mist pass in the mask in the same way we followed earlier.
Now select lens blur from the Filter drop down panel in Photoshop.
Use the blur setting to create some depth of field. I like to add a bit of grain also. We use our layer mask as the basis for the blur and create some nice camera effects.
You could also use the layer mask to help recolour your final comped image depending on your needs. In this case I made the background have a red glow. A there we have a final image.
It has more depth vibrancy and edge than the initial render.
Let me know if you have any questions or comments on this tutorial.