Here is a tutorial I wrote a while ago in regards to adding dirt to a car in photoshop. Some people may find this useful.
Thought I would post a tutorial on adding dirt do a car since a number of people have been asking me about my cars from the Photoshop competition. I’ll try and be as thorough as possible, but it’s dirt so this is only a basic guideline and it behaves differently on each car.
What I’ve done is taken a screenshot of the car at each stage pretty much of what I have done on the Transit Connect, I can post images of each step of the Sandero Rally car from the January Exercise later on.
One thing I will say is very important before I start, is to use as many layers as possible, I know it is clichéd, but if you use only 1 layer and if you make a mistake with the dirt and try and fix it, it will be noticed. Also, remember to name the layers too, even if it is just as simple as dirt1, dirt2 etc, if you don’t want to get confused that is, becuase you’ll add about 10-15 more layers doing the dirt alone.
What I have done also, is to treat the bodywork and the underside/wheels separately so I could concentrate on one, because the underside requires something slightly different. You could do them at the same time, but it is just my personal preference.
Step 1: Try and have the car as near as possible to being finished as you can, because you don’t want to be adding extra bodywork area after the dirt has been applied. In saying that though, it doesn’t have to be perfect, because the dirt will hide some of the flaws. Here is the start image.
Step 2: New Layer. Start with a largeish brush, try and use one which looks like spattered mud (either in the wet media brush set or natural brush sets), it helps with the realism, turn the opacity right down to about 20% or there abouts and do something almost like a base coat. Go over areas which will have alot of dirt coverage. Choose a colour which is based on the kind of dirt you want your car to be covered in, the transit was for dakar so it was a sandy orange/yellow, you might want a redder one, or darker.
Step 3: New Layer. Decrease the opacity to around 50%ish (can’t remember exactly), and pick out even more where the dirtiest areas of the car will be on the bodywork. Maybe increase the brush size slightly and click lots without dragging the mouse unlike the previous step.
Step 4: New Layer. Make the colour darker, change the opacity and apply the dirt to the areas which will get hit with dirt from the wheels, so behind the wheel arches, the wing mirrors. Also it’s a good time to try and add dirt to the front of the car, light amounts to the bonnet. Change brush size depending on area working on, go for smaller for the wing mirror since this will not need much more.
Step 5: New Layer. Change the colour, and decrease the brush size. look for smaller areas which will get dirt build up, eg the channels down the side of the transit. and along the bottom of the wing mirror.
Step 6: New Layer. Increase brush size, darken colour and increase the opacity slightly compared to last setting. Go over most of the car, showing the extremities of where the dirt reaches. Along the back, on the light gantry on the roof etc. Slowly building up where the dirt needs to be.
Step 7: New Layer(s). Keep building up, going over the areas done, changing the colours to add depth, opacities and brush sizes. If you can, look at pictures of rally cars just to see how they look when covered in muck.
Step 8: Tidying up the bodywork. Use the eraser tool. To save going onto each layer created and erasing. Make a copy of each of the dirt layers, merge them and hide the originals, this way you can erase easily and quickly.
Step 9: Do the underside of the car and the wheels in the same way as the bodywork with the exception of putting down a base layer. Also use darker colours as lighter ones will stand out too much. If you can see the tyre treads, try and make them stand out. Once finished, clean up the underside in the same way the bodywork was done.