This is meant to be just a quick post to answer Chris’s question about the color effect on the front of the Mach 4 image that was my entry for last month’s Rendering Contest. 

In short, that effect is achieved by using a solid color as a decal and a mask, only instead of black and white the mask is a gradient of grey tones that act pretty much like a sifter, allowing more of the color to be seen in the areas where the gray is less concentrated, thus creating the effect that the color is more or less intense on one side and then goes gradually vanishing until it completely disappears.  I took the idea from the Step-by-Step PhotoWorks Self-Study Guide. At the risk of sounding like a commercial, yet again, I strongly recommend you get yourself a copy of the book. It’s really good!

While I’m not a PhotoShop expert, I can at least create a gradient and a doodle with an airbrush. This is more than enough (for now) to explain about this kind of use for a decal and a mask. The decal can be a solid color or a Photoshop (or any other similar software) pattern or texture.  The mask can be a gradient such as this one.

Or it can also be a doodle like this one that I made in Photoshop by using an airbrush tool and blurring it a bit afterwards.  My idea with this one was to create an effect of graffiti over a wall.

So, as a decal I used the following image, which is merely a 2 in x 2 in square of solid color.

And my mask was the doodle show previously. Notice though that I had to invert the mask in the decal property manager. This is because Photoshop will only let the color through the white or lighter areas in the mask.

The effect kind of looks like a wall that got scribbled with graffiti, doesn’t it? At least a bit?