Photoshop Advanced

Introduction

This page covers advanced topics for Photoshop:

Alpha channel

When rendering your scene in Maya, a alpha channel is included. If you want to use this alpha channel, save the render as Targa or Tiff extension. The alpha channel contains the information of the contour of the outer edges of the geometry. You can view the alpha channel by clicking the alpha channel icon in the top section of the renderview. Empty space shows as black, geometry will be white. (or grey, depending on the geometry transparency.)

With the RGB coloured button left to the alpha channel you can switch back to normal mode. The alpha channel enables easy selection of the background of your render in Photoshop. The saved selection can be found in the Photoshops channel menu.

Image composition

Layer masks

When adding a background image, the alpha channel can be used to paste in the background image. The background, or inverse, the geometry outline can be easily selected with load selection, under the selection in the menu bar. From the drop down menu the alpha channel can be selected.

When having the building (the part that will NOT be transparent)selected, a layer mask can be created with the add vector mask button. A layer mask controls the transparency of a layer. As with the alpha channel, black is completely transparent, white is opaque. Because transparency is acquired by the mask and NOT by erasing in the image itself, i can be easily undone. Erased image data is lost, but the mask can be made transparent or opaque at any time!

Now a background image can be added. New images will always be placed in an new layer. Each new layer can have its own layermask, in order to make parts transparent.

To add another sky, a layer mask for the background is created. Since there is no alpha channel in the background image, the mask must be manually created . this is done by making a completely white masks, and then use the paint tool to 'paint' the parts black where transparency is required. Make sure the mask icon next to the layer icon in the layer bar is selected when editing.

Adding geometry

In Photoshop it is also possible to add missing geometry or replace existing material by using data already present in the image. Copy, past en transform this material to use as the extension. To prevent obvious tiling effects or other clear edges, use a grey brush in the layer mask to make the edges semi-transparent so they blur into the surrounding.

If a part is completed and all its components are is place, merge the layers containing the components.

When adjusting the edges of the pasted parts, do not use the eraser! erased data is lost, use layer masks. Instead of a black brush to make edges completely transparent, use a grey brush, thus creating a smooth, half transparent border.

Another method for re-using existing image data is the clone stamp, which is more appropriate for small regions. The clone stamp uses a reference area to copy somewhere else in your image. The reference point may be defined from all layers in the file.

Adding people and trees

To give a better feeling of scale to an image, add elements like people and trees. As in all previous examples, use layers mask to cut out the objects. When it is cut out correctly, delete and apply the layermask. Photoshop will automatically ask whether or not you want to apply the layers mask. After applying, the black part will become transparent. When adding other object, take into account that light direction, light intensity, light colour an image distortion (perspective) should more or less match with their new environment.

Shadows are made by making a copy of the object and then rotating and scaling it. Change the colour of the layer and then decrease the opacity to make it transparent.

Effects

Adjustment layers

When the final composition is ready, colour and brightness can be adjusted. See the basic Photoshop information for more information about adjusting contrast, brightness, colour and lightness. The adjustments can me made by individual layer, or by several layers at once. In the last case, an adjustment layer is used. This is a special layer that contains the adjustments, and applies it to all underlying layers. An extra advantage is that its effects can be (temporarily) undone by switching off or deleting the layer. A layer mask can be used to localise the effect.

above right: adjustment layer on top of the layerstacking.

In the images below, perspective has been corrected. Keep in mind that in Photoshop huge alterations can be made after rendering. The same effects can often be much easier achieved in Photoshop then in Maya. Our example can be changed into this...

or this...

Depth effect

There are several ways to simulate depth effect in your image. One is to desaturate (de-intensify colour) and lighten objects or landscape in the background, or saturate foreground objects. This simulates atmospheric dust or high air humidity.

original image

desaturated background

Another technique is blurring objects in the foreground or background, this creates an out of focus effect.

out of focus effect

Lens effect

The depth effects are in a way methods to attract the viewers attention to a certain area of the image. Another way to do this, is simulating the lens effect of a camera. Due to a camera's lens, photographs will be just slightly darker and a little desaturated around the edges. The eye will focus on the centre of the image. Make a circular selection almost filling the complete image, in order to create a gradual change from centre to edges use a high feather setting for the selection tool. Then invert the selection and slightly darken and desaturate it.

Glow

There is a simple method of generating a subtle glow effect generated by the white areas in your image. The effect simulates the glare of a real camera and enhances the softens of the image. To apply the effect use the following work flow:

Select - Colour range.
Select the white areas in your image
Use the Fuzziness to extend the selection
Copy that selection
Paste the selection
The new layer contains a copy of the white areas of your image
Blur this layer
The layer simulates a subtle glow
Use the opacity settings in your layer menu to soften the effect

Motion

Giving the illusion of motion makes the image less static. In the menu bar select filter -> blur -> motion blur. In the motion blur settings you can adjust direction and intensity of the blur.

Adding detail with blend options

A big problem with renders of buildings is that behind the glass there is often no interiors visible because they are not modelled. A simple method of simulating the effect of interiors is pasting an image of an interior onto the glass.

first select the window
find an image of an interior with an approximate similar perspective on the web
copy paste the image into the selection
use the layer blend options to simulate the effect of a room behind the glass.

Tips & tricks

Making a tillable texture

Avoid obvious repetition of texture files:

Loading the player...

Using the Vanishing point tool

In order to make some fast perspective transformations in a picture you van use the Vanishing point tool in Photoshop: