How to get the render pixels coordinates in compositing

When fine-tuning the finished render in “Compositing”, sometimes it is necessary to refer to the pixels coordinates of the processed image, for example, to apply effects distributed over the entire width or height of the image.

We can get the distribution factor of coordinates along with the height or width of the rendered image using texture nodes.

How to render an object with reflections on a white background

The single object visualization most often is performed on a clear white background. It is difficult to achieve this through the common configuring the scene – increasing the illumination of the scene “lights up” the object, decreasing – the background becomes gray instead of white. If the object itself can be simply rendered on a transparent background and then imposed on white, but what about its reflections?

Let’s consider the way how we can render the object and its reflection on a white background.

Fast intermediate nodes view in compositing

Creating a node tree in the compositing window, sometimes it is necessary to see the intermediate result given by some parts of the node tree. For fast viewing click left mouse button on the desired node with the “ctrl” and “shift” keys pressed. Blender adds a new View node (or uses one of the existing) and connects the output of the selected node to it. The result is displayed on the backdrop (if the corresponding checkbox checked) or in the UV/Image Editor window in “Viewer Node” mode.

If the clicked node has several outputs, each subsequent click on that node switches the view to its next output.

How to render object with shadows on a transparent background

Sometimes it is necessary to create a render of an object with shadows on a transparent background. This occurs when you need to realistically embed a 3D into the photo or when creating an image to use it as a sprite in a computer game.

There is no special shader in Blender, like “Shadow catcher” in 3D Studio Max, which remains transparent display shadows. However, it is possible to achieve the desired result.

Let’s consider how we can get a shadow render on a transparent background using Blender:

Fighting with gradient aliasing when saving image as JPG

Background with simple gradient can greatly improve the final image. For example, a heart with gradient background looks like significantly better than the same heart with white background.

However, if you need to save such image as JPG, the gradient becomes aliased that fails the impression of the image. That problem is named “banding”. Is it possible to defeat the gradient aliasing?