Chapter 3. POV-Ray Interaction

Rendering the Scene

Once you have created a scene, you will want to render it. KPovModeler uses POV-Ray 3.1g to render the scene, so you need a correct installation of POV-Ray. At the time of writing POV-Ray 3.5 was released. This version is not supported in the KPovModeler 1.0 version.

Go to www.povray.org to get a version of POV-Ray and for installation instructions.

To render the current scene, press the render icon The render icon in the toolbar, or select the ViewRender menu entry.

Render Modes

A render mode is similar to POV-Rays ini file entries. It specifies the image size and quality levels for rendering. If you would like to render your scene with different qualities and sizes, you can add as many render modes as you need, from quick previews to fullscreen high quality images.

Render Modes Configuration

When you press the render settings icon The render settings in the toolbar or select the ViewRender Modes... menu icon, the following dialog opens:


The render modes selection dialog

This dialog shows the list of all available render modes.

Add

Adds a default render mode to the list.

Remove

Removes the selected render mode.

Edit

Opens a dialog to edit the selected render mode.

Up

Moves the selected render mode one position up.

Down

Moves the selected render mode one position down.

The Edit Button opens the following configuration dialog:


The render modes size tab

Each render mode has a description. You can enter any description, but it should reflect the render mode's properties.

In the Size tab you can enter the width and height of the rendered image. If you want to render only a small part of the image, check the Subselection check box and enter the part of the image in the fields below.


The render modes quality tab

In the Quality tab you can select various quality levels for the rendered image.

In the Quality combo box you can select the features POV-Ray uses while rendering. The possibilities range from a very simple coloring and lighting model, to one which has complex diffuse inter-reflection lighting. See the POV-Ray user documentation for a detailed description of the rendering features.

If an image is rendered with only one sample per pixel, various errors can occur. These images often have moiré or stepped effects in curves and lines, and details can get lost if they are smaller in appearance then one pixel. This effect is called aliasing.

POV-Ray uses a technique called anti-aliasing to reduce the impact of these errors. In general images will look smoother with this feature.

If you enable anti-aliasing, POV-Ray will calculate and combine more then one sample per pixel. This is called super-sampling.

POV-Ray supports two methods of super-sampling. The default is an adaptive non-recursive method; adaptive because the super-sampling depends on the local neighborhood of the pixel. Not every pixel is super-sampled with this method. The second method is an adaptive recursive one; recursive because every pixel is divided and sub-divided recursively, and adaptive because the recursion depth depends on the computed color values.

When you select the first method, povray traces one ray per pixel. If the difference between its color value and that of its neighbor exceeds the given threshold, both pixels are super-sampled by tracing a fixed number of additional rays. If you set the depth value to 4, a 4x4 grid of additional points will be calculated, a depth value of 5 will result in 5x5 (25) samples per pixel.

The difference between two pixels is computed as follows: r1, g1 and b1 are the red, green and blue values of the first pixel; r2, g2 and b2 are the red, green and blue values of the second pixel. The difference is then:

diff = abs(r1-r2) + abs(g1-g2) + abs(b1-b2)

The recursive method starts with 4 samples per pixel. If the resulting color values differ more than the given threshold, the pixel is sub-divided into 4 sub pixels that are separately traced and tested for further subdivision. You can specify the maximum recursive depth with the depth value.

An additional method to reduce aliasing effects is to add noise to the sampling process, called jittering. If you enable jittering, POV-Ray jitters the samples a tiny amount to reduce regular patterns.

The last quality setting is radiosity. Radiosity is an experimental POV-Ray feature that computes inter-diffuse light reflection. Be patient when rendering a scene with this feature.


The render modes output tab

In the last tab, you can configure whether or not the alpha channel should be calculated by povray. A pixel will then be transparent if the corresponding ray did not hit a single object.

Choosing a render mode

You can select the render mode in the combo box in the rendering toolbar.


The render modes toolbar

The Render Window

When you started to render a scene, this window will open:


The render window

It shows the rendered image, the progress and the current rendering speed.

Stop

Terminates POV-Ray.

Suspend

Suspends rendering.

Resume

Resumes rendering.

Povray Output...

Opens another window that displays the POV-Ray console output. If POV-Ray exits abnormally, you can find the reason in that window.

Save...

Lets you save the image when it is rendered.

Close

Closes the render window.