Brazil Rendering System Options

This page lists most of the options that are available in the Brazil for Rhino plugin. There is a brief explanation of the purpose and effects of each one. Since Brazil for Rhino is not yet completed, some options have not been implemented at this stage.

Options

The Brazil options dialog can be opened via the Brazil menu, in which case you get a modeless dialog. It is also possible to access the options in a modal way through the regular Rhino Options dialog. The options have been grouped in a number of categories, each of which is represented by a collapsable frame.

These settings refer to the properties of the Brazil render engine, not to the properties of objects and lights. Light and object settings can be reached through the Rhino Properties dialog box.

System Options

Brazil does not render an image in one go, instead it divides the entire image into a grid of square buckets, each of which is solved individually. These buckets can have different sizes, they can be processed in a specific order and they can be distributed over a network, so that multiple computers can render into the same image by completing the buckets they are assigned. 

The General options specify the progression of a rendering.

Bucketing options

Size:  The size of a bucket defined in pixels. This setting makes little difference in practice. Small buckets render faster, but there are more of them so the rendering time at large is not affected. However, if you're running a complex rendering, you may want to switch to smaller bucket sizes to get a more frequent visual update of the progress. Note: Pixels near the edges of a bucket are slightly harder to solve correctly than interior pixels. This means that renderings made with small buckets tend to have more bucket artifacts than renderings made with large buckets. However, bucket artifacts occur only under very special conditions.

Order:  Order and Interlace refer to the sequence of buckets in the queue. Orders include Hilbert, Top-to-Bottom, Left-to-Right, Center-out, and Random. 

R:  Reverses the specified order, so you can also get Right-to-Left for example.

Output Size

These options specify dimensions and ratios. By default, the rendering has the same dimensions as the active viewport, but you can override this behavior.

Use custom size:  If you do not use the viewport size or an exact multiple of the viewport size, the preview will not match the aspect ratio of the rendered image. Enable Safe Frame in order to see what part of the viewport will be rendered. Safe Frame options are located in the Document Properties dialog box.

View

The View options control the behavior of the virtual camera. 

Lens

Use viewport lens:

Brazil currently comes with four lenses:

Perspective: The Perspective lens gives a three-point perspective projection just like the Rhino viewport. This is technically an impossible projection, but our brain accepts the illusion with longer lens-lengths.

Spherical: A spherical projection is physically correct, because it uses a six-point perspective (two vanishing points for every axis instead of just one). Straight lines in space become curved under most conditions, which makes it less useful for a CAD modeling environment. With short lens-lengths, the spherical projection starts to behave as a fish-eye lens. Note: Since the spherical projection cannot be represented in the viewport, you cannot use the Rhino view to accurately position the camera.

Orthographic: An Orthographic projection in Brazil is the same as a Parallel viewport in Rhino.

Depth of field

The Depth-of-field options specify settings that will introduce an imperfection that makes the virtual camera behave more like biological eyes and photographic lenses. In physics, a lens system always has a focus distance at which the image is at maximum crispness. Objects that are closer to or farther away from the camera than this focal distance start to become blurry.

Wireframe

These options control the post-effect addition of curves in the rendering and the way Rendered Viewport mode behaves. 

Image Sampling

This is one of the most important features of Brazil, one that must be mastered by professional users. See Brazil sampling

When sampling is set too high, the rendering will progress slowly without apparent increase in image quality. If the sampling is too low, the image will become grainy or blurry when certain conditions are met. 

The Adaptive Tests frame gives you control over the fine-tuning of adaptive thresholds which control when Brazil switches from minimum sampling to maximum sampling.

Sampling parameters

P1:  Preview quality

P2:  Medium quality

P3:  Production quality

Motion Blur

Motion blur only works when the Bongo animation plugin for Rhino is installed. 

When you have moving objects in your scene, Brazil can ask Bongo where objects are headed and where they came from. The direction and speed of objects is then combined with the camera's shutter speed to calculate the region of space that the moving object occupies for the duration of a single rendering (the shutter time). 

Motion blur can be enabled for moving objects. For a moving camera, all objects have a speed relative to the camera and thus all objects are rendered with motion blur.

Ray Server

These settings control how accurate reflections and refractions are calculated.  

For example, a ray caught between two parallel mirrors could theoretically bounce forever, but since only the first few bounces contribute vital data, there is usually no need to refine the reflection further.  The default settings usually suffice for normal scenes, but for models with lots of glass and mirrors, ray tracing depth for reflection and/or refraction may have to be increased. 

You can also specify an exit color that will override the color in the ray-tracer when a threshold is reached.

Luma Server

The Luma Server is all about scene lighting and how it propagates through the scene. Light objects have their own settings that influence the behavior of individual lights such as shadows, decay, attenuation, and projection.

General

These settings enable or disable the default light and shadow casting. The default light is only used when you have not specified any light source objects in your scene. Without any light sources the rendering will become completely black. However, if you have defined materials that cast photons, you may not want to use the default light. 

Direct illumination

This is the simplest possible lighting scheme. Every point in a scene checks to see how many lights are visible from its location. Every visible light contributes to the brightness of the sample. 

QMC sampler

Point and area lights are represented by light objects in the Rhino model. 

Sky light is derived from Brazil's Environment settings. The settings for sly light behavior are located at the bottom of the Luma Server dialog box. 

Global illumination

This advanced lighting scheme takes lit geometry into account. Since global illumination is potentially an endless process, there are many tricks to short-circuit a calculation and get a premature, but fairly accurate result. This requires a fair understanding of how GI works. For more information, see Wikipedia's Global Illumination article.

Render Cache Options

This option reduces the large overhead of a global illumination rendering by performing an indirect-light-only prepass at low resolution and then using that image to control the illumination of the final rendering. One of the biggest advantages of using an irradiance cache is that is can be saved (cached) between renderings, drastically decreasing the render time for animations.

Render Pass Control Options

These options override a number of settings prior to rendering. If you have defined a scene with complex materials (lots of reflection, lots of refraction, sub-surface scattering , etc.), it will take a long time to render. However, if you are  interested only in camera location, you will not want to render the scene at full complexity for a quick indication of the perspective distortion or the object occlusion. In the Render Pass controller you can assign simple materials to all objects or override lighting schemes without losing your actual settings.

Photon Map Options

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