Support Technical Support: Frequently Asked Questions

Radiosity and RenderWorks
Radiosity rendering is very different from other rendering modes, and requires a different workflow process to achieve a successful result.

1: What is Radiosity?
Radiosity is one way for a computer to simulate the indirect lighting that occurs when lit surfaces transfer their energy to other surfaces. To calculate this lighting, all the surfaces in the model are converted into triangles and the brightest triangles are visited in turn. Light from each triangle is re-emitted to its neighbours, until some amount of energy has been accounted for, and then the Radiosity solution is considered to be finished.

2: When should I use Radiosity render modes?
You should use Radiosity render modes when:
• The usual direct lighting and ambient light does not capture the lighting subtlety, contrasts, or colour tones satisfactorily.
• There is a large contrast between the darkest and brightest parts of the model, or there are large colour contrasts among the lit areas in the model.
• You are rendering interiors, where the light energy would eventually be dispersed to many surfaces.
• You are rendering exteriors, and you want to see “washes” of light from overhangs, patios, footpaths, etc.

3: When should I not use Radiosity render modes?
You should not use radiosity render modes when:
• You can quickly produce satisfactory lighting by combining existing VectorWorks light objects, or easily "fake" the indirect lighting with fill lights.
• You can use area lights or a dome of directional lights to provide satisfactory soft lighting effects.
• There is not significant contrast between the brightest and darkest areas of the model, or there is not much colour contrast between the lit surfaces in the model.
• Almost all of the light energy that falls on the model's surfaces will be lost into space and not hit neighbouring surfaces when re-emitted.

4: How do Radiosity and ambient light relate?
Ambient light is a catch-all phrase for the remaining light that is bouncing around in the model. Radiosity can be thought of as a way to correctly calculate and "localise" the ambient light. As more energy is accounted for in the Radiosity solution, the (un-localised) ambient energy decreases until all the light energy has been localised. Radiosity can be used as a "fast" way to produce a more accurate ambient term, and apply some of the brightest light to specific regions of the model. Note that any ambient lighting set by the Set Layer Lighting Options command should be turned off for a radiosity rendering.

5: Why is Radiosity expensive, memory and processor wise?
Radiosity uses a lot of memory because all of the model's geometry must be duplicated and converted into triangles of a certain size, and assigned energy values. The more detailed the geometry in a model, the more memory the Radiosity processing will use and the more time will be required to re-emit light energy from each triangle to its neighbours. Also, the higher the render mode's detail settings, the more triangles are produced, resulting in larger memory requirements and more time to re-emit the light energy onto each triangle’s neighbours. Doubling the number of surfaces in a model actually quadruples the time required for Radiosity processing.

6: How can I modify my model to render faster with Radiosity?
You can modify your model in these ways to help Radiosity render faster:

1. Use the highest-level geometry you can to model your objects. It is much better to model an object as an extrude, sweep, boolean solid, or a NURBS surface than as a mesh. The worst way to model for a Radiosity rendering would be to model a detailed object as a set of small, individual 3D polygons.

2. Eliminate 3D details that are not going to be significant to the rendered image or the indirect lighting. For example, if you model a staircase's individual bolts and threaded screws, each of these will be contributing unnecessarily to the memory and time required for the Radiosity solution. The Median Obj Size shown in the Custom Radiosity Options dialogue box will have an unusually small value when the model consists of mostly tiny geometry.

3. Limit the size of large ground planes and landscape surfaces to the minimum size needed for the rendered image. Depending on the render mode's detail settings, the large surface area can produce millions of triangles that do not significantly light up the building because their energy is emitted mostly into space.

4. If geometry must be visible in the rendered image but will not contribute significantly to the indirect lighting, consider applying per-texture or per-object Radiosity overrides to them to help the Radiosity processor ignore them.

7: How do I control how much light is re-emitted from an object?
The reflectivity shader controls how much light is re-emitted from a surface. To control this amount, apply a texture that uses a reflectivity shader, and adjust the reflectivity shader's Diffuse Factor. The default reflectivity shader when one is not assigned is Matte, whose Diffuse Factor is set to 100% by default. In addition, use Radiosity overrides. "Turn off" or "turn on" Radiosity for specific objects or textures by using the override checkboxes shown in the Edit Texture dialogue box and the Object Info palette's Render tab.

For example, to render a ground plane with direct lighting but not include it in Radiosity processing for efficiency, you can set the Radiosity Override checkboxes to not emit and not receive. This effectively removes the ground plane from Radiosity processing. If a patch of grass needs to re-emit onto the side of a building, split the ground plane into a large one that does not emit or receive and a "skirt" around the building that does emit and receive. Through the Radiosity Optimisations dialogue box, model parameters can be set so that only certain objects re-emit indirect light, and all other objects either just receive indirect light or do not participate at all in the Radiosity processing. One combination that can be produced is one where only the light on a floor is re-emitted onto the rest of the room, i.e. one "bounce".

8: How do I efficiently render exteriors with Radiosity?
You can efficiently render exteriors with Radiosity by:

1. Using Custom Radiosity render mode, select the Include Visible Surfaces Only checkbox in the Radiosity Optimisations dialogue box. This means that only the visible building facade will be involved with Radiosity processing. The objects and surfaces that are behind the facade will not be included in the Radiosity processing.

2. Set large ground planes and tree image props to not emit or receive, using either Edit Texture or Object Info palette radiosity overrides.

3. Set the Obj Inclusion slider in the Custom Radiosity Options dialogue box such that only the largest lit surfaces will emit (grey), and the smaller details like window mullions and door knobs will only receive (red).

4. If any surfaces are not visible that do produce significant indirect lighting (like flat roof surfaces that aren't visible in the current view), they can be forced to participate despite not being visible by setting either an Edit Texture or Object Info palette Radiosity override to emit and receive.

5. In the Custom Radiosity Options dialogue box, deselect the Create Ambient from Remaining Energy checkbox. This makes it possible to stop the Radiosity processor sooner without having additional ambient lighting that makes the model overly bright or overly saturated with colour.

Other radiosity resources:
• NNA Knowledgebase Article by Dave Donley.

Suddenly my drawing has vertical and horizontal dashed lines running to infinity off all edges of the page. What happened?
This is a common question with an easy fix. Go to VectorWorks Preferences/Edit tab and uncheck the Snap to Loci option. When this option is on, any 2D locus on the drawing will exude these lines.

What is the best way to send or receive a file via email?
When you send an email to someone, you have no idea of the route it will take. It may be very direct or travel though a variety of different servers and half way across the country. When that email contains an attachment, the attachment can easily become corrupted by this circuitous route or by an operating system it encounters.

For these reasons, you should always compress attachments because it encapsulates the file and also makes transmission faster. Generally, it is best to use a non platform specific compression method such as Zip, unless you are on a Mac and are sure the file is going to another Mac user. In this case, it is safe to use Stuffit for compression [although Stuffit is cross platform, Windows users need to have Stuffit Expander in order to uncompress the file, which is only standard on the Mac and must be downloaded by Windows users].

In Mac OSX, the Archive feature will create a Zip file that will be valid on both types of machines. To access it, press Ctrl and click on the file you wish to compress, then choose Create Archive Of... from the Contextual menu.

Some Mac email clients (for example Eudora), will automatically encode any attachment using Binhex. As this is a Mac only encoding, it will generally render the file unreadable on Windows machines. If you are unsure of the platform the desired recipient uses, choose Mime or if that is unavailable, Uuencode as the encoding protocol.

One final point. In an effort to reduce the spread of viruses, ISPs are increasingly taking it into their own hands to remove attachments from suspicious looking emails, or relegating them to the SPAM folder. For this reason it is best to keep your email content as simple as possible. Use plain text (no styles), avoid text colours, do not add multiple links to URLs (one or two are OK) and do not include a graphic of your company logo. Although this tip is about sending attachments, taking these precautions will also see fewer of your general emails getting caught by SPAM filters.

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