Archive site for Autodesk Ecotect Analysis educational resources, notes and tutorials



SolarTool: Sun-Path Panel

Controls in the SUN-PATH PANEL

The Sun-Path Panel sits within the main Sun-Path Window and controls the display of the sun-path diagram in the display area. You can open and/or close this panel by clicking in its title area. If you click on the status icon on the right-hand side, the panel will open/close without affecting any of the other panels around it.

Projection

Use this selector to choose the type of projection used to translate the hemispherical sky dome onto a flat 2D drawing surface. The following options are available.

Stereographic Diagram
Equidistant Projections
Spherical Projections
BRE Sun-Path indicator

These are all polar projections, displaying the sun-path and overshadowing information on a circular diagram with concentric circles representing altitude angles. The different projections vary in how they calculate the radius of points on the circle from their altitude. The type of diagram you use depends on which part of the altitude range you are most interested in - the spherical projection most exposes angles closest to the zenith whilst the BRE Sun-Path Indicator most exposes angles closest to the horizon.

Orthographic Projection
Waldram Diagram

An alternate method primarily used in the US is to display the same information as a 2D graph using essentially cylindrical projection with azimuth as the X axis and and altitude in the Y.

Tabulated Data

Select this item to display the sun position and overshadowing as a single-day table, as shown immediately below.

Shadowing

The items in this area determine how overshadowing information is displayed within the main graph.

Fully Shaded

Displays the area on the sun-path diagram where the window is totally overshadowed by shading devices and/or external objects, basically when it is 100% in shade. This is shown as a light grey area in the graph.

Percentage Shade

Displays a table of shading percentages within the graph. The colour of each square varies with percentage in shade, a light grey colour indicating 100% whilst the background colour indicates 0%. You can find out the exact percentage by dragging the current sun position over the selected square, in which case text describing the percentage shading will update in the bottom left corner of the graph.

To obtain this table, a quick ray-tracing calculation is performed. The window is first divided into a 10x10 grid. A single ray randomly positioned within each grid square is then generated and intersected with shading devices and external objects. This gives 100 parallel rays for each direction over the full extent of the window. The number of rays found to hit one or more objects in the mode gives the percentage the window is in shade when the sun comers from the given direction.

This is done in 5° increments over the full 180° horizontal and 90° vertical field of view in front of the window. The path of the sun through the sky on the first day of each month is then overlayed.

Centre Point

In addition to full shading, this displays an area on the graph closely corresponding to 50% shading. It is actually the area when the geometric centre point of the window is in shade.

None

Use this setting to clear the graph of overshadowing information.

Shading Coefficients

This button displays a table of monthly and annual shading coefficients. These are average shading ratios taken over all hours of each month. They can be used in other applications which use simplified single-figure overshadowing values.

SolarTool: Location Panel
SolarTool: Window Panel

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