F1 approach

As shown in Figure 58, the F1 approach involves the use of a single surface as the F aperture. The Radiance definition for this surface has been saved in the file fports/F1.rad. Figure 62 explains the procedure for assigning hemispherical sampling basis for this surface. Figure 63 shows an objview screen capture of the scene along with this surface. The F aperture needs to be large enough to cover the front portion of the façade completely and should be at a slight offset from the non-coplanar shading device (grates in the current example). The orientation of the surface-normal is crucial to the simulation and should be assigned as per the same conventions for the V Matrix apertures i.e. the surface normal should face towards the room. As shown in Figure 63, the Radiance glow material can be used to check if the F aperture is oriented in the correct direction.

Figure 62. The definition for the F1 F-matrix aperture (saved as fports/F1.rad). The first line is the rfluxmtx comment that assigns Klems-Full basis for hemispherical sampling (h=kf) and indicates that the hemisphere-up direction is +z (u=+z). As the direction of the surface-normal is in +Y direction, +z is an appropriate value for u.

Figure 63. Objview screen capture of the scene with the F1 aperture. The image on the left shows a surface for which the surface normal is correctly oriented (i.e. facing towards the room) and the image on the left shows a surface for which the surface normal is oriented away from the room. As shown in Figure 62, the surface representing the F aperture is assigned a glow primitive. Surfaces with glow and light modifiers will only emit light in the direction that their surface-normal faces.

The F-Matrix can now be created with rfluxmtx as:

rfluxmtx -v -ff -ab 4 -ad 10000 -lw 1e-5 -c 5000 -n 8 objects/GlazingVmtx.rad fports/F1.rad -i roomFmtx.oct > matrices/fmtx/F1.fmx

The corresponding daylight (D) matrix that accounts for flux transfer between the F aperture and the sky and ground can be created as:

rfluxmtx -v -ff -ad 10000 -ab 4 -lw 1e-5 -c 5000 -n 8 fports/F1.rad skyDomes/skyglow.rad -i roomFmtx.oct > matrices/dmtx/DF1.dmx

The F-Matrix and D-Matrix can now be merged into a single matrix through matrix multiplication as:

dctimestep -of matrices/fmtx/F1.fmx matrices/dmtx/DF1.dmx > matrices/dmtx/DF1.dfmx

The commands for generating results with this approach are described in section 7.5.