| Visualizing illuminance levels, generated in Radiance, in a Maya environment |
| Richard Gillibrand & Patrick Ledda | |
| University of Bristol, UK | |
| Slide 2 |
| Introduction |
| The real world can presents luminance levels ranging from 10-4 cd/m2 (starlit) to 106 cd/m2 (sunlight). | |
| Knowing the luminance levels in an environment can be very useful in light design. | |
| Illuminance standards |
| National standards proscribe minimum illuminance levels for a variety of tasks and situations. | |
| From these standards it is then possible to determine suitable lighting conditions. | |
| These standards (at least UK ones) take into account only illuminance and therefore are not view dependent. |
| "Probably the easiest way to..." |
| Probably the easiest way to visualize luminance levels in an environment is to generate a false color version of the scene. | |
| This can be easily done in Radiance. | |
| Depending on rendering options we can create luminance or illuminance false colored images. | |
| False-coloring |
| Radiance falsecolor program |
| Radiance produces false color images based on irradiance/radiance data. | ||
| This is achieved by: | ||
| Reading radiance/irradiance values from a .pic image | ||
| Calculating luminance/illuminance | ||
| Re-displaying or compositing based on a color scheme. | ||
| Setting the correct scaling |
| The scale used is very important because it can affect the visualisation and understanding of the scene. |
| A problem |
| Because Radiance takes data from a .pic file, it can only generate false color images from the same view point. | |
| It would be nice if we could know the illuminance in a particular area of a scene even if it has not been rendered. |
| Our approach |
| Visualise the lighting levels of an environment in 3D. | |
| This is possible because illuminance is inherently view independent. |
| How does it work? |
| We developed a tool for Maya that directly generates Radiance files. | |
| Using the GUI, materials, geometry and lights can be created and easily modified | |
| Our approach (2) |
| The GUI allows us to simultaneously generate geometry in Radiance (.rad file) and in Maya (on screen) | |
| In Maya the position of the geometry can be easily modified. The new position is the re-written to the Radiance file. | |
| Our approach (3) |
| Lights and models can be easily imported into any scene and saved to .rad file. | |
| VIDEO |
| Generating a .rif file |
| The GUI enables us to create a .rif file for the scene | ||
| Similar to trad | ||
| However the advantages are that it automatically includes : | ||
| geometry | ||
| Materials | ||
| View descriptions | ||
| ZONE, AMB, OCT | ||
| Generating a .rif file - GUI |
| Generation of views |
| For every plane, the program generates an individual view. | |
| Each view is a parallel projection | |
| The view parameters |
| For each plane, the view point is determined by finding the center of the plane and its normal. | |
| The view point (-vp) is then located along the normal at a very short distance from the surface. |
| The view parameters (2) |
| The view direction (-vd) is simply the vector from the view point previously calculated back to the surface (along the normal). | |
| The view up (-vu) is determined by interrogating the surfaces orientation. | |
| The width & height (-vh, -vv) are matched to the dimensions of the surface. |
| Non-planar objects |
| We are still working on this feature | |
| We can already create luminance data for non planar objects such as spheres, cones and cylinders but it still needs some improvements | |
| Useful Features |
| Automatically both falsecolored and rendered images can be produced separately and as a combined contoured image. |
| Other features |
| Also, the tool automatically generates a Radiance view based on the current perspective view. | |
| Another nice feature is that animation paths can be easily created and written as view files for Radiance. | |
| Video |
| Conclusions |
| We have presented a tool that allows the user to model in Maya and then automatically writes Radiance files. | |
| This tools is mainly used to visualize luminances in a true 3D way. | |
| Normal renderings and other features such as animation are also possible. | |
| However, much work still needs to be done to make it more useful in light design |
| Future work |
| Extend the tool to include arbitrary shapes | |
| Use both NURBS & polygons | |
| Allow the use of modifiers for materials (this has little effect on the illuminance calculation) | |
| It would be nice to include modifiers for the light material. | |
| So far only plastic, metal, dielectric, trans, glass and light can be used. Other materials just need to be hard-coded in |
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AMcneil
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last modified
Feb 29, 2016 12:26 PM