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Interior Lighting Using Radiosity

In this lesson we are going to look at the advanced lighting feature called Radiosity which is a very effective method inside 3DS Max for calculating Indirect Illumination. Radiosity is a Physically Accurate method of calculating Indirect Lighting compared to 3DS Max's other Advanced Lighting feature 'Light Tracer', which depends on a bit of approximation.


01          The rule of thumb for fetching the best results with Radiosity is to model the scene on real world scale units and to use the 'Photometric' lights. A Photometric Light is meant to be a lot more physically accurate so it is actually based on a little bit more real world values instead of simple arbitrary brightness or color values like the 'Standard' lights.


02          We will start working with the 'Photometric' lights by creating a 'Target Light' in the scene from the 'Photometric' lights menu. But whenever we start to create a Photometric Light in the scene, 3DS Max is going to ask us if we want to use Logarithmic Exposure Control. Click 'Yes' as we are going to use the Logarithmic Exposure Control which works quite similar to the exposure control that we use on a real world camera.


03          Place the 'Target Light' inside the black lamp on the right wall while placing its target on the wall in a way that the light angle becomes similar to the the lamp's direction. Activate the effect of Scene Lights in the view-port by choosing 'Illuminate Scene with Scene Lights' under the 'Lighting and Shadows' tab from the View-port Configuration dialogue box. Also from the 'View-ports' tab inside the 'Preference Settings' dialogue box choose 'Nitrous Direct3D 11' as the 'Display Driver' for better view-port display results. 


04          Right now the Photometric light is emitting the light in an Omni directional pattern which is a 360 degree spherical pattern which is not the desired result as we want our light to emit and distribute light according to a real world lamp light. So our next step will be to apply a real world light distribution data from an actual light manufacturer onto this light by choosing 'Photometric Web' as the 'Light Distribution' type from it's modify panel.


05          As soon as we enable 'Photometric Web' as the 'Light Distribution' type, a new little roll-out with the name of 'Distribution (Photometric Web)' will appear in the light's modify panel. This roll-out will enable us to plug-in a 'Photometric' distribution file to this light. Hit 'Choose Photometric File' button and browse the photometric files which are usually in an .ies or .cibse format and are easily available on the internet or in the default 3DS Max directory.


06          In order to view the Photometric Data contained in these .ies files we can use a program called 'IES viewer' (check the project files of this lesson) which will give a diagrammatic representation of the photometric data for easy understanding. This program also provide us with the option of rendering the Photometric Data which will give us a better idea of what that light distribution pattern looks like. Switch back to 3DS Max and choose 'DFX_LTL11744.ies' file as the 'Photometric Distribution' file as it matches our lamp model more than the others.


07          Right now the the Photometric Light distribution is visible in the Realistic View-port depicting the exact details of the light pattern stored in the 'DFX_LTL11744.ies' file. Photometric lights also contains the intensity values of the real world light and in this case we are getting a very high intensity of light from the Photometric File (903.0 cd) and that is because the file is actually meant to be used for a big room. Therefore we will now reduce the intensity of this light close to a 400 watt light bulb that is only 500-600 candelas.


08          We now have real world lighting information on our light, like the real world light lens, the light distribution pattern, the real world light intensity and the falloff. These parameters will definitely help us in adding just that little bit of extra realism in our scene. Now as we are having 2 light lamps in our scene we will create an instance of this 'Photometric Light' and place it on the second lamp on the left hand side wall.


09          Overall the room is still very dark so we will add in a few lights in our scene before we actually begin 'Radiosity' calculations. Create a new Photometric 'Target Light' in the middle of the room and choose a 100 W Bulb preset for it from the 'Template' parameters. At first this Photometric Light will be emitting warm color which is a bit on the Orange side. So in order to minimize the warm effect of the light we will bring up the 'Kelvin' temperature value to '4800' from the 'Intensity/Color/Attenuation' parameters.


10          Right now the Photometric Light is distributing light evenly in the scene which is not the case inside the real world scenario as the light will diminish when its far from its source. Now in order to make this light emit light in a more realistic way with some attenuation we will change the light unit to 'lx at' from the 'Intensity' parameters with the values of '30' and '20.0 ft'. Turn on the Shadows for each light in the scene with the shadow calculation method set to 'Ray Traced Shadows'.


11          After setting up the basic lights in the scene we are now ready to begin the process of Radiosity to start introducing some indirect light calculation and to splash some light around. As the first step we will activate the 'Radiosity' lighting plug-in from the 'Advanced Lighting' tab of the 'Render Setup' Dialogue Box. Radiosity works a little bit differently than the Light Tracer as it actually stores the illumination data in the vertices of the scene's geometry.


12          The more geometry we have in the scene or the more denser the mesh is the more of this indirect illumination data can be stored at a per vertex level. So in order to test the indirect illumination that we get in the current set of geometry of the scene we will 'Start' calculating the Radiosity with a very small initial quality value of '50 %'. Once the calculation is done we can see the result of the Radiosity Calculation being presented inside the view port.


13          Right now we are getting a bit unpleasant result after the render which is because we are not having a good amount of geometry to be able to store all the Radiosity data. We can switch to Edged Faces mode from the view port parameters in order to see how 3Ds Max has tried to subdivide the geometry in order to try to Store some data. But eventually we are getting a very less amount of veritces in the geometry which will not let us store much data.


14          In this step we will try to refine our Radiosity result by enhancing the Radiosity Processing Parameters. Refinement Iterations will help us in improving the quality by running the Radiosity calculations through some refinement processes in order to smooth things out and help eliminate noise and speckles. Increase the 'Refine Iterations (All Objects)' value to '2' in order to give a couple of iterations for refinement of the result.


15          The results from these Iteration Refinement settings will get a little more apparent once we actually starts to get a little bit better subdivision in these areas. So in order to do that we will switch to the 'Radiosity Meshing Parameters' and 'Enable' the 'Global Subdivision Settings'. Enabling the 'Use Adaptive Subdivision' option will help 3DS Max to automatically decide where it needs to have more vertices in order to store more color information like in the areas of high contrast which can be defined through the 'Contrast Threshold' parameter.


16          In this case we will fill in a lower value of '30' inside the 'Contrast Threshold' parameter as we want to add in a higher amount of vertices in the high contrast areas in our pursuit of a good result. We can further subdivide the geometry in our scene by filling in lower values i.e. '0.65 ft' and '0.065 ft' inside the 'Maximum Mesh Size' and 'Minimum Mesh Size' parameters respectively, where Max Mesh Size defines the size of largest mesh triangles generated because of the Radiosity Subdivisions.


17          Hit render to see the result that we got so far from the current Radiosity settings. The render now has started looking more realistic but along with some harsh speckles and noise in some areas. So in order to filter the result we will increase the value of 'Indirect Light' and 'Direct Light Filtering' to '2' respectively. The result of this filtration can be clearly viewed inside the view port as it smoothened our result a little bit more. But the render result still shows that the things are a little bit more washed out than our expectations. 


18          So in order to correct that and to get the results that we want, we can alter the 'Exposure Control' settings from the 'Environment and Effects' roll-out. Inside the 'Exposure Control' tab hit 'Render Preview' button in order to render a preview image quickly so that the changes that we bring inside this tab can be viewed inside the preview window. Bring up the Contrast value to '95' while bringing down the 'Brightness' and 'Mid Tones' value to '62.5' and '0.25' respectively in order to bring some contrast in our scene and to bring some darkness into the shadowed areas.


19          We are still left with some of the blotchy areas in our scene that have to be taken care of in order to get a good result. This can be done or rather alleviated by using the regathering parameters inside the 'Rendering Parameters' tab. Turn on the 'Regather Indirect Illumination' parameter in order to regather and recalculate the indirect illumination from the Radiosity at the render time, which will hopefully smooth out the result a little bit more. Increase the 'Rays per Sample' and 'Filter Radius (pixels)' to '250' and '10' respectively in order to get a better refined result of Indirect Illumination.


20          Now as the final step and in order to keep things nice and sharp we can bring the 'Indirect Light Filtering' and 'Direct Light Filtering' level back down to '0'. Once we are finished with setting up of Radiosity parameters we can reset the Radiosity calculations by hitting 'Reset All' button and recalculating Radiosity with the 'Initial Quality' value of '90%'. This will make a huge difference in our final result by refining the quality of the final result with less or no noise.


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