The Path Map standalone module implements the Light Path Map approach for indirect lighting.Its purpose is to add realism to computer games by computing dynamically changing indirect illumination. It is an improvement over ambient lighting or static light maps. Not unlike light maps, global illumination computations are performed in a precomputing step, using ray casting and indirect photon mapping (the virtual light sources method). The contributions of virtual light samples are computed on the GPU, with depth mapping. However, instead of computing a single light map, multiple texture atlases (constituting the PRM) are generated for the scene objects, all corresponding to a cluster of indirect lighting samples. Then these atlases are combined according to actual lighting conditions. Weighting factors depend on how much light actually arrives at the sample points used for PRM generation. This computation is also performed in a GPU pass.


Run
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Copy PathMap.exe (from the Debug or Release directory) to the solution'S directory and run.

Build
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Simply load and build the solution file (PathMap_2003.sln)

Usage
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There is a number of on-screen controls available to navigate the scene and adjust lighting. Use the mouse to look around, the A, S, D, W keys to move. If the “Move light” box is checked, the same controls move the light source. If “Look from light” is checked, the scene is rendered as seen from the light source instead of the camera. It is convenient to check both boxes when positioning the light source. Selecting the “Entry points” checkbox will add small squares to the scene to indicate entry points. Colors indicate weights. The clustering also becomes visible. The “Turbo” checkbox toggles camera movement speed. Pressing the “Tab” button will display a PRM texture, or revert to scene rendering. The technique ShowTex may be modified to display other internal textures for illustration. The slider “Tone scale” allows scaling the resulting image, which can also be viewed as changing the light source intensity.