Transmission and Punctual Light Support with KHR extensions
3D models displayed in basic viewers often have an artificial appearance due to the lack of meaningful lighting. The Punctual Light Support extension by the Khronos Group glTF extension gives us the possibility to define light sources within a scene, which are preserved in compatible glTF viewers. This and the Transission extension is now also supported by RapidCompact, making it possible to optimize models, while preserving the ligthing in the scene.
To carry out this demonstration, one of our 3D artists created the Newspaper Recycled Lamp. This model is high-poly, as it was sculpted in 3D, and includes 5 light sources, thanks to the KHR_lights_punctual extension. In addition to this one, the model also makes use of the KHR_materials_transmission and the KHR_materials_emission extensions, in order to recreate the subsurface scattering of paper and the shining of the lightbulb, respectively.
The optimization took place in 2 stages: Firstly, the model was decimated with RapidCompact. The second stage was texture baking, after which the 7 materials from the input lamp were translated into 3. With the purpose of measuring the capabilities of normal baking from RapidCompact, the normals of the lamp were also baked in an industry-standard texturing software. The comparison between the results of the 2 workflows show that the use of RapidCompact avoided artifacts that were found in the version baked with another tool.
After all, the original lamp, which was 63.6MB heavy and contained 790K polygons and 7 materials, was optimized to a 4.3MB model, made out of 6K faces and 3 materials. The lighting of the scene was preserved, making it look like an actual, light-emissive lamp.