| Lightmaps from HDR Probes |
| Bernhard Spanlang | |
| VECG Group | |
| University College London [email protected] |
|
| Overview |
| What are Lightmaps | |
| Related Work | |
| Motivation for using Radiance | |
| Capturing HDR Probes | |
| Creating Lightmaps | |
| Results | |
| Conclusion |
| What are Lightmaps |
| Precomputed illumination for interactive walkthroughs stored in texture memory | |
| Only view independent surfaces (Lambertian) | |
| Not vertex colour (usually Radiosity) | |
| Can be stored in low-res texture for blending original texture if MultiTexture hardware |
| Related Work |
| Radiosity solution (LightScape, stored in vertex colour, adaptive mesh subdivision) |
|
| Games Engines (eg. Quakes qrad) | |
| Texture bakers in Lightwave and 3D Studio Max5, Brazil, FinalRender, etc. |
| Motivation for using Radiance |
| Physically accurate rendering | |
| Natural lighting with HDR | |
| Postprocessing using Radiance tools (exposure, falsecolor, etc.) |
|
| Daylight simulation with real surroundings |
| Capturing HDR Probes |
| Camera response | |
| Merging multiple exposures | |
| For image alignment use a remotly controlled camera | |
| Reflective sphere (Ball bearing) |
|
| Cubic mapping HDRShop |
|
| Removing Camera??? |
| Lightmap Flow Chart |
| Placing Radiance Cameras |
| In front of each triangle |
|
| Centre of surrounding rectangle |
|
| An orthographic camera (-vtl) |
| Rendering the Surfaces |
| Using Radiances view file (normally used for walkthrough animations) | |
| Exploiting the ambient cache (-af file) | |
| Allows parallel execution | |
| Unfortunately there is no way to set the resolution in the view file. | |
| Bug in Desktop Radiance pa option ignored. |
| Lightmap Composing |
| Aim is to merge all rendered surfaces to a single texture for efficient hardware rendering | |
| Simplest approach: use pcompos placing the images next to and above each other. | |
| UV coordinates of resulting VRML file have to reflect this. | |
| ra_ppm e converts Radiance file to ppm file at a specified exposure. |
| Results(1/4) |
| Results(2/4) |
| Results(3/4) |
| Results(4/4) |
| Possible Improvements |
| Maintain connectivity of 3D triangles for 2D UV texture coordinates | |
| Where not possible add extra pixels for interpolation (Sand pixels) | |
| Triangle areas reflected in texture size | |
| Coplanar surfaces represented by one lightmap element | |
| Packing lightmap elements |
| Summary |
| What are Lightmaps | |
| Related Work | |
| Motivation for using Radiance | |
| Capturing HDR Probes | |
| Creating Lightmaps | |
| Results | |
| Conclusion |
| Questions |
| Contact : [email protected] www.cs.ucl.ac.uk/staff/b.spanlang |
by
AMcneil
—
last modified
Feb 29, 2016 12:27 PM