| Listed in: | Technical backgrounds |
| Date: | 2000-05-29 |
| Author: | ali |
| 13:01 | Antimorph: | Laser I have a question for you |
| 13:02 | Antimorph: | On some custom cars I've downloaded, every face of the model is reflecting light oddly |
| 13:02 | LaserBeams: | hrm? |
| 13:02 | LaserBeams: | like - examples? |
| 13:02 | Antimorph: | hmm, cant think of one, let me rephrase |
| 13:02 | Antimorph: | how do you control the glossiness on cars? |
| 13:03 | LaserBeams: | in the parameters.txt |
| 13:03 | Antimorph: | hmm, ok, for the car your working on with ST, you mentioned that you were going to make the fenders reflect differently from the body |
| 13:03 | LaserBeams: | yes |
| 13:04 | Antimorph: | how is such a thing achieved? |
| 13:04 | LaserBeams: | the vertex normals will not be matched there |
| 13:04 | LaserBeams: | you mean in max? |
| 13:04 | Antimorph: | yes please |
| 13:04 | LaserBeams: | I have not a clue - I know how to do it in Rhino... |
| 13:05 | Antimorph: | What do you do in Rhino? |
| 13:05 | LaserBeams: | weld wherever you want the reflections to flow smoothly across body |
| 13:05 | Antimorph: | weld vertices? |
| 13:05 | LaserBeams: | do not weld where you want reflection "creases" - yes |
| 13:05 | Antimorph: | kewl |
| 13:05 | LaserBeams: | if it looks smooth in perspective, the reflection will be smooth |
| 13:06 | LaserBeams: | if it looks faceted, the reflection will be faceted |
| 13:06 | Antimorph: | thankyou, I was having an epi fit wondering if it was something to do with smoothing groups, but I thought that couldn't be |
| 13:06 | LaserBeams: | It does |
| 13:06 | LaserBeams: | want to know how it eorks? |
| 13:06 | LaserBeams: | works? |
| 13:06 | Antimorph: | yes please |
| 13:07 | LaserBeams: | Expl follows... |
| 13:07 | LaserBeams: | Each model has a list of vertexes and vertex normals |
| 13:08 | LaserBeams: | each polygon is defined by indexing into that list of vertices |
| 13:09 | LaserBeams: | flat surfaces have normals that point straight (perpendicularly) away from the face |
| 13:09 | LaserBeams: | When two vertexes are blended, their normals are averaged |
| 13:09 | LaserBeams: | and converted into one vertex, with one normal |
| 13:10 | LaserBeams: | the polygons that used the previous two vertexes |
| 13:10 | LaserBeams: | both now index onto the one, blended vertex |
| 13:10 | Antimorph: | I understand Laser |
| 13:10 | LaserBeams: | this is used in gouraud shading to approximate curved surfaces |
| 13:11 | LaserBeams: | the normals are used to calculate reflections |
| 13:11 | Antimorph: | So how do you blend your vertices then? |
| 13:11 | LaserBeams: | weld |
| 13:11 | Antimorph: | ok, nothing to do with SG's then |
| 13:11 | LaserBeams: | I guess not - though maybe |
| 13:12 | LaserBeams: | if it makes it look smooth, then yes. |
| 13:12 | Antimorph: | hmm |
| 13:13 | Antimorph is concerned | |
| 13:13 | LaserBeams: | If the normal is pointing directly at the camera, the coordinate at the center of the env map is set to that point on the secondary texture |
| 13:14 | LaserBeams: | if the normal is pointing directly away from the camera, a point around the edge of a circular area from the env map is set to that point on the secondary texture |
| 13:14 | Antimorph: | I need to go into max and take a look at this |
| 13:15 | Antimorph: | be back in a bit |
| 13:15 | LaserBeams: | normals pointing perpenicular tot he camera are refernced to a point halfway between the center of the env map and the circle inscribed in the env map. |
| 13:15 | Antimorph starts to sweat | |
| 13:16 | SKITCH2: | see ya later peeps |
| 13:16 | LaserBeams: | normals between parallel and perpendicular are calulated with trigonometric functions so the enfironment appears spherical and not squarish |
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