| 8216 | } |
| 8217 | |
| 8218 | function clipLine( s1, s2 ) { |
| 8219 | |
| 8220 | var alpha1 = 0, alpha2 = 1, |
| 8221 | |
| 8222 | // Calculate the boundary coordinate of each vertex for the near and far clip planes, |
| 8223 | // Z = -1 and Z = +1, respectively. |
| 8224 | bc1near = s1.z + s1.w, |
| 8225 | bc2near = s2.z + s2.w, |
| 8226 | bc1far = - s1.z + s1.w, |
| 8227 | bc2far = - s2.z + s2.w; |
| 8228 | |
| 8229 | if ( bc1near >= 0 && bc2near >= 0 && bc1far >= 0 && bc2far >= 0 ) { |
| 8230 | |
| 8231 | // Both vertices lie entirely within all clip planes. |
| 8232 | return true; |
| 8233 | |
| 8234 | } else if ( ( bc1near < 0 && bc2near < 0) || (bc1far < 0 && bc2far < 0 ) ) { |
| 8235 | |
| 8236 | // Both vertices lie entirely outside one of the clip planes. |
| 8237 | return false; |
| 8238 | |
| 8239 | } else { |
| 8240 | |
| 8241 | // The line segment spans at least one clip plane. |
| 8242 | |
| 8243 | if ( bc1near < 0 ) { |
| 8244 | |
| 8245 | // v1 lies outside the near plane, v2 inside |
| 8246 | alpha1 = Math.max( alpha1, bc1near / ( bc1near - bc2near ) ); |
| 8247 | |
| 8248 | } else if ( bc2near < 0 ) { |
| 8249 | |
| 8250 | // v2 lies outside the near plane, v1 inside |
| 8251 | alpha2 = Math.min( alpha2, bc1near / ( bc1near - bc2near ) ); |
| 8252 | |
| 8253 | } |
| 8254 | |
| 8255 | if ( bc1far < 0 ) { |
| 8256 | |
| 8257 | // v1 lies outside the far plane, v2 inside |
| 8258 | alpha1 = Math.max( alpha1, bc1far / ( bc1far - bc2far ) ); |
| 8259 | |
| 8260 | } else if ( bc2far < 0 ) { |
| 8261 | |
| 8262 | // v2 lies outside the far plane, v2 inside |
| 8263 | alpha2 = Math.min( alpha2, bc1far / ( bc1far - bc2far ) ); |
| 8264 | |
| 8265 | } |
| 8266 | |
| 8267 | if ( alpha2 < alpha1 ) { |
| 8268 | |
| 8269 | // The line segment spans two boundaries, but is outside both of them. |
| 8270 | // (This can't happen when we're only clipping against just near/far but good |
| 8271 | // to leave the check here for future usage if other clip planes are added.) |
| 8272 | return false; |
| 8273 | |
| 8274 | } else { |
| 8275 | |