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これがGPUの力!three.jsによる“リアルタイム”なレイトレーシング 〜宝石編〜 ref: http://qiita.com/gam0022/items/9875480d33e03fe2113c
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// 3次正方行列の行列式をクラメルの公式で計算する | |
float det( vec3 a, vec3 b, vec3 c ) { | |
return (a.x * b.y * c.z) | |
+ (a.y * b.z * c.x) | |
+ (a.z * b.x * c.y) | |
- (a.x * b.z * c.y) | |
- (a.y * b.x * c.z) | |
- (a.z * b.y * c.x); | |
} | |
// ポリゴン(三角形)とレイ(半直線)の衝突判定する | |
void rayIntersectsTriangle( vec3 origin, vec3 ray, vec3 v0, vec3 v1, vec3 v2, inout Intersect nearest ) { | |
vec3 invRay = -ray; | |
vec3 edge1 = v1 - v0; | |
vec3 edge2 = v2 - v0; | |
float denominator = det( edge1, edge2, invRay ); | |
if ( denominator == 0.0 ) return; | |
float invDenominator = 1.0 / denominator; | |
vec3 d = origin - v0; | |
float u = det( d, edge2, invRay ) * invDenominator; | |
if ( u < 0.0 || u > 1.0 ) return; | |
float v = det( edge1, d, invRay ) * invDenominator; | |
if ( v < 0.0 || u + v > 1.0 ) return; | |
float t = det( edge1, edge2, d ) * invDenominator; | |
if ( t < 0.0 || t > nearest.distance ) return; | |
nearest.isHit = true; | |
nearest.position = origin + ray * t; | |
nearest.distance = t; | |
nearest.normal = normalize( cross( edge1, edge2 ) ) * sign( invDenominator ); | |
nearest.material = DIAMOND_MATERIAL; | |
nearest.isFront = invDenominator > 0.0; | |
} | |
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