GPU Pro 7

2. Interactive Sparse Eulerian Fluid 295

float2 IntersectBox ( Ray r , float3 boxmin , float3 boxmax)

{

// Compute i n t e r s e c t i o n o f ray with a l l s i x bounding box p la ne s .

float3 invR =1.0 /r . d ;

float3 tbot = invR ∗ ( boxmin . xyz − r . o );

float3 ttop = invR ∗ ( boxmax . xyz − r . o );

// Reorder intersections to find smallest and largest on

// each axis .

float3 tmin = min ( ttop , tbot );

float3 tmax = max ( ttop , tbot );

// Find the largest tmin and the smallest tmax.

float2 t0 = max ( tmin . xx , tmin . yz );

tnear = max ( t0 . x , t0 . y );

t0 = min ( tmax . xx , tmax . yz );

tfar = min ( t0 . x , t0 . y );

return float2 ( tnear ...