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@zeux zeux/vfc5.cpp
Created Feb 12, 2016

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View frustum culling optimization: Representation matters
#include <stdbool.h>
#include <spu_intrinsics.h>
// shuffle helpers
#define L0 0x00010203
#define L1 0x04050607
#define L2 0x08090a0b
#define L3 0x0c0d0e0f
#define R0 0x10111213
#define R1 0x14151617
#define R2 0x18191a1b
#define R3 0x1c1d1e1f
#define ZERO 0x80808080
#define SHUFFLE(l, r, x, y, z, w) si_shufb(l, r, ((qword)(vec_uint4){x, y, z, w}))
// splat helper
#define SPLAT(v, idx) si_shufb(v, v, (qword)(vec_uint4)(L ## idx))
struct matrix_t
{
vec_float4 row0;
vec_float4 row1;
vec_float4 row2;
vec_float4 row3;
};
struct aabb_t
{
vec_float4 min;
vec_float4 max;
};
static inline void transform_points_4(qword* dest, qword x, qword y, qword z, const struct matrix_t* mat)
{
#define COMP(c) \
qword res_ ## c = SPLAT((qword)mat->row3, c); \
res_ ## c = si_fma(z, SPLAT((qword)mat->row2, c), res_ ## c); \
res_ ## c = si_fma(y, SPLAT((qword)mat->row1, c), res_ ## c); \
res_ ## c = si_fma(x, SPLAT((qword)mat->row0, c), res_ ## c); \
dest[c] = res_ ## c;
COMP(0);
COMP(1);
COMP(2);
COMP(3);
#undef COMP
}
static inline void transform_matrix(struct matrix_t* dest, const struct matrix_t* lhs, const struct matrix_t* rhs)
{
#define COMP_0(c) \
qword res_ ## c = si_fm((qword)lhs->row2, SPLAT((qword)rhs->row ## c, 2)); \
res_ ## c = si_fma((qword)lhs->row1, SPLAT((qword)rhs->row ## c, 1), res_ ## c); \
res_ ## c = si_fma((qword)lhs->row0, SPLAT((qword)rhs->row ## c, 0), res_ ## c); \
dest->row ## c = (vec_float4)res_ ## c;
#define COMP_1(c) \
qword res_ ## c = si_fma((qword)lhs->row2, SPLAT((qword)rhs->row ## c, 2), (qword)lhs->row3); \
res_ ## c = si_fma((qword)lhs->row1, SPLAT((qword)rhs->row ## c, 1), res_ ## c); \
res_ ## c = si_fma((qword)lhs->row0, SPLAT((qword)rhs->row ## c, 0), res_ ## c); \
dest->row ## c = (vec_float4)res_ ## c;
COMP_0(0);
COMP_0(1);
COMP_0(2);
COMP_1(3);
#undef COMP_0
#undef COMP_1
}
__attribute__((noinline)) unsigned int is_visible(const struct matrix_t* transform, const struct aabb_t* aabb, const struct matrix_t* frustum)
{
qword min = (qword)aabb->min;
qword max = (qword)aabb->max;
// get aabb points (SoA)
qword minmax_x = SHUFFLE(min, max, L0, R0, L0, R0); // x X x X
qword minmax_y = SHUFFLE(min, max, L1, L1, R1, R1); // y y Y Y
qword minmax_z_0 = SPLAT(min, 2); // z z z z
qword minmax_z_1 = SPLAT(max, 2); // Z Z Z Z
// get clipping matrix
struct matrix_t clip;
transform_matrix(&clip, frustum, transform);
// transform points to clip space
qword points_cs_0[4];
qword points_cs_1[4];
transform_points_4(points_cs_0, minmax_x, minmax_y, minmax_z_0, &clip);
transform_points_4(points_cs_1, minmax_x, minmax_y, minmax_z_1, &clip);
// calculate -w
qword points_cs_0_negw = si_xor(points_cs_0[3], (qword)(vec_uint4)(0x80000000));
qword points_cs_1_negw = si_xor(points_cs_1[3], (qword)(vec_uint4)(0x80000000));
// for each plane...
#define NOUT(a, b, c, d) si_orx(si_or(si_fcgt(a, b), si_fcgt(c, d)))
qword nout0 = NOUT(points_cs_0[0], points_cs_0_negw, points_cs_1[0], points_cs_1_negw);
qword nout1 = NOUT(points_cs_0[3], points_cs_0[0], points_cs_1[3], points_cs_1[0]);
qword nout2 = NOUT(points_cs_0[1], points_cs_0_negw, points_cs_1[1], points_cs_1_negw);
qword nout3 = NOUT(points_cs_0[3], points_cs_0[1], points_cs_1[3], points_cs_1[1]);
qword nout4 = NOUT(points_cs_0[2], (qword)(0), points_cs_1[2], (qword)(0));
qword nout5 = NOUT(points_cs_0[3], points_cs_0[2], points_cs_1[3], points_cs_1[2]);
#undef NOUT
// merge "not outside" flags
qword nout01 = si_and(nout0, nout1);
qword nout012 = si_and(nout01, nout2);
qword nout34 = si_and(nout3, nout4);
qword nout345 = si_and(nout34, nout5);
qword nout = si_and(nout012, nout345);
return si_to_uint(nout);
}
// simple ortho frustum
struct matrix_t frustum =
{
{ 0.1f, 0, 0, 0 },
{ 0, 0.1f, 0, 0 },
{ 0, 0, 0.1f, 0 },
{ 0, 0, 0, 1 }
};
// small box
struct aabb_t aabb =
{
{ -1, -2, -3 },
{ 1, 2, 3 }
};
// and some weird matrix
struct matrix_t transform =
{
{ 0.123f, 0.456f, 0.789f },
{ 0.456f, 0.123f, 0.789f },
{ 0.789f, 0.123f, 0.456f },
{ 1.f, -1.f, 1.f }
};
int main()
{
is_visible(&transform, &aabb, &frustum);
si_stop(0);
}
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