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[spline/bezier]Add spline derivative calculation for normal generation.
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@xebra
xebra committed Oct 7, 2018
1 parent 5c7284f commit a9ac860
Showing 1 changed file with 50 additions and 69 deletions.
119 changes: 50 additions & 69 deletions GPU/Common/SplineCommon.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -160,29 +160,33 @@ struct KnotDiv {
float _3_2 = 1.0f; // Always 1
};

static void spline_n_4(int i, float t, float *knot, const KnotDiv &div, float *splineVal) {
static void spline_n_4(int i, float t, float *knot, const KnotDiv &div, float *splineVal, float *derivs) {
knot += i;

#ifdef _M_SSE
const __m128 knot012 = _mm_loadu_ps(knot);
const __m128 t012 = _mm_sub_ps(_mm_set_ps1(t), knot012);
const __m128 f30_41_52 = _mm_mul_ps(t012, _mm_loadu_ps(&div._3_0));
const __m128 f52_31_42 = _mm_mul_ps(t012, _mm_loadu_ps(&div._5_2));
const float &f32 = t012.m128_f32[2];

// Following comments are for explains order of the multiply.
// float a = (1-f30)*(1-f31);
// float c = (1-f41)*(1-f42);
// float b = ( f31 * f41);
// float d = ( f42 * f52);
const __m128 f30_41_31_42 = _mm_shuffle_ps(f30_41_52, f52_31_42, _MM_SHUFFLE(2, 1, 1, 0));
const __m128 f31_42_41_52 = _mm_shuffle_ps(f52_31_42, f30_41_52, _MM_SHUFFLE(2, 1, 2, 1));
const __m128 c1_1_0_0 = { 1, 1, 0, 0 };
const __m128 acbd = _mm_mul_ps(_mm_sub_ps(c1_1_0_0, f30_41_31_42), _mm_sub_ps(c1_1_0_0, f31_42_41_52));
const float &a = acbd.m128_f32[0];
const float &b = acbd.m128_f32[2];
const float &c = acbd.m128_f32[1];
const float &d = acbd.m128_f32[3];
const __m128 knot012 = _mm_loadu_ps(knot);
const __m128 t012 = _mm_sub_ps(_mm_set_ps1(t), knot012);
const __m128 f30_41_52 = _mm_mul_ps(t012, _mm_loadu_ps(&div._3_0));
const __m128 f52_31_42 = _mm_mul_ps(t012, _mm_loadu_ps(&div._5_2));
const float &f32 = t012.m128_f32[2];

// Following comments are for explains order of the multiply.
// float a = (1-f30)*(1-f31);
// float c = (1-f41)*(1-f42);
// float b = ( f31 * f41);
// float d = ( f42 * f52);
const __m128 f30_41_31_42 = _mm_shuffle_ps(f30_41_52, f52_31_42, _MM_SHUFFLE(2, 1, 1, 0));
const __m128 f31_42_41_52 = _mm_shuffle_ps(f52_31_42, f30_41_52, _MM_SHUFFLE(2, 1, 2, 1));
const __m128 c1_1_0_0 = { 1, 1, 0, 0 };
const __m128 acbd = _mm_mul_ps(_mm_sub_ps(c1_1_0_0, f30_41_31_42), _mm_sub_ps(c1_1_0_0, f31_42_41_52));
const float &a = acbd.m128_f32[0];
const float &b = acbd.m128_f32[2];
const float &c = acbd.m128_f32[1];
const float &d = acbd.m128_f32[3];

// For derivative
const float &f31 = f30_41_31_42.m128_f32[2];
const float &f42 = f30_41_31_42.m128_f32[3];
#else
// TODO: Maybe compilers could be coaxed into vectorizing this code without the above explicitly...
float t0 = (t - knot[0]);
Expand All @@ -206,6 +210,20 @@ static void spline_n_4(int i, float t, float *knot, const KnotDiv &div, float *s
splineVal[1] = 1-a-b+((a+b+c-1)*f32);
splineVal[2] = b+((1-b-c-d)*f32);
splineVal[3] = d*f32;

// Derivative
float i1 = (1 - f31) * (1 - f32);
float i2 = f31 * (1 - f32) + (1 - f42) * f32;
float i3 = f42 * f32;

float f130 = i1 * div._3_0;
float f241 = i2 * div._4_1;
float f352 = i3 * div._5_2;

derivs[0] = 3 * (0 - f130);
derivs[1] = 3 * (f130 - f241);
derivs[2] = 3 * (f241 - f352);
derivs[3] = 3 * (f352 - 0);
}

// knot should be an array sized n + 5 (n + 1 + 1 + degree (cubic))
Expand Down Expand Up @@ -426,6 +444,9 @@ static void SplinePatchFullQuality(u8 *&dest, u16 *indices, int &count, const Sp
Vec3f vert_pos;
vert_pos.SetZero();
Vec3f vert_nrm;
Vec3f du, dv;
du.SetZero();
dv.SetZero();
if (origNrm) {
vert_nrm.SetZero();
}
Expand All @@ -446,6 +467,8 @@ static void SplinePatchFullQuality(u8 *&dest, u16 *indices, int &count, const Sp
// Collect influences from surrounding control points.
float u_weights[4];
float v_weights[4];
float u_derivs[4];
float v_derivs[4];

int iu = (int)u;
int iv = (int)v;
Expand All @@ -455,8 +478,8 @@ static void SplinePatchFullQuality(u8 *&dest, u16 *indices, int &count, const Sp
if (iu >= spatch.count_u - 3) iu = spatch.count_u - 4;
if (iv >= spatch.count_v - 3) iv = spatch.count_v - 4;

spline_n_4(iu, u, knot_u, divs_u[iu], u_weights);
spline_n_4(iv, v, knot_v, divs_v[iv], v_weights);
spline_n_4(iu, u, knot_u, divs_u[iu], u_weights, u_derivs);
spline_n_4(iv, v, knot_v, divs_v[iv], v_weights, v_derivs);

// Handle degenerate patches. without this, spatch.points[] may read outside the number of initialized points.
int patch_w = std::min(spatch.count_u - iu, 4);
Expand Down Expand Up @@ -493,13 +516,15 @@ static void SplinePatchFullQuality(u8 *&dest, u16 *indices, int &count, const Sp
AccumulateWeighted(vert_color, a_color, fv);
}
if (origNrm) {
AccumulateWeighted(vert_nrm, a->nrm, fv);
AccumulateWeighted(du, a->pos, Vec4f::AssignToAll(u_derivs[ii] * v_weights[jj]));
AccumulateWeighted(dv, a->pos, Vec4f::AssignToAll(u_weights[ii] * v_derivs[jj]));
}
}
}
}
vert->pos = vert_pos;
if (origNrm) {
vert_nrm = Cross(du, dv);
#ifdef _M_SSE
const __m128 normalize = SSENormalizeMultiplier(useSSE4, vert_nrm.vec);
vert_nrm.vec = _mm_mul_ps(vert_nrm.vec, normalize);
Expand All @@ -519,52 +544,8 @@ static void SplinePatchFullQuality(u8 *&dest, u16 *indices, int &count, const Sp

delete[] knot_u;
delete[] knot_v;

// Hacky normal generation through central difference.
if (computeNormals && !origNrm) {
#ifdef _M_SSE
const __m128 facing = spatch.patchFacing ? _mm_set_ps1(-1.0f) : _mm_set_ps1(1.0f);
#endif

for (int v = 0; v < patch_div_t + 1; v++) {
Vec3f vl_pos = vertices[v * (patch_div_s + 1)].pos;
Vec3f vc_pos = vertices[v * (patch_div_s + 1)].pos;

for (int u = 0; u < patch_div_s + 1; u++) {
const int t = std::max(0, v - 1);
const int r = std::min(patch_div_s, u + 1);
const int b = std::min(patch_div_t, v + 1);

const Vec3f vr_pos = vertices[v * (patch_div_s + 1) + r].pos;

#ifdef _M_SSE
const __m128 right = _mm_sub_ps(vr_pos.vec, vl_pos.vec);

const Vec3f vb_pos = vertices[b * (patch_div_s + 1) + u].pos;
const Vec3f vt_pos = vertices[t * (patch_div_s + 1) + u].pos;
const __m128 down = _mm_sub_ps(vb_pos.vec, vt_pos.vec);

const __m128 crossed = SSECrossProduct(right, down);
const __m128 normalize = SSENormalizeMultiplier(useSSE4, crossed);

Vec3f finalNrm = _mm_mul_ps(normalize, _mm_mul_ps(crossed, facing));
vertices[v * (patch_div_s + 1) + u].nrm = finalNrm;
#else
const Vec3Packedf &right = vr_pos - vl_pos;
const Vec3Packedf &down = vertices[b * (patch_div_s + 1) + u].pos - vertices[t * (patch_div_s + 1) + u].pos;

vertices[v * (patch_div_s + 1) + u].nrm = Cross(right, down).Normalized();
if (spatch.patchFacing) {
vertices[v * (patch_div_s + 1) + u].nrm *= -1.0f;
}
#endif

// Rotate for the next one to the right.
vl_pos = vc_pos;
vc_pos = vr_pos;
}
}
}
delete[] divs_u;
delete[] divs_v;

GEPatchPrimType prim_type = spatch.primType;
// Tessellate.
Expand Down

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