De-duplicate EWA filter code between renderer and compositor

The title says it all, move the EWA filter to BLI (currently it's
math_interp.c) and use the function from both BI renderer and the
compositor.

This makes more central place of the algorithm, allowing to have
fixes and optimizaitons synchronized across the two usages.

This also fixes T41440: Displacement in compositing creates holes

Reviewers: campbellbarton, lukastoenne

Reviewed By: lukastoenne

Maniphest Tasks: T41440

Differential Revision: https://developer.blender.org/D748

1 files changed, 22 insertions, 159 deletions

diff --git a/source/blender/render/intern/source/imagetexture.c b/source/blender/render/intern/source/imagetexture.c
index 7d4b70cea15..12701099e18 100644
--- a/source/blender/render/intern/source/imagetexture.c
+++ b/source/blender/render/intern/source/imagetexture.c
@@ -791,176 +791,39 @@ static void area_sample(TexResult *texr, ImBuf *ibuf, float fx, float fy, afdata
 	texr->ta = texr->talpha ? texr->ta*xsd : (clip ? cw*xsd : 1.f);
 }
 
-/* table of (exp(ar) - exp(a)) / (1 - exp(a)) for r in range [0, 1] and a = -2
- * used instead of actual gaussian, otherwise at high texture magnifications circular artifacts are visible */
-#define EWA_MAXIDX 255
-static const float EWA_WTS[EWA_MAXIDX + 1] = {
-	1.f, 0.990965f, 0.982f, 0.973105f, 0.96428f, 0.955524f, 0.946836f, 0.938216f, 0.929664f,
-	0.921178f, 0.912759f, 0.904405f, 0.896117f, 0.887893f, 0.879734f, 0.871638f, 0.863605f,
-	0.855636f, 0.847728f, 0.839883f, 0.832098f, 0.824375f, 0.816712f, 0.809108f, 0.801564f,
-	0.794079f, 0.786653f, 0.779284f, 0.771974f, 0.76472f, 0.757523f, 0.750382f, 0.743297f,
-	0.736267f, 0.729292f, 0.722372f, 0.715505f, 0.708693f, 0.701933f, 0.695227f, 0.688572f,
-	0.68197f, 0.67542f, 0.66892f, 0.662471f, 0.656073f, 0.649725f, 0.643426f, 0.637176f,
-	0.630976f, 0.624824f, 0.618719f, 0.612663f, 0.606654f, 0.600691f, 0.594776f, 0.588906f,
-	0.583083f, 0.577305f, 0.571572f, 0.565883f, 0.56024f, 0.55464f, 0.549084f, 0.543572f,
-	0.538102f, 0.532676f, 0.527291f, 0.521949f, 0.516649f, 0.511389f, 0.506171f, 0.500994f,
-	0.495857f, 0.490761f, 0.485704f, 0.480687f, 0.475709f, 0.470769f, 0.465869f, 0.461006f,
-	0.456182f, 0.451395f, 0.446646f, 0.441934f, 0.437258f, 0.432619f, 0.428017f, 0.42345f,
-	0.418919f, 0.414424f, 0.409963f, 0.405538f, 0.401147f, 0.39679f, 0.392467f, 0.388178f,
-	0.383923f, 0.379701f, 0.375511f, 0.371355f, 0.367231f, 0.363139f, 0.359079f, 0.355051f,
-	0.351055f, 0.347089f, 0.343155f, 0.339251f, 0.335378f, 0.331535f, 0.327722f, 0.323939f,
-	0.320186f, 0.316461f, 0.312766f, 0.3091f, 0.305462f, 0.301853f, 0.298272f, 0.294719f,
-	0.291194f, 0.287696f, 0.284226f, 0.280782f, 0.277366f, 0.273976f, 0.270613f, 0.267276f,
-	0.263965f, 0.26068f, 0.257421f, 0.254187f, 0.250979f, 0.247795f, 0.244636f, 0.241502f,
-	0.238393f, 0.235308f, 0.232246f, 0.229209f, 0.226196f, 0.223206f, 0.220239f, 0.217296f,
-	0.214375f, 0.211478f, 0.208603f, 0.20575f, 0.20292f, 0.200112f, 0.197326f, 0.194562f,
-	0.191819f, 0.189097f, 0.186397f, 0.183718f, 0.18106f, 0.178423f, 0.175806f, 0.17321f,
-	0.170634f, 0.168078f, 0.165542f, 0.163026f, 0.16053f, 0.158053f, 0.155595f, 0.153157f,
-	0.150738f, 0.148337f, 0.145955f, 0.143592f, 0.141248f, 0.138921f, 0.136613f, 0.134323f,
-	0.132051f, 0.129797f, 0.12756f, 0.125341f, 0.123139f, 0.120954f, 0.118786f, 0.116635f,
-	0.114501f, 0.112384f, 0.110283f, 0.108199f, 0.106131f, 0.104079f, 0.102043f, 0.100023f,
-	0.0980186f, 0.09603f, 0.094057f, 0.0920994f, 0.0901571f, 0.08823f, 0.0863179f, 0.0844208f,
-	0.0825384f, 0.0806708f, 0.0788178f, 0.0769792f, 0.0751551f, 0.0733451f, 0.0715493f, 0.0697676f,
-	0.0679997f, 0.0662457f, 0.0645054f, 0.0627786f, 0.0610654f, 0.0593655f, 0.0576789f, 0.0560055f,
-	0.0543452f, 0.0526979f, 0.0510634f, 0.0494416f, 0.0478326f, 0.0462361f, 0.0446521f, 0.0430805f,
-	0.0415211f, 0.039974f, 0.0384389f, 0.0369158f, 0.0354046f, 0.0339052f, 0.0324175f, 0.0309415f,
-	0.029477f, 0.0280239f, 0.0265822f, 0.0251517f, 0.0237324f, 0.0223242f, 0.020927f, 0.0195408f,
-	0.0181653f, 0.0168006f, 0.0154466f, 0.0141031f, 0.0127701f, 0.0114476f, 0.0101354f, 0.00883339f,
-	0.00754159f, 0.00625989f, 0.00498819f, 0.00372644f, 0.00247454f, 0.00123242f, 0.f
-};
-
 /* test if a float value is 'nan'
  * there is a C99 function for this: isnan(), but blender seems to use C90 (according to gcc warns),
  * and may not be supported by other compilers either */
+/* TODO(sergey): Consider using isnan(), it's used in the other areas. */
 #ifndef ISNAN
-#define ISNAN(x) ((x) != (x))
+#  define ISNAN(x) ((x) != (x))
 #endif
-//static int ISNAN(float x) { return (x != x); }
 
-static void radangle2imp(float a2, float b2, float th, float *A, float *B, float *C, float *F)
-{
-	float ct2 = cosf(th);
-	const float st2 = 1.0f - ct2 * ct2;	/* <- sin(th)^2 */
-	ct2 *= ct2;
-	*A = a2*st2 + b2*ct2;
-	*B = (b2 - a2)*sinf(2.f*th);
-	*C = a2*ct2 + b2*st2;
-	*F = a2*b2;
-}
+typedef struct ReadEWAData {
+	ImBuf *ibuf;
+	afdata_t *AFD;
+} ReadEWAData;
 
-/* all tests here are done to make sure possible overflows are hopefully minimized */
-static void imp2radangle(float A, float B, float C, float F, float *a, float *b, float *th, float *ecc)
+static void ewa_read_pixel_cb(void *userdata, int x, int y, float result[4])
 {
-	if (F <= 1e-5f) {	/* use arbitrary major radius, zero minor, infinite eccentricity */
-		*a = sqrtf(A > C ? A : C);
-		*b = 0.f;
-		*ecc = 1e10f;
-		*th = 0.5f*(atan2f(B, A - C) + (float)M_PI);
-	}
-	else {
-		const float AmC = A - C, ApC = A + C, F2 = F*2.f;
-		const float r = sqrtf(AmC*AmC + B*B);
-		float d = ApC - r;
-		*a = (d <= 0.f) ? sqrtf(A > C ? A : C) : sqrtf(F2 / d);
-		d = ApC + r;
-		if (d <= 0.f) {
-			*b = 0.f;
-			*ecc = 1e10f;
-		}
-		else {
-			*b = sqrtf(F2 / d);
-			*ecc = *a / *b;
-		}
-		/* incr theta by 0.5*pi (angle of major axis) */
-		*th = 0.5f*(atan2f(B, AmC) + (float)M_PI);
-	}
+	ReadEWAData *data = (ReadEWAData *) userdata;
+	ibuf_get_color_clip(result, data->ibuf, x, y, data->AFD->extflag);
 }
 
 static void ewa_eval(TexResult *texr, ImBuf *ibuf, float fx, float fy, afdata_t *AFD)
 {
-	/* scaling dxt/dyt by full resolution can cause overflow because of huge A/B/C and esp. F values,
-	 * scaling by aspect ratio alone does the opposite, so try something in between instead... */
-	const float ff2 = ibuf->x, ff = sqrtf(ff2), q = ibuf->y / ff;
-	const float Ux = AFD->dxt[0]*ff, Vx = AFD->dxt[1]*q, Uy = AFD->dyt[0]*ff, Vy = AFD->dyt[1]*q;
-	float A = Vx*Vx + Vy*Vy;
-	float B = -2.f*(Ux*Vx + Uy*Vy);
-	float C = Ux*Ux + Uy*Uy;
-	float F = A*C - B*B*0.25f;
-	float a, b, th, ecc, a2, b2, ue, ve, U0, V0, DDQ, U, ac1, ac2, BU, d; /* TXF alpha: cw = 0.f; */
-	int u, v, u1, u2, v1, v2; /* TXF alpha: clip = 0; */
-
-	/* The so-called 'high' quality ewa method simply adds a constant of 1 to both A & C,
-	 * so the ellipse always covers at least some texels. But since the filter is now always larger,
-	 * it also means that everywhere else it's also more blurry then ideally should be the case.
-	 * So instead here the ellipse radii are modified instead whenever either is too low.
-	 * Use a different radius based on interpolation switch, just enough to anti-alias when interpolation is off,
-	 * and slightly larger to make result a bit smoother than bilinear interpolation when interpolation is on
-	 * (minimum values: const float rmin = intpol ? 1.f : 0.5f;) */
-	const float rmin = (AFD->intpol ? 1.5625f : 0.765625f)/ff2;
-	imp2radangle(A, B, C, F, &a, &b, &th, &ecc);
-	if ((b2 = b*b) < rmin) {
-		if ((a2 = a*a) < rmin) {
-			B = 0.f;
-			A = C = rmin;
-			F = A*C;
-		}
-		else {
-			b2 = rmin;
-			radangle2imp(a2, b2, th, &A, &B, &C, &F);
-		}
-	}
-
-	ue = ff*sqrtf(C);
-	ve = ff*sqrtf(A);
-	d = (float)(EWA_MAXIDX + 1) / (F*ff2);
-	A *= d;
-	B *= d;
-	C *= d;
-
-	U0 = fx*ibuf->x;
-	V0 = fy*ibuf->y;
-	u1 = (int)(floorf(U0 - ue));
-	u2 = (int)(ceilf(U0 + ue));
-	v1 = (int)(floorf(V0 - ve));
-	v2 = (int)(ceilf(V0 + ve));
-	U0 -= 0.5f;
-	V0 -= 0.5f;
-	DDQ = 2.f*A;
-	U = u1 - U0;
-	ac1 = A*(2.f*U + 1.f);
-	ac2 = A*U*U;
-	BU = B*U;
+	ReadEWAData data;
+	float uv[2] = {fx, fy};
+	data.ibuf = ibuf;
+	data.AFD = AFD;
+	BLI_ewa_filter(ibuf->x, ibuf->y,
+	               AFD->intpol != 0,
+	               texr->talpha,
+	               uv, AFD->dxt, AFD->dyt,
+	               ewa_read_pixel_cb,
+	               &data,
+	               &texr->tr);
 
-	d = texr->tr = texr->tb = texr->tg = texr->ta = 0.f;
-	for (v=v1; v<=v2; ++v) {
-		const float V = v - V0;
-		float DQ = ac1 + B*V;
-		float Q = (C*V + BU)*V + ac2;
-		for (u=u1; u<=u2; ++u) {
-			if (Q < (float)(EWA_MAXIDX + 1)) {
-				float tc[4];
-				const float wt = EWA_WTS[(Q < 0.f) ? 0 : (unsigned int)Q];
-				/*const int out =*/ ibuf_get_color_clip(tc, ibuf, u, v, AFD->extflag);
-				/* TXF alpha: clip |= out;
-				 * TXF alpha: cw += out ? 0.f : wt; */
-				texr->tr += tc[0]*wt;
-				texr->tg += tc[1]*wt;
-				texr->tb += tc[2]*wt;
-				texr->ta += texr->talpha ? tc[3]*wt : 0.f;
-				d += wt;
-			}
-			Q += DQ;
-			DQ += DDQ;
-		}
-	}
-
-	/* d should hopefully never be zero anymore */
-	d = 1.f/d;
-	texr->tr *= d;
-	texr->tg *= d;
-	texr->tb *= d;
-	/* clipping can be ignored if alpha used, texr->ta already includes filtered edge */
-	texr->ta = texr->talpha ? texr->ta*d : 1.f; /* TXF alpha (clip ? cw*d : 1.f); */
 }
 
 static void feline_eval(TexResult *texr, ImBuf *ibuf, float fx, float fy, afdata_t *AFD)
@@ -1304,7 +1167,7 @@ static int imagewraposa_aniso(Tex *tex, Image *ima, ImBuf *ibuf, const float tex
 		const float C = Ux*Ux + Uy*Uy;
 		const float F = A*C - B*B*0.25f;
 		float a, b, th, ecc;
-		imp2radangle(A, B, C, F, &a, &b, &th, &ecc);
+		BLI_ewa_imp2radangle(A, B, C, F, &a, &b, &th, &ecc);
 		if (tex->texfilter == TXF_FELINE) {
 			float fProbes;
 			a *= ff;
@@ -1408,7 +1271,7 @@ static int imagewraposa_aniso(Tex *tex, Image *ima, ImBuf *ibuf, const float tex
 			const float C = Ux*Ux + Uy*Uy;
 			const float F = A*C - B*B*0.25f;
 			float a, b, th, ecc, fProbes;
-			imp2radangle(A, B, C, F, &a, &b, &th, &ecc);
+			BLI_ewa_imp2radangle(A, B, C, F, &a, &b, &th, &ecc);
 			a *= ff;
 			b *= ff;
 			a = max_ff(a, 1.0f);