[Mesa-dev] [PATCH] Anisotropic filtering extension for swrast
Andreas Faenger
a.faenger at e-sign.com
Tue May 17 04:08:36 PDT 2011
Anisotropic filtering extension for swrast intended to be used by osmesato create high quality renderings.
Based on Higher Quality Elliptical Weighted Avarage Filter (EWA).
A 2nd implementation using footprint assembly is also provided.
---
src/mesa/main/extensions.c | 3 +
src/mesa/swrast/s_span.c | 7 +
src/mesa/swrast/s_texcombine.c | 13 ++
src/mesa/swrast/s_texfilter.c | 387 ++++++++++++++++++++++++++++++++++++++++
4 files changed, 410 insertions(+), 0 deletions(-)
diff --git a/src/mesa/main/extensions.c b/src/mesa/main/extensions.c
index 8672ac2..77fc47b 100644
--- a/src/mesa/main/extensions.c
+++ b/src/mesa/main/extensions.c
@@ -503,6 +503,9 @@ _mesa_enable_sw_extensions(struct gl_context *ctx)
ctx->Extensions.EXT_texture_env_add = GL_TRUE;
ctx->Extensions.EXT_texture_env_combine = GL_TRUE;
ctx->Extensions.EXT_texture_env_dot3 = GL_TRUE;
+ /* Anisotropic filtering extension begin */
+ ctx->Extensions.EXT_texture_filter_anisotropic = GL_TRUE;
+ /* Anisotropic filtering extension end */
ctx->Extensions.EXT_texture_mirror_clamp = GL_TRUE;
ctx->Extensions.EXT_texture_lod_bias = GL_TRUE;
ctx->Extensions.EXT_texture_shared_exponent = GL_TRUE;
diff --git a/src/mesa/swrast/s_span.c b/src/mesa/swrast/s_span.c
index f0524e0..6ea5531 100644
--- a/src/mesa/swrast/s_span.c
+++ b/src/mesa/swrast/s_span.c
@@ -492,6 +492,13 @@ interpolate_texcoords(struct gl_context *ctx, SWspan *span)
const struct gl_texture_image *img = obj->Image[0][obj->BaseLevel];
needLambda = (obj->Sampler.MinFilter != obj->Sampler.MagFilter)
|| ctx->FragmentProgram._Current;
+ /* Anisotropic filtering extension begin */
+ /* LOD is calculated directly in the ansiotropic filter, we can skip the normal lambda
+ * function as the result is ignored anyways
+ */
+ if (obj->Sampler.MaxAnisotropy > 1.0 &&
+ obj->Sampler.MinFilter == GL_LINEAR_MIPMAP_LINEAR) needLambda = GL_FALSE;
+ /* Anisotropic filtering extension end */
texW = img->WidthScale;
texH = img->HeightScale;
}
diff --git a/src/mesa/swrast/s_texcombine.c b/src/mesa/swrast/s_texcombine.c
index 7f49b6f..178d360 100644
--- a/src/mesa/swrast/s_texcombine.c
+++ b/src/mesa/swrast/s_texcombine.c
@@ -710,6 +710,19 @@ _swrast_texture_span( struct gl_context *ctx, SWspan *span )
}
}
}
+ /* Anisotropic filtering extension begin */
+ else if(curObj->Sampler.MaxAnisotropy > 1.0 &&
+ curObj->Sampler.MinFilter == GL_LINEAR_MIPMAP_LINEAR) {
+ /* sample_lambda_2d_aniso is beeing used as texture_sample_func,
+ * it requires the current SWspan *span as an additional parameter.
+ * In order to keep the same function signature, the unused lambda
+ * parameter will be modified to actually contain the SWspan pointer.
+ * This is a Hack. To make it right, the texture_sample_func
+ * signature and all implementing functions need to be modified.
+ */
+ lambda = (GLfloat *)span; /* "hide" SWspan struct; cast to (GLfloat *) to suppress warning */
+ }
+ /* Anisotropic filtering extension end */
/* Sample the texture (span->end = number of fragments) */
swrast->TextureSample[unit]( ctx, texUnit->_Current, span->end,
diff --git a/src/mesa/swrast/s_texfilter.c b/src/mesa/swrast/s_texfilter.c
index 106f8b7..6b1d7f4 100644
--- a/src/mesa/swrast/s_texfilter.c
+++ b/src/mesa/swrast/s_texfilter.c
@@ -1531,6 +1531,388 @@ sample_lambda_2d(struct gl_context *ctx,
}
+/* Anisotropic filtering extension begin */
+
+#define WEIGHT_LUT_SIZE 1024
+
+static GLfloat *weightLut;
+
+/**
+ * Creates the lookup table used to speedup ewa sampling
+ */
+static void
+create_filter_table()
+{
+ GLuint i;
+ if (!weightLut) {
+ weightLut = (GLfloat *) malloc(WEIGHT_LUT_SIZE * sizeof(GLfloat));
+
+ for (i = 0; i < WEIGHT_LUT_SIZE; ++i) {
+ GLfloat alpha = 2;
+ GLfloat r2 = (GLfloat)i / (GLfloat)(WEIGHT_LUT_SIZE - 1);
+ GLfloat weight = (GLfloat)exp(-alpha * r2);
+ weightLut[i] = weight;
+ }
+ }
+}
+
+/**
+ * Elliptical weighted average (EWA) filter for producing high quality
+ * anisotropic filtered results.
+ * Based on the Higher Quality Elliptical Weighted Avarage Filter
+ * published by Paul S. Heckbert in his Master's Thesis
+ * "Fundamentals of Texture Mapping and Image Warping" (1989)
+ */
+static void
+sample_2d_ewa(struct gl_context *ctx,
+ const struct gl_texture_object *tObj,
+ const GLfloat texcoord[4],
+ const GLfloat dudx, const GLfloat dvdx,
+ const GLfloat dudy, const GLfloat dvdy, const GLint lod,
+ GLfloat rgba[])
+{
+ GLint level=lod > 0 ? lod : 0;
+ GLfloat scaling = 1.0 / (1 << level);
+
+ const struct gl_texture_image *img = tObj->Image[0][level];
+
+ const struct gl_texture_image *mostDetailedImage = tObj->Image[0][tObj->BaseLevel];
+ GLfloat tex_u=-0.5 + texcoord[0] * mostDetailedImage->WidthScale * scaling;
+ GLfloat tex_v=-0.5 + texcoord[1] * mostDetailedImage->HeightScale * scaling;
+
+ GLfloat ux = dudx * scaling;
+ GLfloat vx = dvdx * scaling;
+ GLfloat uy = dudy * scaling;
+ GLfloat vy = dvdy * scaling;
+
+ /* compute ellipse coefficients to bound the region:
+ * A*x*x + B*x*y + C*y*y = F.
+ */
+ GLfloat A = vx*vx+vy*vy+1;
+ GLfloat B = -2*(ux*vx+uy*vy);
+ GLfloat C = ux*ux+uy*uy+1;
+ GLfloat F = A*C-B*B/4.0;
+
+ /* check if it is an ellipse */
+ /* ASSERT(F > 0.0); */
+
+ /* Compute the ellipse's (u,v) bounding box in texture space */
+ GLfloat d = -B*B+4.0*C*A;
+ GLfloat box_u = 2.0 / d * sqrt(d*C*F); /* box_u -> half of bbox with */
+ GLfloat box_v = 2.0 / d * sqrt(A*d*F); /* box_v -> half of bbox height */
+
+ GLint u0 = floor(tex_u - box_u);
+ GLint u1 = ceil (tex_u + box_u);
+ GLint v0 = floor(tex_v - box_v);
+ GLint v1 = ceil (tex_v + box_v);
+
+ GLfloat num[4]={0, 0, 0, 0};
+ GLfloat newCoord[2];
+ GLfloat den = 0;
+ GLfloat ddq;
+ GLfloat U = u0 - tex_u;
+ GLint v;
+
+ /* Scale ellipse formula to directly index the Filter Lookup Table.
+ * i.e. scale so that F = WEIGHT_LUT_SIZE-1
+ */
+ register double formScale = (double)(WEIGHT_LUT_SIZE-1)/F;
+ A *= formScale;
+ B *= formScale;
+ C *= formScale;
+ /* F *= formScale; */ /* no need to scale F as we don't use it below here */
+
+ /* Heckbert MS thesis, p. 59; scan over the bounding box of the ellipse
+ * and incrementally update the value of Ax^2+Bxy*Cy^2; when this
+ * value, q, is less than F, we're inside the ellipse
+ */
+ ddq = 2 * A;
+ for (v = v0; v <= v1; ++v) {
+ GLfloat V = v - tex_v;
+ GLfloat dq = A*(2*U+1) + B*V;
+ GLfloat q = (C*V + B*U)*V + A*U*U;
+
+ GLint u;
+ for (u = u0; u <= u1; ++u) {
+ /* Note that the ellipse has been pre-scaled so F = WEIGHT_LUT_SIZE - 1 */
+ if (q < WEIGHT_LUT_SIZE) {
+ /* as a LUT is used, q must never be negative;
+ * should not happen, though
+ */
+ const GLint qClamped = q >= 0 ? q : 0;
+ GLfloat weight = weightLut[qClamped];
+
+ newCoord[0]=u /((GLfloat)img->Width2);
+ newCoord[1]=v /((GLfloat)img->Height2);
+
+ sample_2d_nearest(ctx, tObj, img, newCoord, rgba);
+ num[0]+= weight * rgba[0];
+ num[1]+= weight * rgba[1];
+ num[2]+= weight * rgba[2];
+ num[3]+= weight * rgba[3];
+
+ den += weight;
+ }
+ q += dq;
+ dq += ddq;
+ }
+ }
+
+ if (den <= 0)
+ {
+ /* Reaching this place would mean
+ * that no pixels intersected the ellipse.
+ * This should never happen because
+ * the filter we use always
+ * intersects at least one pixel.
+ */
+
+ /*rgba[0]=0;
+ rgba[1]=0;
+ rgba[2]=0;
+ rgba[3]=0;*/
+ /* not enough pixels in resampling, resort to direct interpolation */
+ sample_2d_linear(ctx, tObj, img, texcoord, rgba);
+ return;
+ }
+
+ rgba[0]=num[0] / den;
+ rgba[1]=num[1] / den;
+ rgba[2]=num[2] / den;
+ rgba[3]=num[3] / den;
+}
+
+/* Anisotropic filtering using footprint assembly as outlined in the
+ * EXT_texture_filter_anisotropic spec:
+ * http://www.opengl.org/registry/specs/EXT/texture_filter_anisotropic.txt
+ * Faster than EWA but has less quality (more aliasing effects)
+ */
+static void
+sample_2d_footprint(struct gl_context *ctx,
+ const struct gl_texture_object *tObj,
+ const GLfloat texcoord[4],
+ const GLfloat dudx, const GLfloat dvdx,
+ const GLfloat dudy, const GLfloat dvdy, const GLint lod,
+ GLfloat rgba[])
+{
+ GLint level=lod > 0 ? lod : 0;
+ GLfloat scaling = 1.0 / (1 << level);
+
+ const struct gl_texture_image *img = tObj->Image[0][level];
+
+ GLfloat ux = dudx * scaling;
+ GLfloat vx = dvdx * scaling;
+ GLfloat uy = dudy * scaling;
+ GLfloat vy = dvdy * scaling;
+
+ GLfloat Px2 = ux * ux + vx * vx; /* squared length of dx */
+ GLfloat Py2 = uy * uy + vy * vy; /* squared length of dy */
+
+ GLint numSamples;
+ GLfloat ds;
+ GLfloat dt;
+
+ GLfloat num[4]={0, 0, 0, 0};
+ GLfloat newCoord[2];
+ GLint s;
+
+ /* Calculate the per anisotropic sample offsets in s,t space. */
+ if(Px2 > Py2) {
+ numSamples=ceil(SQRTF(Px2));
+ ds=ux / ((GLfloat)img->Width2);
+ dt=vx / ((GLfloat)img->Height2);
+ }
+ else {
+ numSamples=ceil(SQRTF(Py2));
+ ds=uy / ((GLfloat)img->Width2);
+ dt=vy / ((GLfloat)img->Height2);
+ }
+
+ for(s = 0; s<numSamples; s++) {
+ newCoord[0]=texcoord[0]+ds*((GLfloat)(s+1)/(numSamples+1)-0.5);
+ newCoord[1]=texcoord[1]+dt*((GLfloat)(s+1)/(numSamples+1)-0.5);
+
+ sample_2d_linear(ctx, tObj, img, newCoord, rgba);
+ num[0]+= rgba[0];
+ num[1]+= rgba[1];
+ num[2]+= rgba[2];
+ num[3]+= rgba[3];
+ }
+
+ rgba[0]=num[0] / numSamples;
+ rgba[1]=num[1] / numSamples;
+ rgba[2]=num[2] / numSamples;
+ rgba[3]=num[3] / numSamples;
+}
+
+/**
+ * Returns the index of the specified texture object in the
+ * gl_context texture unit array.
+ */
+static INLINE GLuint
+texture_unit_index(const struct gl_context *ctx,
+ const struct gl_texture_object *tObj) {
+ const GLuint maxUnit
+ = (ctx->Texture._EnabledCoordUnits > 1) ? ctx->Const.MaxTextureUnits : 1;
+ GLuint u;
+
+ /* XXX CoordUnits vs. ImageUnits */
+ for (u = 0; u < maxUnit; u++) {
+ if (ctx->Texture.Unit[u]._Current == tObj) break; // found
+ }
+ if(u >= maxUnit) u = 0; /* not found, use 1st one; should never happen */
+
+ return u;
+}
+
+/**
+ * Sample 2D texture using an anisotropic filter.
+ * NOTE: the const GLfloat lambda_iso[] parameter does *NOT* contain
+ * the lambda float array but a "hidden" SWspan struct which is required
+ * by this function but is not available in the texture_sample_func signature.
+ * See _swrast_texture_span( struct gl_context *ctx, SWspan *span ) on how
+ * this function is called.
+ */
+static void
+sample_lambda_2d_aniso(struct gl_context *ctx,
+ const struct gl_texture_object *tObj,
+ GLuint n, const GLfloat texcoords[][4],
+ const GLfloat lambda_iso[], GLfloat rgba[][4])
+{
+ const struct gl_texture_image *tImg = tObj->Image[0][tObj->BaseLevel];
+ const GLfloat maxEccentricity = tObj->Sampler.MaxAnisotropy * tObj->Sampler.MaxAnisotropy;
+
+ /* re-calculate the lambda values so that they are usable with anisotropic
+ * filtering
+ */
+ SWspan *span=(SWspan *)lambda_iso; /* access the "hidden" SWspan struct */
+
+ /* based on interpolate_texcoords(struct gl_context *ctx, SWspan *span)
+ * in swrast/s_span.c
+ */
+
+ /* find the texture unit index by looking up the current texture object
+ * from the context list of available texture obbjects.
+ */
+ const GLuint u = texture_unit_index(ctx, tObj);
+ const GLuint attr = FRAG_ATTRIB_TEX0 + u;
+ GLfloat texW, texH;
+
+ const GLfloat dsdx = span->attrStepX[attr][0];
+ const GLfloat dsdy = span->attrStepY[attr][0];
+ const GLfloat dtdx = span->attrStepX[attr][1];
+ const GLfloat dtdy = span->attrStepY[attr][1];
+ const GLfloat dqdx = span->attrStepX[attr][3];
+ const GLfloat dqdy = span->attrStepY[attr][3];
+ GLfloat s = span->attrStart[attr][0] + span->leftClip * dsdx;
+ GLfloat t = span->attrStart[attr][1] + span->leftClip * dtdx;
+ GLfloat q = span->attrStart[attr][3] + span->leftClip * dqdx;
+
+ /* from swrast/s_texcombine.c _swrast_texture_span */
+ const struct gl_texture_unit *texUnit = &ctx->Texture.Unit[u];
+ const GLboolean adjustLOD=(texUnit->LodBias + tObj->Sampler.LodBias != 0.0F)
+ || (tObj->Sampler.MinLod != -1000.0 || tObj->Sampler.MaxLod != 1000.0);
+
+ GLuint i;
+
+ /* on first access create the lookup table containing the filter weights. */
+ if(!weightLut) {
+ create_filter_table();
+ }
+
+ texW = tImg->WidthScale;
+ texH = tImg->HeightScale;
+
+ for (i = 0; i < n; i++) {
+ const GLfloat invQ = (q == 0.0F) ? 1.0F : (1.0F / q);
+
+ GLfloat dudx = texW * ((s + dsdx) / (q + dqdx) - s * invQ);
+ GLfloat dvdx = texH * ((t + dtdx) / (q + dqdx) - t * invQ);
+ GLfloat dudy = texW * ((s + dsdy) / (q + dqdy) - s * invQ);
+ GLfloat dvdy = texH * ((t + dtdy) / (q + dqdy) - t * invQ);
+
+ /* note: instead of working with Px and Py, we will use the
+ * squared length instead, to avoid sqrt.
+ */
+ GLfloat Px2=dudx*dudx + dvdx*dvdx;
+ GLfloat Py2=dudy*dudy + dvdy*dvdy;
+
+ GLfloat Pmax2;
+ GLfloat Pmin2;
+ GLfloat e;
+ GLfloat lod;
+
+ s += dsdx;
+ t += dtdx;
+ q += dqdx;
+
+ if (Px2 < Py2) {
+ Pmax2=Py2;
+ Pmin2=Px2;
+ }
+ else {
+ Pmax2=Px2;
+ Pmin2=Py2;
+ }
+
+ /* if the eccentricity of the ellipse is too big, scale up the shorter
+ * of the two vectors to limit the maximum amount of work per pixel
+ */
+ e = Pmax2 / Pmin2;
+ if (e > maxEccentricity) {
+ /* GLfloat s=e / maxEccentricity;
+ minor[0] *= s;
+ minor[1] *= s;
+ Pmin2 *= s; */
+ Pmin2 = Pmax2 / maxEccentricity;
+ }
+
+ /* note: we need to have Pmin=sqrt(Pmin2) here, but we can avoid
+ * this since 0.5*log(x) = log(sqrt(x))
+ */
+ lod = 0.5 * LOG2(Pmin2);
+
+ if(adjustLOD) {
+ /* from swrast/s_texcombine.c _swrast_texture_span */
+ if (texUnit->LodBias + tObj->Sampler.LodBias != 0.0F) {
+ /* apply LOD bias, but don't clamp yet */
+ const GLfloat bias = CLAMP(texUnit->LodBias + tObj->Sampler.LodBias,
+ -ctx->Const.MaxTextureLodBias,
+ ctx->Const.MaxTextureLodBias);
+ lod += bias;
+
+ if (tObj->Sampler.MinLod != -1000.0 ||
+ tObj->Sampler.MaxLod != 1000.0) {
+ /* apply LOD clamping to lambda */
+ const GLfloat min = tObj->Sampler.MinLod;
+ const GLfloat max = tObj->Sampler.MaxLod;
+ lod = CLAMP(lod, min, max);
+ }
+ }
+ }
+
+ /* If the ellipse covers the whole image, we can
+ * simply return the average of the whole image.
+ */
+ if (lod >= tObj->_MaxLevel) {
+ sample_2d_linear(ctx, tObj, tObj->Image[0][tObj->_MaxLevel],
+ texcoords[i], rgba[i]);
+ }
+ else {
+ /* don't bother interpolating between multiple LODs; it doesn't
+ * seem to be worth the extra running time.
+ */
+ sample_2d_ewa(ctx, tObj, texcoords[i],
+ dudx, dvdx, dudy, dvdy, floor(lod), rgba[i]);
+/* sample_2d_footprint(ctx, tObj, texcoords[i],
+ dudx, dvdx, dudy, dvdy, floor(lod), rgba[i]);
+*/
+ }
+ }
+}
+/* Anisotropic filtering extension end */
+
+
/**********************************************************************/
/* 3-D Texture Sampling Functions */
@@ -3221,6 +3603,11 @@ _swrast_choose_texture_sample_func( struct gl_context *ctx,
return &sample_depth_texture;
}
else if (needLambda) {
+ /* Anisotropic filtering extension. Activated only if mipmaps are used */
+ if (t->Sampler.MaxAnisotropy > 1.0 &&
+ t->Sampler.MinFilter == GL_LINEAR_MIPMAP_LINEAR) {
+ return &sample_lambda_2d_aniso;
+ }
return &sample_lambda_2d;
}
else if (t->Sampler.MinFilter == GL_LINEAR) {
--
1.7.0.2.msysgit.0
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