Mesa (master): softpipe: Anisotropic filtering extension.
Brian Paul
brianp at kemper.freedesktop.org
Mon Jun 6 14:31:43 UTC 2011
Module: Mesa
Branch: master
Commit: f4537f99cc83cb8133f66dc97c613e95dc0fe162
URL: http://cgit.freedesktop.org/mesa/mesa/commit/?id=f4537f99cc83cb8133f66dc97c613e95dc0fe162
Author: Andreas Faenger <a.faenger at e-sign.com>
Date: Mon Jun 6 07:13:16 2011 +0000
softpipe: Anisotropic filtering extension.
Reference implementation which produces high quality renderings.
Based on Higher Quality Elliptical Weighted Avarage Filter (EWA).
Signed-off-by: Brian Paul <brianp at vmware.com>
---
src/gallium/drivers/softpipe/sp_screen.c | 4 +-
src/gallium/drivers/softpipe/sp_tex_sample.c | 338 +++++++++++++++++++++++++-
2 files changed, 336 insertions(+), 6 deletions(-)
diff --git a/src/gallium/drivers/softpipe/sp_screen.c b/src/gallium/drivers/softpipe/sp_screen.c
index 48aabc1..30f53a9 100644
--- a/src/gallium/drivers/softpipe/sp_screen.c
+++ b/src/gallium/drivers/softpipe/sp_screen.c
@@ -81,7 +81,7 @@ softpipe_get_param(struct pipe_screen *screen, enum pipe_cap param)
case PIPE_CAP_SM3:
return 1;
case PIPE_CAP_ANISOTROPIC_FILTER:
- return 0;
+ return 1;
case PIPE_CAP_POINT_SPRITE:
return 1;
case PIPE_CAP_MAX_RENDER_TARGETS:
@@ -161,7 +161,7 @@ softpipe_get_paramf(struct pipe_screen *screen, enum pipe_cap param)
case PIPE_CAP_MAX_POINT_WIDTH_AA:
return 255.0; /* arbitrary */
case PIPE_CAP_MAX_TEXTURE_ANISOTROPY:
- return 16.0; /* not actually signficant at this time */
+ return 16.0;
case PIPE_CAP_MAX_TEXTURE_LOD_BIAS:
return 16.0; /* arbitrary */
default:
diff --git a/src/gallium/drivers/softpipe/sp_tex_sample.c b/src/gallium/drivers/softpipe/sp_tex_sample.c
index 1446aee..90766f4 100644
--- a/src/gallium/drivers/softpipe/sp_tex_sample.c
+++ b/src/gallium/drivers/softpipe/sp_tex_sample.c
@@ -1709,6 +1709,317 @@ mip_filter_none(struct tgsi_sampler *tgsi_sampler,
}
+/* For anisotropic filtering */
+#define WEIGHT_LUT_SIZE 1024
+
+static float *weightLut = NULL;
+
+/**
+ * Creates the look-up table used to speed-up EWA sampling
+ */
+static void
+create_filter_table(void)
+{
+ unsigned i;
+ if (!weightLut) {
+ weightLut = (float *) malloc(WEIGHT_LUT_SIZE * sizeof(float));
+
+ for (i = 0; i < WEIGHT_LUT_SIZE; ++i) {
+ float alpha = 2;
+ float r2 = (float) i / (float) (WEIGHT_LUT_SIZE - 1);
+ float weight = (float) 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
+img_filter_2d_ewa(struct tgsi_sampler *tgsi_sampler,
+ const float s[QUAD_SIZE],
+ const float t[QUAD_SIZE],
+ const float p[QUAD_SIZE],
+ const float c0[QUAD_SIZE],
+ enum tgsi_sampler_control control,
+ const float dudx, const float dvdx,
+ const float dudy, const float dvdy,
+ float rgba[NUM_CHANNELS][QUAD_SIZE])
+{
+ const struct sp_sampler_variant *samp = sp_sampler_variant(tgsi_sampler);
+ const struct pipe_resource *texture = samp->view->texture;
+
+ unsigned level0 = samp->level > 0 ? samp->level : 0;
+ float scaling = 1.0 / (1 << level0);
+ int width = u_minify(texture->width0, level0);
+ int height = u_minify(texture->height0, level0);
+
+ float ux = dudx * scaling;
+ float vx = dvdx * scaling;
+ float uy = dudy * scaling;
+ float vy = dvdy * scaling;
+
+ /* compute ellipse coefficients to bound the region:
+ * A*x*x + B*x*y + C*y*y = F.
+ */
+ float A = vx*vx+vy*vy+1;
+ float B = -2*(ux*vx+uy*vy);
+ float C = ux*ux+uy*uy+1;
+ float 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 */
+ float d = -B*B+4.0*C*A;
+ float box_u = 2.0 / d * sqrt(d*C*F); /* box_u -> half of bbox with */
+ float box_v = 2.0 / d * sqrt(A*d*F); /* box_v -> half of bbox height */
+
+ float rgba_temp[NUM_CHANNELS][QUAD_SIZE];
+ float s_buffer[QUAD_SIZE];
+ float t_buffer[QUAD_SIZE];
+ float weight_buffer[QUAD_SIZE];
+ unsigned buffer_next;
+ int j;
+ float den;// = 0.0F;
+ float ddq;
+ float U;// = u0 - tex_u;
+ int v;
+
+ /* Scale ellipse formula to directly index the Filter Lookup Table.
+ * i.e. scale so that F = WEIGHT_LUT_SIZE-1
+ */
+ 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 */
+
+ /* For each quad, the du and dx values are the same and so the ellipse is
+ * also the same. Note that texel/image access can only be performed using
+ * a quad, i.e. it is not possible to get the pixel value for a single
+ * tex coord. In order to have a better performance, the access is buffered
+ * using the s_buffer/t_buffer and weight_buffer. Only when the buffer is full,
+ * then the pixel values are read from the image.
+ */
+ ddq = 2 * A;
+
+ for (j = 0; j < QUAD_SIZE; j++) {
+ /* 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
+ */
+ float tex_u=-0.5 + s[j] * texture->width0 * scaling;
+ float tex_v=-0.5 + t[j] * texture->height0 * scaling;
+
+ int u0 = floor(tex_u - box_u);
+ int u1 = ceil (tex_u + box_u);
+ int v0 = floor(tex_v - box_v);
+ int v1 = ceil (tex_v + box_v);
+
+ float num[4] = {0.0F, 0.0F, 0.0F, 0.0F};
+ buffer_next = 0;
+ den = 0;
+ U = u0 - tex_u;
+ for (v = v0; v <= v1; ++v) {
+ float V = v - tex_v;
+ float dq = A * (2 * U + 1) + B * V;
+ float q = (C * V + B * U) * V + A * U * U;
+
+ int 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 int qClamped = q >= 0.0F ? q : 0;
+ float weight = weightLut[qClamped];
+
+ weight_buffer[buffer_next] = weight;
+ s_buffer[buffer_next] = u / ((float) width);
+ t_buffer[buffer_next] = v / ((float) height);
+
+ buffer_next++;
+ if (buffer_next == QUAD_SIZE) {
+ /* 4 texel coords are in the buffer -> read it now */
+ int jj;
+ /* it is assumed that samp->min_img_filter is set to
+ * img_filter_2d_nearest or one of the
+ * accelerated img_filter_2d_nearest_XXX functions.
+ */
+ samp->min_img_filter(tgsi_sampler, s_buffer, t_buffer, p, NULL,
+ tgsi_sampler_lod_bias, rgba_temp);
+ for (jj = 0; jj < buffer_next; jj++) {
+ num[0] += weight_buffer[jj] * rgba_temp[0][jj];
+ num[1] += weight_buffer[jj] * rgba_temp[1][jj];
+ num[2] += weight_buffer[jj] * rgba_temp[2][jj];
+ num[3] += weight_buffer[jj] * rgba_temp[3][jj];
+ }
+
+ buffer_next = 0;
+ }
+
+ den += weight;
+ }
+ q += dq;
+ dq += ddq;
+ }
+ }
+
+ /* if the tex coord buffer contains unread values, we will read them now.
+ * Note that in most cases we have to read more pixel values than required,
+ * however, as the img_filter_2d_nearest function(s) does not have a count
+ * parameter, we need to read the whole quad and ignore the unused values
+ */
+ if (buffer_next > 0) {
+ int jj;
+ /* it is assumed that samp->min_img_filter is set to
+ * img_filter_2d_nearest or one of the
+ * accelerated img_filter_2d_nearest_XXX functions.
+ */
+ samp->min_img_filter(tgsi_sampler, s_buffer, t_buffer, p, NULL,
+ tgsi_sampler_lod_bias, rgba_temp);
+ for (jj = 0; jj < buffer_next; jj++) {
+ num[0] += weight_buffer[jj] * rgba_temp[0][jj];
+ num[1] += weight_buffer[jj] * rgba_temp[1][jj];
+ num[2] += weight_buffer[jj] * rgba_temp[2][jj];
+ num[3] += weight_buffer[jj] * rgba_temp[3][jj];
+ }
+ }
+
+ if (den <= 0.0F) {
+ /* 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 */
+ samp->min_img_filter(tgsi_sampler, s, t, p, NULL, tgsi_sampler_lod_bias, rgba_temp);
+ den = 1;
+ num[0] = rgba_temp[0][j];
+ num[1] = rgba_temp[1][j];
+ num[2] = rgba_temp[2][j];
+ num[3] = rgba_temp[3][j];
+ }
+
+ rgba[0][j] = num[0] / den;
+ rgba[1][j] = num[1] / den;
+ rgba[2][j] = num[2] / den;
+ rgba[3][j] = num[3] / den;
+ }
+}
+
+
+/**
+ * Sample 2D texture using an anisotropic filter.
+ */
+static void
+mip_filter_linear_aniso(struct tgsi_sampler *tgsi_sampler,
+ const float s[QUAD_SIZE],
+ const float t[QUAD_SIZE],
+ const float p[QUAD_SIZE],
+ const float c0[QUAD_SIZE],
+ enum tgsi_sampler_control control,
+ float rgba[NUM_CHANNELS][QUAD_SIZE])
+{
+ struct sp_sampler_variant *samp = sp_sampler_variant(tgsi_sampler);
+ const struct pipe_resource *texture = samp->view->texture;
+ int level0;
+ float lambda;
+ float lod[QUAD_SIZE];
+
+ float s_to_u = u_minify(texture->width0, samp->view->u.tex.first_level);
+ float t_to_v = u_minify(texture->height0, samp->view->u.tex.first_level);
+ float dudx = (s[QUAD_BOTTOM_RIGHT] - s[QUAD_BOTTOM_LEFT]) * s_to_u;
+ float dudy = (s[QUAD_TOP_LEFT] - s[QUAD_BOTTOM_LEFT]) * s_to_u;
+ float dvdx = (t[QUAD_BOTTOM_RIGHT] - t[QUAD_BOTTOM_LEFT]) * t_to_v;
+ float dvdy = (t[QUAD_TOP_LEFT] - t[QUAD_BOTTOM_LEFT]) * t_to_v;
+
+ if (control == tgsi_sampler_lod_bias) {
+ /* note: instead of working with Px and Py, we will use the
+ * squared length instead, to avoid sqrt.
+ */
+ float Px2 = dudx * dudx + dvdx * dvdx;
+ float Py2 = dudy * dudy + dvdy * dvdy;
+
+ float Pmax2;
+ float Pmin2;
+ float e;
+ const float maxEccentricity = samp->sampler->max_anisotropy * samp->sampler->max_anisotropy;
+
+ 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) {
+ /* float 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))
+ */
+ lambda = 0.5 * util_fast_log2(Pmin2) + samp->sampler->lod_bias;
+ compute_lod(samp->sampler, lambda, c0, lod);
+ }
+ else {
+ assert(control == tgsi_sampler_lod_explicit);
+
+ memcpy(lod, c0, sizeof(lod));
+ }
+
+ /* XXX: Take into account all lod values.
+ */
+ lambda = lod[0];
+ level0 = samp->view->u.tex.first_level + (int)lambda;
+
+ /* If the ellipse covers the whole image, we can
+ * simply return the average of the whole image.
+ */
+ if (level0 >= texture->last_level) {
+ samp->level = texture->last_level;
+ samp->min_img_filter(tgsi_sampler, s, t, p, NULL, tgsi_sampler_lod_bias, rgba);
+ }
+ else {
+ /* don't bother interpolating between multiple LODs; it doesn't
+ * seem to be worth the extra running time.
+ */
+ samp->level = level0;
+ img_filter_2d_ewa(tgsi_sampler, s, t, p, NULL, tgsi_sampler_lod_bias,
+ dudx, dvdx, dudy, dvdy, rgba);
+ }
+
+ if (DEBUG_TEX) {
+ print_sample(__FUNCTION__, rgba);
+ }
+}
+
+
/**
* Specialized version of mip_filter_linear with hard-wired calls to
@@ -2316,14 +2627,33 @@ sp_create_sampler_variant( const struct pipe_sampler_state *sampler,
sampler->normalized_coords &&
sampler->wrap_s == PIPE_TEX_WRAP_REPEAT &&
sampler->wrap_t == PIPE_TEX_WRAP_REPEAT &&
- sampler->min_img_filter == PIPE_TEX_FILTER_LINEAR)
- {
+ sampler->min_img_filter == PIPE_TEX_FILTER_LINEAR) {
samp->mip_filter = mip_filter_linear_2d_linear_repeat_POT;
}
- else
- {
+ else {
samp->mip_filter = mip_filter_linear;
}
+
+ /* Anisotropic filtering extension. */
+ if (sampler->max_anisotropy > 1) {
+ samp->mip_filter = mip_filter_linear_aniso;
+
+ /* Override min_img_filter:
+ * min_img_filter needs to be set to NEAREST since we need to access
+ * each texture pixel as it is and weight it later; using linear
+ * filters will have incorrect results.
+ * By setting the filter to NEAREST here, we can avoid calling the
+ * generic img_filter_2d_nearest in the anisotropic filter function,
+ * making it possible to use one of the accelerated implementations
+ */
+ samp->min_img_filter = get_img_filter(key, PIPE_TEX_FILTER_NEAREST, sampler);
+
+ /* on first access create the lookup table containing the filter weights. */
+ if (!weightLut) {
+ create_filter_table();
+ }
+ }
+
break;
}
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