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gfx/blur/gaussian: Fix Gaussian Kernel generation 

While the previous method worked, it matches no other implementation including a reference implementation. The new implementation almost perfectly matches the reference implementation and uses oversampling to achieve the goal. This has the downside of limiting the blur size to just 64, but it is necessary in order to achieve correct results.

Fixes #573
This commit is contained in:
Michael Fabian 'Xaymar' Dirks 2021-06-08 10:35:34 +02:00
parent 8a10ca93e5
commit 011bee032a
3 changed files with 137 additions and 91 deletions
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99
data/effects/blur/gaussian.effect
View File

@ -1,28 +1,42 @@
#include "common.effect"
//------------------------------------------------------------------------------
// Uniforms
//------------------------------------------------------------------------------
// This shader requires that pSize is the number of samples, not the size of the
// kernel. That way oversampling can be performed, which is much more accurate than
//------------------------------------------------------------------------------
// Defines
//------------------------------------------------------------------------------
#define MAX_BLUR_SIZE 128
#define MAX_SAMPLES 128
//------------------------------------------------------------------------------
// Technique: Directional / Area
//------------------------------------------------------------------------------
float4 PSBlur1D(VertexInformation vtx) : TARGET {
float4 final = pImage.Sample(LinearClampSampler, vtx.uv) * kernelAt(0);
float2 uvstep = pImageTexel * pStepScale;
float weights = 0;
// Loop unrolling is only possible with a fixed known maximum.
// Some compilers may unroll up to x iterations, but most will not.
for (int n = 1; n <= MAX_BLUR_SIZE; n++) {
float2 nstep = (pImageTexel * pStepScale) * n;
float kernel = kernelAt(n);
final += pImage.Sample(LinearClampSampler, vtx.uv + nstep) * kernel;
final += pImage.Sample(LinearClampSampler, vtx.uv - nstep) * kernel;
// Move to texel center.
vtx.uv.xy += pImageTexel.xy / 2.;
if (n >= pSize) {
break;
}
// Calculate the actual Gaussian Blur
// 1. Sample the center immediately.
float kernel = kernelAt(0);
weights += kernel;
float4 final = pImage.Sample(LinearClampSampler, vtx.uv) * kernel;
// 2. Then sample both + and - coordinates in one go to reduce code iterations.
for (uint step = 1; (step < pSize) && (step < MAX_SAMPLES); step++) {
float2 offset = uvstep * step;
kernel = kernelAt(step);
weights += kernel * 2;
final += pImage.Sample(LinearClampSampler, vtx.uv + offset) * kernel;
final += pImage.Sample(LinearClampSampler, vtx.uv - offset) * kernel;
}
// 3. Ensure we always have a total of 1.0, even if the kernel is bad.
final /= weights;
return final;
}
@ -38,22 +52,29 @@ technique Draw {
// Technique: Rotate
//------------------------------------------------------------------------------
float4 PSRotate(VertexInformation vtx) : TARGET {
float4 final = pImage.Sample(LinearClampSampler, vtx.uv) * kernelAt(0);
float angstep = pAngle * pStepScale.x;
float weights = 0.;
// Loop unrolling is only possible with a fixed known maximum.
// Some compilers may unroll up to x iterations, but most will not.
for (int n = 1; n <= MAX_BLUR_SIZE; n++) {
float kernel = kernelAt(n);
final += pImage.Sample(LinearClampSampler, rotateAround(vtx.uv, pCenter, angstep * n)) * kernel;
final += pImage.Sample(LinearClampSampler, rotateAround(vtx.uv, pCenter, angstep * -n)) * kernel;
// Move to texel center.
vtx.uv.xy += pImageTexel.xy / 2.;
if (n >= pSize) {
break;
}
// Calculate the actual Gaussian Blur
// 1. Sample the center immediately.
float kernel = kernelAt(0);
weights += kernel;
float4 final = pImage.Sample(LinearClampSampler, vtx.uv) * kernel;
// 2. Then sample both + and - coordinates in one go to reduce code iterations.
for (uint step = 1; (step < pSize) && (step < MAX_SAMPLES); step++) {
float offset = angstep * step;
kernel = kernelAt(step);
weights += kernel * 2;
final += pImage.Sample(LinearClampSampler, rotateAround(vtx.uv, pCenter, offset)) * kernel;
final += pImage.Sample(LinearClampSampler, rotateAround(vtx.uv, pCenter, -offset)) * kernel;
}
// 3. Ensure we always have a total of 1.0, even if the kernel is bad.
final /= weights;
return final;
}
@ -68,23 +89,29 @@ technique Rotate {
// Technique: Zoom
//------------------------------------------------------------------------------
float4 PSZoom(VertexInformation vtx) : TARGET {
float4 final = pImage.Sample(LinearClampSampler, vtx.uv) * kernelAt(0);
// step is calculated from the direction relative to the center
float2 dir = normalize(vtx.uv - pCenter) * pStepScale * pImageTexel;
float dist = distance(vtx.uv, pCenter);
float weights = 0.;
// Loop unrolling is only possible with a fixed known maximum.
// Some compilers may unroll up to x iterations, but most will not.
for (int n = 1; n <= MAX_BLUR_SIZE; n++) {
float kernel = kernelAt(n);
final += pImage.Sample(LinearClampSampler, vtx.uv + (dir * n) * dist) * kernel;
final += pImage.Sample(LinearClampSampler, vtx.uv - (dir * n) * dist) * kernel;
// Move to texel center.
vtx.uv.xy += pImageTexel.xy / 2.;
if (n >= pSize) {
break;
}
// Calculate the actual Gaussian Blur
// 1. Sample the center immediately.
float kernel = kernelAt(0);
weights += kernel;
float4 final = pImage.Sample(LinearClampSampler, vtx.uv) * kernel;
// 2. Then sample both + and - coordinates in one go to reduce code iterations.
for (uint step = 1; (step < pSize) && (step < MAX_SAMPLES); step++) {
float2 offset = dir * step * dist;
kernel = kernelAt(step);
weights += kernel * 2;
final += pImage.Sample(LinearClampSampler, vtx.uv + offset) * kernel;
final += pImage.Sample(LinearClampSampler, vtx.uv - offset) * kernel;
}
// 3. Ensure we always have a total of 1.0, even if the kernel is bad.
final /= weights;
return final;
}

125
source/gfx/blur/gfx-blur-gaussian.cpp
View File

@ -16,6 +16,7 @@
// Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA
#include "gfx-blur-gaussian.hpp"
#include <algorithm>
#include <stdexcept>
#include "obs/gs/gs-helper.hpp"
#include "plugin.hpp"
@ -30,51 +31,74 @@
#pragma warning(pop)
#endif
// FIXME: This breaks when MAX_KERNEL_SIZE is changed, due to the way the Gaussian
// function first goes up at the point, and then once we pass the critical point
// will go down again and it is not handled well. This is a pretty basic
// approximation anyway at the moment.
#define ST_MAX_KERNEL_SIZE 128
#define ST_MAX_BLUR_SIZE (ST_MAX_KERNEL_SIZE - 1)
#define ST_SEARCH_DENSITY double_t(1. / 500.)
#define ST_SEARCH_THRESHOLD double_t(1. / (ST_MAX_KERNEL_SIZE * 5))
#define ST_SEARCH_EXTENSION 1
#define ST_SEARCH_RANGE ST_MAX_KERNEL_SIZE * 2
// TODO: It may be possible to optimize to run much faster: https://rastergrid.com/blog/2010/09/efficient-gaussian-blur-with-linear-sampling/
#define ST_KERNEL_SIZE 128u
#define ST_OVERSAMPLE_MULTIPLIER 2
#define ST_MAX_BLUR_SIZE ST_KERNEL_SIZE / ST_OVERSAMPLE_MULTIPLIER
streamfx::gfx::blur::gaussian_data::gaussian_data()
{
auto gctx = streamfx::obs::gs::context();
_effect = streamfx::obs::gs::effect::create(streamfx::data_file_path("effects/blur/gaussian.effect").u8string());
using namespace streamfx::util;
// Precalculate Kernels
for (std::size_t kernel_size = 1; kernel_size <= ST_MAX_BLUR_SIZE; kernel_size++) {
std::vector<double_t> kernel_math(ST_MAX_KERNEL_SIZE);
std::vector<float_t> kernel_data(ST_MAX_KERNEL_SIZE);
double_t actual_width = 1.;
std::vector<double> kernel_dbl(ST_KERNEL_SIZE);
std::vector<float> kernel(ST_KERNEL_SIZE);
// Find actual kernel width.
for (double_t h = ST_SEARCH_DENSITY; h < ST_SEARCH_RANGE; h += ST_SEARCH_DENSITY) {
if (streamfx::util::math::gaussian<double_t>(double_t(kernel_size + ST_SEARCH_EXTENSION), h)
> ST_SEARCH_THRESHOLD) {
actual_width = h;
break;
}
{
auto gctx = streamfx::obs::gs::context();
_effect =
streamfx::obs::gs::effect::create(streamfx::data_file_path("effects/blur/gaussian.effect").u8string());
}
//#define ST_USE_PASCAL_TRIANGLE
// Pre-calculate Kernel Information for all Kernel sizes
for (size_t size = 1; size <= ST_MAX_BLUR_SIZE; size++) {
#ifdef ST_USE_PASCAL_TRIANGLE
// The Pascal Triangle can be used to generate Gaussian Kernels, which is
// significantly faster than doing the same task with searching. It is also
// much more accurate at the same time, so it is a 2-in-1 solution.
// Generate the required row and sum.
size_t offset = size;
size_t row = size * 2;
auto triangle = math::pascal_triangle<double>(row);
double sum = pow(2, row);
// Convert all integers to floats.
double accum = 0.;
for (size_t idx = offset; idx < std::min<size_t>(triangle.size(), ST_KERNEL_SIZE); idx++) {
double v = static_cast<double>(triangle[idx]) / sum;
kernel_dbl[idx - offset] = v;
// Accumulator needed as we end up with float inaccuracies above a certain threshold.
accum += v * (idx > offset ? 2 : 1);
}
// Calculate and normalize
double_t sum = 0;
for (std::size_t p = 0; p <= kernel_size; p++) {
kernel_math[p] = streamfx::util::math::gaussian<double_t>(double_t(p), actual_width);
sum += kernel_math[p] * (p > 0 ? 2 : 1);
// Rescale all values back into useful ranges.
accum = 1. / accum;
for (size_t idx = offset; idx < ST_KERNEL_SIZE; idx++) {
kernel[idx - offset] = kernel_dbl[idx - offset] * accum;
}
#else
size_t oversample = size * ST_OVERSAMPLE_MULTIPLIER;
// Generate initial weights and calculate a total from them.
double total = 0.;
for (size_t idx = 0; (idx < oversample) && (idx < ST_KERNEL_SIZE); idx++) {
kernel_dbl[idx] = math::gaussian<double>(static_cast<double>(idx), static_cast<double>(size));
total += kernel_dbl[idx] * (idx > 0 ? 2 : 1);
}
// Normalize to fill the entire 0..1 range over the width.
double_t inverse_sum = 1.0 / sum;
for (std::size_t p = 0; p <= kernel_size; p++) {
kernel_data.at(p) = float_t(kernel_math[p] * inverse_sum);
// Scale the weights according to the total gathered, and convert to float.
for (size_t idx = 0; (idx < oversample) && (idx < ST_KERNEL_SIZE); idx++) {
kernel_dbl[idx] /= total;
kernel[idx] = static_cast<float>(kernel_dbl[idx]);
}
_kernels.push_back(std::move(kernel_data));
#endif
// Store Kernel
_kernels.insert_or_assign(size, kernel);
}
}
@ -91,12 +115,8 @@ streamfx::obs::gs::effect streamfx::gfx::blur::gaussian_data::get_effect()
std::vector<float_t> const& streamfx::gfx::blur::gaussian_data::get_kernel(std::size_t width)
{
if (width < 1)
width = 1;
if (width > ST_MAX_BLUR_SIZE)
width = ST_MAX_BLUR_SIZE;
width -= 1;
return _kernels[width];
width = std::clamp<size_t>(width, 1, ST_MAX_BLUR_SIZE);
return _kernels.at(width);
}
streamfx::gfx::blur::gaussian_factory::gaussian_factory() {}
@ -303,12 +323,12 @@ std::shared_ptr<::streamfx::obs::gs::texture> streamfx::gfx::blur::gaussian::ren
#endif
streamfx::obs::gs::effect effect = _data->get_effect();
auto kernel = _data->get_kernel(size_t(_size));
if (!effect || ((_step_scale.first + _step_scale.second) < std::numeric_limits<double_t>::epsilon())) {
return _input_texture;
}
auto kernel = _data->get_kernel(size_t(_size));
float_t width = float_t(_input_texture->get_width());
float_t height = float_t(_input_texture->get_height());
@ -326,13 +346,13 @@ std::shared_ptr<::streamfx::obs::gs::texture> streamfx::gfx::blur::gaussian::ren
gs_stencil_function(GS_STENCIL_BOTH, GS_ALWAYS);
gs_stencil_op(GS_STENCIL_BOTH, GS_ZERO, GS_ZERO, GS_ZERO);
effect.get_parameter("pImage").set_texture(_input_texture);
effect.get_parameter("pStepScale").set_float2(float_t(_step_scale.first), float_t(_step_scale.second));
effect.get_parameter("pSize").set_float(float_t(_size));
effect.get_parameter("pKernel").set_value(kernel.data(), ST_MAX_KERNEL_SIZE);
effect.get_parameter("pSize").set_float(float_t(_size * ST_OVERSAMPLE_MULTIPLIER));
effect.get_parameter("pKernel").set_value(kernel.data(), ST_KERNEL_SIZE);
// First Pass
if (_step_scale.first > std::numeric_limits<double_t>::epsilon()) {
effect.get_parameter("pImage").set_texture(_input_texture);
effect.get_parameter("pImageTexel").set_float2(float_t(1.f / width), 0.f);
{
@ -348,11 +368,11 @@ std::shared_ptr<::streamfx::obs::gs::texture> streamfx::gfx::blur::gaussian::ren
}
std::swap(_rendertarget, _rendertarget2);
effect.get_parameter("pImage").set_texture(_rendertarget->get_texture());
}
// Second Pass
if (_step_scale.second > std::numeric_limits<double_t>::epsilon()) {
effect.get_parameter("pImage").set_texture(_rendertarget->get_texture());
effect.get_parameter("pImageTexel").set_float2(0.f, float_t(1.f / height));
{
@ -409,12 +429,12 @@ std::shared_ptr<::streamfx::obs::gs::texture> streamfx::gfx::blur::gaussian_dire
#endif
streamfx::obs::gs::effect effect = _data->get_effect();
auto kernel = _data->get_kernel(size_t(_size));
if (!effect || ((_step_scale.first + _step_scale.second) < std::numeric_limits<double_t>::epsilon())) {
return _input_texture;
}
auto kernel = _data->get_kernel(size_t(_size));
float_t width = float_t(_input_texture->get_width());
float_t height = float_t(_input_texture->get_height());
@ -436,10 +456,9 @@ std::shared_ptr<::streamfx::obs::gs::texture> streamfx::gfx::blur::gaussian_dire
effect.get_parameter("pImageTexel")
.set_float2(float_t(1.f / width * cos(m_angle)), float_t(1.f / height * sin(m_angle)));
effect.get_parameter("pStepScale").set_float2(float_t(_step_scale.first), float_t(_step_scale.second));
effect.get_parameter("pSize").set_float(float_t(_size));
effect.get_parameter("pKernel").set_value(kernel.data(), ST_MAX_KERNEL_SIZE);
effect.get_parameter("pSize").set_float(float_t(_size * ST_OVERSAMPLE_MULTIPLIER));
effect.get_parameter("pKernel").set_value(kernel.data(), ST_KERNEL_SIZE);
// First Pass
{
auto op = _rendertarget->render(uint32_t(width), uint32_t(height));
gs_ortho(0, 1., 0, 1., 0, 1.);
@ -468,12 +487,12 @@ std::shared_ptr<::streamfx::obs::gs::texture> streamfx::gfx::blur::gaussian_rota
#endif
streamfx::obs::gs::effect effect = _data->get_effect();
auto kernel = _data->get_kernel(size_t(_size));
if (!effect || ((_step_scale.first + _step_scale.second) < std::numeric_limits<double_t>::epsilon())) {
return _input_texture;
}
auto kernel = _data->get_kernel(size_t(_size));
float_t width = float_t(_input_texture->get_width());
float_t height = float_t(_input_texture->get_height());
@ -494,10 +513,10 @@ std::shared_ptr<::streamfx::obs::gs::texture> streamfx::gfx::blur::gaussian_rota
effect.get_parameter("pImage").set_texture(_input_texture);
effect.get_parameter("pImageTexel").set_float2(float_t(1.f / width), float_t(1.f / height));
effect.get_parameter("pStepScale").set_float2(float_t(_step_scale.first), float_t(_step_scale.second));
effect.get_parameter("pSize").set_float(float_t(_size));
effect.get_parameter("pSize").set_float(float_t(_size * ST_OVERSAMPLE_MULTIPLIER));
effect.get_parameter("pAngle").set_float(float_t(m_angle / _size));
effect.get_parameter("pCenter").set_float2(float_t(m_center.first), float_t(m_center.second));
effect.get_parameter("pKernel").set_value(kernel.data(), ST_MAX_KERNEL_SIZE);
effect.get_parameter("pKernel").set_value(kernel.data(), ST_KERNEL_SIZE);
// First Pass
{
@ -577,7 +596,7 @@ std::shared_ptr<::streamfx::obs::gs::texture> streamfx::gfx::blur::gaussian_zoom
effect.get_parameter("pStepScale").set_float2(float_t(_step_scale.first), float_t(_step_scale.second));
effect.get_parameter("pSize").set_float(float_t(_size));
effect.get_parameter("pCenter").set_float2(float_t(m_center.first), float_t(m_center.second));
effect.get_parameter("pKernel").set_value(kernel.data(), ST_MAX_KERNEL_SIZE);
effect.get_parameter("pKernel").set_value(kernel.data(), ST_KERNEL_SIZE);
// First Pass
{

4
source/gfx/blur/gfx-blur-gaussian.hpp
View File

@ -27,8 +27,8 @@
namespace streamfx::gfx {
namespace blur {
class gaussian_data {
streamfx::obs::gs::effect _effect;
std::vector<std::vector<float_t>> _kernels;
streamfx::obs::gs::effect _effect;
std::map<size_t, std::vector<float>> _kernels;
public:
gaussian_data();