mirror of
https://github.com/RGBCube/serenity
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95 lines
2.4 KiB
C++
95 lines
2.4 KiB
C++
/*
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* Copyright (c) 2021, Stephan Unverwerth <s.unverwerth@serenityos.org>
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*
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* SPDX-License-Identifier: BSD-2-Clause
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*/
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#include "Sampler2D.h"
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#include <LibGL/Tex/Texture2D.h>
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#include <math.h>
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namespace GL {
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static constexpr float wrap_repeat(float value)
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{
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return value - floorf(value);
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}
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static constexpr float wrap_mirrored_repeat(float value)
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{
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float integer = floorf(value);
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float frac = value - integer;
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bool iseven = fmodf(integer, 2.0f) == 0.0f;
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return iseven ? frac : 1 - frac;
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}
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static constexpr float wrap_clamp(float value)
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{
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return clamp(value, 0.0f, 1.0f);
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}
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static constexpr float wrap(float value, GLint mode)
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{
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switch (mode) {
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case GL_REPEAT:
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return wrap_repeat(value);
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// FIXME: These clamp modes actually have slightly different behaviour
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case GL_CLAMP:
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case GL_CLAMP_TO_BORDER:
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case GL_CLAMP_TO_EDGE:
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return wrap_clamp(value);
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case GL_MIRRORED_REPEAT:
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return wrap_mirrored_repeat(value);
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break;
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default:
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VERIFY_NOT_REACHED();
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}
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}
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FloatVector4 Sampler2D::sample(FloatVector2 const& uv) const
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{
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// FIXME: Calculate the correct mipmap level here, need to receive uv derivatives for that
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unsigned lod = 0;
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MipMap const& mip = m_texture.mipmap(lod);
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float x = wrap(uv.x(), m_wrap_t_mode);
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float y = wrap(uv.y(), m_wrap_s_mode);
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x *= mip.width() - 1;
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y *= mip.height() - 1;
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// Sampling implemented according to https://www.khronos.org/registry/OpenGL/specs/gl/glspec121.pdf Chapter 3.8
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if (m_mag_filter == GL_NEAREST) {
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return mip.texel(static_cast<unsigned>(x) % mip.width(), static_cast<unsigned>(y) % mip.height());
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} else if (m_mag_filter == GL_LINEAR) {
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// FIXME: Implement different sampling points for wrap modes other than GL_REPEAT
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x -= 0.5f;
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y -= 0.5f;
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unsigned i0 = static_cast<unsigned>(x) % mip.width();
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unsigned j0 = static_cast<unsigned>(y) % mip.height();
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unsigned i1 = (i0 + 1) % mip.width();
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unsigned j1 = (j0 + 1) % mip.height();
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auto t0 = mip.texel(i0, j0);
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auto t1 = mip.texel(i1, j0);
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auto t2 = mip.texel(i0, j1);
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auto t3 = mip.texel(i1, j1);
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float frac_x = x - floorf(x);
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float frac_y = y - floorf(y);
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return t0 * (1 - frac_x) * (1 - frac_y) + t1 * frac_x * (1 - frac_y) + t2 * (1 - frac_x) * frac_y + t3 * frac_x * frac_y;
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} else {
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VERIFY_NOT_REACHED();
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}
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}
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}
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