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LibGL: Fix texture sampling texel coordinate calculation

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Previously we multiplied the interpolated texture coordinates by
width - 1 and height - 1 instead of width and height which resulted in
some wrongly mapped textures, especially visible in the glquake light
maps.

This also corrects the wrap mode being wrongly swapped for s/t
coordinates.

Since we do not have texture borders implemented yet we always use
GL_CLAMP_TO_EDGE for all clamping wrap modes for the time being.
This commit is contained in:
Stephan Unverwerth 2021-12-12 23:47:28 +01:00 • committed by Brian Gianforcaro
parent 3d63e688f7
commit 47a4737110
Notes: sideshowbarker 2024-07-17 22:34:30 +09:00
1 changed files with 16 additions and 15 deletions
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31
Userland/Libraries/LibGL/Tex/Sampler2D.cpp
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@ -16,33 +16,34 @@ static constexpr float wrap_repeat(float value)
return value - floorf(value);
}
static constexpr float wrap_mirrored_repeat(float value)
static constexpr float wrap_clamp_to_edge(float value, int num_texels)
{
float const clamp_limit = 1.f / (2 * num_texels);
return clamp(value, clamp_limit, 1.0f - clamp_limit);
}
static constexpr float wrap_mirrored_repeat(float value, int num_texels)
{
float integer = floorf(value);
float frac = value - integer;
bool iseven = fmodf(integer, 2.0f) == 0.0f;
return iseven ? frac : 1 - frac;
return wrap_clamp_to_edge(iseven ? frac : 1 - frac, num_texels);
}
static constexpr float wrap_clamp(float value)
{
return clamp(value, 0.0f, 1.0f);
}
static constexpr float wrap(float value, GLint mode)
static constexpr float wrap(float value, GLint mode, int num_texels)
{
switch (mode) {
case GL_REPEAT:
return wrap_repeat(value);
// FIXME: These clamp modes actually have slightly different behavior
// FIXME: These clamp modes actually have slightly different behavior. Currently we use GL_CLAMP_TO_EDGE for all of them.
case GL_CLAMP:
case GL_CLAMP_TO_BORDER:
case GL_CLAMP_TO_EDGE:
return wrap_clamp(value);
return wrap_clamp_to_edge(value, num_texels);
case GL_MIRRORED_REPEAT:
return wrap_mirrored_repeat(value);
return wrap_mirrored_repeat(value, num_texels);
default:
VERIFY_NOT_REACHED();
@ -59,11 +60,11 @@ FloatVector4 Sampler2D::sample(FloatVector2 const& uv) const
if (mip.width() < 1 || mip.height() < 1)
return { 1, 1, 1, 1 };
float x = wrap(uv.x(), m_wrap_t_mode);
float y = wrap(uv.y(), m_wrap_s_mode);
float x = wrap(uv.x(), m_wrap_s_mode, mip.width());
float y = wrap(uv.y(), m_wrap_t_mode, mip.height());
x *= mip.width() - 1;
y *= mip.height() - 1;
x *= mip.width();
y *= mip.height();
// Sampling implemented according to https://www.khronos.org/registry/OpenGL/specs/gl/glspec121.pdf Chapter 3.8
if (m_mag_filter == GL_NEAREST) {