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LibGL: Implement fog effect in Software Rasterizer

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We support three of the possible fog modes, EXP, EXP2 and LINEAR.
This commit is contained in:
Jesse Buhagiar 2021-08-25 18:10:44 +10:00 • committed by Ali Mohammad Pur
parent d73cc3d0eb
commit 924d890bfe
3 changed files with 41 additions and 9 deletions
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43
Userland/Libraries/LibGL/SoftwareRasterizer.cpp
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@ -28,6 +28,12 @@ constexpr static T interpolate(const T& v0, const T& v1, const T& v2, const Floa
return v0 * barycentric_coords.x() + v1 * barycentric_coords.y() + v2 * barycentric_coords.z();
}
template<typename T>
constexpr static T mix(const T& x, const T& y, float interp)
{
return x * (1 - interp) + y * interp;
}
static Gfx::RGBA32 to_rgba32(const FloatVector4& v)
{
auto clamped = v.clamped(0, 1);
@ -368,7 +374,11 @@ static void rasterize_triangle(const RasterizerOptions& options, Gfx::Bitmap& re
triangle.vertices[2].tex_coord,
barycentric);
*pixel = pixel_shader(uv, vertex_color);
// Calculate depth of fragment for fog
float z = interpolate(triangle.vertices[0].position.z(), triangle.vertices[1].position.z(), triangle.vertices[2].position.z(), barycentric);
z = options.depth_min + (options.depth_max - options.depth_min) * (z + 1) / 2;
*pixel = pixel_shader(uv, vertex_color, z);
}
}
@ -470,16 +480,9 @@ SoftwareRasterizer::SoftwareRasterizer(const Gfx::IntSize& min_size)
{
}
void SoftwareRasterizer::submit_triangle(const GLTriangle& triangle)
{
rasterize_triangle(m_options, *m_render_target, *m_depth_buffer, triangle, [](const FloatVector2&, const FloatVector4& color) -> FloatVector4 {
return color;
});
}
void SoftwareRasterizer::submit_triangle(const GLTriangle& triangle, const Array<TextureUnit, 32>& texture_units)
{
rasterize_triangle(m_options, *m_render_target, *m_depth_buffer, triangle, [&texture_units](const FloatVector2& uv, const FloatVector4& color) -> FloatVector4 {
rasterize_triangle(m_options, *m_render_target, *m_depth_buffer, triangle, [this, &texture_units](const FloatVector2& uv, const FloatVector4& color, float z) -> FloatVector4 {
// TODO: We'd do some kind of multitexturing/blending here
// Construct a vector for the texel we want to sample
FloatVector4 texel = color;
@ -494,6 +497,28 @@ void SoftwareRasterizer::submit_triangle(const GLTriangle& triangle, const Array
texel = texel * static_ptr_cast<Texture2D>(texture_unit.bound_texture())->sampler().sample(uv);
}
// Calculate fog
// Math from here: https://opengl-notes.readthedocs.io/en/latest/topics/texturing/aliasing.html
if (m_options.fog_enabled) {
float factor = 0.0f;
switch (m_options.fog_mode) {
case GL_LINEAR:
factor = (m_options.fog_end - z) / (m_options.fog_end - m_options.fog_start);
break;
case GL_EXP:
factor = exp(-((m_options.fog_density * z)));
break;
case GL_EXP2:
factor = exp(-((m_options.fog_density * z) * (m_options.fog_density * z)));
break;
default:
break;
}
// Mix texel with fog
texel = mix(m_options.fog_color, texel, factor);
}
return texel;
});
}