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LibSoftGPU: Clamp polygon depth values to 0.f - 1.f

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According to the OpenGL spec, we're expected to clamp the fragment
depth values to the range `0.f - 1.f` for all polygons.

This fixes Z-fighting issues with the sky in Quake 3.
This commit is contained in:
Jelle Raaijmakers 2022-05-10 23:55:25 +02:00 • committed by Andreas Kling
parent f505f1ab5e
commit 5861f1821e
1 changed files with 7 additions and 6 deletions
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13
Userland/Libraries/LibSoftGPU/Device.cpp
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@ -728,11 +728,6 @@ void Device::rasterize_triangle(Triangle& triangle)
auto const half_pixel_offset = Vector2<i32x4> { expand4(subpixel_factor / 2), expand4(subpixel_factor / 2) };
auto const window_z_coordinates = Vector3<f32x4> {
expand4(vertex0.window_coordinates.z()),
expand4(vertex1.window_coordinates.z()),
expand4(vertex2.window_coordinates.z()),
};
auto const window_w_coordinates = Vector3<f32x4> {
expand4(vertex0.window_coordinates.w()),
expand4(vertex1.window_coordinates.w()),
@ -774,6 +769,12 @@ void Device::rasterize_triangle(Triangle& triangle)
depth_offset = depth_max_slope * m_options.depth_offset_factor + NumericLimits<float>::epsilon() * m_options.depth_offset_constant;
}
auto const window_z_coordinates = Vector3<f32x4> {
expand4(vertex0.window_coordinates.z() + depth_offset),
expand4(vertex1.window_coordinates.z() + depth_offset),
expand4(vertex2.window_coordinates.z() + depth_offset),
};
rasterize(
render_bounds,
[&](auto& quad) {
@ -791,7 +792,7 @@ void Device::rasterize_triangle(Triangle& triangle)
quad.barycentrics = quad.barycentrics * one_over_area;
// Because the Z coordinates were divided by W, we can interpolate between them
quad.depth = window_z_coordinates.dot(quad.barycentrics) + depth_offset;
quad.depth = AK::SIMD::clamp(window_z_coordinates.dot(quad.barycentrics), 0.f, 1.f);
},
[&](auto& quad) {
auto const interpolated_reciprocal_w = window_w_coordinates.dot(quad.barycentrics);