838cee37a2
By setting the clip plane normals' W coordinate to 1, we can skip two coordinate retrievals and three additions. This works because the Vector `.dot()` operation multiplies the W coordinates of both vectors.
105 lines
4 KiB
C++
105 lines
4 KiB
C++
/*
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* Copyright (c) 2021, Jesse Buhagiar <jooster669@gmail.com>
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* Copyright (c) 2021, Stephan Unverwerth <s.unverwerth@serenityos.org>
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* Copyright (c) 2022, Jelle Raaijmakers <jelle@gmta.nl>
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* Copyright (c) 2022, the SerenityOS developers.
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*
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* SPDX-License-Identifier: BSD-2-Clause
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*/
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#include <AK/Vector.h>
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#include <LibGPU/Vertex.h>
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#include <LibGfx/Vector4.h>
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#include <LibSoftGPU/Clipper.h>
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namespace SoftGPU {
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template<Clipper::ClipPlane plane>
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static constexpr bool point_within_clip_plane(FloatVector4 const& vertex)
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{
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if constexpr (plane == Clipper::ClipPlane::LEFT)
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return vertex.x() >= -vertex.w();
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else if constexpr (plane == Clipper::ClipPlane::RIGHT)
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return vertex.x() <= vertex.w();
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else if constexpr (plane == Clipper::ClipPlane::TOP)
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return vertex.y() <= vertex.w();
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else if constexpr (plane == Clipper::ClipPlane::BOTTOM)
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return vertex.y() >= -vertex.w();
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else if constexpr (plane == Clipper::ClipPlane::NEAR)
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return vertex.z() >= -vertex.w();
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else if constexpr (plane == Clipper::ClipPlane::FAR)
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return vertex.z() <= vertex.w();
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return false;
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}
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template<Clipper::ClipPlane plane>
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static constexpr GPU::Vertex clip_intersection_point(GPU::Vertex const& p1, GPU::Vertex const& p2)
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{
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constexpr FloatVector4 clip_plane_normals[] = {
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{ 1, 0, 0, 1 }, // Left Plane
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{ -1, 0, 0, 1 }, // Right Plane
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{ 0, -1, 0, 1 }, // Top Plane
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{ 0, 1, 0, 1 }, // Bottom plane
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{ 0, 0, 1, 1 }, // Near Plane
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{ 0, 0, -1, 1 } // Far Plane
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};
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constexpr auto clip_plane_normal = clip_plane_normals[to_underlying(plane)];
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// See https://www.microsoft.com/en-us/research/wp-content/uploads/1978/01/p245-blinn.pdf
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// "Clipping Using Homogeneous Coordinates" Blinn/Newell, 1978
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// Clip plane normals have W=1 so the vertices' W coordinates are included in x1 and x2.
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auto const x1 = clip_plane_normal.dot(p1.clip_coordinates);
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auto const x2 = clip_plane_normal.dot(p2.clip_coordinates);
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auto const a = x1 / (x1 - x2);
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GPU::Vertex out;
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out.position = mix(p1.position, p2.position, a);
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out.eye_coordinates = mix(p1.eye_coordinates, p2.eye_coordinates, a);
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out.clip_coordinates = mix(p1.clip_coordinates, p2.clip_coordinates, a);
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out.color = mix(p1.color, p2.color, a);
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for (size_t i = 0; i < GPU::NUM_SAMPLERS; ++i)
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out.tex_coords[i] = mix(p1.tex_coords[i], p2.tex_coords[i], a);
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out.normal = mix(p1.normal, p2.normal, a);
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return out;
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}
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template<Clipper::ClipPlane plane>
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FLATTEN static constexpr void clip_plane(Vector<GPU::Vertex>& input_list, Vector<GPU::Vertex>& output_list)
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{
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output_list.clear_with_capacity();
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auto input_list_size = input_list.size();
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if (input_list_size == 0)
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return;
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auto const* prev_vec = &input_list.data()[0];
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auto is_prev_point_within_clip_plane = point_within_clip_plane<plane>(prev_vec->clip_coordinates);
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for (size_t i = 1; i <= input_list_size; i++) {
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auto const& curr_vec = input_list[i % input_list_size];
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auto const is_curr_point_within_clip_plane = point_within_clip_plane<plane>(curr_vec.clip_coordinates);
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if (is_curr_point_within_clip_plane != is_prev_point_within_clip_plane)
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output_list.append(clip_intersection_point<plane>(*prev_vec, curr_vec));
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if (is_curr_point_within_clip_plane)
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output_list.append(curr_vec);
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prev_vec = &curr_vec;
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is_prev_point_within_clip_plane = is_curr_point_within_clip_plane;
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}
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}
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void Clipper::clip_triangle_against_frustum(Vector<GPU::Vertex>& input_verts)
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{
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// FIXME C++23. Static reflection will provide looping over all enum values.
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clip_plane<ClipPlane::LEFT>(input_verts, m_vertex_buffer);
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clip_plane<ClipPlane::RIGHT>(m_vertex_buffer, input_verts);
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clip_plane<ClipPlane::TOP>(input_verts, m_vertex_buffer);
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clip_plane<ClipPlane::BOTTOM>(m_vertex_buffer, input_verts);
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clip_plane<ClipPlane::NEAR>(input_verts, m_vertex_buffer);
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clip_plane<ClipPlane::FAR>(m_vertex_buffer, input_verts);
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}
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}
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