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87 lines
3.0 KiB
C++
87 lines
3.0 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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*
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* SPDX-License-Identifier: BSD-2-Clause
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*/
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#include <AK/Format.h>
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#include <AK/ScopeGuard.h>
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#include <LibSoftGPU/Clipper.h>
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namespace SoftGPU {
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bool Clipper::point_within_clip_plane(const FloatVector4& vertex, ClipPlane plane)
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{
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switch (plane) {
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case ClipPlane::LEFT:
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return vertex.x() >= -vertex.w();
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case ClipPlane::RIGHT:
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return vertex.x() <= vertex.w();
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case ClipPlane::TOP:
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return vertex.y() <= vertex.w();
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case ClipPlane::BOTTOM:
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return vertex.y() >= -vertex.w();
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case ClipPlane::NEAR:
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return vertex.z() >= -vertex.w();
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case ClipPlane::FAR:
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return vertex.z() <= vertex.w();
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}
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return false;
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}
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Vertex Clipper::clip_intersection_point(const Vertex& p1, const Vertex& p2, ClipPlane plane_index)
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{
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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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float w1 = p1.clip_coordinates.w();
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float w2 = p2.clip_coordinates.w();
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float x1 = clip_plane_normals[plane_index].dot(p1.clip_coordinates);
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float x2 = clip_plane_normals[plane_index].dot(p2.clip_coordinates);
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float a = (w1 + x1) / ((w1 + x1) - (w2 + x2));
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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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out.tex_coord = mix(p1.tex_coord, p2.tex_coord, 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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void Clipper::clip_triangle_against_frustum(Vector<Vertex>& input_verts)
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{
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list_a = input_verts;
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list_b.clear_with_capacity();
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auto read_from = &list_a;
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auto write_to = &list_b;
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for (size_t plane = 0; plane < NUMBER_OF_CLIPPING_PLANES; plane++) {
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write_to->clear_with_capacity();
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// Save me, C++23
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for (size_t i = 0; i < read_from->size(); i++) {
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const auto& curr_vec = read_from->at((i + 1) % read_from->size());
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const auto& prev_vec = read_from->at(i);
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if (point_within_clip_plane(curr_vec.clip_coordinates, static_cast<ClipPlane>(plane))) {
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if (!point_within_clip_plane(prev_vec.clip_coordinates, static_cast<ClipPlane>(plane))) {
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auto intersect = clip_intersection_point(prev_vec, curr_vec, static_cast<ClipPlane>(plane));
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write_to->append(intersect);
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}
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write_to->append(curr_vec);
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} else if (point_within_clip_plane(prev_vec.clip_coordinates, static_cast<ClipPlane>(plane))) {
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auto intersect = clip_intersection_point(prev_vec, curr_vec, static_cast<ClipPlane>(plane));
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write_to->append(intersect);
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}
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}
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swap(write_to, read_from);
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}
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input_verts = *read_from;
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}
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}
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