cocos-engine/native/cocos/scene/Frustum.cpp

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#include "scene/Frustum.h"
#include "scene/Define.h"

namespace cc {
namespace scene {
namespace {
const std::vector<cc::Vec3> VEC_VALS{
    {1, 1, 1},
    {-1, 1, 1},
    {-1, -1, 1},
    {1, -1, 1},
    {1, 1, -1},
    {-1, 1, -1},
    {-1, -1, -1},
    {1, -1, -1}};
} // namespace

// Define from 3 vertices.
void Plane::define(const Vec3 &v0, const Vec3 &v1, const Vec3 &v2) {
    const Vec3 dist1 = v1 - v0;
    const Vec3 dist2 = v2 - v0;

    Vec3 dist;
    Vec3::crossProduct(dist1, dist2, &dist);
    define(dist, v0);
}

// Define from a normal vector and a point on the plane.
void Plane::define(const Vec3 &normal, const Vec3 &point) {
    n = normal.getNormalized();
    d = n.dot(point);
}

// Return signed distance to a point.
float Plane::distance(const Vec3 &point) const {
    return n.dot(point) - d;
}

Plane Plane::clone() const {
    Plane plane;
    plane.n.set(n);
    plane.d = d;

    return plane;
}

void Frustum::createOrtho(const float width, const float height, const float near, const float far, const Mat4 &transform) {
    const float halfWidth  = width * 0.5F;
    const float halfHeight = height * 0.5F;

    vertices[0].transformMat4(Vec3(halfWidth, halfHeight, -near), transform);
    vertices[1].transformMat4(Vec3(-halfWidth, halfHeight, -near), transform);
    vertices[2].transformMat4(Vec3(-halfWidth, -halfHeight, -near), transform);
    vertices[3].transformMat4(Vec3(halfWidth, -halfHeight, -near), transform);
    vertices[4].transformMat4(Vec3(halfWidth, halfHeight, -far), transform);
    vertices[5].transformMat4(Vec3(-halfWidth, halfHeight, -far), transform);
    vertices[6].transformMat4(Vec3(-halfWidth, -halfHeight, -far), transform);
    vertices[7].transformMat4(Vec3(halfWidth, -halfHeight, -far), transform);

    updatePlanes();
}

void Frustum::split(float start, float end, float aspect, float fov, const Mat4 &transform) {
    const float h = tanf(fov * 0.5F);
    const float w = h * aspect;
    const Vec3  nearTemp(start * w, start * h, start);
    const Vec3  farTemp(end * w, end * h, end);

    vertices[0].transformMat4(Vec3(nearTemp.x, nearTemp.y, nearTemp.z), transform);
    vertices[1].transformMat4(Vec3(-nearTemp.x, nearTemp.y, nearTemp.z), transform);
    vertices[2].transformMat4(Vec3(-nearTemp.x, -nearTemp.y, nearTemp.z), transform);
    vertices[3].transformMat4(Vec3(nearTemp.x, -nearTemp.y, nearTemp.z), transform);
    vertices[4].transformMat4(Vec3(farTemp.x, farTemp.y, farTemp.z), transform);
    vertices[5].transformMat4(Vec3(-farTemp.x, farTemp.y, farTemp.z), transform);
    vertices[6].transformMat4(Vec3(-farTemp.x, -farTemp.y, farTemp.z), transform);
    vertices[7].transformMat4(Vec3(farTemp.x, -farTemp.y, farTemp.z), transform);

    updatePlanes();
}

void Frustum::updatePlanes() {
    // left plane
    planes[0].define(vertices[1], vertices[6], vertices[5]);
    // right plane
    planes[1].define(vertices[3], vertices[4], vertices[7]);
    // bottom plane
    planes[2].define(vertices[6], vertices[3], vertices[7]);
    // top plane
    planes[3].define(vertices[0], vertices[5], vertices[4]);
    // near plane
    planes[4].define(vertices[2], vertices[0], vertices[3]);
    // far plane
    planes[5].define(vertices[7], vertices[5], vertices[6]);
}

void Frustum::update(const Mat4 &m, const Mat4 &inv) {
    // left plane
    planes[0].n.set(m.m[3] + m.m[0], m.m[7] + m.m[4], m.m[11] + m.m[8]);
    planes[0].d = -(m.m[15] + m.m[12]);
    // right plane
    planes[1].n.set(m.m[3] - m.m[0], m.m[7] - m.m[4], m.m[11] - m.m[8]);
    planes[1].d = -(m.m[15] - m.m[12]);
    // bottom plane
    planes[2].n.set(m.m[3] + m.m[1], m.m[7] + m.m[5], m.m[11] + m.m[9]);
    planes[2].d = -(m.m[15] + m.m[13]);
    // top plane
    planes[3].n.set(m.m[3] - m.m[1], m.m[7] - m.m[5], m.m[11] - m.m[9]);
    planes[3].d = -(m.m[15] - m.m[13]);
    // near plane
    planes[4].n.set(m.m[3] + m.m[2], m.m[7] + m.m[6], m.m[11] + m.m[10]);
    planes[4].d = -(m.m[15] + m.m[14]);
    // far plane
    planes[5].n.set(m.m[3] - m.m[2], m.m[7] - m.m[6], m.m[11] - m.m[10]);
    planes[5].d = -(m.m[15] - m.m[14]);

    if (type != ShapeEnums::SHAPE_FRUSTUM_ACCURATE) {
        return;
    }

    for (Plane &plane : planes) {
        float invDist = 1 / plane.n.length();
        plane.n *= invDist;
        plane.d *= invDist;
    }
    uint32_t i = 0;
    for (const Vec3 &vec : VEC_VALS) {
        vertices[i].transformMat4(vec, inv);
        i++;
    }
}

Frustum Frustum::clone() {
    Frustum frustum;
    for (uint i = 0; i < planes.size(); ++i) {
        frustum.planes[i] = planes[i].clone();
    }

    frustum.type = type;

    for (uint i = 0; i < vertices.size(); ++i) {
        frustum.vertices[i].set(vertices[i]);
    }

    return frustum;
}

void Frustum::transform(const Mat4 &transform) {
    vertices[0].transformMat4(vertices[0], transform);
    vertices[1].transformMat4(vertices[1], transform);
    vertices[2].transformMat4(vertices[2], transform);
    vertices[3].transformMat4(vertices[3], transform);
    vertices[4].transformMat4(vertices[4], transform);
    vertices[5].transformMat4(vertices[5], transform);
    vertices[6].transformMat4(vertices[6], transform);
    vertices[7].transformMat4(vertices[7], transform);
}

} // namespace scene
} // namespace cc