axmol/core/3d/Skybox.cpp

/****************************************************************************
 Copyright (c) 2015-2016 Chukong Technologies Inc.
 Copyright (c) 2017-2018 Xiamen Yaji Software Co., Ltd.

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#include "3d/Skybox.h"
#include "base/Macros.h"
#include "base/Configuration.h"
#include "base/Director.h"
#include "renderer/Renderer.h"
#include "renderer/RenderState.h"
#include "renderer/TextureCube.h"
#include "renderer/Shaders.h"
#include "2d/Camera.h"

namespace ax
{

Skybox::Skybox() : _texture(nullptr) {}

Skybox::~Skybox()
{
    _texture->release();
}

Skybox* Skybox::create(std::string_view positive_x,
                       std::string_view negative_x,
                       std::string_view positive_y,
                       std::string_view negative_y,
                       std::string_view positive_z,
                       std::string_view negative_z)
{
    auto ret = new Skybox();
    ret->init(positive_x, negative_x, positive_y, negative_y, positive_z, negative_z);

    ret->autorelease();
    return ret;
}

bool Skybox::init()
{
    _customCommand.setTransparent(false);
    _customCommand.set3D(true);

    _customCommand.setBeforeCallback(AX_CALLBACK_0(Skybox::onBeforeDraw, this));
    _customCommand.setAfterCallback(AX_CALLBACK_0(Skybox::onAfterDraw, this));

    // create and set our custom shader
    setProgramStateByProgramId(backend::ProgramType::SKYBOX_3D);

    auto& pipelineDescriptor = _customCommand.getPipelineDescriptor();

    pipelineDescriptor.programState = _programState;
    // disable blend
    pipelineDescriptor.blendDescriptor.blendEnabled = false;

    _uniformColorLoc     = _programState->getUniformLocation("u_color");
    _uniformCameraRotLoc = _programState->getUniformLocation("u_cameraRot");
    _uniformEnvLoc       = _programState->getUniformLocation("u_Env");

    initBuffers();
    return true;
}

bool Skybox::init(std::string_view positive_x,
                  std::string_view negative_x,
                  std::string_view positive_y,
                  std::string_view negative_y,
                  std::string_view positive_z,
                  std::string_view negative_z)
{
    auto texture = TextureCube::create(positive_x, negative_x, positive_y, negative_y, positive_z, negative_z);
    if (texture == nullptr)
        return false;

    init();
    setTexture(texture);
    texture->release();
    return true;
}

void Skybox::initBuffers()
{

    // The skybox is rendered using a purpose-built shader which makes use of
    // the shader language's inherent support for cubemaps. Hence there is no
    // need to build a cube mesh. All that is needed is a single quad that
    // covers the entire screen. The vertex shader will draw the appropriate
    // view of the cubemap onto that quad.
    //
    // The vertex shader does not apply either the model/view matrix or the
    // projection matrix, so the appropriate quad is one with unit coordinates
    // in the x and y dimensions. Such a quad will exactly cover the screen.
    // To ensure that the skybox is rendered behind all other objects, z needs
    // to be 1.0, but the vertex shader overwrites z to 1.0, so - for the sake
    // of z-buffering - it is unimportant what we set it to for the vertices
    // of the quad.
    //
    // The quad vertex positions are also used in deriving a direction
    // vector for the cubemap lookup. We choose z = -1 which matches the
    // negative-z pointing direction of the camera and gives a field of
    // view of 90deg in both x and y, if not otherwise adjusted. That fov
    // is then adjusted to exactly match the camera by applying a prescaling
    // to the camera's world transformation before sending it to the shader.

    // init vertex buffer object
    Vec3 vexBuf[] = {Vec3(1, -1, -1), Vec3(1, 1, -1), Vec3(-1, 1, -1), Vec3(-1, -1, -1)};

    uint16_t idxBuf[] = {0, 1, 2, 0, 2, 3};

    _customCommand.createVertexBuffer(sizeof(Vec3), sizeof(vexBuf), CustomCommand::BufferUsage::STATIC);
    _customCommand.createIndexBuffer(CustomCommand::IndexFormat::U_SHORT, 6, CustomCommand::BufferUsage::STATIC);

    _customCommand.updateVertexBuffer(&vexBuf[0], sizeof(vexBuf));
    _customCommand.updateIndexBuffer(&idxBuf[0], sizeof(idxBuf));
}

void Skybox::draw(Renderer* renderer, const Mat4& transform, uint32_t flags)
{
    _customCommand.init(_globalZOrder);

    renderer->addCommand(&_customCommand);

    auto camera = Camera::getVisitingCamera();

    Mat4 cameraModelMat = camera->getNodeToWorldTransform();
    Mat4 projectionMat  = camera->getProjectionMatrix();
    // Ignore the translation
    cameraModelMat.m[12] = cameraModelMat.m[13] = cameraModelMat.m[14] = 0;
    // prescale the matrix to account for the camera fov
    cameraModelMat.scale(1 / projectionMat.m[0], 1 / projectionMat.m[5], 1.0);

    Vec4 color(_displayedColor.r / 255.f, _displayedColor.g / 255.f, _displayedColor.b / 255.f, 1.f);
    _programState->setUniform(_uniformColorLoc, &color, sizeof(color));
    _programState->setUniform(_uniformCameraRotLoc, cameraModelMat.m, sizeof(cameraModelMat.m));

    AX_INCREMENT_GL_DRAWN_BATCHES_AND_VERTICES(1, 4);
}

void Skybox::setTexture(TextureCube* texture)
{
    AXASSERT(texture != nullptr, __FUNCTION__);
    AX_SAFE_RELEASE_NULL(_texture);
    texture->retain();
    _texture = texture;
    _programState->setTexture(_uniformEnvLoc, 0, _texture->getBackendTexture());
}

void Skybox::reload()
{
    initBuffers();
}

void Skybox::onBeforeDraw()
{
    auto* renderer = _director->getRenderer();

    _rendererDepthTestEnabled = renderer->getDepthTest();
    _rendererDepthCmpFunc     = renderer->getDepthCompareFunction();
    _rendererCullMode         = renderer->getCullMode();

    renderer->setDepthTest(true);
    renderer->setDepthCompareFunction(backend::CompareFunction::LESS_EQUAL);
    renderer->setCullMode(CullMode::BACK);
}

void Skybox::onAfterDraw()
{
    auto* renderer = _director->getRenderer();
    renderer->setDepthTest(_rendererDepthTestEnabled);
    renderer->setDepthCompareFunction(_rendererDepthCmpFunc);
    renderer->setCullMode(_rendererCullMode);
}

}