axmol/core/3d/Skybox.cpp

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

 https://axmolengine.github.io/

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 of this software and associated documentation files (the "Software"), to deal
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 The above copyright notice and this permission notice shall be included in
 all copies or substantial portions of the Software.

 THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
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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"

NS_AX_BEGIN

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
    auto* program = backend::Program::getBuiltinProgram(backend::ProgramType::SKYBOX_3D);
    setProgramState(new backend::ProgramState(program), false);

    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);
}

NS_AX_END