XCEngine/engine/src/RHI/OpenGL/OpenGLRenderTargetView.cpp

#include "XCEngine/RHI/OpenGL/OpenGLRenderTargetView.h"
#include <glad/glad.h>

namespace XCEngine {
namespace RHI {

static unsigned int ToGLRenderTargetType(RenderTargetType type) {
    switch (type) {
        case RenderTargetType::Texture2D: return GL_TEXTURE_2D;
        case RenderTargetType::Texture2DArray: return GL_TEXTURE_2D_ARRAY;
        case RenderTargetType::Texture3D: return GL_TEXTURE_3D;
        case RenderTargetType::TextureCube: return GL_TEXTURE_CUBE_MAP;
        case RenderTargetType::TextureCubeArray: return GL_TEXTURE_CUBE_MAP_ARRAY;
        default: return GL_TEXTURE_2D;
    }
}

OpenGLRenderTargetView::OpenGLRenderTargetView() 
    : m_texture(0)
    , m_framebuffer(0)
    , m_mipLevel(0)
    , m_width(0)
    , m_height(0)
    , m_type(RenderTargetType::Texture2D) {
}

OpenGLRenderTargetView::~OpenGLRenderTargetView() {
    Shutdown();
}

bool OpenGLRenderTargetView::Initialize(unsigned int texture, const OpenGLRenderTargetViewDesc& desc) {
    m_texture = texture;
    m_mipLevel = desc.mipLevel;
    m_type = desc.type;

    glGenFramebuffers(1, &m_framebuffer);
    glBindFramebuffer(GL_FRAMEBUFFER, m_framebuffer);

    unsigned int target = ToGLRenderTargetType(desc.type);
    GLenum attachment = GL_COLOR_ATTACHMENT0;

    switch (desc.type) {
        case RenderTargetType::Texture2D:
            glFramebufferTexture2D(GL_FRAMEBUFFER, attachment, GL_TEXTURE_2D, texture, desc.mipLevel);
            break;
        case RenderTargetType::Texture2DArray:
            glFramebufferTextureLayer(GL_FRAMEBUFFER, attachment, texture, desc.mipLevel, desc.baseArraySlice);
            break;
        case RenderTargetType::Texture3D:
            glFramebufferTextureLayer(GL_FRAMEBUFFER, attachment, texture, desc.mipLevel, desc.layer);
            break;
        case RenderTargetType::TextureCube:
            glFramebufferTexture2D(GL_FRAMEBUFFER, attachment, GL_TEXTURE_CUBE_MAP_POSITIVE_X + desc.baseArraySlice, texture, desc.mipLevel);
            break;
        case RenderTargetType::TextureCubeArray:
            glFramebufferTextureLayer(GL_FRAMEBUFFER, attachment, texture, desc.mipLevel, desc.baseArraySlice);
            break;
    }

    if (glCheckFramebufferStatus(GL_FRAMEBUFFER) != GL_FRAMEBUFFER_COMPLETE) {
        glBindFramebuffer(GL_FRAMEBUFFER, 0);
        return false;
    }

    glBindFramebuffer(GL_FRAMEBUFFER, 0);
    return true;
}

bool OpenGLRenderTargetView::Initialize(unsigned int texture, int mipLevel) {
    OpenGLRenderTargetViewDesc desc;
    desc.type = RenderTargetType::Texture2D;
    desc.mipLevel = mipLevel;
    return Initialize(texture, desc);
}

bool OpenGLRenderTargetView::InitializeCubemap(unsigned int cubemap, int face, int mipLevel) {
    m_texture = cubemap;
    m_mipLevel = mipLevel;
    m_type = RenderTargetType::TextureCube;

    glGenFramebuffers(1, &m_framebuffer);
    glBindFramebuffer(GL_FRAMEBUFFER, m_framebuffer);
    glFramebufferTexture2D(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT0, GL_TEXTURE_CUBE_MAP_POSITIVE_X + face, cubemap, mipLevel);

    if (glCheckFramebufferStatus(GL_FRAMEBUFFER) != GL_FRAMEBUFFER_COMPLETE) {
        glBindFramebuffer(GL_FRAMEBUFFER, 0);
        return false;
    }

    glBindFramebuffer(GL_FRAMEBUFFER, 0);
    return true;
}

void OpenGLRenderTargetView::Shutdown() {
    if (m_framebuffer) {
        glDeleteFramebuffers(1, &m_framebuffer);
        m_framebuffer = 0;
    }
    if (!m_framebuffers.empty()) {
        glDeleteFramebuffers(static_cast<GLsizei>(m_framebuffers.size()), m_framebuffers.data());
        m_framebuffers.clear();
    }
}

void OpenGLRenderTargetView::Bind(unsigned int slot) {
    glBindFramebuffer(GL_FRAMEBUFFER, m_framebuffer);
    (void)slot;
}

void OpenGLRenderTargetView::Bind(unsigned int count, const unsigned int* framebuffers, const int* drawBuffers) {
    if (count == 1) {
        glBindFramebuffer(GL_FRAMEBUFFER, framebuffers[0]);
    } else {
        glBindFramebuffer(GL_FRAMEBUFFER, 0);
        for (unsigned int i = 0; i < count; i++) {
            glBindFramebuffer(GL_FRAMEBUFFER, framebuffers[i]);
            glDrawBuffers(1, (const GLenum*)&drawBuffers[i]);
        }
    }
    (void)count;
}

void OpenGLRenderTargetView::Unbind() {
    glBindFramebuffer(GL_FRAMEBUFFER, 0);
}

void OpenGLRenderTargetView::Clear(float r, float g, float b, float a) {
    glBindFramebuffer(GL_FRAMEBUFFER, m_framebuffer);
    glClearColor(r, g, b, a);
    glClear(GL_COLOR_BUFFER_BIT);
}

void OpenGLRenderTargetView::Clear(float r, float g, float b, float a, float depth, uint8_t stencil) {
    glBindFramebuffer(GL_FRAMEBUFFER, m_framebuffer);
    glClearColor(r, g, b, a);
    glClearDepth(depth);
    glClearStencil(stencil);
    glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT | GL_STENCIL_BUFFER_BIT);
}

void OpenGLRenderTargetView::BindFramebuffer(unsigned int framebuffer) {
    glBindFramebuffer(GL_FRAMEBUFFER, framebuffer);
}

void OpenGLRenderTargetView::UnbindFramebuffer() {
    glBindFramebuffer(GL_FRAMEBUFFER, 0);
}

} // namespace RHI
} // namespace XCEngine