ShadowMap.cpp

#include "ShadowMap.h"
#include <stdexcept>

ShadowMap::ShadowMap(int w, int h) : width_(w), height_(h)
{
    glGenFramebuffers(1, &FBO);
    glGenTextures(1, &depthMap);

    glBindTexture(GL_TEXTURE_2D, depthMap);
    glTexImage2D(GL_TEXTURE_2D, 0, GL_DEPTH_COMPONENT, width_, height_, 0,
        GL_DEPTH_COMPONENT, GL_FLOAT, nullptr);
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST);
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST);
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_BORDER);
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_BORDER);
    float borderColor[] = { 1.0f, 1.0f, 1.0f, 1.0f };
    glTexParameterfv(GL_TEXTURE_2D, GL_TEXTURE_BORDER_COLOR, borderColor);

    glBindFramebuffer(GL_FRAMEBUFFER, FBO);
    glFramebufferTexture2D(GL_FRAMEBUFFER, GL_DEPTH_ATTACHMENT, GL_TEXTURE_2D, depthMap, 0);
    glDrawBuffer(GL_NONE);
    glReadBuffer(GL_NONE);

    if (glCheckFramebufferStatus(GL_FRAMEBUFFER) != GL_FRAMEBUFFER_COMPLETE)
        throw std::runtime_error("ShadowMap FBO incomplete!");

    glBindFramebuffer(GL_FRAMEBUFFER, 0);
}

ShadowMap::~ShadowMap()
{
    glDeleteTextures(1, &depthMap);
    glDeleteFramebuffers(1, &FBO);
}

void ShadowMap::bindForWriting()
{
    glViewport(0, 0, width_, height_);
    glBindFramebuffer(GL_FRAMEBUFFER, FBO);
    glClear(GL_DEPTH_BUFFER_BIT);
}

void ShadowMap::bindForReading(GLenum textureUnit)
{
    glActiveTexture(textureUnit);
    glBindTexture(GL_TEXTURE_2D, depthMap);
}