SnowTrailMap.cpp

#include "SnowTrailMap.h"
#include <iostream>

SnowTrailMap::SnowTrailMap(int w, int h) : width_(w), height_(h)
{
    glGenFramebuffers(1, &fbo);
    glGenTextures(1, &texture);

    glBindTexture(GL_TEXTURE_2D, texture);
    glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA8, width_, height_, 0, GL_RGBA, GL_UNSIGNED_BYTE, nullptr);
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE);
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE);

    glBindFramebuffer(GL_FRAMEBUFFER, fbo);
    glFramebufferTexture2D(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT0, GL_TEXTURE_2D, texture, 0);
    GLenum drawBuffers[1] = { GL_COLOR_ATTACHMENT0 };
    glDrawBuffers(1, drawBuffers);

    if (glCheckFramebufferStatus(GL_FRAMEBUFFER) != GL_FRAMEBUFFER_COMPLETE)
        std::cerr << "SnowTrailMap FBO incomplete!" << std::endl;

    glBindFramebuffer(GL_FRAMEBUFFER, 0);

    // Initial full snow (white = 255 = full height)
    clear();
}

SnowTrailMap::~SnowTrailMap()
{
    glDeleteTextures(1, &texture);
    glDeleteFramebuffers(1, &fbo);
}

void SnowTrailMap::bindForWriting()
{
    glBindFramebuffer(GL_FRAMEBUFFER, fbo);
    glViewport(0, 0, width_, height_);
}

void SnowTrailMap::bindForReading(GLenum unit)
{
    glActiveTexture(unit);
    glBindTexture(GL_TEXTURE_2D, texture);
}

void SnowTrailMap::clear()
{
    bindForWriting();
    glClearColor(1.0f, 1.0f, 1.0f, 1.0f);  // FULL SNOW
    glClear(GL_COLOR_BUFFER_BIT);
    glBindFramebuffer(GL_FRAMEBUFFER, 0);
}