[solved] OpenGL calls in RenderTarget not working

[Gambit]

Hey all.. again.

This is somewhat related to my last post (http://en.sfml-dev.org/forums/index.php?topic=20979.0) where I am trying to render lighting in OpenGL and have it work with SFML.

My LightEngine class has it's own RenderTexture which I'm using to contain all the state required for rendering the lights. Each frame the RenderTexture is activated, VAO is bound and for each light, uniforms are set and elements are drawn. At the end of that, the state is cleaned up and the render window (passed to the LightEngine render function) is set to draw a sprite containing the RenderTexture's Texture. Unfortunately this doesnt work. Instead, I'm presented with a black screen (since the sprite is rendered with multiply blending). If I dont use the RenderTexture it works fine.

Code:

(click to show/hide)

main.cpp

#include <vector>

#include <SFML/Graphics.hpp>
#include <GL/glew.h>

sf::RenderTexture* poRT = nullptr;
sf::RenderTexture* poRTNorm = nullptr;

class Light : public sf::Transformable
{
public:
   sf::Color color;
   sf::Vector3f falloff;

   void draw() const
   {
      glUniform2f(2, getPosition().x, getPosition().y);
      glUniform4f(3, color.r / 255.0f, color.g / 255.0f, color.b / 255.0f, color.a / 255.0f);
      glUniform3f(4, falloff.x, falloff.y, falloff.z);
   }
};

class LightEngine
{
private:
   GLuint m_u32VAO, m_u32VBO, m_u32EBO;
   std::vector<Light> m_aoLights;
   sf::RenderTexture m_oTex;
   sf::Sprite m_oSprite;
   sf::Shader m_oShader;

public:
   LightEngine()
   {
      m_oTex.create(1024, 768);
      m_oTex.setActive(true);
      m_oSprite.setTexture(m_oTex.getTexture());

      m_oShader.loadFromFile("shaders/Vertex.vert", "shaders/Fragment.frag");

      glGenVertexArrays(1, &m_u32VAO);
      glBindVertexArray(m_u32VAO);

      // Data for VBO
      const GLfloat verts[]
      {
         -1.0f,  1.0f, 0.0f, 0.0f, // Top left
          1.0f,  1.0f, 1.0f, 0.0f, // Top right
          1.0f, -1.0f, 1.0f, 1.0f, // Bottom right
         -1.0f, -1.0f, 0.0f, 1.0f, // Bottom left
      };

      glGenBuffers(1, &m_u32VBO);
      glBindBuffer(GL_ARRAY_BUFFER, m_u32VBO);
      glBufferData(GL_ARRAY_BUFFER, sizeof(verts), verts, GL_STATIC_DRAW);
      glEnableVertexAttribArray(0);
      glVertexAttribPointer(0, 2, GL_FLOAT, GL_FALSE, 4 * sizeof(GLfloat), nullptr);
      glEnableVertexAttribArray(1);
      glVertexAttribPointer(1, 2, GL_FLOAT, GL_FALSE, 4 * sizeof(GLfloat), reinterpret_cast<void*>(2 * sizeof(GLfloat)));

      // Data for EBO
      const GLuint elements[]
      {
         0, 1, 2,
         2, 3, 0
      };

      glGenBuffers(1, &m_u32EBO);
      glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, m_u32EBO);
      glBufferData(GL_ELEMENT_ARRAY_BUFFER, sizeof(elements), elements, GL_STATIC_DRAW);

      glBindVertexArray(0);
      glBindBuffer(GL_ARRAY_BUFFER, 0);
      glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, 0);
      m_oTex.setActive(false);

      // Create a test light
      Light oLight;
      oLight.setPosition({512, 384});
      oLight.color = sf::Color::White;
      oLight.falloff = {0.4f, 3.0f, 20.0f};
      m_aoLights.push_back(oLight);

      // Multiple lights dont work
      Light oLight2;
      oLight2.setPosition({100, 100});
      oLight2.color = sf::Color::Green;
      oLight2.falloff = {0.4f, 3.0f, 20.0f};
      m_aoLights.push_back(oLight2);

      Light oLight3;
      oLight3.setPosition({300, 250});
      oLight3.color = sf::Color::Red;
      oLight3.falloff = {0.4f, 3.0f, 20.0f};
      m_aoLights.push_back(oLight3);
   }

   void render(sf::RenderWindow& rw)
   {
      m_oTex.setActive(true);
      m_oTex.clear();
      glUseProgram(m_oShader.getNativeHandle());

      glActiveTexture(GL_TEXTURE2);
      glBindTexture(GL_TEXTURE_2D, poRT->getTexture().getNativeHandle());
      glUniform1i(0, 2);

      glActiveTexture(GL_TEXTURE3);
      glBindTexture(GL_TEXTURE_2D, poRTNorm->getTexture().getNativeHandle());
      glUniform1i(1, 3);

      glBindVertexArray(m_u32VAO);

      glEnable(GL_BLEND);
      glBlendFunc(GL_SRC_COLOR, GL_ONE);
      for (const auto& rkoLight : m_aoLights)
      {
         rkoLight.draw();
         glDrawElements(GL_TRIANGLES, 6, GL_UNSIGNED_INT, nullptr);
      }
      glDisable(GL_BLEND);

      m_oTex.display();

      glBindVertexArray(0);

      // Cleanup. Reset Texture2 and 3 and unbind any shaders.
      glActiveTexture(GL_TEXTURE2);
      glBindTexture(GL_TEXTURE_2D, 0);
      glActiveTexture(GL_TEXTURE3);
      glBindTexture(GL_TEXTURE_2D, 0);
      glUseProgram(0);
      glActiveTexture(GL_TEXTURE0);

      rw.setActive(true);
      rw.pushGLStates();
      rw.resetGLStates();
      rw.draw(m_oSprite);
      rw.popGLStates();
   }

   ~LightEngine()
   {
      glDeleteBuffers(1, &m_u32EBO);
      glDeleteBuffers(1, &m_u32VBO);
      glDeleteVertexArrays(1, &m_u32VAO);
   }
};

int main()
{
   sf::ContextSettings oContextSettings;
   oContextSettings.antialiasingLevel = 4;
   oContextSettings.depthBits = 24;
   oContextSettings.majorVersion = 3;
   oContextSettings.minorVersion = 3;
   sf::RenderWindow oApp{{1024, 768}, "OpenGL Lighting Test", sf::Style::Default, oContextSettings};

   glewExperimental = 1;
   glewInit();

   sf::RenderTexture oRT, oRTNormals;
   oRT.create(oApp.getSize().x, oApp.getSize().y);
   oRTNormals.create(oApp.getSize().x, oApp.getSize().y);
   poRT = &oRT;
   poRTNorm = &oRTNormals;
   {
      {
         sf::Texture oTex;
         oTex.loadFromFile("bg1.png");
         sf::Sprite oSpr;
         oSpr.setTexture(oTex);
         oSpr.setPosition({5.0f, 5.0f});
         oRT.draw(oSpr);
         oTex.loadFromFile("bg1_n.png");
         oRTNormals.draw(oSpr);
      }
      {
         sf::Texture oTex;
         oTex.loadFromFile("bg2.png");
         sf::Sprite oSpr;
         oSpr.setTexture(oTex);
         oSpr.setPosition({650.0f, 50.0f});
         oRT.draw(oSpr);
         oTex.loadFromFile("bg2_n.png");
         oRTNormals.draw(oSpr);
      }
      {
         sf::Texture oTex;
         oTex.loadFromFile("bg3.png");
         sf::Sprite oSpr;
         oSpr.setTexture(oTex);
         oSpr.setPosition({300.0f, 250.0f});
         oRT.draw(oSpr);
         oTex.loadFromFile("bg3_n.png");
         oRTNormals.draw(oSpr);
      }
   }
   oRT.display();
   oRTNormals.display();

   sf::Sprite oSprite{oRT.getTexture()};

   LightEngine oEngine;

   sf::Clock oClock;
   bool bRunning = true;
   while (bRunning)
   {
      sf::Event oEvent;
      while (oApp.pollEvent(oEvent))
      {
         switch (oEvent.type)
         {
         case sf::Event::Closed:
         {
            bRunning = false;
            break;
         }
         }
      }

      oApp.setActive(true);
      oApp.clear();

      oApp.pushGLStates();
      oApp.resetGLStates();
      oApp.draw(oSprite);
      oApp.popGLStates();

      oEngine.render(oApp);

      oApp.display();
   }
}
 

shaders/Vertex.vert

#version 450 core

layout(location = 0) in vec2 position;
layout(location = 1) in vec2 uv;

layout(location = 0) out vec2 out_uv;

void main()
{
    out_uv = uv;
    gl_Position = vec4(position, 0.0, 1.0);
};
 

shaders/Fragment.frag

#version 450 core

layout(location = 0) uniform sampler2D u_tex;      // Diffuse map
layout(location = 1) uniform sampler2D u_texNorm;  // Normal map
layout(location = 2) uniform vec2      u_lightPos;
layout(location = 3) uniform vec4      u_lightCol;
layout(location = 4) uniform vec3      u_lightFalloff;

layout(location = 0) in vec2 uv; // UV coords for this fragment

layout(location = 0) out vec4 out_color;

void main()
{
   out_color = vec4(0.0, 0.5, 1.0, 1.0);
}
 

Desired effect: http://i.imgur.com/APbsUNE.png
Images can be downloaded here: https://www.dropbox.com/s/lvd8ztlecwvh4w2/lighting.zip?dl=1

Edit:
Well I fixed it by setting:

glViewport(0, 0, 1024, 768)

In the constructor of LightEngine just after making m_oTex active.
Result: http://i.imgur.com/f3lY8KV.gifv