[solved] OpenGL with SFML (Assumed context issue)

[Gambit]

I'm getting a bit of a problem now with the simplest thing.

If I change the body of my LightEngine::draw function to just

   void draw(sf::RenderTarget& rt, sf::RenderStates states) const
   {
      glBindVertexArray(m_u32VAO);
      glBindVertexArray(0);
   }
 

I get this in the console each frame:

An internal OpenGL call failed in Shader.cpp(815).
Expression:
   GLEXT_glUseProgramObject(0)
Error description:
   GL_INVALID_OPERATION
   The specified operation is not allowed in the current state.

Could be worth noting that glGetError is still returning 0, even with this error printing to the console and the sprite is rendering correctly.

[Laurent]

Let's summon binary1248, because this one is out of my knowledge

[Gambit]

For reference, this is my main now.

#include <vector>

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

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;

public:
   LightEngine()
   {
      glGenVertexArrays(1, &m_u32VAO);
      glBindVertexArray(m_u32VAO);

      // Data for VBO
      const GLfloat verts[]
      {
         -1.0f,  1.0f, 0.0f, 1.0f, // 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)));
      glBindBuffer(GL_ARRAY_BUFFER, 0);

      // 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);
      glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, 0);

      glBindVertexArray(0);

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

   void render(sf::RenderTarget& rt)
   {
      glBindVertexArray(m_u32VAO);

      for (const auto& rkoLight : m_aoLights)
      {
         //glDrawElements(GL_TRIANGLES, 6, GL_UNSIGNED_INT, nullptr);
      }

      glBindVertexArray(0);
   }

   ~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::Shader oShader;
   oShader.loadFromFile("shaders/Vertex.vert", "shaders/Fragment.frag");

   sf::RenderTexture oRT, oRTNormals;
   oRT.create(oApp.getSize().x, oApp.getSize().y);
   oRTNormals.create(oApp.getSize().x, oApp.getSize().y);
   {
      {
         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;

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

      oApp.clear();

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

      sf::Shader::bind(&oShader);

      glActiveTexture(GL_TEXTURE2);
      sf::Texture::bind(&oRT.getTexture());
      glUniform1i(0, 2);

      glActiveTexture(GL_TEXTURE3);
      sf::Texture::bind(&oRTNormals.getTexture());
      glUniform1i(1, 3);

      oEngine.render(oApp);

      // 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);
      sf::Shader::bind(nullptr);

      oApp.resetGLStates();
      oApp.display();
   }
}
 

[Gambit]

I changed

sf::Shader::bind(nullptr);
 

To:

glUseProgram(0);
 

The above error is replaced with this one:

An internal OpenGL call failed in RenderTarget.cpp(369).
Expression:
   GLEXT_glClientActiveTexture(GLEXT_GL_TEXTURE0)
Error description:
   GL_INVALID_OPERATION
   The specified operation is not allowed in the current state.

[Gambit]

Ok I finally got it working.

Result: http://i.imgur.com/wnRIzua.gifv

Code:

(click to show/hide)

#include <vector>

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

sf::Vector2i mousepos;

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);
   }
};

Light* mouseLight;

class LightEngine
{
private:
   GLuint m_u32VAO, m_u32VBO, m_u32EBO;
   std::vector<Light> m_aoLights;

public:
   LightEngine()
   {
      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);

      // 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);
      mouseLight = &*m_aoLights.rbegin();

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

      Light oLight3;
      oLight3.setPosition({300, 250});
      oLight3.color = sf::Color::Red;
      m_aoLights.push_back(oLight3);
      */
   }

   void render(sf::RenderTarget& rt)
   {
      mouseLight->setPosition(static_cast<sf::Vector2f>(mousepos));

      glBindVertexArray(m_u32VAO);

      for (const auto& rkoLight : m_aoLights)
      {
         rkoLight.draw();
         glDrawElements(GL_TRIANGLES, 6, GL_UNSIGNED_INT, nullptr);
      }

      glBindVertexArray(0);
   }

   ~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::Shader oShader;
   oShader.loadFromFile("shaders/Vertex.vert", "shaders/Fragment.frag");

   sf::RenderTexture oRT, oRTNormals;
   oRT.create(oApp.getSize().x, oApp.getSize().y);
   oRTNormals.create(oApp.getSize().x, oApp.getSize().y);
   {
      {
         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()};

   oApp.setActive(true);
   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;
         }
         }
      }

      mousepos = sf::Mouse::getPosition(oApp);
      const auto kfSeconds = oClock.getElapsedTime().asSeconds();
      mouseLight->color = {static_cast<sf::Uint8>(255 * std::abs(std::sin(kfSeconds))), static_cast<sf::Uint8>(255 * std::abs(std::cos(kfSeconds))), 255, 255};

      oApp.clear();

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

      glUseProgram(oShader.getNativeHandle());

      glActiveTexture(GL_TEXTURE2);
      glBindTexture(GL_TEXTURE_2D, oRT.getTexture().getNativeHandle());
      glUniform1i(0, 2);

      glActiveTexture(GL_TEXTURE3);
      glBindTexture(GL_TEXTURE_2D, oRTNormals.getTexture().getNativeHandle());
      glUniform1i(1, 3);

      oEngine.render(oApp);

      // 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);

      oApp.display();
   }
}
 

It turns out that NOT setting the active texture to 0 before displaying the RenderWindow makes SFML die.

A few caveats to the result, the final result is actually displayed upside-down and multiple lights dont work and I'm not entirely sure how to fix that(Inverting the y uv coordinate fixed this). I tried adding a RenderTexture member to LightEngine, creating and activating it in the constructor, generating, binding and buffering all my data then making the RenderTexture inactive then each draw call active it again, bind the VAO and do the drawing where all lights are drawn with additive blending then at the end create a sprite from the RenderTexture and render it to the RenderTarget passed to the draw call with multiplicative blending  but it didnt work and I'm pretty sure I'm doing something wrong.