Add some code to average log luminance.

data/shaders/logluminance.frag

@@ -0,0 +1,14 @@
+uniform sampler2D tex;
+
+in vec2 uv;
+out vec4 FragColor;
+
+float delta = 0.0001;
+
+void main()
+{
+    vec3 weight = vec3(0.2125f, 0.7154f, 0.0721f);
+    vec3 col = texture(tex, uv).xyz;
+    float luma = dot(col, weight);
+    FragColor = vec4(log(luma + delta));
+}

src/graphics/post_processing.cpp

@@ -618,6 +618,28 @@ static void renderGodRay(GLuint tex, const core::vector2df &sunpos)
     glEnable(GL_DEPTH_TEST);
 }
 
+static void averageTexture(GLuint tex)
+{
+    glActiveTexture(GL_TEXTURE0);
+    glBindTexture(GL_TEXTURE_2D, tex);
+    glGenerateMipmap(GL_TEXTURE_2D);
+}
+
+static void computeLogLuminance(GLuint tex)
+{
+    glDisable(GL_DEPTH_TEST);
+    glDisable(GL_BLEND);
+    IVideoDriver *const drv = irr_driver->getVideoDriver();
+    drv->setRenderTarget(irr_driver->getRTT(RTT_LOG_LUMINANCE), false, false);
+    glUseProgram(FullScreenShader::LogLuminanceShader::Program);
+    glBindVertexArray(FullScreenShader::LogLuminanceShader::vao);
+    setTexture(0, tex, GL_LINEAR, GL_LINEAR);
+    FullScreenShader::LogLuminanceShader::setUniforms(0);
+
+    glDrawArrays(GL_TRIANGLE_STRIP, 0, 4);
+    averageTexture(getTextureGLuint(irr_driver->getRTT(RTT_LOG_LUMINANCE)));
+}
+
 // ----------------------------------------------------------------------------
 /** Render the post-processed scene */
 void PostProcessing::render()

src/graphics/rtts.cpp

@@ -59,6 +59,7 @@ RTT::RTT()
     rtts[RTT_TMP4] = drv->addRenderTargetTexture(res, "rtt.tmp4", ECF_R16F, stencil);
     rtts[RTT_NORMAL_AND_DEPTH] = drv->addRenderTargetTexture(res, "rtt.normal_and_depth", ECF_G16R16F, stencil);
     rtts[RTT_COLOR] = drv->addRenderTargetTexture(res, "rtt.color", ECF_A16B16G16R16F, stencil);
+    rtts[RTT_LOG_LUMINANCE] = drv->addRenderTargetTexture(shadowsize0, "rtt.logluminance", ECF_R16F, stencil);
 
     rtts[RTT_HALF1] = drv->addRenderTargetTexture(half, "rtt.half1", ECF_A16B16G16R16F, stencil);
     rtts[RTT_HALF2] = drv->addRenderTargetTexture(half, "rtt.half2", ECF_A16B16G16R16F, stencil);

src/graphics/rtts.hpp

@@ -33,6 +33,7 @@ enum TypeRTT
     RTT_TMP4,
     RTT_NORMAL_AND_DEPTH,
     RTT_COLOR,
+    RTT_LOG_LUMINANCE,
 
     RTT_HALF1,
     RTT_HALF2,

src/graphics/shaders.cpp

@@ -314,6 +314,7 @@ void Shaders::loadShaders()
     FullScreenShader::MotionBlurShader::init();
     FullScreenShader::GodFadeShader::init();
     FullScreenShader::GodRayShader::init();
+    FullScreenShader::LogLuminanceShader::init();
 	MeshShader::ColorizeShader::init();
 	MeshShader::NormalMapShader::init();
 	MeshShader::ObjectPass1Shader::init();
@@ -2319,6 +2320,24 @@ namespace FullScreenShader
         glUniform2f(uniform_sunpos, sunpos.X, sunpos.Y);
         glUniform1i(uniform_tex, TU_tex);
     }
+
+    GLuint LogLuminanceShader::Program;
+    GLuint LogLuminanceShader::uniform_tex;
+    GLuint LogLuminanceShader::vao;
+
+    void LogLuminanceShader::init()
+    {
+        Program = LoadProgram(
+            GL_VERTEX_SHADER, file_manager->getAsset("shaders/screenquad.vert").c_str(),
+            GL_FRAGMENT_SHADER, file_manager->getAsset("shaders/logluminance.frag").c_str());
+        uniform_tex = glGetUniformLocation(Program, "tex");
+        vao = createVAO(Program);
+    }
+
+    void LogLuminanceShader::setUniforms(unsigned TU_tex)
+    {
+        glUniform1i(uniform_tex, TU_tex);
+    }
 }
 
 namespace UIShader

src/graphics/shaders.hpp

@@ -665,6 +665,17 @@ public:
     static void setUniforms(const core::vector2df &sunpos, unsigned TU_tex);
 };
 
+class LogLuminanceShader
+{
+public:
+    static GLuint Program;
+    static GLuint uniform_tex;
+    static GLuint vao;
+
+    static void init();
+    static void setUniforms(unsigned TU_tex);
+};
+
 }
 
 namespace UIShader