add ability to render textures to Screen quad for dbg

include/openspace/rendering/renderengine.h

@@ -151,6 +151,8 @@ public:
      */
     static scripting::LuaLibrary luaLibrary();
 
+    void setDebugTextureRendering(GLuint texture);
+
     glm::ivec2 renderingResolution() const;
     glm::ivec2 fontResolution() const;
 
@@ -176,6 +178,8 @@ private:
     ghoul::Dictionary _resolveData;
     ScreenLog* _log = nullptr;
 
+    GLuint _debugTextureRender = 0;
+
     ghoul::opengl::OpenGLStateCache* _openglStateCache = nullptr;
 
     properties::BoolProperty _showOverlayOnClients;

modules/base/shaders/dbg_tex_fs.glsl

@@ -0,0 +1,12 @@
+#include "fragment.glsl"
+
+uniform sampler2D tex;
+
+in vec2 uv;
+
+Fragment getFragment() {
+  Fragment frag;
+  frag.disableLDR2HDR = true;
+  frag.color = texture(tex, uv).rrrr;
+  return frag;
+}

modules/base/shaders/dbg_tex_vs.glsl

@@ -0,0 +1,11 @@
+#version __CONTEXT__
+
+layout(location=0) in vec2 vertex_position;
+
+out vec2 uv;
+
+void main()
+{
+    uv = 2 * (vertex_position - 0.5);
+    gl_Position = vec4(vertex_position, 0.0, 1.0);
+}

src/rendering/renderengine.cpp

@@ -710,6 +710,56 @@ void RenderEngine::render(const glm::mat4& sceneMatrix, const glm::mat4& viewMat
         }
         glDisable(GL_BLEND);
     }
+
+    if (_debugTextureRender > 0) {
+        static constexpr GLfloat vertices[] = {
+            0.5f, 0.5f,
+            1.f, 0.5f,
+            0.5f,  1.f,
+            0.5f,  1.f,
+            1.f, 0.5f,
+            1.f,  1.f,
+        };
+
+        static GLuint vao = 0, vbo;
+        static std::unique_ptr<ghoul::opengl::ProgramObject> prog;
+        if (vao == 0) {
+            glGenVertexArrays(1, &vao);
+            glBindVertexArray(vao);
+
+            glGenBuffers(1, &vbo);
+            glBindBuffer(GL_ARRAY_BUFFER, vbo);
+            glBufferData(GL_ARRAY_BUFFER, sizeof(vertices), vertices, GL_STATIC_DRAW);
+            glEnableVertexAttribArray(0);
+            glVertexAttribPointer(
+                0,
+                2,
+                GL_FLOAT,
+                GL_FALSE,
+                2 * sizeof(GL_FLOAT),
+                reinterpret_cast<void*>(0)
+            );
+            glBindBuffer(GL_ARRAY_BUFFER, 0);
+            glBindVertexArray(0);
+
+            prog = buildRenderProgram(
+                "PlanetaryTrailBlurProgram",
+                absPath("${MODULE_BASE}/shaders/dbg_tex_vs.glsl"),
+                absPath("${MODULE_BASE}/shaders/dbg_tex_fs.glsl")
+            );
+        }
+
+        prog->activate();
+        prog->setUniform("tex", 0);
+
+        glBindTexture(GL_TEXTURE_2D, _debugTextureRender);
+
+        glBindVertexArray(vao);
+        glDrawArrays(GL_TRIANGLES, 0, 6);
+        glBindVertexArray(0);
+
+        glBindTexture(GL_TEXTURE_2D, 0);
+    }
     LTRACE("RenderEngine::render(end)");
 }
 
@@ -1032,6 +1082,10 @@ scripting::LuaLibrary RenderEngine::luaLibrary() {
     };
 }
 
+void RenderEngine::setDebugTextureRendering(GLuint texture) {
+    _debugTextureRender = texture;
+}
+
 void RenderEngine::addScreenSpaceRenderable(std::unique_ptr<ScreenSpaceRenderable> s) {
     const std::string identifier = s->identifier();