OpenGL Framebuffer always black Hello Folks, I'm writing a plugin for a simulator called 'X-Plane 11'. My plugin essentially calls on a DLL (Which I've written) that makes OpenGL calls to draw graphics onto the active draw target (it does no OpenGL initialization). I want this external DLL to represent the logic behind a computer screen, but not be directly coupled with the OpenGL context that it is being drawn to. In this current instance for example, I am drawing it to the screen in X-Plane, however, I may at some point want to draw it to the screen of a different game engine, or perhaps even just a windows program. The way I am trying to achieve this: Generate a frame buffer and texture Initialize texture and add it to the framebuffer On the drawcall... Bind to the frame buffer Call the dll's draw method Un-bind the frame buffer Bind to the host applications framebuffer Bind to the associated texture Draw a quad in the corner of the screen with appropriate texture coordinates Un-bind the texture I have the problem though that the output is always just a black square...(See attached image) The code goes a little like this (Only showing the relevant bits): #include #include #include "PluginHeader.h" #include #include #include #include "MFDSim.h" HINSTANCE g_MfdSimLibHandle = 0; XPLMWindowID g_MfdWindowID = 0; GLuint g_FrameBufferID = 0; GLuint g_fbTex = 0; GLuint g_rbo = 0; unsigned int g_MfdScreenWidth = 0; unsigned int g_MfdScreenHeight = 0; ///////////////////////////////////////////////////// // Standard plugin functions ------------------------ PLUGIN_API int XPluginStart( char* outName, char* outSig, char* outDesc) { strcpy(outName,"MFD Sim"); strcpy(outSig, "mfd"); strcpy(outDesc, "); int retVal = TRUE; glewInit(); HINSTANCE g_MfdSimLibHandle = LoadLibrary("./Resources/plugins/MFD_Sim_Plugin/win_x64/MFDSim.dll"); if (g_MfdSimLibHandle != nullptr) { try { MFD::mfdInit("./Resources/plugins/MFD_Sim_Plugin/config/layout.xml"); MFD::mfdGetWidthHeight(g_MfdScreenWidth, g_MfdScreenHeight); } catch (const std::exception& ex) { retVal = FALSE; } } else { retVal = FALSE; } return retVal; } PLUGIN_API void XPluginStop() { FreeLibrary(g_MfdSimLibHandle); } PLUGIN_API int XPluginEnable() { // We need to revert back to the appropriate frame buffer after we're done GLint currentReadFB = 0; GLint currentDrawFB = 0; glGetIntegerv(GL_READ_FRAMEBUFFER, ¤tReadFB); glGetIntegerv(GL_DRAW_FRAMEBUFFER, ¤tDrawFB); XPLMRegisterDrawCallback(OnDrawCall, xplm_Phase_LastCockpit, TRUE, nullptr); // Generate OPENGL stuff we need glGenFramebuffers(1, &g_FrameBufferID); glBindFramebuffer(GL_FRAMEBUFFER, g_FrameBufferID); glGenTextures(1, &g_fbTex); glBindTexture(GL_TEXTURE_2D, g_fbTex); glTexImage2D(GL_TEXTURE_2D, 0, GL_RGB, g_MfdScreenWidth, g_MfdScreenHeight, 0, GL_RGB, GL_UNSIGNED_BYTE, nullptr); glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR); glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR); glBindTexture(GL_TEXTURE_2D, 0); glFramebufferTexture2D(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT0, GL_TEXTURE_2D, g_fbTex, 0); glGenRenderbuffers(1, &g_rbo); glBindRenderbuffer(GL_RENDERBUFFER, g_rbo); glRenderbufferStorage(GL_RENDERBUFFER, GL_DEPTH24_STENCIL8, g_MfdScreenWidth, g_MfdScreenHeight); glBindRenderbuffer(GL_RENDERBUFFER, 0); glFramebufferRenderbuffer(GL_FRAMEBUFFER, GL_DEPTH_STENCIL_ATTACHMENT, GL_RENDERBUFFER, g_rbo); glBindFramebuffer(GL_READ_FRAMEBUFFER, currentReadFB); glBindFramebuffer(GL_DRAW_FRAMEBUFFER, currentDrawFB); return TRUE; } PLUGIN_API void XPluginDisable() { XPLMUnregisterDrawCallback(OnDrawCall, xplm_Phase_LastCockpit, TRUE, nullptr); glDeleteFramebuffers(1, &g_FrameBufferID); glDeleteTextures(1, &g_fbTex); } PLUGIN_API void XPluginReceiveMessage( XPLMPluginID inFrom, int inMsg, void* inParam) { } // Boilerplate DLL stuff BOOL WINAPI DLLMain( _In_ HINSTANCE hInstance, _In_ DWORD fdwReason, _In_ LPVOID lpvReserved) { return TRUE; } ///////////////////////////////////////////////////// // MFD functions ----------------------------------- void HandleWindowKeyEvent(XPLMWindowID inWindowID, char inKey, XPLMKeyFlags inFlags, char inVirtualKey, void * inRefcon, int losingFocus) { if (inWindowID == g_MfdWindowID) { } } int OnDrawCall(XPLMDrawingPhase inPhase, int inIsBefore, void * refCon) { // We need to revert back to the appropriate frame buffer after we're done GLint currentReadFB = 0; GLint currentDrawFB = 0; glGetIntegerv(GL_READ_FRAMEBUFFER, ¤tReadFB); glGetIntegerv(GL_DRAW_FRAMEBUFFER, ¤tDrawFB); // Bind to our own frame buffer and draw our MFD glBindFramebuffer(GL_DRAW_FRAMEBUFFER, g_FrameBufferID); glBindFramebuffer(GL_READ_FRAMEBUFFER, g_FrameBufferID); glBindTexture(GL_TEXTURE_2D, g_fbTex); glClear(GL_COLOR_BUFFER_BIT); glClearColor(0.0f, 0.0f, 0.0f, 1.0f); glEnable(GL_TEXTURE_2D); if (!MFD::mfdDraw(1.0f)) { // TODO: Handle failure to draw } glBegin(GL_LINES); glColor4f(1.0f, 0.1f, 0.1f, 1.0f); glVertex2f(0.0f, 0.0f); glVertex2f(100.0f, 100.0f); glEnd(); glBindFramebuffer(GL_READ_FRAMEBUFFER, currentReadFB); glBindFramebuffer(GL_DRAW_FRAMEBUFFER, currentDrawFB); glEnable(GL_TEXTURE_2D); glBegin(GL_QUADS); glVertex2f(0, 0); glTexCoord2f(0.0f, 0.0f); glVertex2f(0, g_MfdScreenHeight); glTexCoord2f(0.0f, 1.0f); glVertex2f(g_MfdScreenWidth, g_MfdScreenHeight); glTexCoord2f(1.0f, 1.0f); glVertex2f(g_MfdScreenWidth, 0); glTexCoord2f(1.0f, 0.0f); glEnd(); glBindTexture(GL_TEXTURE_2D, 0); return 0; } https://ift.tt/eA8V8J

Hello Folks, I'm writing a plugin for a simulator called 'X-Plane 11'. My plugin essentially calls on a DLL (Which I've written) that makes OpenGL calls to draw graphics onto the active draw target (it does no OpenGL initialization). I want this external DLL to represent the logic behind a computer screen, but not be directly coupled with the OpenGL context that it is being drawn to. In this current instance for example, I am drawing it to the screen in X-Plane, however, I may at some point want to draw it to the screen of a different game engine, or perhaps even just a windows program. The way I am trying to achieve this: Generate a frame buffer and texture Initialize texture and add it to the framebuffer On the drawcall... Bind to the frame buffer Call the dll's draw method Un-bind the frame buffer Bind to the host applications framebuffer Bind to the associated texture Draw a quad in the corner of the screen with appropriate texture coordinates Un-bind the texture I have the problem though that the output is always just a black square...(See attached image) The code goes a little like this (Only showing the relevant bits): #include <Windows.h> #include <string> #include "PluginHeader.h" #include <GL\glew.h> #include <gl\GL.h> #include <gl\GLU.h> #include "MFDSim.h" HINSTANCE g_MfdSimLibHandle = 0; XPLMWindowID g_MfdWindowID = 0; GLuint g_FrameBufferID = 0; GLuint g_fbTex = 0; GLuint g_rbo = 0; unsigned int g_MfdScreenWidth = 0; unsigned int g_MfdScreenHeight = 0; ///////////////////////////////////////////////////// // Standard plugin functions ------------------------ PLUGIN_API int XPluginStart( char* outName, char* outSig, char* outDesc) { strcpy(outName,"MFD Sim"); strcpy(outSig, "mfd"); strcpy(outDesc, "); int retVal = TRUE; glewInit(); HINSTANCE g_MfdSimLibHandle = LoadLibrary("./Resources/plugins/MFD_Sim_Plugin/win_x64/MFDSim.dll"); if (g_MfdSimLibHandle != nullptr) { try { MFD::mfdInit("./Resources/plugins/MFD_Sim_Plugin/config/layout.xml"); MFD::mfdGetWidthHeight(g_MfdScreenWidth, g_MfdScreenHeight); } catch (const std::exception& ex) { retVal = FALSE; } } else { retVal = FALSE; } return retVal; } PLUGIN_API void XPluginStop() { FreeLibrary(g_MfdSimLibHandle); } PLUGIN_API int XPluginEnable() { // We need to revert back to the appropriate frame buffer after we're done GLint currentReadFB = 0; GLint currentDrawFB = 0; glGetIntegerv(GL_READ_FRAMEBUFFER, &currentReadFB); glGetIntegerv(GL_DRAW_FRAMEBUFFER, &currentDrawFB); XPLMRegisterDrawCallback(OnDrawCall, xplm_Phase_LastCockpit, TRUE, nullptr); // Generate OPENGL stuff we need glGenFramebuffers(1, &g_FrameBufferID); glBindFramebuffer(GL_FRAMEBUFFER, g_FrameBufferID); glGenTextures(1, &g_fbTex); glBindTexture(GL_TEXTURE_2D, g_fbTex); glTexImage2D(GL_TEXTURE_2D, 0, GL_RGB, g_MfdScreenWidth, g_MfdScreenHeight, 0, GL_RGB, GL_UNSIGNED_BYTE, nullptr); glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR); glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR); glBindTexture(GL_TEXTURE_2D, 0); glFramebufferTexture2D(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT0, GL_TEXTURE_2D, g_fbTex, 0); glGenRenderbuffers(1, &g_rbo); glBindRenderbuffer(GL_RENDERBUFFER, g_rbo); glRenderbufferStorage(GL_RENDERBUFFER, GL_DEPTH24_STENCIL8, g_MfdScreenWidth, g_MfdScreenHeight); glBindRenderbuffer(GL_RENDERBUFFER, 0); glFramebufferRenderbuffer(GL_FRAMEBUFFER, GL_DEPTH_STENCIL_ATTACHMENT, GL_RENDERBUFFER, g_rbo); glBindFramebuffer(GL_READ_FRAMEBUFFER, currentReadFB); glBindFramebuffer(GL_DRAW_FRAMEBUFFER, currentDrawFB); return TRUE; } PLUGIN_API void XPluginDisable() { XPLMUnregisterDrawCallback(OnDrawCall, xplm_Phase_LastCockpit, TRUE, nullptr); glDeleteFramebuffers(1, &g_FrameBufferID); glDeleteTextures(1, &g_fbTex); } PLUGIN_API void XPluginReceiveMessage( XPLMPluginID inFrom, int inMsg, void* inParam) { } // Boilerplate DLL stuff BOOL WINAPI DLLMain( _In_ HINSTANCE hInstance, _In_ DWORD fdwReason, _In_ LPVOID lpvReserved) { return TRUE; } ///////////////////////////////////////////////////// // MFD functions ----------------------------------- void HandleWindowKeyEvent(XPLMWindowID inWindowID, char inKey, XPLMKeyFlags inFlags, char inVirtualKey, void * inRefcon, int losingFocus) { if (inWindowID == g_MfdWindowID) { } } int OnDrawCall(XPLMDrawingPhase inPhase, int inIsBefore, void * refCon) { // We need to revert back to the appropriate frame buffer after we're done GLint currentReadFB = 0; GLint currentDrawFB = 0; glGetIntegerv(GL_READ_FRAMEBUFFER, &currentReadFB); glGetIntegerv(GL_DRAW_FRAMEBUFFER, &currentDrawFB); // Bind to our own frame buffer and draw our MFD glBindFramebuffer(GL_DRAW_FRAMEBUFFER, g_FrameBufferID); glBindFramebuffer(GL_READ_FRAMEBUFFER, g_FrameBufferID); glBindTexture(GL_TEXTURE_2D, g_fbTex); glClear(GL_COLOR_BUFFER_BIT); glClearColor(0.0f, 0.0f, 0.0f, 1.0f); glEnable(GL_TEXTURE_2D); if (!MFD::mfdDraw(1.0f)) { // TODO: Handle failure to draw } glBegin(GL_LINES); glColor4f(1.0f, 0.1f, 0.1f, 1.0f); glVertex2f(0.0f, 0.0f); glVertex2f(100.0f, 100.0f); glEnd(); glBindFramebuffer(GL_READ_FRAMEBUFFER, currentReadFB); glBindFramebuffer(GL_DRAW_FRAMEBUFFER, currentDrawFB); glEnable(GL_TEXTURE_2D); glBegin(GL_QUADS); glVertex2f(0, 0); glTexCoord2f(0.0f, 0.0f); glVertex2f(0, g_MfdScreenHeight); glTexCoord2f(0.0f, 1.0f); glVertex2f(g_MfdScreenWidth, g_MfdScreenHeight); glTexCoord2f(1.0f, 1.0f); glVertex2f(g_MfdScreenWidth, 0); glTexCoord2f(1.0f, 0.0f); glEnd(); glBindTexture(GL_TEXTURE_2D, 0); return 0; }

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