opengl: Fix OpenGL 3.1 support on Windows

Properly check version and report error in the viewer.

In OpenGL processor, FBOs must have read buffer properly set up.

It's possible viewer's shader version 330 needs to be ported to
version 140, but no bugs were encountered at the moment.

Author: xlz

examples/viewer.cpp

@@ -1,4 +1,5 @@
 #include "viewer.h"
+#include <cstdlib>
 
 Viewer::Viewer() : shader_folder("src/shader/")
 {
@@ -7,19 +8,37 @@ Viewer::Viewer() : shader_folder("src/shader/")
 
 }
 
+static void glfwErrorCallback(int error, const char* description)
+{
+  std::cerr << "GLFW error " << error << " " << description << std::endl;
+}
+
 void Viewer::initialize()
 {
+    GLFWerrorfun prev_func = glfwSetErrorCallback(glfwErrorCallback);
+    if (prev_func)
+      glfwSetErrorCallback(prev_func);
+
     // setup context
     glfwDefaultWindowHints();
     glfwWindowHint(GLFW_CONTEXT_VERSION_MAJOR, 3);
-    glfwWindowHint(GLFW_CONTEXT_VERSION_MINOR, 3);
 #ifdef __APPLE__
+    glfwWindowHint(GLFW_CONTEXT_VERSION_MINOR, 3);
     glfwWindowHint(GLFW_OPENGL_FORWARD_COMPAT, GL_TRUE);
-#endif
     glfwWindowHint(GLFW_OPENGL_PROFILE, GLFW_OPENGL_CORE_PROFILE);
+#else
+    glfwWindowHint(GLFW_CONTEXT_VERSION_MINOR, 1);
+    glfwWindowHint(GLFW_OPENGL_PROFILE, GLFW_OPENGL_ANY_PROFILE);
+#endif
     //glfwWindowHint(GLFW_VISIBLE, debug ? GL_TRUE : GL_FALSE);
 
-    window = glfwCreateWindow(1280, 800, "Viewer", 0, NULL);
+    window = glfwCreateWindow(1280, 800, "Viewer (press ESC to exit)", 0, NULL);
+    if (window == NULL)
+    {
+        std::cerr << "Failed to create opengl window." << std::endl;
+        exit(-1);
+    }
+
     glfwMakeContextCurrent(window);
     OpenGLBindings *b = new OpenGLBindings();
     flextInit(b);

src/opengl_depth_packet_processor.cpp

@@ -585,50 +585,54 @@ struct OpenGLDepthPacketProcessorImpl : public WithOpenGLBindings, public WithPe
     GLenum debug_attachment = do_debug ? GL_COLOR_ATTACHMENT0 : GL_NONE;
 
     gl()->glGenFramebuffers(1, &stage1_framebuffer);
-    gl()->glBindFramebuffer(GL_DRAW_FRAMEBUFFER, stage1_framebuffer);
+    gl()->glBindFramebuffer(GL_FRAMEBUFFER, stage1_framebuffer);
 
     const GLenum stage1_buffers[] = { debug_attachment, GL_COLOR_ATTACHMENT1, GL_COLOR_ATTACHMENT2, GL_COLOR_ATTACHMENT3, GL_COLOR_ATTACHMENT4 };
     gl()->glDrawBuffers(5, stage1_buffers);
+    glReadBuffer(GL_COLOR_ATTACHMENT4);
 
     if(do_debug) gl()->glFramebufferTexture2D(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT0, GL_TEXTURE_RECTANGLE, stage1_debug.texture, 0);
     gl()->glFramebufferTexture2D(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT1, GL_TEXTURE_RECTANGLE, stage1_data[0].texture, 0);
     gl()->glFramebufferTexture2D(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT2, GL_TEXTURE_RECTANGLE, stage1_data[1].texture, 0);
     gl()->glFramebufferTexture2D(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT3, GL_TEXTURE_RECTANGLE, stage1_data[2].texture, 0);
     gl()->glFramebufferTexture2D(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT4, GL_TEXTURE_RECTANGLE, stage1_infrared.texture, 0);
-    checkFBO(GL_DRAW_FRAMEBUFFER);
+    checkFBO(GL_FRAMEBUFFER);
 
     gl()->glGenFramebuffers(1, &filter1_framebuffer);
-    gl()->glBindFramebuffer(GL_DRAW_FRAMEBUFFER, filter1_framebuffer);
+    gl()->glBindFramebuffer(GL_FRAMEBUFFER, filter1_framebuffer);
 
     const GLenum filter1_buffers[] = { debug_attachment, GL_COLOR_ATTACHMENT1, GL_COLOR_ATTACHMENT2, GL_COLOR_ATTACHMENT3 };
     gl()->glDrawBuffers(4, filter1_buffers);
+    glReadBuffer(GL_NONE);
 
     if(do_debug) gl()->glFramebufferTexture2D(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT0, GL_TEXTURE_RECTANGLE, filter1_debug.texture, 0);
     gl()->glFramebufferTexture2D(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT1, GL_TEXTURE_RECTANGLE, filter1_data[0].texture, 0);
     gl()->glFramebufferTexture2D(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT2, GL_TEXTURE_RECTANGLE, filter1_data[1].texture, 0);
     gl()->glFramebufferTexture2D(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT3, GL_TEXTURE_RECTANGLE, filter1_max_edge_test.texture, 0);
-    checkFBO(GL_DRAW_FRAMEBUFFER);
+    checkFBO(GL_FRAMEBUFFER);
 
     gl()->glGenFramebuffers(1, &stage2_framebuffer);
-    gl()->glBindFramebuffer(GL_DRAW_FRAMEBUFFER, stage2_framebuffer);
+    gl()->glBindFramebuffer(GL_FRAMEBUFFER, stage2_framebuffer);
 
     const GLenum stage2_buffers[] = { debug_attachment, GL_COLOR_ATTACHMENT1, GL_COLOR_ATTACHMENT2 };
     gl()->glDrawBuffers(3, stage2_buffers);
+    glReadBuffer(GL_COLOR_ATTACHMENT1);
 
     if(do_debug) gl()->glFramebufferTexture2D(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT0, GL_TEXTURE_RECTANGLE, stage2_debug.texture, 0);
     gl()->glFramebufferTexture2D(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT1, GL_TEXTURE_RECTANGLE, stage2_depth.texture, 0);
     gl()->glFramebufferTexture2D(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT2, GL_TEXTURE_RECTANGLE, stage2_depth_and_ir_sum.texture, 0);
-    checkFBO(GL_DRAW_FRAMEBUFFER);
+    checkFBO(GL_FRAMEBUFFER);
 
     gl()->glGenFramebuffers(1, &filter2_framebuffer);
-    gl()->glBindFramebuffer(GL_DRAW_FRAMEBUFFER, filter2_framebuffer);
+    gl()->glBindFramebuffer(GL_FRAMEBUFFER, filter2_framebuffer);
 
     const GLenum filter2_buffers[] = { debug_attachment, GL_COLOR_ATTACHMENT1 };
     gl()->glDrawBuffers(2, filter2_buffers);
+    glReadBuffer(GL_COLOR_ATTACHMENT1);
 
     if(do_debug) gl()->glFramebufferTexture2D(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT0, GL_TEXTURE_RECTANGLE, filter2_debug.texture, 0);
     gl()->glFramebufferTexture2D(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT1, GL_TEXTURE_RECTANGLE, filter2_depth.texture, 0);
-    checkFBO(GL_DRAW_FRAMEBUFFER);
+    checkFBO(GL_FRAMEBUFFER);
 
     Vertex bl = {-1.0f, -1.0f, 0.0f, 0.0f }, br = { 1.0f, -1.0f, 512.0f, 0.0f }, tl = {-1.0f, 1.0f, 0.0f, 424.0f }, tr = { 1.0f, 1.0f, 512.0f, 424.0f };
     Vertex vertices[] = {