<div dir="ltr">>>Is the program linked at this point? MatrixID should be GLint and you should test that MatrixID != -1. <div> </div><div>Yes. The shader program is able to compile and link. I have changed it to Glint and the MatrixID is valid.</div><div> </div><div>>>Are you calling glGetError() to check for errors? </div><div> </div><div>glGetError() is not throwing any errors.</div><div> </div><div>glGetProgramInfoLog() and glGetShaderInfoLog() are also checked in the shader.cpp. </div><div> </div><div>Thank you so much Brian!! will look into the type checks and shader validations and update.</div><div> </div><div> </div><div>Regards,</div><div>Vikram</div><div> </div></div><div class="gmail_extra"> <div class="gmail_quote">On Tue, Mar 8, 2016 at 3:10 AM, Brian Paul <<a href="mailto:brianp@vmware.com" target="_blank">brianp@vmware.com</a>> wrote: <blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">On 03/07/2016 12:13 AM, vikramnrao wrote: <blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"> Hi Brian, Currently I am unable to view anything the render using glsl shader. I have tried rendering a simple triangle in immediate mode and it renders fine(off-screen). But not able to clear background color. My renderScene code for Immediate mode looks something like this: glClear(GL_COLOR_BUFFER_BIT); glClear(GL_DEPTH_BUFFER_BIT); glClearColor(0.0f, 0.0f, 0.4f, 0.0f); </blockquote> You should set the color before calling glClear(). <blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"> // Enable depth test glEnable(GL_DEPTH_TEST); // Accept fragment if it closer to the camera than the former one glDepthFunc(GL_LESS); // Cull triangles which normal is not towards the camera glEnable(GL_CULL_FACE); glBegin(GL_TRIANGLES); glColor3f(0.5f, 0.0f, 0.0f); glVertex3f(-1.0f, 0.0f, -1.0f); glColor3f(0.0f, 0.5f, 0.0f); glVertex3f(1.0f, 0.0f, -1.0f); glColor3f(0.0f, 0.0f, 0.5f); glVertex3f(0.0f, 1.0f, 0.0f); glEnd(); glFinish(); SaveScreenGrab("mesa_snapshot.tga"); But same triangle using shader doesn't render at all. However the glClearColor clears the screen color correctly. Below is the bit of code that I took from (<a href="http://opengl.org" rel="noreferrer" target="_blank">opengl.org</a> <<a href="https://urldefense.proofpoint.com/v2/url?u=http-3A__opengl.org&d=BQMFaQ&c=Sqcl0Ez6M0X8aeM67LKIiDJAXVeAw-YihVMNtXt-uEs&r=T0t4QG7chq2ZwJo6wilkFznRSFy-8uDKartPGbomVj8&m=QEdFbrBKV_Dbv7s3zEN_t8kUV5UYxjVym60nXIWrkDI&s=J_tgBAEFHUAblpGuLppBJyqZRh-n_F_7Jlv3_aK-DQo&e=" rel="noreferrer" target="_blank">https://urldefense.proofpoint.com/v2/url?u=http-3A__opengl.org&d=BQMFaQ&c=Sqcl0Ez6M0X8aeM67LKIiDJAXVeAw-YihVMNtXt-uEs&r=T0t4QG7chq2ZwJo6wilkFznRSFy-8uDKartPGbomVj8&m=QEdFbrBKV_Dbv7s3zEN_t8kUV5UYxjVym60nXIWrkDI&s=J_tgBAEFHUAblpGuLppBJyqZRh-n_F_7Jlv3_aK-DQo&e=</a>>) which render the scene into a targa image. // Dark blue background glClearColor(0.0f, 0.0f, 0.4f, 0.0f); // Enable depth test glEnable(GL_DEPTH_TEST); // Accept fragment if it closer to the camera than the former one glDepthFunc(GL_LESS); // Create and compile our GLSL program from the shaders GLuint programID = LoadShaders("camera.vertexshader", "camera.fragmentshader"); // Get a handle for our "MVP" uniform GLuint MatrixID = glGetUniformLocation(programID, "MVP"); </blockquote> Is the program linked at this point? MatrixID should be GLint and you should test that MatrixID != -1. <blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"> // Get a handle for our buffers GLuint vertexPosition_modelspaceID = glGetAttribLocation(programID, "vertexPosition_modelspace"); GLuint vertexColorID = glGetAttribLocation(programID, "vertexColor"); </blockquote> GLint as well, and check for non-negative values. <blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><div><div class="h5"> // Projection matrix : 45° Field of View, 4:3 ratio, display range : 0.1 unit <-> 100 units glm::mat4 Projection = glm::perspective(45.0f, 4.0f / 3.0f, 0.1f, 100.0f); // Camera matrix glm::mat4 View = glm::lookAt( glm::vec3(4, 3, -3), // Camera is at (4,3,-3), in World Space glm::vec3(0, 0, 0), // and looks at the origin glm::vec3(0, 1, 0) // Head is up (set to 0,-1,0 to look upside-down) ); // Model matrix : an identity matrix (model will be at the origin) glm::mat4 Model = glm::mat4(1.0f); // Our ModelViewProjection : multiplication of our 3 matrices glm::mat4 MVP = Projection * View * Model; // Remember, matrix multiplication is the other way around GLuint vertexbuffer; glGenBuffers(1, &vertexbuffer); glBindBuffer(GL_ARRAY_BUFFER, vertexbuffer); glBufferData(GL_ARRAY_BUFFER, sizeof(g_vertex_buffer_data), g_vertex_buffer_data, GL_STATIC_DRAW); GLuint colorbuffer; glGenBuffers(1, &colorbuffer); glBindBuffer(GL_ARRAY_BUFFER, colorbuffer); glBufferData(GL_ARRAY_BUFFER, sizeof(g_color_buffer_data), g_color_buffer_data, GL_STATIC_DRAW); // Clear the screen glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT); // Use our shader glUseProgram(programID); // Send our transformation to the currently bound shader, // in the "MVP" uniform glUniformMatrix4fv(MatrixID, 1, GL_FALSE, &MVP[0][0]); // 1rst attribute buffer : vertices glEnableVertexAttribArray(vertexPosition_modelspaceID); glBindBuffer(GL_ARRAY_BUFFER, vertexbuffer); glVertexAttribPointer( vertexPosition_modelspaceID, // The attribute we want to configure 3, // size GL_FLOAT, // type GL_FALSE, // normalized? 0, // stride (void*)0 // array buffer offset ); // 2nd attribute buffer : colors glEnableVertexAttribArray(vertexColorID); glBindBuffer(GL_ARRAY_BUFFER, colorbuffer); glVertexAttribPointer( vertexColorID, // The attribute we want to configure 3, // size GL_FLOAT, // type GL_FALSE, // normalized? 0, // stride (void*)0 // array buffer offset ); // Draw the triangleS ! glDrawArrays(GL_TRIANGLES, 0, 12 * 3); // 12*3 indices starting at 0 -> 12 triangles glDisableVertexAttribArray(vertexPosition_modelspaceID); glDisableVertexAttribArray(vertexColorID); SaveScreenGrab("mesa_snapshot.tga"); // Cleanup VBO and shader glDeleteBuffers(1, &vertexbuffer); glDeleteBuffers(1, &colorbuffer); glDeleteProgram(programID); </div></div> *vertex shader code:* #version 120 // Input vertex data, different for all executions of this shader. attribute vec3 vertexPosition_modelspace; attribute vec3 vertexColor; // Output data ; will be interpolated for each fragment. varying vec3 fragmentColor; // Values that stay constant for the whole mesh. uniform mat4 MVP; void main(){ // Output position of the vertex, in clip space : MVP * position gl_Position = MVP * vec4(vertexPosition_modelspace,1); // The color of each vertex will be interpolated // to produce the color of each fragment fragmentColor = vertexColor; } *fragment shader code:* * * #version 120 // Interpolated values from the vertex shaders varying vec3 fragmentColor; void main(){ gl_FragColor = fragmentColor; } Please guide me if I am doing something wrong here. </blockquote> Hard to say without running the program and debugging things (which I don't have time to do). If the window is blank, it could be a transformation matrix mistake. Maybe you could start with identity matrices for the model, view and projection and see if anything shows up. Are you calling glGetError() to check for errors? Also, glGetProgramInfoLog() and glGetShaderInfoLog() should be checked for shader compiler/linker errors. -Brian </blockquote></div> </div>