VBO display nothing, but VAO yes

texel3d · 2014-11-14T11:31:53

Hi, i want to display a triangle using OpenGL 3.3 and QT. I have tried an example on the web which display a triangle using VBO + VAO + GLSL it works. But now, i want to modify the code to use only VBO+GLSL (no VAO)(i want to make it compatible with OpenGL ES for the future). But it displays nothing. This is the code which works unsing VAO: void MyGLWindow::InitVAO() { const float vertexData[] = { // x y z w 0.0f, 0.5f, 0.0f, 1.0f, 0.5f, -0.366f, 0.0f, 1.0f, -0.5f, -0.366f, 0.0f, 1.0f, // R G B A 1.0f, 0.0f, 0.0f, 1.0f, 0.0f, 1.0f, 0.0f, 1.0f, 0.0f, 0.0f, 1.0f, 1.0f, }; // create Vertex Buffer Object glGenBuffers(1, &VB_Position); glBindBuffer(GL_ARRAY_BUFFER, VB_Position); glBufferData(GL_ARRAY_BUFFER, sizeof(vertexData), vertexData, GL_STATIC_DRAW); glBindBuffer(GL_ARRAY_BUFFER, 0); // create Vertex Array Object glGenVertexArrays(1, &VAO); glBindVertexArray(VAO); glBindBuffer(GL_ARRAY_BUFFER, VB_Position); glEnableVertexAttribArray(0); glEnableVertexAttribArray(1); glVertexAttribPointer(0, 4, GL_FLOAT, GL_FALSE, 0, 0); glVertexAttribPointer(1, 4, GL_FLOAT, GL_FALSE, 0, (void*)48); glBindVertexArray(0); glBindBuffer(GL_ARRAY_BUFFER, 0); } void MyGLWindow::RenderWithVAO() { m_context->makeCurrent(this); glClearColor(0.0f, 0.0f, 0.0f, 0.0f); glClear(GL_COLOR_BUFFER_BIT); glUseProgram(m_program->programId()); glBindVertexArray(VAO); glDrawArrays(GL_TRIANGLES, 0, 3); glBindVertexArray(0); glUseProgram(0); m_context->swapBuffers(this); } This is my code which do not use VAO, just VBO. I don't know why it does not work. void MyGLWindow::InitVBOSeveralArrays() { float vertexPositionData[] = { // x y z w 0.0f, 0.5f, 0.0f, 1.0f, 0.5f, -0.366f, 0.0f, 1.0f, -0.5f, -0.366f, 0.0f, 1.0f }; float vertexColorData[] = { // R G B A 1.0f, 0.0f, 0.0f, 1.0f, 0.0f, 1.0f, 0.0f, 1.0f, 0.0f, 0.0f, 1.0f, 1.0f }; int indexData[] = { 0,1,2 }; glGenBuffers(1, &VB_Position); // create Vertex Buffer Object glBindBuffer(GL_ARRAY_BUFFER, VB_Position); // bind it to the GL_ARRAY_BUFFER glBufferData(GL_ARRAY_BUFFER, 4*3*sizeof(float), vertexPositionData, GL_STATIC_DRAW); // copy data to GPU glBindBuffer(GL_ARRAY_BUFFER, 0); // bind the GL_ARRAY_BUFFER to 0 glGenBuffers(1, &VB_Color); // create Vertex Buffer Object glBindBuffer(GL_ARRAY_BUFFER, VB_Color); // bind it to the GL_ARRAY_BUFFER glBufferData(GL_ARRAY_BUFFER, 4*3*sizeof(float), vertexColorData, GL_STATIC_DRAW); // copy data to GPU glBindBuffer(GL_ARRAY_BUFFER, 0); // bind the GL_ARRAY_BUFFER to 0 glGenBuffers( 1, &VB_Index ); glBindBuffer( GL_ELEMENT_ARRAY_BUFFER_ARB, VB_Index ); glBufferData( GL_ELEMENT_ARRAY_BUFFER_ARB, 3*sizeof(int), indexData, GL_STATIC_DRAW_ARB ); glBindBuffer(GL_ARRAY_BUFFER, 0); } void MyGLWindow::RenderWithVBOSeveralArrays() { m_context->makeCurrent(this); glClearColor(0.0f, 0.0f, 0.0f, 0.0f); glClear(GL_COLOR_BUFFER_BIT); glUseProgram(m_program->programId()); GLuint positionIndex = glGetAttribLocation(m_program->programId(), "position"); GLuint colorIndex = glGetAttribLocation(m_program->programId(), "color"); // Vertices glBindBuffer(GL_ARRAY_BUFFER_ARB, VB_Position); glVertexAttribPointer(positionIndex, 4, GL_FLOAT, GL_FALSE, 0, 0); glEnableVertexAttribArray(positionIndex); // Color glBindBuffer(GL_ARRAY_BUFFER_ARB, VB_Color); glVertexAttribPointer(colorIndex, 4, GL_FLOAT, GL_FALSE, 0, 0); glEnableVertexAttribArray(colorIndex); // Indices glBindBuffer(GL_ELEMENT_ARRAY_BUFFER_ARB, VB_Index); glDrawElements(GL_TRIANGLES, 3, GL_UNSIGNED_INT, nullptr); // Draw glDisableVertexAttribArray(positionIndex); glDisableVertexAttribArray(colorIndex); glUseProgram(0); m_context->swapBuffers(this); } Do you have some ideas ? I have attached a very simple source code of the project. Thanks.

Graphics and GPU Programming Programming OpenGL

Started by texel3d November 13, 2014 01:56 PM

9 comments, last by Xycaleth 9 years, 5 months ago

Xycaleth

2,391

November 14, 2014 11:31 AM

VAOs weren't introduced into ES until 3.0.

Yay, GL extensions. My driver is happily supporting VAO in a GLES 2.0 context - I assumed it was doing the expected thing, but I see not.

Does anyone maintain a database of extension support on mobile chipsets?

Not an exhaustive list, but there is this:

http://delphigl.de/glcapsviewer/gles_listreports.php

VBO display nothing, but VAO yes

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