I have coded a small OpenGL program using OpenGL and GLSL shaders. Here's a screen of my application :
Now, my objective is to mix my opengl frame and the one from my webcam in a unique frame using OpenCV. Before to do this with GLSL shaders, I tried to make a very simple program drawing a colored triangle with some basic OpenGL functions (glBengin, glVertex, etc.).
static int initGL()
{
if (!glfwInit())
return (-1);
if (!glfwOpenWindow(500, 500, 8, 8, 8, 0, 24, 0, GLFW_WINDOW)) {
glfwTerminate();
return (-1);
}
glEnable(GL_PROJECTION);
glLoadIdentity();
gluPerspective(45.0f, 500.0f / 500.0f, 0.1f, 100.0f);
gluLookAt(0.0f, 0.0f, 5.0f, 0.0f, 0.0f, 0.0f, 0.0f, 1.0f, 0.0f);
return (0);
}
static void drawGL()
{
glBegin(GL_TRIANGLES);
glColor3ub(255, 0, 0);
glVertex3f(-1.0f, 0.0f, 0.0f);
glColor3ub(0, 255, 0);
glVertex3f(0.0f, 1.0f, 0.0f);
glColor3ub(0, 0, 255);
glVertex3f(1.0f, 0.0f, 0.0f);
glEnd();
}
int main(void)
{
initGL();
CvCapture *capture = cvCaptureFromCAM(CV_CAP_ANY);
if (!capture) {
fprintf(stderr, "ERROR: capture is NULL \n");
getchar();
return (-1);
}
while (1)
{
glClear(GL_COLOR_BUFFER_BIT);
glEnable(GL_MODELVIEW);
IplImage *frame = cvQueryFrame(capture);
if (!frame) {
fprintf(stderr, "ERROR: frame is null...\n");
getchar();
break;
}
glDrawPixels(frame->width, frame->height, GL_RGB, GL_UNSIGNED_BYTE, frame->imageData);
drawGL();
glfwSwapBuffers();
if ( (cvWaitKey(10) & 255) == 27 ) break;
}
cvReleaseCapture(&capture);
cvDestroyWindow("mywindow");
return (EXIT_SUCCESS);
}
Here's the render :
As you can see the result is correct. Now, I wanted to try my first program using GLSL shaders with OpenCV like below but when my application is launched I have a black screen. I tried several tests and the problem seems to begin when I call glUseProgram function (so when I want to bind the program shader -> in my code it corresponds to the program->bind() call). But here I use the glDrawPixels function to load my video frame. I think it's not the good function to call if I want to use GLSL shaders. Here's a piece of my C++ code :
[...]
/*My GLSL shaders initialization*/
[...]
int main(int ac, char **av)
{
bool isAlive = true;
unsigned int vaoID = 0;
SDL_Event event;
GLuint textureID = 0;
ShaderProgram *program = NULL;
if (!glfwInit())
return (-1);
if (!glfwOpenWindow(WIDTH, HEIGHT, 8, 8, 8, 0, 24, 0, GLFW_WINDOW)) {
glfwTerminate();
return (-1);
}
glEnable(GL_DEPTH_TEST);
//Viewport initialization
glViewport(0, 0, WIDTH, HEIGHT);
//Vertex declaration
VertexDeclaration *vDeclar = initVertexDeclaration();
//Glew init component
glewInit();
//VBO initialization
VertexBuffer *vBuffer = initVBO();
//Shaders initialization
program = initShaders("triangle-pf.vert", "triangle-pf.frag");
//Texture initialization
textureID = loadBMPTexture("Box.bmp");
//VAO initialization
initVAO(vaoID, vBuffer, textureID, vDeclar);
//Screen capture Initialization
CvCapture *capture = cvCaptureFromCAM(CV_CAP_ANY);
if (!capture) {
fprintf(stderr, "ERROR: capture is NULL \n");
getchar();
return (-1);
}
//Main loop
while (isAlive == true)
{
//eventListener(&event, &isAlive);
if (glfwGetKey(GLFW_KEY_ESC))
isAlive = false;
glClearDepth(1.0f);
glClearColor(0.13f, 0.12f, 0.13f, 1.0f);
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
//---------------------------------------------------
IplImage *frame = cvQueryFrame(capture);
if (!frame) {
fprintf(stderr, "ERROR: frame is null...\n");
getchar();
break;
}
//---------------------------------------------------
program->bind();
//Projection matrix
glm::mat4 ProjectionMatrix = glm::perspective(45.0f, 500.0f / 500.0f, 0.1f, 100.0f);
//View matrix
glm::mat4 ViewMatrix = glm::lookAt(glm::vec3(0.0f, 0.0f, 8.0f), glm::vec3(0.0f, 0.0f, 0.0f), glm::vec3(0.0f, 1.0f, 0.0f));
//Model matrix
glm::mat4 ModelMatrix = glm::mat4(1.0f);
ModelMatrix = glm::translate(ModelMatrix, glm::vec3(0.0f, 0.0f, 0.0f));
ModelMatrix = glm::rotate(ModelMatrix, angle, glm::vec3(1.0f, 1.0f, 1.0f));
ModelMatrix = glm::scale(ModelMatrix, glm::vec3(1.0f, 1.0f, 1.0f));
//Prepare matrix
glm::mat4 ModelViewMatrix = ViewMatrix * ModelMatrix;
glm::mat3 NormalMatrix = glm::mat3(glm::vec3(ModelViewMatrix[0]), glm::vec3(ModelViewMatrix[1]), glm::vec3(ModelViewMatrix[2]));
glm::mat4 ModelViewProjectionMatrix = ProjectionMatrix * ModelViewMatrix;
glm::vec4 LightPositionVec1 = ViewMatrix * glm::vec4(LightPosition1[0], LightPosition1[1], LightPosition1[2], LightPosition1[3]);
//Send source light properties
program->setUniform("LightInfos[0].La", glm::vec3(0.000000f, 0.000000f, 0.000000f));
program->setUniform("LightInfos[0].Ld", glm::vec3(0.800000f, 0.800000f, 0.800000f));
program->setUniform("LightInfos[0].Ls", glm::vec3(1.000000f, 1.000000f, 1.000000f));
program->setUniform("LightInfos[0].Le", glm::vec3(0.200000f, 0.200000f, 0.200000f));
/*program->setUniform("LightInfos[1].La", glm::vec3(0.000000f, 0.000000f, 0.000000f));
program->setUniform("LightInfos[1].Ld", glm::vec3(0.800000f, 0.800000f, 0.800000f));
program->setUniform("LightInfos[1].Ls", glm::vec3(0.000000f, 1.000000f, 1.000000f));
program->setUniform("LightInfos[1].Le", glm::vec3(0.200000f, 0.200000f, 0.200000f));*/
//Send model materials properties
program->setUniform("MaterialInfos.Ka", glm::vec3(0.000000f, 0.000000f, 0.000000f));
program->setUniform("MaterialInfos.Kd", glm::vec3(1.000000f, 1.000000f, 1.000000f));
program->setUniform("MaterialInfos.Ks", glm::vec3(1.000000f, 1.000000f, 1.000000f));
program->setUniform("MaterialInfos.Ke", glm::vec3(0.200000f, 0.000000f, 0.200000f));
program->setUniform("MaterialInfos.Shininess", 10.0f);
//Send light position
program->setUniform("LightInfos[0].Position", LightPositionVec1);
//Send matrix
program->setUniform("ProjectionMatrix", ProjectionMatrix);
program->setUniform("NormalMatrix", NormalMatrix);
program->setUniform("ModelViewMatrix", ModelViewMatrix);
program->setUniform("ModelMatrix", ModelMatrix);
program->setUniform("MVP", ModelViewProjectionMatrix);
glDrawPixels(frame->width, frame->height, GL_RGB, GL_UNSIGNED_BYTE, frame->imageData);
//VAO binding
glBindVertexArray(vaoID);
//Render meshes
glDrawArrays(GL_TRIANGLES, 0, vBuffer->getSize());
glBindVertexArray(0);
program->release();
angle += 0.50f;
glFlush();
glfwSwapBuffers();
}
unsigned int vboID = vBuffer->getHandle();
glDeleteBuffers(1, &vboID);
glDeleteVertexArrays(1, &vaoID);
return (0);
}
So I think the problem comes from glDrawPixels which cannot be used with GLSL shaders. I tried several possible ways without any success. Maybe I have to send the video frame buffer directly to the pixel shader ? In this case, how can I do that ? I'm really lost. Does anyone can help me?
