I have coded a N-Body/GPU program with OpenCL and GLUT functions, and it works fine. I try now to convert it in order to get the main GLUT window into a QGLWidget subclass ("here GLWidget") with a Qt graphical interface.
My problem is that the "program vertex shader" link fails. Here is this part of the source file "GLWidget.cpp" where I get in " _compileProgram
" the error " Failed to link program
" :
extern const char *vertexShader;
void GLWidget::GLInit()
{
LoadGLTextures(); // load the textures.
glClearColor(0.0 ,0.0, 0.0, 0.0);
glMatrixMode(GL_PROJECTION);
glLoadIdentity();
m_program = _compileProgram(vertexShader);
glClampColor(GL_CLAMP_VERTEX_COLOR, GL_FALSE);
glClampColor(GL_CLAMP_FRAGMENT_COLOR, GL_FALSE);
// memsize of GPU data
unsigned int memSize = sizeof(cl_double4) * 4 * Galaxy->getNumParticles();
createVBO(memSize);
}
void GLWidget::createVBO(uint size)
{
GLuint vbo;
glGenBuffers(1, &vbo);
glBindBuffer(GL_ARRAY_BUFFER, vbo);
glBufferData(GL_ARRAY_BUFFER, size, Galaxy->pos, GL_DYNAMIC_DRAW);
}
GLuint GLWidget::_compileProgram(const char *vsource)
{
GLuint vertexShader = glCreateShader(GL_VERTEX_SHADER);
glShaderSource(vertexShader, 1, &vsource, 0);
glCompileShader(vertexShader);
GLuint program = glCreateProgram();
glAttachShader(program, vertexShader);
glLinkProgram(program);
// check if program linked
GLint success = 0;
glGetProgramiv(program, GL_LINK_STATUS, &success);
if (!success) {
char temp[256];
glGetProgramInfoLog(program, 256, 0, temp);
printf("Failed to link program:\n%s\n", temp);
glDeleteProgram(program);
program = 0;
}
return program;
}
I use the following vertex shader program in shader.cpp :
#define STRINGIFY(A) #A
// vertex shader
const char *vertexShader = STRINGIFY(
uniform float pointRadius; // point size in world space
uniform float pointScale; // scale to calculate size in pixels
void main()
{
// calculate window-space point size
vec3 posEye = vec3(gl_ModelViewMatrix * vec4(gl_Vertex.xyz, 1.0));
float dist = length(posEye);
gl_PointSize = pointRadius * (pointScale / dist);
gl_TexCoord[0] = gl_MultiTexCoord0;
gl_Position = gl_ModelViewProjectionMatrix * vec4(gl_Vertex.xyz, 1.0);
gl_FrontColor = gl_Color;
}
);
I make you notice that the "GLuint m_program" is a data member of the subclass GLWidget.
Anyone could see what's wrong?
More generally, can I use directly the same GLUT functions " glAttachShader
", " glLinkProgram
" on a GLWidget object like I did it with the first version of my code (ie without Qt user interface)?
Depending on which OpenGL / GLSL version you're targeting, don't you need a trivial fragment shader in order to link successfully? You mention OpenGL 4.1 but your vertex shader code is using GLSL variable names which are deprecated in GLSL 3.3 (gl_TexCoord, for example)
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