gl_PointCoord always zero
- by Jonathan
I am trying to draw point sprites in OpenGL with a shader but gl_PointCoord is always zero.
Here is my code
Setup:
//Shader creation..(includes glBindAttribLocation(program, ATTRIB_P, "p");)
glEnableVertexAttribArray(ATTRIB_P);
In the rendering loop:
glUseProgram(shader_particles);
float vertices[]={0.0f,0.0f,0.0f};
glEnable(GL_TEXTURE_2D);
glEnable(GL_POINT_SPRITE);
glEnable(GL_VERTEX_PROGRAM_POINT_SIZE);
//glTexEnvi(GL_POINT_SPRITE, GL_COORD_REPLACE, GL_TRUE);(tried with this on/off, doesn't work)
glVertexAttribPointer(ATTRIB_P, 3, GL_FLOAT, GL_FALSE, 0, vertices);
glDrawArrays(GL_POINTS, 0, 1);
Vertex Shader:
attribute highp vec4 p;
void main() {
gl_PointSize = 40.0f;
gl_Position = p;
}
Fragment Shader:
void main() {
gl_FragColor = vec4(gl_PointCoord.st, 0, 1);//if the coords range from 0-1, this should draw a square with black,red,green,yellow corners
}
But this only draws a black square with a size of 40.
What am I doing wrong?
Edit: Point sprites work when i use the fixed function, but I need to use shaders because in the end the code will be for opengl es 2.0
glUseProgram(0);
glEnable(GL_TEXTURE_2D);
glEnable(GL_POINT_SPRITE);
glTexEnvi(GL_POINT_SPRITE, GL_COORD_REPLACE, GL_TRUE);
glPointSize(40);
glBegin(GL_POINTS);
glVertex3f(0.0f,0.0f,0.0f);
glEnd();
Is anyone able to get point sprites working with shader? If so, please share some code.
