Question

vertex shader:

#version 150

in vec3 MCVertex;
in float pointvar;

uniform mat4 MVMatrix;
uniform mat4 MPMatrix;

void main()
{
    gl_Position = MPMatrix * MVMatrix * vec4(MCVertex, 1.0);
}

i need ‘pointvar’ attribute

but when i call :

glGetProgramiv(program, GL_ACTIVE_ATTRIBUTES, &numAttributes);

numAttribute = 1;

there are 2 attribute in my code, numAttribute must be 2.

and if i do it like this, i can active this attribute:

gl_Position = MPMatrix * MVMatrix * vec4(MCVertex + vec3(pointvar), 1.0);

then numAttributes = 2, is there any other ways to active this attribute?
i have try to #pragma optimize(off), but not work.

Answer 1

I’m pretty sure that GLSL will “erase/forget” any uniform / attribute not used in it’s code.

All the info here.

EDIT:

Like uniforms, attributes can be active or inactive. Attributes that
are unused are inactive; they do not have a binding.