GLSL float/vec3/vec4 array max size = GL_MAX_VERTEX_UNIFORM_VECTORS?

Question

I run

glGetIntegerv(GL_MAX_VERTEX_UNIFORM_VECTORS, &maxVertUniformsVect);

and get 1024.

Than in GLSL I do

uniform mediump vec4[1020] instance_mat

and that was ok. But with vec3/vec2/float it fails:

uniform mediump float[1030] instance_mat;          // fails
//uniform mediump vec2[1030] instance_mat;         // and this
//uniform mediump vec3[1030] instance_mat;         // and this

With following error:

cannot locate suitable resource to bind variable "instance_mat". Possibly large array.

The question is: Does GL_MAX_VERTEX_UNIFORM_VECTORS return the number of all kind of arrays, no matter what size they are? I mean, no matter does this float/vec2/vec3/vec4 - all counts as one VERTEX_UNIFORM_VECTOR?

---

Vertex shader code, as is:

#version 120
uniform mediump float[1200] instance_mat;        //mat4x3
attribute mediump float instaceIdF;             // in range 0..1000 Will be converted to int

attribute mediump vec3 vertex_;
attribute lowp vec4 color;
uniform mediump mat4 matrix;
varying lowp vec4 v_color;

void main(void)
{
    v_color = color;


        int instaceId = int(instaceIdF) * 12;
        mediump mat4 offsetMat = mat4(
                                    vec4(instance_mat[instaceId],   instance_mat[instaceId+1], instance_mat[instaceId+2], 0),
                                    vec4(instance_mat[instaceId+3], instance_mat[instaceId+4], instance_mat[instaceId+5], 0),
                                    vec4(instance_mat[instaceId+6], instance_mat[instaceId+7], instance_mat[instaceId+8], 0),
                                    vec4(instance_mat[instaceId+9], instance_mat[instaceId+10], instance_mat[instaceId+11], 1)
                                 );

        /*mediump mat4 offsetMat = mat4(
                                    vec4(instance_mat[instaceId].xyz, 0),
                                    vec4(instance_mat[instaceId+1].xyz, 0),
                                    vec4(instance_mat[instaceId+2].xyz, 0),
                                    vec4(instance_mat[instaceId+3].xyz, 1)
                                 );*/
        gl_Position = matrix * offsetMat * vec4(vertex_, 1.0);
        //gl_Position = matrix * vec4(vertex, 1.0);


}

Answer 1

According to http://www.opengl.org/wiki/Uniform_%28GLSL%29 (Implementation limits):

Implementation note: OpenGL implementations are allowed to reject shaders for implementation-dependent reasons. So you can have fewer active uniform components by your reckoning and still fail to link due to uniform limits. This is usually on hardware that is innately vector hardware. Pre-GeForce 8xxx hardware, and all ATi hardware does this. In this case, you should assume that each separate uniform takes up 4 components, much like it would in D3D. That means a "uniform float" is 4 components, a mat2x4 is 16 components (each row is 4 components), but a mat4x2 is 8 components.

Which is my case, also. But it not has to be always like that. Of course, for compatible reasons it is always better to count each float/vec2/vec3 uniform value, as max size value (vec4)