uniform sampler2D brush_texture;

uniform vec2 inv_brush_texture_size;

uniform vec3 inv_matrix_m0;

uniform vec3 inv_matrix_m1;

uniform vec3 inv_matrix_m2;

vec4 brush()

{

    mat3 mat;

    mat[0] = inv_matrix_m0;

    mat[1] = inv_matrix_m1;

    mat[2] = inv_matrix_m2;

    vec3 hcoords = mat * vec3(gl_FragCoord.xy, 1);

    vec2 coords = hcoords.xy / hcoords.z;

    coords *= inv_brush_texture_size;

    return texture2D(brush_texture, coords);

}