#version 300 es

in vec4 a_position;
uniform mat4 u_world;
uniform mat4 u_matrix;
uniform vec3 u_lightPos;
uniform vec3 u_light;
uniform float u_pointSize;

out vec3 v_surfaceToLight;

void main() {
    // convert the position from pixels to 0.0 to 1.0
    vec4 pos = a_position * u_matrix;
    gl_Position = pos;
    gl_PointSize = u_pointSize;

    vec3 surfaceWorldPosition = (u_world * pos).xyz;

    v_surfaceToLight = u_lightPos - surfaceWorldPosition;
}