GLSL shader time uniform freezed?

Question

I have a simple fragment shader to simulate "falling water". I'm using Ogre3D and opengles2, this is my code:

#version 130

uniform sampler2D valveTex;
uniform sampler2D noiseTex;
uniform float time;

uniform vec3 sprayColor;

varying vec2 uv;
varying float rand;

    void main()
    {
        gl_FragColor.w = texture2D(valveTex, uv).w;
        float noiseW = texture2D(noiseTex, uv + vec2(rand, -time)).x;
        gl_FragColor.w *= noiseW + noiseW;
        gl_FragColor.xyz = sprayColor;
    }

The shader works well and I see the animation happening, but after some time running the animation stops like if the variable time stopped updating, and the water stream looks still. What can be causing this?

Edit1: variable time is derived from Ogre's time_0_1.

Answer 1

It sounds like your noiseTex you're looking up into might be configured with wrapping mode CLAMP_TO_EDGE - once your time uniform gets large enough to take it outside the [0, 1] texture coordinate range, texture samples start just repeating the same values they had at the edge of the texture.

Ensure your texture is a power of two in size and configured with wrapping mode REPEAT.