Is it possible to modify a material/shader in code?

Questions & Answers
1

Hello, Im creating a simple Vr project where i am attempting to mix two “chemicals”. I followed a nice video on a pouring effect by VR with ANdrew. He uses a panning diffuse shader to create a very nice stream. I am attempting to modify this stream if I pour a red chemical into a blue chemical i want the blue chemical to turn to pink and its stream to reflect that. I can change the vials contents etc however i cannot seem to change the stream as i cant seem to effect the material and or shader thats drawing it. Here is the shader:

  Properties
   {
        _MainTex ("Sprite Texture", 2D) = "white" {}
        _Color ("Tint", Color) = (1,1,1,1)
		_Speed("Speed", float) = 0.0
        [MaterialToggle] PixelSnap ("Pixel snap", Float) = 0
        [HideInInspector] _RendererColor ("RendererColor", Color) = (1,1,1,1)
        [HideInInspector] _Flip ("Flip", Vector) = (1,1,1,1)
        [PerRendererData] _AlphaTex ("External Alpha", 2D) = "white" {}
        [PerRendererData] _EnableExternalAlpha ("Enable External Alpha", Float) = 0
    }

Here is one of my attempts to force change the stream

    private void Awake()
    {
        //chemicalColor = GetComponent<Material>().color;

        lineRenderer = GetComponent<LineRenderer>();
        Material mat = lineRenderer.material;
        
        mat.color = Color.green;
        //float alpha = 1.0f;
        //Gradient gradient = new Gradient();
        //gradient.SetKeys(
        //    new GradientColorKey[] { new GradientColorKey(Color.green, 0.0f), new GradientColorKey(Color.red, 1.0f) },
        //    new GradientAlphaKey[] { new GradientAlphaKey(alpha, 0.0f), new GradientAlphaKey(alpha, 1.0f) }
        //);
        //lineRenderer.colorGradient = gradient;
        print("Hello");
        splashParticle = GetComponentInChildren<ParticleSystem>();
    }
2

To change a variable inside a shader you need to use the Set_ functions on the material.

So to change the tint to green you’d use:
mat.SetColor("_Color", Color.green);

Setting this via string can however be a little expensive so you can improve this by caching the nameId:
private static readonly int ColorShaderId = Shader.PropertyToID("_Color");