Graphics.Blit image effect not working after upgrading to 2017.3.1

Hello:

I'm still learning the basics of shader programming, so this may be a silly problem.

I adapted some code I found online for displaying a "blast" image effect (my changes made possible for multiple blasts). After I upgraded Unity from 5.6 to 2017.3.1, the effect stopped working. I noticed there is a new option on Player Settings for Android (my target platform) to specify a Blit Type, and I mess around with it, but with no success. Besides, the effect no longer works on Standalone either.

The effect is something similar to this (not my game):




You can download a sample project here.

Also, here's the code responsible for the effect:

ExplosionEffect.cs

Code (CSharp):

1. using System.Collections;
2. using System.Collections.Generic;
3. using UnityEngine;
4.  
5. public class ExplosionEffect : MonoBehaviour {
6.     public Material explosionMaterial;
7.     [Range(-10f, 10f)]
8.     public float amplitude = 0.035f;
9.     private readonly int maxExplosions = 6;
10.     private Explosion[] explosions;
11.  
12.     private int amplitudeID;
13.     private int explosionRadiusID;
14.     private int explosionSizesID;
15.     private int explosionActivesID;
16.     private int explosionPositionsID;
17.  
18.     private RenderTexture renderTexture;
19.     private Camera cam;
20.  
21.     private void Start() {
22.         cam = Camera.main;
23.         explosions = new Explosion[maxExplosions];
24.  
25.         amplitudeID = Shader.PropertyToID("_Amplitude");
26.         explosionRadiusID = Shader.PropertyToID("_ExplosionRadius");
27.         explosionSizesID = Shader.PropertyToID("_ExplosionSizes");
28.         explosionActivesID = Shader.PropertyToID("_ExplosionActives");
29.         explosionPositionsID = Shader.PropertyToID("_ExplosionPositions");
30.  
31.         explosionMaterial.SetFloat(amplitudeID, amplitude);
32.         explosionMaterial.SetFloatArray(explosionRadiusID, GetAllRadius());
33.         explosionMaterial.SetFloatArray(explosionSizesID, GetAllSizes());
34.         explosionMaterial.SetFloatArray(explosionActivesID, GetAllActives());
35.         explosionMaterial.SetVectorArray(explosionPositionsID, GetAllPositions());
36.     }
37.  
38.     private void Update() {
39.         for (int i = 0; i < maxExplosions; i++) {
40.             if (explosions[i].IsActive) {
41.                 explosions[i].SetActiveTime(explosions[i].ActiveTime + Time.deltaTime);
42.                 if (explosions[i].ActiveTime >= explosions[i].time) {
43.                     explosions[i].SetActiveTime(0f);
44.                     explosions[i].radius = 0f;
45.                     explosions[i].DeActivate();
46.                 }
47.                 else {
48.                     explosions[i].radius = (explosions[i].ActiveTime / explosions[i].time) * explosions[i].size;
49.                 }
50.             }        
51.         }
52.  
53.         explosionMaterial.SetFloatArray(explosionRadiusID, GetAllRadius());
54.         explosionMaterial.SetFloatArray(explosionSizesID, GetAllSizes());
55.         explosionMaterial.SetFloatArray(explosionActivesID, GetAllActives());
56.         explosionMaterial.SetVectorArray(explosionPositionsID, GetAllPositions());
57.     }
58.  
59.     public void SetExplosion(float _time, float _size, Vector2 _position) {
60.         for (int i = 0; i < maxExplosions; i++) {
61.             if (!explosions[i].IsActive) {
62.                 explosions[i].time = _time;
63.                 explosions[i].size = SetScreenExplosionSize(_size);
64.                 explosions[i].position = _position;
65.                 explosions[i].radius = 0f;
66.                 explosions[i].SetActiveTime(0f);
67.  
68.                 explosions[i].Activate();
69.                 break;
70.             }
71.         }
72.     }
73.  
74.     private float SetScreenExplosionSize(float _size) {
75.         if (cam.orthographicSize > 0) {
76.             return _size / cam.orthographicSize;
77.         }
78.         return 0f;
79.     }
80.  
81.     private float[] GetAllRadius() {
82.         float[] radius = new float[maxExplosions];
83.         for (int i = 0; i < maxExplosions; i++) {
84.             radius[i] = explosions[i].radius;
85.         }
86.         return radius;
87.     }
88.  
89.     private float[] GetAllSizes() {
90.         float[] sizes = new float[maxExplosions];
91.         for (int i = 0; i < maxExplosions; i++) {
92.             sizes[i] = explosions[i].size;
93.         }
94.         return sizes;
95.     }
96.  
97.     private float[] GetAllActives() {
98.         float[] actives = new float[maxExplosions];
99.         for (int i = 0; i < maxExplosions; i++) {
100.             actives[i] = explosions[i].IsActive ? 1 : 0;
101.         }
102.         return actives;
103.     }
104.  
105.     private Vector4[] GetAllPositions() {
106.         Vector4[] positions = new Vector4[maxExplosions];
107.         for (int i = 0; i < maxExplosions; i++) {
108.             positions[i] = cam.WorldToViewportPoint(explosions[i].position);
109.         }
110.         return positions;
111.     }
112.  
113.  
114.     void OnPreRender() {
115.         renderTexture = RenderTexture.GetTemporary(Screen.width, Screen.height, 16);
116.         cam.targetTexture = renderTexture;
117.     }
118.  
119.     void OnPostRender() {
120.         cam.targetTexture = null; //null means framebuffer
121.         Graphics.Blit(renderTexture, null as RenderTexture, explosionMaterial);
122.         RenderTexture.ReleaseTemporary(renderTexture);
123.     }
124.  
125. }

ExplosionEffectShader.shader

Code (CSharp):

1. Shader "CerosWare/ExplosionEffectShader"
2. {
3.     Properties
4.     {
5.         _MainTex("Texture", 2D) = "white" {}
6.     }
7.     SubShader
8.     {
9.         Tags { "RenderType"="Opaque" }
10.         LOD 100
11.  
12.         Pass
13.         {
14.             CGPROGRAM
15.  
16.             #pragma vertex vert
17.             #pragma fragment frag
18.          
19.             #include "UnityCG.cginc"
20.  
21.             struct appdata
22.             {
23.                 float4 vertex : POSITION;
24.                 float2 uv : TEXCOORD0;
25.             };
26.  
27.             struct v2f
28.             {
29.                 float2 uv : TEXCOORD0;
30.                 float4 vertex : SV_POSITION;
31.             };
32.  
33.             sampler2D _MainTex;
34.             float4 _MainTex_ST;
35.             uniform float _ExplosionActives[6];
36.             uniform float _ExplosionRadius[6];
37.             uniform float _ExplosionSizes[6];
38.             uniform float4 _ExplosionPositions[6];
39.             uniform float _Amplitude;
40.  
41.             v2f vert (appdata v)
42.             {
43.                 v2f o;
44.                 o.vertex = UnityObjectToClipPos(v.vertex);
45.                 o.uv = MultiplyUV(UNITY_MATRIX_TEXTURE0, v.uv.xy);        
46.  
47.                 return o;
48.             }
49.          
50.             float4 frag (v2f i) : SV_Target
51.             {
52.                 for (int expIndex = 0; expIndex < 6; expIndex++) {
53.                     float active = _ExplosionActives[expIndex];
54.                     if (active == 1) {
55.                         float4 position = _ExplosionPositions[expIndex];
56.                         float2 diff = float2(i.uv.x - position.x, i.uv.y - position.y);
57.                         float dist = sqrt(diff.x * diff.x + diff.y * diff.y);
58.                         float radius = _ExplosionRadius[expIndex];
59.  
60.                         if (dist < radius) {
61.                             float size = _ExplosionSizes[expIndex];
62.                             if (dist < radius + size) {
63.                                 float angle = (dist - radius) * 2 * 3.141592654 / size;
64.                                 float cossin = (1 - cos(angle)) * 0.5;
65.                                 i.uv.x -= cossin * diff.x * _Amplitude / dist;
66.                                 i.uv.y -= cossin * diff.y * _Amplitude / dist;
67.                                 break;
68.                             }
69.                         }
70.                     }
71.                 }
72.                 return tex2D(_MainTex, i.uv);
73.             }
74.  
75.             ENDCG
76.         }
77.     }
78. }