Support trail effects (#1251)

packages/core/src/shader/ShaderPool.ts

@@ -5,6 +5,8 @@ import blinnPhongFs from "../shaderlib/extra/blinn-phong.fs.glsl";
 import blinnPhongVs from "../shaderlib/extra/blinn-phong.vs.glsl";
 import particleFs from "../shaderlib/extra/particle.fs.glsl";
 import particleVs from "../shaderlib/extra/particle.vs.glsl";
+import trailFs from "../shaderlib/extra/trail.fs.glsl";
+import trailVs from "../shaderlib/extra/trail.vs.glsl";
 import pbrSpecularFs from "../shaderlib/extra/pbr-specular.fs.glsl";
 import pbrFs from "../shaderlib/extra/pbr.fs.glsl";
 import pbrVs from "../shaderlib/extra/pbr.vs.glsl";
@@ -43,6 +45,7 @@ export class ShaderPool {
 
     Shader.create("skybox", [new ShaderPass(skyboxVs, skyboxFs, forwardPassTags)]);
     Shader.create("particle-shader", [new ShaderPass(particleVs, particleFs, forwardPassTags)]);
+    Shader.create("trail-shader", [new ShaderPass(trailVs, trailFs, forwardPassTags)]);
     Shader.create("SpriteMask", [new ShaderPass(spriteMaskVs, spriteMaskFs, forwardPassTags)]);
     Shader.create("Sprite", [new ShaderPass(spriteVs, spriteFs, forwardPassTags)]);
     Shader.create("background-texture", [new ShaderPass(backgroundTextureVs, backgroundTextureFs, forwardPassTags)]);

packages/core/src/shaderlib/extra/trail.fs.glsl

@@ -0,0 +1,12 @@
+varying vec4 vColor;
+varying vec2 v_uv;
+uniform sampler2D u_texture;
+void main(void)
+{
+  #ifdef trailTexture
+    vec4 textureColor = texture2D(u_texture, v_uv);
+    gl_FragColor = vColor * textureColor;
+  #else
+    gl_FragColor = vColor;
+  #endif
+}

packages/core/src/shaderlib/extra/trail.vs.glsl

@@ -0,0 +1,36 @@
+uniform mat4 u_projMat;
+uniform mat4 u_viewMat;
+uniform mat4 u_modelMat;
+
+uniform float u_textureTileS;
+uniform float u_textureTileT;
+
+uniform vec4 u_headColor;
+uniform vec4 u_tailColor;
+
+uniform float u_currentTime;
+uniform float u_trailLifeTime;
+
+attribute vec3 a_position;
+attribute vec3 a_nodeCenter;
+
+attribute float a_nodeIndex;
+attribute float a_vertexNodeIndex;
+attribute float a_trailBirthTime;
+
+varying vec2 v_uv;
+varying vec4 vColor;
+
+void main(){
+  float s = a_nodeIndex / 80.0 * u_textureTileS;
+  float t = a_vertexNodeIndex * u_textureTileT;
+  v_uv = vec2( s, t );
+
+  float normalizeTime = (u_currentTime - a_trailBirthTime) / u_trailLifeTime;
+  vec4 realPosition = vec4( ( 1.0 - normalizeTime ) * a_position.xyz + normalizeTime * a_position.xyz, 1.0 ); 
+  gl_Position = u_projMat * u_viewMat * realPosition;
+
+  if (normalizeTime < 1.0){
+    vColor = ( 1.0 - normalizeTime ) * u_headColor + normalizeTime * u_tailColor;
+  }
+}